Trace Context in Logs
Overview
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.
Configuration
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 usesActiveSupport::Logger::SimpleFormatter < Logger::Formatter
ActiveSupport::TaggedLogging
which usually extendsLogger::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
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|
AppOpticsAPM::SDK.current_trace.hash_for_log
end
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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