From 178538f884862e897eae6f38b0ea08500da91ca7 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Thu, 11 Nov 2021 12:11:23 -0500
Subject: [PATCH 01/14] feat: add WIP metrics SDK

---
 .../src/Aggregation.ts                        |  25 +++
 .../src/Instruments.ts                        |  24 +++
 .../src/Measurement.ts                        |  24 +++
 .../src/Meter.ts                              |  60 +++++++
 .../src/MeterProvider.ts                      | 166 ++++++++++++++++++
 .../src/Metric.ts                             |  74 ++++++++
 .../src/MetricExporter.ts                     |  42 +++++
 .../src/MetricReader.ts                       |  42 +++++
 .../src/View.ts                               | 112 ++++++++++++
 .../src/index.ts                              |   4 +-
 10 files changed, 572 insertions(+), 1 deletion(-)
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/Aggregation.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts
 create mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Aggregation.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Aggregation.ts
new file mode 100644
index 00000000000..fac07ef4c20
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Aggregation.ts
@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Measurement } from './Measurement';
+
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#aggregation
+
+export interface Aggregator {
+    aggregate(measurement: Measurement): void;
+}
+
+// TODO define actual aggregator classes
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
new file mode 100644
index 00000000000..63288df0f80
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
@@ -0,0 +1,24 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export enum InstrumentType {
+    COUNTER = 'COUNTER',
+    HISTOGRAM = 'HISTOGRAM',
+    UP_DOWN_COUNTER = 'UP_DOWN_COUNTER',
+    OBSERVABLE_COUNTER = 'OBSERVABLE_COUNTER',
+    OBSERVABLE_GAUGE = 'OBSERVABLE_GAUGE',
+    OBSERVABLE_UP_DOWN_COUNTER = 'OBSERVABLE_UP_DOWN_COUNTER',
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
new file mode 100644
index 00000000000..17b6cee8f05
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
@@ -0,0 +1,24 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as api from '@opentelemetry/api'
+
+export type Measurement = {
+    value: number;
+    // TODO use common attributes
+    attributes: api.SpanAttributes;
+    context?: api.Context;
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
new file mode 100644
index 00000000000..0ee0096ba24
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
@@ -0,0 +1,60 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as metrics from '@opentelemetry/api-metrics';
+import { InstrumentationLibrary } from '@opentelemetry/core';
+import { Measurement } from './Measurement';
+import { MeterProvider } from './MeterProvider';
+import { Histogram, Metric } from './Metric';
+
+export class Meter implements metrics.Meter {
+    // instrumentation library required by spec to be on meter
+    // spec requires provider config changes to apply to previously created meters, achieved by holding a reference to the provider
+    constructor(private _provider: MeterProvider, private _instrumentationLibrary: InstrumentationLibrary, private _schemaUrl?: string) { }
+
+    /** this exists just to prevent ts errors from unused variables and may be removed */
+    getSchemaUrl(): string | undefined {
+        return this._schemaUrl;
+    }
+
+    /** this exists just to prevent ts errors from unused variables and may be removed */
+    getInstrumentationLibrary(): InstrumentationLibrary {
+        return this._instrumentationLibrary;
+    }
+
+    createHistogram(_name: string, _options?: metrics.MetricOptions): Histogram {
+        throw new Error('Method not implemented.');
+    }
+    createCounter(_name: string, _options?: metrics.MetricOptions): metrics.Counter {
+        throw new Error('Method not implemented.');
+    }
+    createUpDownCounter(_name: string, _options?: metrics.MetricOptions): metrics.UpDownCounter {
+        throw new Error('Method not implemented.');
+    }
+    createObservableGauge(_name: string, _options?: metrics.MetricOptions, _callback?: (observableResult: metrics.ObservableResult) => void): metrics.ObservableBase {
+        throw new Error('Method not implemented.');
+    }
+    createObservableCounter(_name: string, _options?: metrics.MetricOptions, _callback?: (observableResult: metrics.ObservableResult) => void): metrics.ObservableBase {
+        throw new Error('Method not implemented.');
+    }
+    createObservableUpDownCounter(_name: string, _options?: metrics.MetricOptions, _callback?: (observableResult: metrics.ObservableResult) => void): metrics.ObservableBase {
+        throw new Error('Method not implemented.');
+    }
+
+    public aggregate(metric: Metric, measurement: Measurement) {
+        this._provider.aggregate(this, metric, measurement);
+    }
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
new file mode 100644
index 00000000000..9780ef2d66f
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -0,0 +1,166 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as api from '@opentelemetry/api';
+import * as metrics from '@opentelemetry/api-metrics';
+import { Resource } from '@opentelemetry/resources';
+import { Measurement } from './Measurement';
+import { Meter } from './Meter';
+import { Metric } from './Metric';
+import { MetricExporter } from './MetricExporter';
+import { MetricReader } from './MetricReader';
+import { View } from './View';
+
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#meterprovider
+
+export type MeterProviderOptions = {
+    resource?: Resource;
+}
+
+export class MeterProvider {
