This page describes the troubleshooting process for errors you might encounter whileusing App Engine. For information about incidents affecting Google Cloudservices, refer to theGoogle Cloud Service Health Dashboard andAll incidents reported for App Engine.

See the following pages for guidance on how to resolve issues related to your app:

• Troubleshoot deployment issues
• Troubleshoot serving issues
• Troubleshoot elevated latency in your app
• App Engine connectivity strategies

App Engine troubleshooting strategies

The following sections explain how you can apply general troubleshootingstrategies to resolve your error. If you continue to encounter errorseven after following the steps in the troubleshooting guides, seeWhat's next.

Output good logs using Cloud Logging

Troubleshooting your app running on App Engine is easier if you have goodapplication logs for debugging. Ensure your application writes logs in a way thatcorrelates request logs with the application logs.

With correlated logs you can identify the request that needs further analysis,find the request trace, and analyze the root cause of the issue. For moreinformation on writing logs, seeWrite application logs.

Resolve unexpected latency

If you encounter issues with latency, do the following:

1. Check if the latency is affecting all requests to your service or only asmall percentage. TheApp Engine latency dashboard shows 50th,95th, and 99th percentile latency.

   If you have high latency on all three of these metrics, you have high latencyfor at least 50% of your requests. If you only see high latency in the99th percentile graph, you have high latency in 1% of your requests.

2. Identify the request with high latency to understand the source oflatency. You can use Cloud Trace or Cloud Logging to understand howlong a particular request has taken. For more information, seeUnderstanding app latency.

   To identify requests with high latency using Cloud Logging, apply thetraceSampled=true filter to correlate logs in Cloud Logging with traces in Cloud Trace. For more information, seeIntegrate with Cloud Logging.

3. Try the following steps to fix latency issues, and improve service performance:

   • Increase theinstance class settings.

   • Reduce cold start latency byconfiguring warmup requests.

   • Adjustscaling settings.

   • Consider usingProfiler.

   • Modify your source code.

For more information on how to troubleshoot elevated latency issues, seeTroubleshoot elevated latency in your app.

Resolve issues with connectivity

By default, your App Engine service is accessible on the public internet, however,you can modify the service to have more restrictions on ingress and egressnetwork connectivity.

You can restrict ingress connections with the ingress settings, or through App Engine firewall rules. If you have trouble connecting to your App Engine service fromVPC networks or internet resources, check the following:

• Ingress settings
• App Engine firewall

To resolve other connectivity issues, do the following:

• Run anetwork connectivity test.

• To resolve problems with traffic egress to a VPC network, check the VPC networkfirewall rules or use connection pooling in your client. For more information,seeFirewall rules.

• Ensure that you aren'toverloading your VPC connector with more services andconnections beyond its threshold. To improve throughput, consider the VPC connectorsize and instance count for your connectors. For more information, seeServerless VPC Access.

• For problems accessing VPC resources, review theVPC connector throughput charts.

For more information on how to troubleshoot connectivity issues, seeApp Engine connectivity strategies.

What's next

If you can't find a solution to your problem in the App Enginedocumentation, follow these steps:

• Open a support case by contactingCloud Customer Care.
• Get support from the community byasking questions on StackOverflow, or search for similar issues using thegoogle-app-engine tag.
• Open bugs or feature requests by using thepublic issue tracker.

For more information, seeApp Engine community.