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# Recording Exceptions with ereporter

Eric Higgins
April 2010

In the words of Professor Farnsworth: "Good news, everyone!". Using the `google.appengine.ext.ereporter` package available in the App Engine SDK, developers can receive exception reports from their applications by email.

Here's an example of a typical exception being logged.

    try:
      db.put(models)
    except (db.Timeout, db.InternalError):
      logging.exception('Some or all of the models could not be written.')

If your application is already logging caught exceptions in this manner, as it should be, then implementing will be a snap! The webapp framework, like many others, automatically logs uncaught exceptions, which will be included in the email report as well.

## Using ereporter in your applications

In your handler script(s), add:

    import logging
    from google.appengine.ext import ereporter

    ereporter.register_logger()

In your `app.yaml`, add:

    handlers:
    - url: /_ereporter.*
      script: $PYTHON_LIB/google/appengine/ext/ereporter/report_generator.py
      login: admin

In your `cron.yaml`, add:

    cron:
    - description: Daily exception report
      url: /_ereporter?sender=you@yourdomain.com  # The sender must be an app admin.
      schedule: every day 00:00

This will send an email report of all exceptions at midnight UTC everyday. Refer to the schedule format documentation to customize your `cron.yaml` further.

If you anticipate a lot of exception traces (for example, if you're deploying many minor versions, each of which may have its own set of exceptions), you can ensure that the traces from the newest minor versions get included by adding this to your `index.yaml`:

    indexes:
    - kind: ExceptionRecord
      properties:
      - name: date
      - name: major_version
      - name: minor_version
        direction: desc

Note: The `google.appengine.ext.ereporter` package uses the datastore to maintain logged exceptions. This will affect what is displayed in the Datastore Viewer, and the data exported using the Bulkloader.

## Customizing your reports

Developers can customize exception email reports by using the following URL query string arguments in `cron.yaml`. Valid query string arguments include:

`delete`

  Set to `false` to prevent deletion of exception records from the datastore after sending a report. Defaults to `true`.

`debug`

  Set to `true` to return the report in the response instead of emailing it.

`date`

  The date to generate the report for, in yyyy-mm-dd format. Defaults to yesterday's date. Useful for debugging.

`max_results`

  Maximum number of entries to include in a report. The default is 100.

`sender`

  The email address to use as the sender. Must be an active administrator.

`to`

  If specified, send reports to this address. If not specified, all admins are sent the report.

`versions`

  Set to `all` to report on all minor versions, or `latest` for the latest.

### Customized report example

The following cron.yaml will send an exception report from only the latest deployed minor version at midnight UTC to all application developers without deleting the records from the datastore:

    cron:
    - description: Daily exception report
      url: /_ereporter?sender=you@yourdomain.com&versions=latest&delete=false
      schedule: every day 00:00