+    private _resource: Resource;
+    private _shutdown = false;
+    private _metricReaders: MetricReader[] = [];
+    private _metricExporters: MetricExporter[] = [];
+    private _views: View[] = [];
+
+    constructor(options: MeterProviderOptions) {
+        this._resource = options.resource ?? Resource.empty();
+    }
+
+    /**
+     * **Unstable**
+     * 
+     * This method is only here to prevent typescript from complaining and may be removed.
+     */
+    getResource() {
+        return this._resource;
+    }
+
+    getMeter(name: string, version = '', options: metrics.MeterOptions = {}): metrics.Meter {
+        // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#meter-creation
+        if (this._shutdown) {
+            api.diag.warn('A shutdown MeterProvider cannot provide a Meter')
+            return metrics.NOOP_METER;
+        }
+
+        // Spec leaves it unspecified if creating a meter with duplicate
+        // name/version returns the same meter. We create a new one here
+        // for simplicity. This may change in the future.
+        return new Meter(this, { name, version }, options.schemaUrl);
+    }
+
+    addMetricReader(metricReader: MetricReader) {
+        this._metricReaders.push(metricReader);
+    }
+
+    addView(view: View) {
+        // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#view
+        this._views.push(view);
+    }
+
+    async shutdown(): Promise<void> {
+        // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#shutdown
+
+        // TODO add a timeout - spec leaves it up the the SDK if this is configurable
+        this._shutdown = true;
+
+        // Shut down all exporters and readers.
+        // Throw the first error and log all others.
+        let err: unknown;
+        for (const exporter of this._metricExporters) {
+            try {
+                await exporter.shutdown();
+            } catch (e) {
+                if (e instanceof Error) {
+                    api.diag.error(`Error shutting down: ${e.message}`)
+                }
+                err = err || e;
+            }
+        }
+
+        for (const reader of this._metricReaders) {
+            try {
+                await reader.shutdown();
+            } catch (e) {
+                if (e instanceof Error) {
+                    api.diag.error(`Error shutting down: ${e.message}`)
+                }
+                err = err || e;
+            }
+        }
+
+        if (err != null) {
+            throw err;
+        }
+    }
+
+    async forceFlush(): Promise<void> {
+        // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#forceflush
+
+        // TODO add a timeout - spec leaves it up the the SDK if this is configurable
+
+        // do not flush after shutdown
+        if (this._shutdown) {
+            return;
+        }
+
+        // Flush all exporters and readers.
+        // Throw the first error and log all others.
+        let err: unknown;
+        for (const exporter of this._metricExporters) {
+            try {
+                await exporter.forceFlush();
+            } catch (e) {
+                if (e instanceof Error) {
+                    api.diag.error(`Error force flushing: ${e.message}`)
+                }
+                err = err || e;
+            }
+        }
+
+        for (const reader of this._metricReaders) {
+            try {
+                await reader.forceFlush();
+            } catch (e) {
+                if (e instanceof Error) {
+                    api.diag.error(`Error force flushing: ${e.message}`)
+                }
+                err = err || e;
+            }
+        }
+
+        if (err != null) {
+            throw err;
+        }
+    }
+
+    public aggregate(_meter: Meter, _metric: Metric, _measurement: Measurement) {
+        // TODO actually aggregate
+
+        /**
+         * if there are no views:
+         *   apply the default configuration
+         * else:
+         *   for each view:
+         *     if view matches:
+         *       apply view configuration
+         *   if no view matched:
+         *     if user has not disabled default fallback:
+         *       apply default configuration
+         */
+    }
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts
new file mode 100644
index 00000000000..aceef7fd6ad
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts
@@ -0,0 +1,74 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as api from '@opentelemetry/api';
+import * as metrics from '@opentelemetry/api-metrics';
+import { Measurement } from './Measurement';
+import { Meter } from './Meter';
+
+export class Metric {
+    constructor(private _meter: Meter, private _name: string, private _version?: string) { }
+
+    getName(): string {
+        return this._name;
+    }
+
+    /**
+     * This only exists to stop typescript complaining about unused variable and may be removed. 
+     */
+    getVersion(): string | undefined {
+        return this._version;
+    }
+
+    aggregate(measurement: Measurement) {
+        this._meter.aggregate(this, measurement);
+    }
+}
+
+export class UpDownCounter extends Metric implements metrics.Counter {
+    add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
+        if (typeof value != 'number') {
+            api.diag.warn(`invalid type value provided to counter ${this.getName()}: ${typeof value}`);
+            return;
+        }
+
+        attributes = attributes ?? {};
+        ctx = ctx ?? api.context.active();
+
+        this.aggregate({
+            value,
+            attributes,
+            context: ctx,
+        });
+    }
+}
+
+export class Counter extends UpDownCounter implements metrics.Counter {
