README.md

nexus_semantic_logger

Configures a semantic_logger as required for NexusMods components.

Telemetry

As well as providing a semantic logger, this gem handles datadog telemetry associated with the logging approach:

• logs
• traces
• metrics
  • statsd is automatically attached to datadog runtime metrics and may also be used for custom metrics.
  • ResponseCodeStatsMiddleware is included to capture response code metrics from rack applications

Customise log level per logger

For example, to show debug logging for MySubscriber while having all other logs on info.

# The log level must be set to the lowest level which can be dynamically controlled.
LOG_LEVEL=DEBUG
# The default level for filtered logs.
LOG_NAMES_DEFAULT_LEVEL=INFO
# Per level overrides for filtered logs.
LOG_NAMES_DEBUG=MySubscriber

• Customised log names are available for each level e.g. LOG_NAMES_TRACE
• Log names are matched on prefix.
• Multiple log names are supported via comma separated values.

Changing log level dynamically

The default level for filtered logs (LOG_NAMES_DEFAULT_LEVEL) may be changed on a running instance with the WINCH signal. This cycles through the available levels [trace debug info warn error fatal].

Note that you cannot dynamically enable a level lower than the LOG_LEVEL. Instead the env var must be adjusted and the instance restarted.

Send signal: pkill --signal WINCH --count --full "^puma.*"

Instance output: WINCH signal changed LOG_NAMES_DEFAULT_LEVEL from debug to info

Querying current log level

The SYS signal will print the levels used by the running instance.

Send signal: pkill --signal SYS --count --full "^puma.*"

Instance output: SYS signal reports LOG_LEVEL=debug LOG_NAMES_DEFAULT_LEVEL=warn

Sending metrics

Ensure the metric name is in the format: nexus.{component}.{major}.{minor}