It's been several months, let's look at the current state of affairs:

* MediaWiki core - <https://github.com/wikimedia/mediawiki/blob/61696a0bd/includes/exception/MWExceptionHandler.php>
 * `exception`: PSR-3 structured message with exception context via `MWExceptionHandler::getLogContext` (includes trace)
 * `exception-json`: JSON-formatted structured data with exception context via `getStructuredExceptionData()`  (includes trace)
 * `error`: (Non-suppressed only) PSR-3 structured message with exception context (includes trace)
 * `error-json` (Includes suppressed errors) JSON-formatted structured data with exception context (includes trace)
* wikimedia/operations-mediawiki-config - <https://github.com/wikimedia/operations-mediawiki-config/tree/f750c8930f/wmf-config>
 * `exception`: Enabled (to mwlog and to logstash)
 * `exception-json`: Disabled (to mwlog only)
 * `error`: Enabled (to mwlog and to logstash)
 * `error-json`: Disabled
* Logstash config - <https://github.com/wikimedia/puppet/blob/87740eaedc/modules/role/files/logstash/filter-mediawiki.conf>
 * Augments `channel=exception`
 * Converts any `channel=exception-json` to `channel=exception` (Unused, todo: remove)
* logstash.wikimedia.org receives:
 * `type:hhvm` - All non-suppressed error messages and fatal errors (no trace)
 * `type:mediawiki channel:exception` - Fatals and caught exceptions logged by MediaWiki, structured and includes trace.
 * `type:mediawiki channel:error` - Non-suppressed error messages, structured and includes trace.

Known issues or remaining tasks:
* **Nothing?** {icon check color=green} **Resolved**?

Clean up or optimisation:
* [ ] Avoid duplicate logging under `type:hhvm` – Pending review: https://gerrit.wikimedia.org/r/338911
* [ ] Remove unused `exception-json` conversion filter from `filter-mediawiki.conf` in `operations/puppet.git`
* [ ] Fix de-duplication and message counting by ensuring `normalized_message` does not include the exception_id. – Pending review: https://gerrit.wikimedia.org/r/374895