+    override add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
+        if (value < 0) {
+            api.diag.warn(`negative value provided to counter ${this.getName()}: ${value}`);
+            return;
+        }
+
+        return super.add(value, attributes, ctx);
+    }
+}
+
+export class Histogram extends Metric implements metrics.Histogram {
+    record(_measurement: number, _labels?: metrics.Labels, _context?: api.Context): void {
+        throw new Error('Method not implemented.');
+    }
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
new file mode 100644
index 00000000000..bdbbf708491
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
@@ -0,0 +1,42 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export abstract class MetricExporter {
+    private _shutdown = false;
+
+    async shutdown(): Promise<void> {
+        try {
+            await this.forceFlush();
+        } finally {
+            this._shutdown = true;
+        }
+    }
+
+    abstract forceFlush(): Promise<void>;
+
+    isShutdown() {
+        return this._shutdown;
+    }
+}
+
+export class ConsoleMetricExporter extends MetricExporter {
+    export() {
+        throw new Error('Method not implemented');
+    }
+
+    // nothing to do
+    async forceFlush() {}
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts
new file mode 100644
index 00000000000..7b4e0e2a5c2
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts
@@ -0,0 +1,42 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { MetricExporter } from '.';
+
+export class MetricReader {
+    private _shutdown = false;
+
+    constructor(private _exporter: MetricExporter) {}
+
+    async shutdown(): Promise<void> {
+        if (this._shutdown) {
+            return;
+        }
+
+        this._shutdown = true;
+        // errors thrown to caller
+        await this._exporter.shutdown();
+    }
+
+    async forceFlush(): Promise<void> {
+        if (this._shutdown) {
+            return;
+        }
+
+        // errors thrown to caller
+        await this._exporter.forceFlush();
+    }
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts
new file mode 100644
index 00000000000..ef5870c18d4
--- /dev/null
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts
@@ -0,0 +1,112 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { InstrumentType } from './Instruments';
+
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#view
+
+/**
+ * A metric view selects a stream of metrics from a MeterProvider and applies
+ * a configuration to that stream. If no configuration is provided, the default
+ * configuration is used.
+ */
+export class View {
+    private _selector: Partial<ViewMetricSelector>;
+
+    /**
+     * Construct a metric view
+     * 
+     * @param options a required object which describes the view selector and configuration
+     */
+    constructor(options: ViewOptions) {
+        if (typeof options.selector == null) {
+            throw new Error('Missing required view selector')
+        }
+
+        if (
+            options.selector.instrumentType == null &&
+            options.selector.instrumentName == null &&
+            options.selector.meterName == null &&
+            options.selector.meterVersion == null &&
+            options.selector.meterSchemaUrl == null
+        ) {
+            // It is recommended by the SDK specification to fail fast when invalid options are provided
+            throw new Error('Cannot create a view which selects no options');
+        }
+
+        this._selector = options.selector;
+    }
+
+    /**
+     * Given a metric selector, determine if all of this view's metric selectors match.
+     * 
+     * @param selector selector to match
+     * @returns boolean
+     */
+    public match(selector: ViewMetricSelector) {
+        return this._matchSelectorProperty('instrumentType', selector.instrumentType) &&
+            this._matchInstrumentName(selector.instrumentName) &&
+            this._matchSelectorProperty('meterName', selector.meterName) &&
+            this._matchSelectorProperty('meterVersion', selector.meterVersion) &&
+            this._matchSelectorProperty('meterSchemaUrl', selector.meterSchemaUrl);
+    }
+
+    /**
+     * Match instrument name against the configured selector metric name, which may include wildcards
+     */
+    private _matchInstrumentName(name: string) {
+        if (this._selector.instrumentName == null) {
+            return true;
+        }
+
+        return this._selector.instrumentName === name;
+    }
+
+    private _matchSelectorProperty<Prop extends keyof ViewMetricSelector>(property: Prop, metricProperty: ViewMetricSelector[Prop]): boolean {
+        if (this._selector[property] == null) {
+            return true;
+        }
+
+        if (this._selector[property] === metricProperty) {
+            return true;
+        }
+
+        return false;
+    }
+}
+
+export type ViewMetricSelector = {
+    instrumentType: InstrumentType;
+    instrumentName: string;
+    meterName: string;
+    meterVersion?: string;
+    meterSchemaUrl?: string;
+}
+
+export type ViewOptions = {
+    name?: string;
+    selector: Partial<ViewMetricSelector>;
+    streamConfig?: ViewStreamConfig;
+}
+
+export type ViewStreamConfig = {
+    description: string;
+    attributeKeys?: string[];
+
+    // TODO use these types when they are defined
+    aggregation?: unknown;
+    exemplarReservoir?: unknown;
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/index.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/index.ts
index f4fa9c64729..ef6f9b17d23 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/index.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/index.ts
@@ -14,4 +14,6 @@
  * limitations under the License.
  */
 
