# Structured Logging A structured logging system can be useful when your logs are destined for a machine to parse and process. By maintaining its machine-readable characteristics, it enables more efficient searching and aggregations when consumed by software such as the "ELK stack". Synapse's structured logging system is configured via the file that Synapse's `log_config` config option points to. The file should include a formatter which uses the `synapse.logging.TerseJsonFormatter` class included with Synapse and a handler which uses the above formatter. There is also a `synapse.logging.JsonFormatter` option which does not include a timestamp in the resulting JSON. This is useful if the log ingester adds its own timestamp. A structured logging configuration looks similar to the following: ```yaml version: 1 formatters: structured: class: synapse.logging.TerseJsonFormatter handlers: file: class: logging.handlers.TimedRotatingFileHandler formatter: structured filename: /path/to/my/logs/homeserver.log when: midnight backupCount: 3 # Does not include the current log file. encoding: utf8 loggers: synapse: level: INFO handlers: [remote] synapse.storage.SQL: level: WARNING ``` The above logging config will set Synapse as 'INFO' logging level by default, with the SQL layer at 'WARNING', and will log to a file, stored as JSON. It is also possible to figure Synapse to log to a remote endpoint by using the `synapse.logging.RemoteHandler` class included with Synapse. It takes the following arguments: - `host`: Hostname or IP address of the log aggregator. - `port`: Numerical port to contact on the host. - `maximum_buffer`: (Optional, defaults to 1000) The maximum buffer size to allow. A remote structured logging configuration looks similar to the following: ```yaml version: 1 formatters: structured: class: synapse.logging.TerseJsonFormatter handlers: remote: class: synapse.logging.RemoteHandler formatter: structured host: 10.1.2.3 port: 9999 loggers: synapse: level: INFO handlers: [remote] synapse.storage.SQL: level: WARNING ``` The above logging config will set Synapse as 'INFO' logging level by default, with the SQL layer at 'WARNING', and will log JSON formatted messages to a remote endpoint at 10.1.2.3:9999.