App Engine maintains a log of messages that your application emits using thelogging modulefrom the Python standard library, as well as other messages printedto the standard error stream.App Engine also records each request in the log. Each log severity level(4 for CRITICAL, 3 for ERROR, 2 for WARNING, 1 for INFO, 0 for DEBUG)has a fixed buffer size that controls the amount of log information you canaccess. Normally, you use logging features more at lower log levels; thus, thetime window is smaller for log events at these levels.Each request logged is assigned arequest ID,a globally unique identifier based on the request's start time.

To browse your app's logs of the last 90 days, you can also use theLogs page in the Google Cloud console.

Requesting the logs

Theappcfg tool is nowshut down.The replacement,Google Cloud CLI, does not support the ability todownload logs; however, you can view your logs using thegcloud app logs commands.