-export * from './version';
+export { MeterProvider, MeterProviderOptions } from './MeterProvider';
+export * from './MetricExporter';
+export * from './MetricReader';

From 9ac4f10d5c9ffa513315b84e685f48e25a4530fc Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Thu, 11 Nov 2021 12:15:13 -0500
Subject: [PATCH 02/14] chore: update ts references

---
 .../opentelemetry-exporter-metrics-otlp-grpc/tsconfig.json     | 3 ---
 .../opentelemetry-exporter-metrics-otlp-http/tsconfig.esm.json | 3 ---
 .../opentelemetry-exporter-metrics-otlp-http/tsconfig.json     | 3 ---
 .../opentelemetry-exporter-metrics-otlp-proto/tsconfig.json    | 3 ---
 .../packages/opentelemetry-exporter-prometheus/tsconfig.json   | 3 ---
 experimental/packages/opentelemetry-sdk-node/tsconfig.json     | 3 ---
 6 files changed, 18 deletions(-)

diff --git a/experimental/packages/opentelemetry-exporter-metrics-otlp-grpc/tsconfig.json b/experimental/packages/opentelemetry-exporter-metrics-otlp-grpc/tsconfig.json
index b3ff4e84578..64ff561763b 100644
--- a/experimental/packages/opentelemetry-exporter-metrics-otlp-grpc/tsconfig.json
+++ b/experimental/packages/opentelemetry-exporter-metrics-otlp-grpc/tsconfig.json
@@ -20,9 +20,6 @@
     },
     {
       "path": "../opentelemetry-exporter-trace-otlp-http"
-    },
-    {
-      "path": "../opentelemetry-sdk-metrics-base"
     }
   ]
 }
diff --git a/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.esm.json b/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.esm.json
index 484461f470a..063825713f5 100644
--- a/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.esm.json
+++ b/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.esm.json
@@ -14,9 +14,6 @@
     },
     {
       "path": "../opentelemetry-exporter-trace-otlp-http/tsconfig.esm.json"
-    },
-    {
-      "path": "../opentelemetry-sdk-metrics-base/tsconfig.esm.json"
     }
   ]
 }
diff --git a/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.json b/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.json
index 13dc2e7744d..d9595b8a987 100644
--- a/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.json
+++ b/experimental/packages/opentelemetry-exporter-metrics-otlp-http/tsconfig.json
@@ -14,9 +14,6 @@
     },
     {
       "path": "../opentelemetry-exporter-trace-otlp-http"
-    },
-    {
-      "path": "../opentelemetry-sdk-metrics-base"
     }
   ]
 }
diff --git a/experimental/packages/opentelemetry-exporter-metrics-otlp-proto/tsconfig.json b/experimental/packages/opentelemetry-exporter-metrics-otlp-proto/tsconfig.json
index 35c3f6d9c73..50c20b23e2e 100644
--- a/experimental/packages/opentelemetry-exporter-metrics-otlp-proto/tsconfig.json
+++ b/experimental/packages/opentelemetry-exporter-metrics-otlp-proto/tsconfig.json
@@ -20,9 +20,6 @@
     },
     {
       "path": "../opentelemetry-exporter-trace-otlp-proto"
-    },
-    {
-      "path": "../opentelemetry-sdk-metrics-base"
     }
   ]
 }
diff --git a/experimental/packages/opentelemetry-exporter-prometheus/tsconfig.json b/experimental/packages/opentelemetry-exporter-prometheus/tsconfig.json
index 3c062d3feb2..948abef3ceb 100644
--- a/experimental/packages/opentelemetry-exporter-prometheus/tsconfig.json
+++ b/experimental/packages/opentelemetry-exporter-prometheus/tsconfig.json
@@ -11,9 +11,6 @@
   "references": [
     {
       "path": "../opentelemetry-api-metrics"
-    },
-    {
-      "path": "../opentelemetry-sdk-metrics-base"
     }
   ]
 }
diff --git a/experimental/packages/opentelemetry-sdk-node/tsconfig.json b/experimental/packages/opentelemetry-sdk-node/tsconfig.json
index 36c71e90d8d..b0e33797f42 100644
--- a/experimental/packages/opentelemetry-sdk-node/tsconfig.json
+++ b/experimental/packages/opentelemetry-sdk-node/tsconfig.json
@@ -14,9 +14,6 @@
     },
     {
       "path": "../opentelemetry-instrumentation"
-    },
-    {
-      "path": "../opentelemetry-sdk-metrics-base"
     }
   ]
 }

From 769d16fb76449f7aaa6a005d2eba7c24c9504563 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Thu, 11 Nov 2021 12:34:20 -0500
Subject: [PATCH 03/14] chore: fix versions in wip metrics

---
 .../packages/opentelemetry-sdk-metrics-base/package.json      | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/package.json b/experimental/packages/opentelemetry-sdk-metrics-base/package.json
index b03868fd5fd..30ef6073e2e 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/package.json
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@opentelemetry/sdk-metrics-base-wip",
-  "version": "0.26.0",
+  "version": "0.27.0",
   "private": true,
   "description": "Work in progress OpenTelemetry metrics SDK",
   "main": "build/src/index.js",
@@ -64,7 +64,7 @@
     "@opentelemetry/api": "^1.0.0"
   },
   "dependencies": {
-    "@opentelemetry/api-metrics": "0.26.0",
+    "@opentelemetry/api-metrics": "0.27.0",
     "@opentelemetry/core": "1.0.0",
     "@opentelemetry/resources": "1.0.0",
     "lodash.merge": "^4.6.2"

From e04ea5937ae97a10049ae804e14cc368184d8235 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Thu, 11 Nov 2021 12:34:44 -0500
Subject: [PATCH 04/14] chore: rename metric to instrument

---
 .../src/Instruments.ts                        | 59 +++++++++++++++
 .../src/Meter.ts                              |  4 +-
 .../src/MeterProvider.ts                      |  4 +-
 .../src/Metric.ts                             | 74 -------------------
 4 files changed, 63 insertions(+), 78 deletions(-)
 delete mode 100644 experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
index 63288df0f80..5d91ced65f7 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
@@ -14,6 +14,11 @@
  * limitations under the License.
  */
 
+import * as api from '@opentelemetry/api';
+import * as metrics from '@opentelemetry/api-metrics';
+import { Measurement } from './Measurement';
+import { Meter } from './Meter';
+
 export enum InstrumentType {
     COUNTER = 'COUNTER',
     HISTOGRAM = 'HISTOGRAM',
@@ -22,3 +27,57 @@ export enum InstrumentType {
     OBSERVABLE_GAUGE = 'OBSERVABLE_GAUGE',
     OBSERVABLE_UP_DOWN_COUNTER = 'OBSERVABLE_UP_DOWN_COUNTER',
 }
+
+export class Instrument {
+    constructor(private _meter: Meter, private _name: string, private _version?: string) { }
+
+    getName(): string {
+        return this._name;
+    }
+
+    /**
+     * This only exists to stop typescript complaining about unused variable and may be removed. 
+     */
+    getVersion(): string | undefined {
+        return this._version;
+    }
+
+    aggregate(measurement: Measurement) {
+        this._meter.aggregate(this, measurement);
+    }
+}
+
+export class UpDownCounter extends Instrument implements metrics.Counter {
+    add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
+        if (typeof value != 'number') {
+            api.diag.warn(`invalid type value provided to counter ${this.getName()}: ${typeof value}`);
+            return;
+        }
+
+        attributes = attributes ?? {};
+        ctx = ctx ?? api.context.active();
+
+        this.aggregate({
+            value,
+            attributes,
+            context: ctx,
+        });
+    }
+}
+
+export class Counter extends UpDownCounter implements metrics.Counter {
+    override add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
+        if (value < 0) {
+            api.diag.warn(`negative value provided to counter ${this.getName()}: ${value}`);
+            return;
+        }
+
+        return super.add(value, attributes, ctx);
+    }
+}
+
+export class Histogram extends Instrument implements metrics.Histogram {
+    record(_measurement: number, _labels?: metrics.Attributes, _context?: api.Context): void {
+        throw new Error('Method not implemented.');
+    }
+}
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
index 0ee0096ba24..f7b5a9b5206 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
@@ -18,7 +18,7 @@ import * as metrics from '@opentelemetry/api-metrics';
 import { InstrumentationLibrary } from '@opentelemetry/core';
 import { Measurement } from './Measurement';
 import { MeterProvider } from './MeterProvider';
-import { Histogram, Metric } from './Metric';
+import { Histogram, Instrument } from './Instruments';
 
 export class Meter implements metrics.Meter {
     // instrumentation library required by spec to be on meter
@@ -54,7 +54,7 @@ export class Meter implements metrics.Meter {
         throw new Error('Method not implemented.');
     }
 
