Once your app is up and running on App Engine, you’ll want to monitor, analyze, and manage its behavior. The Administration Console and the AppCfg tool include several important features for doing this. One of the most important is the application’s request and message log.
App Engine maintains a log of every request for the app, including the date and time of the request; the IP address of the client; the URL requested; the HTTP status the server returned; and information provided by the client, such as the user agent (the browser identification string) and the referrer (if the user followed a link, which page contained the link). App Engine also records resource usage for each request.
An application can also write its own messages to the log, to associate diagnostic information with the request. We looked at the interfaces for doing this back in Chapter 3.
You can browse your application’s logs using the Administration Console. To do so, visit the Console, select your app, then choose Logs from the sidebar menu. Separate logs are maintained for each version of the app, so make sure the version whose logs you want to browse is selected.
The log browser can show all recent requests for the app, or just recent log messages emitted by the app at a given log level. Each entry can be expanded to view the request details. Figure 15-3 shows an example of the “Info”-level messages for an app, with one request expanded.
Figure 15-3. The Administration Console log ...