update some config files from server

etc/matrix-synapse/homeserver.yaml

@@ -806,7 +806,7 @@ caches:
   # accessed before being evicted. Defaults to None, which means
   # entries are never evicted based on time.
   #
-  expiry_time: 24h
+  #expiry_time: 24h
 
   # Controls how long the results of a /sync request are cached for after
   # a successful response is returned. A higher duration can help clients with

etc/matrix-synapse/log.yaml

@@ -7,7 +7,7 @@
 # be ingested by ELK stacks. See [2] for details.
 #
 # [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
-# [2]: https://github.com/matrix-org/synapse/blob/master/docs/structured_logging.md
+# [2]: https://matrix-org.github.io/synapse/latest/structured_logging.html
 
 version: 1
 
@@ -24,18 +24,31 @@ handlers:
         backupCount: 3  # Does not include the current log file.
         encoding: utf8
 
-    # Default to buffering writes to log file for efficiency. This means that
-    # will be a delay for INFO/DEBUG logs to get written, but WARNING/ERROR
-    # logs will still be flushed immediately.
+    # 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: logging.handlers.MemoryHandler
+        class: synapse.logging.handlers.PeriodicallyFlushingMemoryHandler
         target: file
-        # The capacity is the number of log lines that are buffered before
-        # being written to disk. Increasing this will lead to better
+
+        # 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
-        flushLevel: 30  # Flush for WARNING logs as well
+
+        # 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.

etc/matrix-synapse/workers/appservice_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_appservice.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/federation_sender1_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_federation_sender1.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/federation_sender2_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_federation_sender2.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/federation_sender3_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_federation_sender3.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/generic_worker1_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_generic_worker1.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/generic_worker2_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_generic_worker2.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/generic_worker3_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_generic_worker3.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/generic_worker4_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_generic_worker4.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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

etc/matrix-synapse/workers/pusher_log_config.yaml

@@ -1,42 +1,84 @@
+# Log configuration for Synapse.
+#
+# This is a YAML file containing a standard Python logging configuration
+# dictionary. See [1] for details on the valid settings.
+#
+# Synapse also supports structured logging for machine readable logs which can
+# be ingested by ELK stacks. See [2] for details.
+#
+# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [2]: 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'
 
-filters:
-    context:
-        (): synapse.util.logcontext.LoggingContextFilter
-        request: ""
-
 handlers:
     file:
-        class: logging.handlers.RotatingFileHandler
+        class: logging.handlers.TimedRotatingFileHandler
         formatter: precise
         filename: /var/log/matrix-synapse/worker_pusher.log
-        maxBytes: 104857600
-        backupCount: 5
-        filters: [context]
+        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
-        filters: [context]
 
 loggers:
-    synapse:
-        level: WARN
-
     synapse.storage.SQL:
         # beware: increasing this to DEBUG will make synapse log sensitive
         # information such as access tokens.
         level: WARN
 
+    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: WARN
-    handlers: [file, console]
 
-    precise:
-        format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
+    # 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