-    public aggregate(metric: Metric, measurement: Measurement) {
+    public aggregate(metric: Instrument, measurement: Measurement) {
         this._provider.aggregate(this, metric, measurement);
     }
 }
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
index 9780ef2d66f..718599005b5 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -17,9 +17,9 @@
 import * as api from '@opentelemetry/api';
 import * as metrics from '@opentelemetry/api-metrics';
 import { Resource } from '@opentelemetry/resources';
+import { Instrument } from './Instruments';
 import { Measurement } from './Measurement';
 import { Meter } from './Meter';
-import { Metric } from './Metric';
 import { MetricExporter } from './MetricExporter';
 import { MetricReader } from './MetricReader';
 import { View } from './View';
@@ -148,7 +148,7 @@ export class MeterProvider {
         }
     }
 
-    public aggregate(_meter: Meter, _metric: Metric, _measurement: Measurement) {
+    public aggregate(_meter: Meter, _metric: Instrument, _measurement: Measurement) {
         // TODO actually aggregate
 
         /**
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts
deleted file mode 100644
index aceef7fd6ad..00000000000
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Metric.ts
+++ /dev/null
@@ -1,74 +0,0 @@
-/*
- * Copyright The OpenTelemetry Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-import * as api from '@opentelemetry/api';
-import * as metrics from '@opentelemetry/api-metrics';
-import { Measurement } from './Measurement';
-import { Meter } from './Meter';
-
-export class Metric {
-    constructor(private _meter: Meter, private _name: string, private _version?: string) { }
-
-    getName(): string {
-        return this._name;
-    }
-
-    /**
-     * This only exists to stop typescript complaining about unused variable and may be removed. 
-     */
-    getVersion(): string | undefined {
-        return this._version;
-    }
-
-    aggregate(measurement: Measurement) {
-        this._meter.aggregate(this, measurement);
-    }
-}
-
-export class UpDownCounter extends Metric implements metrics.Counter {
-    add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
-        if (typeof value != 'number') {
-            api.diag.warn(`invalid type value provided to counter ${this.getName()}: ${typeof value}`);
-            return;
-        }
-
-        attributes = attributes ?? {};
-        ctx = ctx ?? api.context.active();
-
-        this.aggregate({
-            value,
-            attributes,
-            context: ctx,
-        });
-    }
-}
-
-export class Counter extends UpDownCounter implements metrics.Counter {
-    override add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
-        if (value < 0) {
-            api.diag.warn(`negative value provided to counter ${this.getName()}: ${value}`);
-            return;
-        }
-
-        return super.add(value, attributes, ctx);
-    }
-}
-
-export class Histogram extends Metric implements metrics.Histogram {
-    record(_measurement: number, _labels?: metrics.Labels, _context?: api.Context): void {
-        throw new Error('Method not implemented.');
-    }
-}

From 42a329846a2ee07ff350317eded9d2dc63d77dec Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Thu, 11 Nov 2021 13:00:48 -0500
Subject: [PATCH 05/14] chore: simplify counter inheritance

---
 .../src/Instruments.ts                        | 36 ++++++++-----------
 .../src/Measurement.ts                        |  3 +-
 2 files changed, 16 insertions(+), 23 deletions(-)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
index 5d91ced65f7..c257cf05480 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
@@ -16,7 +16,7 @@
 
 import * as api from '@opentelemetry/api';
 import * as metrics from '@opentelemetry/api-metrics';
-import { Measurement } from './Measurement';
+import { Attributes } from '@opentelemetry/api-metrics';
 import { Meter } from './Meter';
 
 export enum InstrumentType {
@@ -42,22 +42,8 @@ export class Instrument {
         return this._version;
     }
 
-    aggregate(measurement: Measurement) {
-        this._meter.aggregate(this, measurement);
-    }
-}
-
-export class UpDownCounter extends Instrument implements metrics.Counter {
-    add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
-        if (typeof value != 'number') {
-            api.diag.warn(`invalid type value provided to counter ${this.getName()}: ${typeof value}`);
-            return;
-        }
-
-        attributes = attributes ?? {};
-        ctx = ctx ?? api.context.active();
-
-        this.aggregate({
+    aggregate(value: number, attributes: Attributes = {}, ctx: api.Context = api.context.active()) {
+        this._meter.aggregate(this, {
             value,
             attributes,
             context: ctx,
@@ -65,19 +51,25 @@ export class UpDownCounter extends Instrument implements metrics.Counter {
     }
 }
 
-export class Counter extends UpDownCounter implements metrics.Counter {
-    override add(value: number, attributes?: api.SpanAttributes, ctx?: api.Context): void {
+export class UpDownCounter extends Instrument implements metrics.Counter {
+    add(value: number, attributes?: Attributes, ctx?: api.Context): void {
+        this.aggregate(value, attributes, ctx);
+    }
+}
+
+export class Counter extends Instrument implements metrics.Counter {
+    add(value: number, attributes?: Attributes, ctx?: api.Context): void {
         if (value < 0) {
             api.diag.warn(`negative value provided to counter ${this.getName()}: ${value}`);
             return;
         }
 
