feat: add OpenTelemetry tracing to spanner calls

docs/index.rst

@@ -23,6 +23,7 @@ API Documentation
 
   api-reference
   advanced-session-pool-topics
+  opentelemetry-tracing
 
 Changelog
 ---------

docs/opentelemetry-tracing.rst

@@ -0,0 +1,36 @@
+Tracing with OpenTelemetry
+==================================
+Python-spanner uses `OpenTelemetry <https://opentelemetry.io/>`_ to automatically generates traces providing insight on calls to Cloud Spanner. 
+For information on the benefits and utility of tracing, see the `Cloud Trace docs <https://cloud.google.com/trace/docs/overview>`_.
+
+To take advantage of these traces, we first need to install opentelemetry:
+
+.. code-block:: sh
+
+    pip install opentelemetry-api opentelemetry-sdk opentelemetry-instrumentation
+
+We also need to tell OpenTelemetry which exporter to use. For example, to export python-spanner traces to `Cloud Tracing <https://cloud.google.com/trace>`_, add the following lines to your application:
+
+.. code:: python
+
+    from opentelemetry import trace
+    from opentelemetry.sdk.trace import TracerProvider
+    from opentelemetry.trace.sampling import ProbabilitySampler
+    from opentelemetry.exporter.cloud_trace import CloudTraceSpanExporter
+    # BatchExportSpanProcessor exports spans to Cloud Trace 
+    # in a seperate thread to not block on the main thread
+    from opentelemetry.sdk.trace.export import BatchExportSpanProcessor
+
+    # create and export one trace every 1000 requests
+    sampler = ProbabilitySampler(1/1000)
+    # Uses the default tracer provider
+    trace.set_tracer_provider(TracerProvider(sampler=sampler))
+    trace.get_tracer_provider().add_span_processor(
+        # initialize the cloud tracing exporter
+        BatchExportSpanProcessor(CloudTraceSpanExporter())
+    )
+
+Generated spanner traces should now be available on `Cloud Trace <https://console.cloud.google.com/traces>`_.
+
+Tracing is most effective when many libraries are instrumented to provide insight over the entire lifespan of a request.
+For a list of libraries that can be instrumented, see the `OpenTelemetry Integrations` section of the `OpenTelemetry Python docs <https://opentelemetry-python.readthedocs.io/en/stable/>`_

google/cloud/spanner_v1/_opentelemetry_tracing.py

@@ -0,0 +1,65 @@
+# Copyright 2020 Google LLC All rights reserved.
+#
+# 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.
+
+"""Manages OpenTelemetry trace creation and handling"""
+
+from contextlib import contextmanager
+
+from google.api_core.exceptions import GoogleAPICallError
+from google.cloud.spanner_v1.gapic import spanner_client
+
+try:
+    from opentelemetry import trace
+    from opentelemetry.trace.status import Status, StatusCanonicalCode
+    from opentelemetry.instrumentation.utils import http_status_to_canonical_code
+
+    HAS_OPENTELEMETRY_INSTALLED = True
+except ImportError:
+    HAS_OPENTELEMETRY_INSTALLED = False
+
+
+@contextmanager
+def trace_call(name, session, extra_attributes=None):
+    if not HAS_OPENTELEMETRY_INSTALLED or not session:
+        # empty context manager. users will have to check if the generated value is None or a span
+        yield None
+        return
+
+    tracer = trace.get_tracer(__name__)
+
+    # base attributes that we know for every trace created
+    attributes = {
+        "db.type": "spanner",
+        "db.url": spanner_client.SpannerClient.SERVICE_ADDRESS,
+        "db.instance": session._database.name,
+        "net.host.name": spanner_client.SpannerClient.SERVICE_ADDRESS,
+    }
+
+    if extra_attributes:
+        attributes.update(extra_attributes)
+
+    with tracer.start_as_current_span(
+        name, kind=trace.SpanKind.CLIENT, attributes=attributes
+    ) as span:
+        try:
+            yield span
+        except GoogleAPICallError as error:
+            if error.code is not None:
+                span.set_status(Status(http_status_to_canonical_code(error.code)))
+            elif error.grpc_status_code is not None:
+                span.set_status(
+                    # OpenTelemetry's StatusCanonicalCode maps 1-1 with grpc status codes
+                    Status(StatusCanonicalCode(error.grpc_status_code.value[0]))
+                )
+            raise

