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Add log statements to your application on the fly with Stackdriver Debugger Logpoints

June 12, 2017
Morgan McLean

Product Manager

In 2014 we launched Snapshots for Stackdriver Debugger, which gave developers the ability to examine their application’s call stack and variables in production with no impact to users. In the past year, developers have taken over three hundred thousand production snapshots across their services running on Google App Engine and on VMs and containers hosted anywhere.

Today we’re showing off Stackdriver Debugger Logpoints. With Logpoints, you can instantly add log statements to your production application without rebuilding or redeploying it. Like Snapshots, this is immensely useful when diagnosing tricky production issues that lack an obvious root cause. Even better, Logpoints fits into existing logs-based workflows.

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Adding a logpoint is as simple as clicking a line in the Debugger source viewer and typing in your new log message (just make sure that you open the Logpoints tab in the right hand pane first). If you haven’t synced your source code, you can add Logpoints by specifying the target file and line number in the right-hand pane or via the gcloud command line tools. Variables can be referenced by {variableName}. You can review the full documentation here.

Because Logpoints writes its output through your app’s existing logging mechanism, it's compatible with any logging aggregation and analysis system, including Splunk or Kibana, or you can read its output from locally stored logs. However, Stackdriver Logging customers benefit from being able to read their log output from within the Stackdriver Debugger UI.

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Logpoints is already available for applications written in Java, Go, Node.js, Python and Ruby via the Stackdriver Debugger agents. As with Snapshots, this same set of languages is supported across VMs (including Google Compute Engine), containers (including Google Container Engine), and Google App Engine. Logpoints has been accessible through the gcloud command line interface for some time, and the process for using Logpoints in the CLI hasn’t changed.

Each logpoint lasts up to twenty-four hours or until it's deleted or when the application is redeployed. Adding a logpoint incurs a performance cost on par with adding an additional log statement to your code directly. However, the Stackdriver Debugger agents automatically throttle any logpoints that negatively impact your application’s performance and any logpoints or snapshots with conditions that take too long to evaluate.

At Google, we use technology like Snapshots and Logpoints to solve production problems every day to make our services more performant and reliable. We’ve heard from our customers how snapshots are the bread and butter of their problem-solving processes, and we’re excited to see how you use Logpoints to make your cloud applications better.

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