-        return super.add(value, attributes, ctx);
+        this.aggregate(value, attributes, ctx);
     }
 }
 
 export class Histogram extends Instrument implements metrics.Histogram {
-    record(_measurement: number, _labels?: metrics.Attributes, _context?: api.Context): void {
-        throw new Error('Method not implemented.');
+    record(value: number, attributes?: Attributes, ctx?: api.Context): void {
+        this.aggregate(value, attributes, ctx);
     }
 }
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
index 17b6cee8f05..1d93945ca0c 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
@@ -15,10 +15,11 @@
  */
 
 import * as api from '@opentelemetry/api'
+import { Attributes } from '@opentelemetry/api-metrics'
 
 export type Measurement = {
     value: number;
     // TODO use common attributes
-    attributes: api.SpanAttributes;
+    attributes: Attributes
     context?: api.Context;
 }

From d80eb916924f40a75d563a7f92f6e3a49ad418a6 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Thu, 11 Nov 2021 13:03:44 -0500
Subject: [PATCH 06/14] chore: fix double import

---
 .../opentelemetry-sdk-metrics-base/src/Instruments.ts    | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
index c257cf05480..f964a069b8e 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
@@ -16,7 +16,6 @@
 
 import * as api from '@opentelemetry/api';
 import * as metrics from '@opentelemetry/api-metrics';
-import { Attributes } from '@opentelemetry/api-metrics';
 import { Meter } from './Meter';
 
 export enum InstrumentType {
@@ -42,7 +41,7 @@ export class Instrument {
         return this._version;
     }
 
-    aggregate(value: number, attributes: Attributes = {}, ctx: api.Context = api.context.active()) {
+    aggregate(value: number, attributes: metrics.Attributes = {}, ctx: api.Context = api.context.active()) {
         this._meter.aggregate(this, {
             value,
             attributes,
@@ -52,13 +51,13 @@ export class Instrument {
 }
 
 export class UpDownCounter extends Instrument implements metrics.Counter {
-    add(value: number, attributes?: Attributes, ctx?: api.Context): void {
+    add(value: number, attributes?: metrics.Attributes, ctx?: api.Context): void {
         this.aggregate(value, attributes, ctx);
     }
 }
 
 export class Counter extends Instrument implements metrics.Counter {
-    add(value: number, attributes?: Attributes, ctx?: api.Context): void {
+    add(value: number, attributes?: metrics.Attributes, ctx?: api.Context): void {
         if (value < 0) {
             api.diag.warn(`negative value provided to counter ${this.getName()}: ${value}`);
             return;
@@ -69,7 +68,7 @@ export class Counter extends Instrument implements metrics.Counter {
 }
 
 export class Histogram extends Instrument implements metrics.Histogram {
-    record(value: number, attributes?: Attributes, ctx?: api.Context): void {
+    record(value: number, attributes?: metrics.Attributes, ctx?: api.Context): void {
         this.aggregate(value, attributes, ctx);
     }
 }

From fa3254dbca5bdeb26dd0cbb73339141070226be3 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 08:26:37 -0500
Subject: [PATCH 07/14] chore: implement basic sync instruments

---
 .../src/Instruments.ts                         | 18 ++++++------------
 .../src/Meter.ts                               | 13 ++++++++-----
 .../src/MeterProvider.ts                       |  3 +--
 3 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
index f964a069b8e..8015af9cb89 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
@@ -27,20 +27,14 @@ export enum InstrumentType {
     OBSERVABLE_UP_DOWN_COUNTER = 'OBSERVABLE_UP_DOWN_COUNTER',
 }
 
-export class Instrument {
-    constructor(private _meter: Meter, private _name: string, private _version?: string) { }
+export class SyncInstrument {
+    constructor(private _meter: Meter, private _name: string) { }
 
     getName(): string {
         return this._name;
     }
 
-    /**
-     * This only exists to stop typescript complaining about unused variable and may be removed. 
-     */
-    getVersion(): string | undefined {
-        return this._version;
-    }
-
+ 
     aggregate(value: number, attributes: metrics.Attributes = {}, ctx: api.Context = api.context.active()) {
         this._meter.aggregate(this, {
             value,
@@ -50,13 +44,13 @@ export class Instrument {
     }
 }
 
-export class UpDownCounter extends Instrument implements metrics.Counter {
+export class UpDownCounter extends SyncInstrument implements metrics.Counter {
     add(value: number, attributes?: metrics.Attributes, ctx?: api.Context): void {
         this.aggregate(value, attributes, ctx);
     }
 }
 
-export class Counter extends Instrument implements metrics.Counter {
+export class Counter extends SyncInstrument implements metrics.Counter {
     add(value: number, attributes?: metrics.Attributes, ctx?: api.Context): void {
         if (value < 0) {
             api.diag.warn(`negative value provided to counter ${this.getName()}: ${value}`);
@@ -67,7 +61,7 @@ export class Counter extends Instrument implements metrics.Counter {
     }
 }
 
-export class Histogram extends Instrument implements metrics.Histogram {
+export class Histogram extends SyncInstrument implements metrics.Histogram {
     record(value: number, attributes?: metrics.Attributes, ctx?: api.Context): void {
         this.aggregate(value, attributes, ctx);
     }
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
index f7b5a9b5206..2c4fd1283ac 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
@@ -16,9 +16,9 @@
 
 import * as metrics from '@opentelemetry/api-metrics';
 import { InstrumentationLibrary } from '@opentelemetry/core';
+import { Counter, Histogram, UpDownCounter } from './Instruments';
 import { Measurement } from './Measurement';
 import { MeterProvider } from './MeterProvider';
-import { Histogram, Instrument } from './Instruments';
 
 export class Meter implements metrics.Meter {
     // instrumentation library required by spec to be on meter
@@ -36,14 +36,17 @@ export class Meter implements metrics.Meter {
     }
 
     createHistogram(_name: string, _options?: metrics.MetricOptions): Histogram {
-        throw new Error('Method not implemented.');
+        return new Histogram(this, _name);
     }
+    
     createCounter(_name: string, _options?: metrics.MetricOptions): metrics.Counter {
-        throw new Error('Method not implemented.');
+        return new Counter(this, _name);
     }
+
     createUpDownCounter(_name: string, _options?: metrics.MetricOptions): metrics.UpDownCounter {
-        throw new Error('Method not implemented.');
+        return new UpDownCounter(this, _name);
     }
+
     createObservableGauge(_name: string, _options?: metrics.MetricOptions, _callback?: (observableResult: metrics.ObservableResult) => void): metrics.ObservableBase {
         throw new Error('Method not implemented.');
     }
@@ -54,7 +57,7 @@ export class Meter implements metrics.Meter {
         throw new Error('Method not implemented.');
     }
 
