Trace context in logs (legacy agent)

The following content pertains to trace context in logs for the legacy AppOptics PHP Agent.

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 AppOptics PHP agent can automatically append the trace context to internal errors/warnings and PHP logs generated with the error_log function. See Automatic Insertion of Trace ID into Logs for information on how to configure automatic insertion.

Logging Frameworks in PHP have their own ways of handling log messages; in this case, you can use the SDK function appoptics_get_log_trace_id() to add the trace context to messages. Below are examples on how to do this for some of the most popular frameworks.

Monolog

Capturing the trace context can be done via a monolog_processor:

$logger->pushProcessor(function ($record) {
  $record['message'] .= sprintf(' [ao.traceId=%s]', appoptics_get_log_trace_id());
  return $record;
});

log4PHP

In log4PHP, either the NDC or the MDC Logger can be used to add the trace context to log mesages.

LoggerNDC

LoggerNDC::push(sprintf('ao.traceId=%s', appoptics_get_log_trace_id()));

In the configuration file use the LoggerLayoutPattern and in the value of the conversion pattern, add %x wherever the trace context should appear.

LoggerMDC

LoggerMDC::put("ao.traceId", sprintf('%s', appoptics_get_log_trace_id()));

In the configuration file use the LoggerLayoutPattern and in the value of the conversion pattern, add ao.traceId=%X{ao.traceId} wherever the trace context should appear.

KLogger

KLogger does not provide a way to automatically insert custom values but it allows for a $context variable, that adds custom KVs to a log message. In order to add the trace context to the logs, create the context:

$context = ['ao.traceId' => appoptics_get_log_trace_id()];

This variable then can be passed in together with the log message:

$logger->error('An error log', $context);

Analog

Analog allows for custom handlers be defined:

function appopticsInit($handler) {
  return function ($info) use ($handler) {
    $info["message"] .= sprintf(' [ao.traceId=%s]', appoptics_get_log_trace_id());
    $handler($info);
  };
}

Register this handler with Analog and pass in any other handler of choice, e.g.:

Analog::handler(appopticsInit(Analog\Handler\Stderr::init()));

or

Analog::handler(appopticsInit(Analog\Handler\File::init('/tmp/myLog.txt')));

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