redislog: shipping PostgreSQL logs to Redis

redislog is an extension that allows PostgreSQL to ship log entries to a Redis server, directly in JSON format.

One of the goals of redislog is to allow administrators to tap PostgreSQL directly into the Logstash pipeline for real-time monitoring. In such an architecture, redislog acts as a "Shipper" component able to send events to a "Broker", such as Redis.

Thanks to hooks made available by PostgreSQL through elog.c, redislog is a logging facility that generates log events in JSON format and sends them to a Redis server over the network.

Requirements

• Hiredis library
• A Redis server for data collection

Installation

redislog can be installed as any other PostgreSQL extension by executing:

make
make install

In order to activate the module, you only need to add the following configuration option in postgresql.conf:

shared_preload_libraries = 'redislog'

redislog will use the default values for any configuration option.

For a detailed list of options, see the following section.

Configuration options

redislog.hosts

: List of HOST[:PORT] pairs separated by commas. If no port is specified, the default 6379 is assumed. By default, redislog.hosts is set to 127.0.0.1. In case of more than a host, the actual behaviour is influenced by the redislog.shuffle_hosts option:

- if set to `on`, multiple hosts are used for load balancing purposes

- if set to `off`, multiple hosts are used for high availability purposes
  and defined as a priority ordered list.

redislog.shuffle_hosts

: Only if redislog.hosts defines more than a host. If set to on, the order of hosts is shuffled and hosts are used in a load balancing scenario.

redislog.connection_timeout

: Redis server connection timeout in milliseconds (by default 1000).

redislog.key

: Redis server key name (by default postgres).

redislog.ship_to_redis_only

: If set to on, log messages that are correctly sent to Redis are not journaled into the main PostgreSQL log (by default off).

redislog.fields

: List of fields to be placed in the output JSON object. Users have the opportunity to customise the list of fields as well as the name of each key in the objects through the following syntax:

    redislog.fields = 'FIELD[:NAME][, ...]'

By default, the list is set to:

• user_name
• database_name
• process_id
• remote_host
• session_id
• session_line_num
• command_tag
• session_start_time
• virtual_transaction_id
• transaction_id
• error_severity
• sql_state_code
• detail_log
• detail
• hint
• internal_query
• internal_query_pos
• context
• query
• query_pos
• file_location
• application_name
• message

redislog.min_error_statement

: Controls which SQL statements that cause an error condition are recorded in the server log. Each level includes all the levels that follow it. The later the level, the fewer messages are sent.

redislog.min_messages

: Set the message levels that are logged. Each level includes all the levels that follow it. The higher the level, the fewer messages are sent.

TODO list

• Support for CSV output format
• Support for channel data type
• Support for custom fields in JSON objects

Authors

• Marco Nenciarini marco.nenciarini@2ndquadrant.it
• Leonardo Cecchi leonardo.cecchi@2ndquadrant.it
• Gabriele Bartolini gabriele.bartolini@2ndquadrant.it

Thanks to Michael Paquier for the initial exchange of ideas and for his previous work on jsonlog.

Licence

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