logger

A powerful logger built on top of Bunyan capable to write logs to stdout, file and send to LogStash out-of-the-box.

Usage

There's a full functional example at the example/index.js file.

Features

• Buffer milions of messages
• Logs to Logstash, local FS and stdout
• setTags() allows to dynamically append to the original set tags

Env Vars

• process.env.NODE_DEBUG: If specified, produces a lot of noise
• process.env.LOGGER_PLUGINS_LOCALFILE_ENABLED: If specified, enables the localfile plugin
• process.env.LOGGER_PLUGINS_LOCALFILE_ROTATION: Set log file rotation. Default: 1d
• process.env.LOGGER_PLUGINS_LOCALFILE_RETENTION: Set log file retention. Default: 5
• process.env.LOGGER_PLUGINS_LOCALFILE_LOG_DIR_NAME: Default directory name. Default: logs
• process.env.LOGGER_PLUGINS_LOCALFILE_MIN_LEVEL: Default: debug
• process.env.LOGGER_PLUGINS_STDOUT_ENABLED: If specified, enables the stdout plugin
• process.env.LOGGER_PLUGINS_STDOUT_MIN_LEVEL: Default: debug
• process.env.LOGGER_PLUGINS_LOGSTASH_ENABLED: If specified, enables the logstash plugin
• process.env.LOGGER_PLUGINS_LOGSTASH_HOST: Set the Logstash host
• process.env.LOGGER_PLUGINS_LOGSTASH_PORT: Set the Logstash port
• process.env.LOGGER_PLUGINS_LOGSTASH_MIN_LEVEL: Default: info

Levels

The log levels in bunyan are as follows. The level descriptions are best practice opinions of the author.

• fatal (60): The service/app is going to stop or become unusable now. An operator should definitely look into this soon.
• error (50): Fatal for a particular request, but the service/app continues servicing other requests. An operator should look at this soon(ish).
• warn (40): A note on something that should probably be looked at by an operator eventually.
• info (30): Detail on regular operation.
• debug (20): Anything else, i.e. too verbose to be included in "info" level.
• trace (10): Logging from external libraries used by your app or very detailed application logging.

Setting a logger instance (or one of its streams) to a particular level implies that all log records at that level and above are logged. E.g. a logger set to level "info" will log records at level info and above (warn, error, fatal).

Source: Bunyan Levels

Logger <-> Logstash Integration

Logstash can take actions based on levels and special tags. Follows the level vs action matrix:

| level | logstash | slack | email | pagerduty | |-------|:--------:|------:|-------|-----------| | debug | no | no | no | no | | info | yes | no | no | no | | warn | yes | no | no | no | | error | yes | yes | no | no | | fatal | yes | yes | yes | yes |

_Notes:

• It requires Logstash to be already setup and integrated with these services
• Logger connects via tcp with Logstash
• If the Logstash server is not available, it will not block the Logger execution

Tips

• Do no concat strings
• Less is more, reduce noise
• If Logstash is routing to ES, pay attention to mapping conflicts
• Do not blindly log objects
• Do not directly logging errors -> mapping conflicts.
• Don't use these fields!
• message
• timestamp
• level
• name
• hostname
• pid
• time
• msg
• src
• Add "outputCapture": "std" to your VSCode launch.json to see logs in debug mode