Add trace ID to log metadata when available

[draffensperger]

This makes the logging-bunyan and logging-winston libraries add the LogEntry.trace field based on the current trace context of the @google-cloud/trace-agent library when available.

Users can override that default LogEntry.trace assignment by specifying a logging.googleapis.com/trace field in the Winston entry metadata or Bunyan structured log entry. That naming makes logging backward-compatible for anyone who might happen to already use a trace field in their logs and it the follows the similar behavior for the Stackdriver logging agent, see https://github.com/GoogleCloudPlatform/fluent-plugin-google-cloud/blob/91835bb12b728ba88f63c38008e539a047d216a6/lib/fluent/plugin/out_google_cloud.rb#L105.

This will make use of the getWriterProjectId function that googleapis/cloud-trace-nodejs#548 adds to cloud-trace-nodejs.

[coveralls]

Coverage decreased (-0.02%) to 99.976% when pulling 67ce8c3 on draffensperger:trace-ids-in-logs into 4292811 on GoogleCloudPlatform:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 0de66c1 on draffensperger:trace-ids-in-logs into 4292811 on GoogleCloudPlatform:master.

[draffensperger]

@matthewloring and @ofrobots could you take a look at this when you get a chance?

The getCurrentTraceFromAgent function is duplicated in both logging-bunyan and logging-winston, but it's pretty short and the alternative would be to move it to the core logging library, but that would require multiple PRs and updating dependencies (which I'm open to do if you prefer).

[matthewloring]

The use of the trace agent looks good. Duplicating the qualified trace ID logic in winston and bunyan separately does seem clunky but if the update -> release -> bump dependency flow is too cumbersome then this is fine.

[ofrobots]

Sgtm

…

On Fri, Sep 8, 2017 at 6:07 AM Dave Raffensperger ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In packages/logging-winston/src/index.js <#2574 (comment)> : > @@ -126,6 +131,30 @@ winston.transports.StackdriverLogging = LoggingWinston; util.inherits(LoggingWinston, winston.Transport); /** + * Gets the current fully qualified trace ID when available from the + * @google-cloud/trace-agent library in the LogEntry.trace field format of: + * "projects/[PROJECT-ID]/traces/[TRACE-ID]". + */ +function getCurrentTraceFromAgent() { @ofrobots <https://github.com/ofrobots>, are you OK with keeping the getCurrentTraceFromAgent duplicated in both logging-winston and logging-bunyan for now? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#2574 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAE0qf0N9VVd0Th_l1CQt2XbjkbCIyt3ks5sgTwggaJpZM4PH1nM> .

[ofrobots]

LGTM. Thanks for being patient on this!

[ofrobots]

@stephenplusplus Is this good to land from your POV?