How to understand log files downloaded from App Engine?

Question

What is the format of Google App Engine log files, as downloaded by appcfg.sh request_logs?

Answer 1

As far as I've been able to determine, the format of the log file is as follows:

CLIENT_IP_ADDRESS - USERNAME [DATE:TIME TIMEZONE] "METHOD URL HTTP/VERSION" RESPONSE_CODE ??? URL USER_AGENT
     LOG_LEVEL:TIMESTAMP MESSAGE
     :
     LOG_LEVEL:TIMESTAMP MESSAGE
     :
     LOG_LEVEL:TIMESTAMP MESSAGE
     :

Each of the indented lines is associated with the non-indented line above it - that's how you determine which request each of them relates to, I think. The solitary colons are used to separate one log message from the next.

The non-indented lines are in reverse chronological order, but the groups of indented lines below them are in chronological order.

A strange client IP address like 0.1.0.2 indicates a within-App-Engine post from your app to your app's task queue. Actually, though, you can also see that it is within-App-Engine by looking at the user agent for that request.