google/cloud/spanner_v1/batch.py

@@ -22,6 +22,7 @@
 from google.cloud.spanner_v1._helpers import _SessionWrapper
 from google.cloud.spanner_v1._helpers import _make_list_value_pbs
 from google.cloud.spanner_v1._helpers import _metadata_with_prefix
+from google.cloud.spanner_v1._opentelemetry_tracing import trace_call
 
 # pylint: enable=ungrouped-imports
 
@@ -147,12 +148,14 @@ def commit(self):
         api = database.spanner_api
         metadata = _metadata_with_prefix(database.name)
         txn_options = TransactionOptions(read_write=TransactionOptions.ReadWrite())
-        response = api.commit(
-            self._session.name,
-            mutations=self._mutations,
-            single_use_transaction=txn_options,
-            metadata=metadata,
-        )
+        trace_attributes = {"num_mutations": len(self._mutations)}
+        with trace_call("CloudSpanner.Commit", self._session, trace_attributes):
+            response = api.commit(
+                self._session.name,
+                mutations=self._mutations,
+                single_use_transaction=txn_options,
+                metadata=metadata,
+            )
         self.committed = _pb_timestamp_to_datetime(response.commit_timestamp)
         return self.committed
 

google/cloud/spanner_v1/session.py

@@ -26,6 +26,7 @@
 from google.cloud.spanner_v1.batch import Batch
 from google.cloud.spanner_v1.snapshot import Snapshot
 from google.cloud.spanner_v1.transaction import Transaction
+from google.cloud.spanner_v1._opentelemetry_tracing import trace_call
 import random
 
 # pylint: enable=ungrouped-imports
@@ -114,7 +115,11 @@ def create(self):
         kw = {}
         if self._labels:
             kw = {"session": {"labels": self._labels}}
-        session_pb = api.create_session(self._database.name, metadata=metadata, **kw)
+
+        with trace_call("CloudSpanner.CreateSession", self, self._labels):
+            session_pb = api.create_session(
+                self._database.name, metadata=metadata, **kw
+            )
         self._session_id = session_pb.name.split("/")[-1]
 
     def exists(self):
@@ -130,10 +135,16 @@ def exists(self):
             return False
         api = self._database.spanner_api
         metadata = _metadata_with_prefix(self._database.name)
-        try:
-            api.get_session(self.name, metadata=metadata)
-        except NotFound:
-            return False
+
+        with trace_call("CloudSpanner.GetSession", self) as span:
+            try:
+                api.get_session(self.name, metadata=metadata)
+                if span:
+                    span.set_attribute("session_found", True)
+            except NotFound:
+                if span:
+                    span.set_attribute("session_found", False)
+                return False
 
         return True
 
@@ -150,8 +161,8 @@ def delete(self):
             raise ValueError("Session ID not set by back-end")
         api = self._database.spanner_api
         metadata = _metadata_with_prefix(self._database.name)
-
-        api.delete_session(self.name, metadata=metadata)
+        with trace_call("CloudSpanner.DeleteSession", self):
+            api.delete_session(self.name, metadata=metadata)
 
     def ping(self):
         """Ping the session to keep it alive by executing "SELECT 1".

google/cloud/spanner_v1/snapshot.py

@@ -30,17 +30,19 @@
 from google.cloud.spanner_v1._helpers import _SessionWrapper
 from google.cloud.spanner_v1.streamed import StreamedResultSet
 from google.cloud.spanner_v1.types import PartitionOptions
+from google.cloud.spanner_v1._opentelemetry_tracing import trace_call
 
 
-def _restart_on_unavailable(restart):
+def _restart_on_unavailable(restart, trace_name=None, session=None, attributes=None):
     """Restart iteration after :exc:`.ServiceUnavailable`.
 
