Below is a sample logging configuration file. This file can be tweaked to control how your homeserver will output logs. A restart of the server is generally required to apply any changes made to this file.
Note that the contents below are not intended to be copied and used as the basis for a real homeserver.yaml. Instead, if you are starting from scratch, please generate a fresh config using Synapse by following the instructions in Installation.
# Log configuration for Synapse. # # This is a YAML file containing a standard Python logging configuration # dictionary. See  for details on the valid settings. # # Synapse also supports structured logging for machine readable logs which can # be ingested by ELK stacks. See  for details. # # : https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema # : https://matrix-org.github.io/synapse/latest/structured_logging.html version: 1 formatters: precise: format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s' handlers: file: class: logging.handlers.TimedRotatingFileHandler formatter: precise filename: /var/log/matrix-synapse/homeserver.log when: midnight backupCount: 3 # Does not include the current log file. encoding: utf8 # Default to buffering writes to log file for efficiency. # WARNING/ERROR logs will still be flushed immediately, but there will be a # delay (of up to `period` seconds, or until the buffer is full with # `capacity` messages) before INFO/DEBUG logs get written. buffer: class: synapse.logging.handlers.PeriodicallyFlushingMemoryHandler target: file # The capacity is the maximum number of log lines that are buffered # before being written to disk. Increasing this will lead to better # performance, at the expensive of it taking longer for log lines to # be written to disk. # This parameter is required. capacity: 10 # Logs with a level at or above the flush level will cause the buffer to # be flushed immediately. # Default value: 40 (ERROR) # Other values: 50 (CRITICAL), 30 (WARNING), 20 (INFO), 10 (DEBUG) flushLevel: 30 # Flush immediately for WARNING logs and higher # The period of time, in seconds, between forced flushes. # Messages will not be delayed for longer than this time. # Default value: 5 seconds period: 5 # A handler that writes logs to stderr. Unused by default, but can be used # instead of "buffer" and "file" in the logger handlers. console: class: logging.StreamHandler formatter: precise loggers: synapse.storage.SQL: # beware: increasing this to DEBUG will make synapse log sensitive # information such as access tokens. level: INFO twisted: # We send the twisted logging directly to the file handler, # to work around https://github.com/matrix-org/synapse/issues/3471 # when using "buffer" logger. Use "console" to log to stderr instead. handlers: [file] propagate: false root: level: INFO # Write logs to the `buffer` handler, which will buffer them together in memory, # then write them to a file. # # Replace "buffer" with "console" to log to stderr instead. (Note that you'll # also need to update the configuration for the `twisted` logger above, in # this case.) # handlers: [buffer] disable_existing_loggers: false