Integrating with Cloud Logging

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This document describes how you can associate a trace with a Cloud Logging LogEntry.

Associating a trace with a log entry

When you use the Trace client libraries, or when you use the OpenCensus library for Python or for Java, you associate a trace with a log entry by setting the trace field in the LogEntry object.

The trace field must be set to a string with the following format:

   projects/PROJECT_ID/traces/TRACE_ID

where PROJECT_ID is your Google Cloud project ID and TRACE_ID is the trace identifier

To associate a span with a log entry when using the REST API, set the span_id field in the LogEntry object to the 16-character hexadecimal encoding of the span's ID. If you are using the gRPC API, then set the spanId field. For example, to associate a span with an ID of 74 to a log entry when using the REST API, set span_id to 000000000000004a.

To indicate that you are using trace sampling and that the trace was sampled for storage when the log entry was written, set the trace_sampled field in the LogEntry object when using the REST API. If you are using the gRPC API, then set the traceSampled field. When you use trace sampling, it's possible that a log entry is created when the trace itself isn't captured.

For more information, see the following resources:

Viewing logs

You can view the log entry for a trace alongside the waterfall graph or in the Logs Explorer. When you use the Logs Explorer, it's automatically restricted to the timestamp range of the trace. If there are no log entries to display, the Logs Explorer displays the message No entries found matching current filter.

From the Trace details pane, to view the log entry for the trace, do one of the following:

  • To display the trace log entries alongside the waterfall graph, go to the waterfall graph and click Show logs. When Show logs isn't displayed, no log entries are available.

  • To view the log entry in the Logs Explorer, click View next to the label Log in the Details section. Note that when you have a Cloud Load Balancing trace, click View next to the label VM Log.

For more information about viewing log entries in Cloud Logging, see Using the Logs Explorer.

Log viewing permissions

To view any log entries, you must have the logging.logEntries.list permission in your project. This permission is provided by the Logs Viewer and Project Viewer Identity and Access Management (IAM) roles.

To view VM instance logs, you must have the compute.instances.get permission in your project. This permission is provided by the Compute Engine Network Viewer and Project Viewer IAM roles.