     :type restart: callable
     :param restart: curried function returning iterator
     """
     resume_token = b""
     item_buffer = []
-    iterator = restart()
+    with trace_call(trace_name, session, attributes):
+        iterator = restart()
     while True:
         try:
             for item in iterator:
@@ -50,7 +52,8 @@ def _restart_on_unavailable(restart):
                     break
         except ServiceUnavailable:
             del item_buffer[:]
-            iterator = restart(resume_token=resume_token)
+            with trace_call(trace_name, session, attributes):
+                iterator = restart(resume_token=resume_token)
             continue
 
         if len(item_buffer) == 0:
@@ -143,7 +146,10 @@ def read(self, table, columns, keyset, index="", limit=0, partition=None):
             metadata=metadata,
         )
 
-        iterator = _restart_on_unavailable(restart)
+        trace_attributes = {"table_id": table, "columns": columns}
+        iterator = _restart_on_unavailable(
+            restart, "CloudSpanner.ReadOnlyTransaction", self._session, trace_attributes
+        )
 
         self._read_request_count += 1
 
@@ -243,7 +249,13 @@ def execute_sql(
             timeout=timeout,
         )
 
-        iterator = _restart_on_unavailable(restart)
+        trace_attributes = {"db.statement": sql}
+        iterator = _restart_on_unavailable(
+            restart,
+            "CloudSpanner.ReadWriteTransaction",
+            self._session,
+            trace_attributes,
+        )
 
         self._read_request_count += 1
         self._execute_sql_count += 1
@@ -309,16 +321,20 @@ def partition_read(
             partition_size_bytes=partition_size_bytes, max_partitions=max_partitions
         )
 
-        response = api.partition_read(
-            session=self._session.name,
-            table=table,
-            columns=columns,
-            key_set=keyset._to_pb(),
-            transaction=transaction,
-            index=index,
-            partition_options=partition_options,
-            metadata=metadata,
-        )
+        trace_attributes = {"table_id": table, "columns": columns}
+        with trace_call(
+            "CloudSpanner.PartitionReadOnlyTransaction", self._session, trace_attributes
+        ):
+            response = api.partition_read(
+                session=self._session.name,
+                table=table,
+                columns=columns,
+                key_set=keyset._to_pb(),
+                transaction=transaction,
+                index=index,
+                partition_options=partition_options,
+                metadata=metadata,
+            )
 
         return [partition.partition_token for partition in response.partitions]
 
@@ -385,15 +401,21 @@ def partition_query(
             partition_size_bytes=partition_size_bytes, max_partitions=max_partitions
         )
 
-        response = api.partition_query(
-            session=self._session.name,
-            sql=sql,
-            transaction=transaction,
-            params=params_pb,
-            param_types=param_types,
-            partition_options=partition_options,
-            metadata=metadata,
-        )
+        trace_attributes = {"db.statement": sql}
+        with trace_call(
+            "CloudSpanner.PartitionReadWriteTransaction",
+            self._session,
+            trace_attributes,
+        ):
+            response = api.partition_query(
+                session=self._session.name,
+                sql=sql,
+                transaction=transaction,
+                params=params_pb,
+                param_types=param_types,
+                partition_options=partition_options,
+                metadata=metadata,
+            )
 
         return [partition.partition_token for partition in response.partitions]
 
@@ -515,8 +537,9 @@ def begin(self):
         api = database.spanner_api
         metadata = _metadata_with_prefix(database.name)
         txn_selector = self._make_txn_selector()
-        response = api.begin_transaction(
-            self._session.name, txn_selector.begin, metadata=metadata
-        )
+        with trace_call("CloudSpanner.BeginTransaction", self._session):
+            response = api.begin_transaction(
+                self._session.name, txn_selector.begin, metadata=metadata
+            )
         self._transaction_id = response.id
         return self._transaction_id