Add factory and new-style config for Prometheus receiver (#42)

This is part of remaining migration to new configuration format.

Github issue: open-telemetry/opentelemetry-collector#33

Testing done: make

receiver/prometheusreceiver/config.go

@@ -0,0 +1,31 @@
+// Copyright 2019, OpenCensus 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
+//
+//     http://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.
+
+package prometheusreceiver
+
+import (
+	"time"
+
+	"github.com/prometheus/prometheus/config"
+
+	"github.com/open-telemetry/opentelemetry-service/internal/configmodels"
+)
+
+// ConfigV2 defines configuration for Prometheus receiver.
+type ConfigV2 struct {
+	configmodels.ReceiverSettings `mapstructure:",squash"`
+	PrometheusConfig              *config.Config `mapstructure:"-"`
+	BufferPeriod                  time.Duration  `mapstructure:"buffer_period"`
+	BufferCount                   int            `mapstructure:"buffer_count"`
+}

receiver/prometheusreceiver/config_test.go

@@ -0,0 +1,54 @@
+// Copyright 2019, OpenCensus 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
+//
+//     http://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.
+
+package prometheusreceiver
+
+import (
+	"path"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/open-telemetry/opentelemetry-service/internal/configmodels"
+	"github.com/open-telemetry/opentelemetry-service/internal/configv2"
+	"github.com/open-telemetry/opentelemetry-service/internal/factories"
+)
+
+var _ = configv2.RegisterTestFactories()
+
+func TestLoadConfig(t *testing.T) {
+	factory := factories.GetReceiverFactory(typeStr)
+
+	config, err := configv2.LoadConfigFile(t, path.Join(".", "testdata", "config.yaml"))
+
+	require.NoError(t, err)
+	require.NotNil(t, config)
+
+	assert.Equal(t, len(config.Receivers), 2)
+
+	r0 := config.Receivers["prometheus"]
+	assert.Equal(t, r0, factory.CreateDefaultConfig())
+
+	r1 := config.Receivers["prometheus/customname"].(*ConfigV2)
+	assert.Equal(t, r1.ReceiverSettings,
+		configmodels.ReceiverSettings{
+			TypeVal:  typeStr,
+			NameVal:  "prometheus/customname",
+			Endpoint: "1.2.3.4:456",
+		})
+	assert.Equal(t, r1.PrometheusConfig.ScrapeConfigs[0].JobName, "demo")
+	assert.Equal(t, time.Duration(r1.PrometheusConfig.ScrapeConfigs[0].ScrapeInterval), 5*time.Second)
+}