-    public aggregate(metric: Instrument, measurement: Measurement) {
+    public aggregate(metric: unknown, measurement: Measurement) {
         this._provider.aggregate(this, metric, measurement);
     }
 }
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
index 718599005b5..7ceb752ff97 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -17,7 +17,6 @@
 import * as api from '@opentelemetry/api';
 import * as metrics from '@opentelemetry/api-metrics';
 import { Resource } from '@opentelemetry/resources';
-import { Instrument } from './Instruments';
 import { Measurement } from './Measurement';
 import { Meter } from './Meter';
 import { MetricExporter } from './MetricExporter';
@@ -148,7 +147,7 @@ export class MeterProvider {
         }
     }
 
-    public aggregate(_meter: Meter, _metric: Instrument, _measurement: Measurement) {
+    public aggregate(_meter: Meter, _metric: unknown, _measurement: Measurement) {
         // TODO actually aggregate
 
         /**

From 3ce902db800d72a18059406fa3c915ad86a9a083 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 08:27:42 -0500
Subject: [PATCH 08/14] chore: check for shutdown in metric exporter

---
 .../src/MetricExporter.ts                     | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
index bdbbf708491..0b197fdd6f2 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
@@ -14,15 +14,22 @@
  * limitations under the License.
  */
 
+// TODO should this just be an interface and exporters can implement their own shutdown?
 export abstract class MetricExporter {
-    private _shutdown = false;
+    protected _shutdown = false;
+
+    // TODO: define the methods that actually export - must allow for push and pull exporters
 
     async shutdown(): Promise<void> {
-        try {
-            await this.forceFlush();
-        } finally {
-            this._shutdown = true;
+        if (this._shutdown) {
+            return;
         }
+
+        // Setting _shutdown before flushing might prevent some exporters from flushing
+        // Waiting until flushing is complete might allow another flush to occur during shutdown
+        const flushPromise = this.forceFlush();
+        this._shutdown = true;
+        await flushPromise;
     }
 
     abstract forceFlush(): Promise<void>;
@@ -33,7 +40,7 @@ export abstract class MetricExporter {
 }
 
 export class ConsoleMetricExporter extends MetricExporter {
-    export() {
+    async export() {
         throw new Error('Method not implemented');
     }
 

From 6d95c402f31de9673486496be5363fff485b55b1 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 08:30:48 -0500
Subject: [PATCH 09/14] chore: add wildcard support todo

---
 experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts
index ef5870c18d4..2abbf8760f3 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/View.ts
@@ -72,6 +72,7 @@ export class View {
             return true;
         }
 
+        // TODO wildcard support
         return this._selector.instrumentName === name;
     }
 

From 8d4223d2db1fd72fd80446c58dc2569cee08f091 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 08:35:49 -0500
Subject: [PATCH 10/14] chore: guard multi-shutdown on meter provider

---
 .../opentelemetry-sdk-metrics-base/src/MeterProvider.ts      | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
index 7ceb752ff97..b71989ae770 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -74,6 +74,11 @@ export class MeterProvider {
     async shutdown(): Promise<void> {
         // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#shutdown
 
+        if (this._shutdown) {
+            api.diag.warn('shutdown may only be called once per MeterProvider');
+            return;
+        }
+
         // TODO add a timeout - spec leaves it up the the SDK if this is configurable
         this._shutdown = true;
 

From 25a55d816b8f6df7c806bdc4efbededaa84e5875 Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 08:35:49 -0500
Subject: [PATCH 11/14] chore: guard against multiple shutdown

---
 .../opentelemetry-sdk-metrics-base/src/MeterProvider.ts      | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
index 7ceb752ff97..b71989ae770 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -74,6 +74,11 @@ export class MeterProvider {
     async shutdown(): Promise<void> {
         // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#shutdown
 
+        if (this._shutdown) {
+            api.diag.warn('shutdown may only be called once per MeterProvider');
+            return;
+        }
+
         // TODO add a timeout - spec leaves it up the the SDK if this is configurable
         this._shutdown = true;
 

From b286dbd83a8bc841d5419f7779867b92463fdedb Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 11:29:30 -0500
Subject: [PATCH 12/14] chore: add throw todo

---
 .../opentelemetry-sdk-metrics-base/src/MeterProvider.ts         | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
index b71989ae770..de0b435fea7 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -59,6 +59,7 @@ export class MeterProvider {
         // Spec leaves it unspecified if creating a meter with duplicate
         // name/version returns the same meter. We create a new one here
         // for simplicity. This may change in the future.
+        // TODO: consider returning the same meter if the same name/version is used
         return new Meter(this, { name, version }, options.schemaUrl);
     }
 
@@ -84,6 +85,7 @@ export class MeterProvider {
 
         // Shut down all exporters and readers.
         // Throw the first error and log all others.
+        // TODO make sure it is acceptable to throw here
         let err: unknown;
         for (const exporter of this._metricExporters) {
             try {

From 753d0f926924d3f0609764ed23ee289ec136a2ee Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Fri, 12 Nov 2021 15:18:06 -0500
Subject: [PATCH 13/14] chore: do not throw in shutdown/flush

