Documentation forAppOptics

Trace Context in Logs


Adding trace context to application logs provides the ability to correlate the log messages from a traced transaction, and if sampled, the log messages to the transaction trace detail.

The Ruby agent can automatically add the trace context to logs. It will do so by adding a string like ‘ao.traceId=7435A9FE510AE4533414D425DADF4E180D2B4E36-0' to the end of each logged line.


This feature can be enabled in the Configuration File via the AppOpticsAPM::Config[:log_traceId] setting, which takes the following options:

  • :never (default)
  • :sampled only include the Trace ID for sampled requests
  • :traced include the Trace ID for all traced requests
  • :always always add a Trace ID, it will be ‘0000000000000000000000000000000000000000-0’ when there is no tracing context.

Automatic Insertion

Automatic insertion works for any Logger that uses Logger::Formatter, including:

  • ActiveSupport::Logger which uses ActiveSupport::Logger::SimpleFormatter < Logger::Formatter
  • ActiveSupport::TaggedLogging which usually extends Logger::Formatter with its own formatter

The gems lumberjack and logging are also supported.

Using the SDK

If your logger is not supported for automatic insertion, or for finer control, you can use the AppOpticsAPM::SDK to add Trace ID to application logs. Below are examples for popular logging libaries.


Lograge is a formatter for Rails logs currently not supported for automatic insertion. Instead you can use its custom_options and our SDK to configure lograge to include the Trace ID:

Lograge.custom_options = lambda do |event|

The hash_for_log SDK method respects the configuration settings for AppOpticsAPM::Config[:log_traceId]. For example: It will return an empty hash if the setting is :never

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