receiver/prometheusreceiver/factory.go

@@ -0,0 +1,131 @@
+// Copyright 2019, OpenCensus 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
+//
+//     http://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.
+
+package prometheusreceiver
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/spf13/viper"
+	"gopkg.in/yaml.v2"
+
+	"github.com/open-telemetry/opentelemetry-service/consumer"
+	"github.com/open-telemetry/opentelemetry-service/internal/configmodels"
+	"github.com/open-telemetry/opentelemetry-service/internal/factories"
+	"github.com/open-telemetry/opentelemetry-service/receiver"
+)
+
+// This file implements config V2 for Prometheus receiver.
+
+var _ = factories.RegisterReceiverFactory(&ReceiverFactory{})
+
+const (
+	// The value of "type" key in configuration.
+	typeStr = "prometheus"
+)
+
+// ReceiverFactory is the factory for receiver.
+type ReceiverFactory struct {
+}
+
+// Type gets the type of the Receiver config created by this factory.
+func (f *ReceiverFactory) Type() string {
+	return typeStr
+}
+
+// CustomUnmarshaler returns custom unmarshaler for this config.
+func (f *ReceiverFactory) CustomUnmarshaler() factories.CustomUnmarshaler {
+	return CustomUnmarshalerFunc
+}
+
+// CustomUnmarshalerFunc performs custom unmarshaling of config.
+func CustomUnmarshalerFunc(v *viper.Viper, viperKey string, intoCfg interface{}) error {
+	// We need custom unmarshaling because prometheus "config" subkey defines its own
+	// YAML unmarshaling routines so we need to do it explicitly.
+
+	// Unmarshal our config values (using viper's mapstructure)
+	err := v.UnmarshalKey(viperKey, intoCfg)
+	if err != nil {
+		return fmt.Errorf("prometheus receiver failed to parse config: %s", err)
+	}
+
+	// Unmarshal prometheus's config values. Since prometheus uses `yaml` tags, so use `yaml`.
+	vSub := v.Sub(viperKey)
+	if vSub == nil || !vSub.IsSet(prometheusConfigKey) {
+		return nil
+	}
+	promCfgMap := vSub.Sub(prometheusConfigKey).AllSettings()
+	out, err := yaml.Marshal(promCfgMap)
+	if err != nil {
+		return fmt.Errorf("prometheus receiver failed to marshal config to yaml: %s", err)
+	}
+
+	config := intoCfg.(*ConfigV2)
+
+	err = yaml.Unmarshal(out, &config.PrometheusConfig)
+	if err != nil {
+		return fmt.Errorf("prometheus receiver failed to unmarshal yaml to prometheus config: %s", err)
+	}
+	if len(config.PrometheusConfig.ScrapeConfigs) == 0 {
+		return errNilScrapeConfig
+	}
+	return nil
+}
+
+// CreateDefaultConfig creates the default configuration for receiver.
+func (f *ReceiverFactory) CreateDefaultConfig() configmodels.Receiver {
+	return &ConfigV2{
+		ReceiverSettings: configmodels.ReceiverSettings{
+			TypeVal:  typeStr,
+			NameVal:  typeStr,
+			Endpoint: "127.0.0.1:9090",
+		},
+	}
+}
+
+// CreateTraceReceiver creates a trace receiver based on provided config.
+func (f *ReceiverFactory) CreateTraceReceiver(
+	ctx context.Context,
+	cfg configmodels.Receiver,
+	nextConsumer consumer.TraceConsumer,
+) (receiver.TraceReceiver, error) {
+	// Prometheus does not support traces
+	return nil, factories.ErrDataTypeIsNotSupported
+}
+
+// CreateMetricsReceiver creates a metrics receiver based on provided config.
+func (f *ReceiverFactory) CreateMetricsReceiver(
+	cfg configmodels.Receiver,
+	consumer consumer.MetricsConsumer,
+) (receiver.MetricsReceiver, error) {
+
+	rCfg := cfg.(*ConfigV2)
+
+	// Create receiver Configuration from our input cfg
+	config := Configuration{
+		BufferCount:  rCfg.BufferCount,
+		BufferPeriod: rCfg.BufferPeriod,
+		ScrapeConfig: rCfg.PrometheusConfig,
+	}
+
+	if config.ScrapeConfig == nil || len(config.ScrapeConfig.ScrapeConfigs) == 0 {
+		return nil, errNilScrapeConfig
+	}
+	pr := &Preceiver{
+		cfg:      &config,
+		consumer: consumer,
+	}
+	return pr, nil
+}

receiver/prometheusreceiver/factory_test.go

@@ -0,0 +1,45 @@
+// Copyright 2019, OpenCensus 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
+//
+//     http://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.
+
+package prometheusreceiver
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/open-telemetry/opentelemetry-service/internal/factories"
+)
+
+func TestCreateDefaultConfig(t *testing.T) {
+	factory := factories.GetReceiverFactory(typeStr)
+	cfg := factory.CreateDefaultConfig()
+	assert.NotNil(t, cfg, "failed to create default config")
+}
+
+func TestCreateReceiver(t *testing.T) {
+	factory := factories.GetReceiverFactory(typeStr)
+	cfg := factory.CreateDefaultConfig()
+
+	tReceiver, err := factory.CreateTraceReceiver(context.Background(), cfg, nil)
+	assert.Equal(t, err, factories.ErrDataTypeIsNotSupported)
+	assert.Nil(t, tReceiver)
+
+	// The default config does not provide scrape_config so we expect that metrics receiver
+	// creation must also fail.
+	mReceiver, err := factory.CreateMetricsReceiver(cfg, nil)
+	assert.Equal(t, err, errNilScrapeConfig)
+	assert.Nil(t, mReceiver)
+}

receiver/prometheusreceiver/testdata/config.yaml

@@ -0,0 +1,22 @@
+receivers:
+  prometheus:
+  prometheus/customname:
+    endpoint: "1.2.3.4:456"
+    buffer_period: 234
+    buffer_count: 45
+    config:
+      scrape_configs:
+        - job_name: 'demo'
+          scrape_interval: 5s
+
+processors:
+  exampleprocessor:
+
+exporters:
+  exampleexporter:
+
+pipelines:
+  traces:
+    receivers: [prometheus]
+    processors: [exampleprocessor]
+    exporters: [exampleexporter]