---
 .../src/MeterProvider.ts                      | 71 ++++++-------------
 1 file changed, 21 insertions(+), 50 deletions(-)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
index de0b435fea7..e8fe86ef027 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MeterProvider.ts
@@ -72,6 +72,10 @@ export class MeterProvider {
         this._views.push(view);
     }
 
+    /**
+     * Flush all buffered data and shut down the MeterProvider and all exporters and metric readers.
+     * Returns a promise which is resolved when all flushes are complete.
+     */
     async shutdown(): Promise<void> {
         // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#shutdown
 
@@ -83,37 +87,13 @@ export class MeterProvider {
         // TODO add a timeout - spec leaves it up the the SDK if this is configurable
         this._shutdown = true;
 
-        // Shut down all exporters and readers.
-        // Throw the first error and log all others.
-        // TODO make sure it is acceptable to throw here
-        let err: unknown;
-        for (const exporter of this._metricExporters) {
-            try {
-                await exporter.shutdown();
-            } catch (e) {
-                if (e instanceof Error) {
-                    api.diag.error(`Error shutting down: ${e.message}`)
-                }
-                err = err || e;
-            }
-        }
-
-        for (const reader of this._metricReaders) {
-            try {
-                await reader.shutdown();
-            } catch (e) {
-                if (e instanceof Error) {
-                    api.diag.error(`Error shutting down: ${e.message}`)
-                }
-                err = err || e;
-            }
-        }
-
-        if (err != null) {
-            throw err;
-        }
+        await this._forceFlush();
     }
 
+    /**
+     * Notifies all exporters and metric readers to flush any buffered data.
+     * Returns a promise which is resolved when all flushes are complete.
+     */
     async forceFlush(): Promise<void> {
         // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#forceflush
 
@@ -121,37 +101,28 @@ export class MeterProvider {
 
         // do not flush after shutdown
         if (this._shutdown) {
+            api.diag.warn('invalid attempt to force flush after shutdown')
             return;
         }
 
-        // Flush all exporters and readers.
-        // Throw the first error and log all others.
-        let err: unknown;
-        for (const exporter of this._metricExporters) {
-            try {
-                await exporter.forceFlush();
-            } catch (e) {
-                if (e instanceof Error) {
-                    api.diag.error(`Error force flushing: ${e.message}`)
-                }
-                err = err || e;
-            }
-        }
+        await this._forceFlush();
+    }
 
-        for (const reader of this._metricReaders) {
+    /** 
+     * A private implementation of force flush which doesn't check if the function is shut down
+     */
+    private async _forceFlush() {
+        // Shut down all exporters and readers.
+        // Catch and log all errors
+        for (const exporter of [...this._metricExporters, ...this._metricReaders]) {
             try {
-                await reader.forceFlush();
+                await exporter.shutdown();
             } catch (e) {
                 if (e instanceof Error) {
-                    api.diag.error(`Error force flushing: ${e.message}`)
+                    api.diag.error(`Error shutting down: ${e.message}`)
                 }
-                err = err || e;
             }
         }
-
-        if (err != null) {
-            throw err;
-        }
     }
 
     public aggregate(_meter: Meter, _metric: unknown, _measurement: Measurement) {

From 892c92ba98a3d14af1d6a99359f30b1caeb7507a Mon Sep 17 00:00:00 2001
From: Daniel Dyla <dyladan@users.noreply.github.com>
Date: Mon, 15 Nov 2021 08:42:08 -0500
Subject: [PATCH 14/14] chore: add links to spec

Co-authored-by: Georg Pirklbauer <georg.pirklbauer@dynatrace.com>
---
 .../packages/opentelemetry-sdk-metrics-base/src/Instruments.ts  | 2 ++
 .../packages/opentelemetry-sdk-metrics-base/src/Measurement.ts  | 2 ++
 .../packages/opentelemetry-sdk-metrics-base/src/Meter.ts        | 2 ++
 .../opentelemetry-sdk-metrics-base/src/MetricExporter.ts        | 2 ++
 .../packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts | 2 ++
 5 files changed, 10 insertions(+)

diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
index 8015af9cb89..8c5d1212d37 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Instruments.ts
@@ -18,6 +18,8 @@ import * as api from '@opentelemetry/api';
 import * as metrics from '@opentelemetry/api-metrics';
 import { Meter } from './Meter';
 
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument
+
 export enum InstrumentType {
     COUNTER = 'COUNTER',
     HISTOGRAM = 'HISTOGRAM',
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
index 1d93945ca0c..215426f9d76 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Measurement.ts
@@ -17,6 +17,8 @@
 import * as api from '@opentelemetry/api'
 import { Attributes } from '@opentelemetry/api-metrics'
 
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#measurement
+
 export type Measurement = {
     value: number;
     // TODO use common attributes
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
index 2c4fd1283ac..c7e16406ba3 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/Meter.ts
@@ -20,6 +20,8 @@ import { Counter, Histogram, UpDownCounter } from './Instruments';
 import { Measurement } from './Measurement';
 import { MeterProvider } from './MeterProvider';
 
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#meter
+
 export class Meter implements metrics.Meter {
     // instrumentation library required by spec to be on meter
     // spec requires provider config changes to apply to previously created meters, achieved by holding a reference to the provider
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
index 0b197fdd6f2..4046f041364 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricExporter.ts
@@ -13,6 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+ 
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#metricexporter
 
 // TODO should this just be an interface and exporters can implement their own shutdown?
 export abstract class MetricExporter {
diff --git a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts
index 7b4e0e2a5c2..9f20299a4f2 100644
--- a/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts
+++ b/experimental/packages/opentelemetry-sdk-metrics-base/src/MetricReader.ts
@@ -16,6 +16,8 @@
 
 import { MetricExporter } from '.';
 
+// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#metricreader
+
 export class MetricReader {
     private _shutdown = false;