Distributed tracing for your PHP services

Distributed tracing allows you to see the entire journey of your requests throughout a distributed system. The PHP agent automatically instruments with distributed tracing a number of native PHP functions, as well as some third party HTTP clients:

• PHP function file_get_contents
• PHP functions curl_exec and curl_multi_exec
• Guzzle 4, Guzzle 5, Guzzle 6
• Drupal's drupal_http_request function
• Laravel's queue jobs

For the PHP agent, we offer two types of distributed tracing (for more details, see How span sampling works):

• Standard (head-based sampling): Before any traces arrive, we determine a set percentage of traces to accept and analyze. This gives you a solid starting point to see how tracing can help you. It is turned on by default in PHP agents 9.21.0 and higher.

• Infinite Tracing (tail-based sampling): Our cloud-based service accepts all your traces and then sorts through them to find the most important. Infinite tracing analyzes all of your traces and gives you configuration options to sample the traces that matter most to you.

Whether you just want to try out standard distributed tracing (head-based sampling) or also want to set up Infinite Tracing (tail-based sampling), you need to start by setting up standard tracing.

Standard distributed tracing

This is the best approach to set up standard distributed tracing if you haven't installed any APM agents for your services yet.

Identify services

Figure out which services touch your request so you can instrument each of them to send trace data to New Relic.

Instrument each service with an APM agent

For each service involved in your transactions, you'll perform separate installations of the agent. If some of your services use other languages, simply repeat the installation steps for those languages.

To start the installation routine, click the tile below. When you're finished installing each agent, return here to see tips for viewing your traces.

Start installation

View traces

After you instrument each of your services with APM agents, generate some traffic in your application so we can capture some traces. Here are some ways to view your traces in the UI:

View traces that include a specific service

Here's one way you can see traces for a particular service:

1. Go to one.newrelic.com > All capabilities > APM & services.
2. Click your entity (service).
3. In the left pane's Monitor section, click Distributed tracing.
4. For details, click on an individual trace. If Group similar traces is on in the top menu, click on a trace group, and then click on an individual trace.
5. If you don't see the traces you want, you can filter by the trace.id.

View traces across accounts

To see traces that cross accounts:

1. Go to one.newrelic.com > All capabilities > Traces.
2. Select your entity (service) in the left pane.
3. For details, click on an individual trace. If Group similar traces is on in the top menu, click on a trace group, and then click on an individual trace.
4. If you don't see the traces you want, you can filter by the trace.id.

Examine logs related to traces

You can bring your logs and tracing details together to make troubleshooting easier and faster. With logs in context, you can see log messages alongside traces in the New Relic UI.

After you've located an interesting trace using the steps in View traces that include a specific service or View traces across accounts, do the following:

1. If you've enabled logs in context, click on the Logs tab (next to Trace details).
2. To view details related to an individual log, click directly on the message.

For more help finding your traces in the UI:

• Understand and use the distributed tracing UI
• Query distributed trace data

Infinite Tracing

Standard distributed tracing for APM agents captures up to 10% of your traces, but if you want us to analyze all your data and find the most relevant traces, you can set up Infinite Tracing.

Before you start, first ensure you meet the requirements.

Set trace detail level

Distributed tracing support depends on the PHP agent's transaction tracer. When distributed tracing is enabled, a span is created for each segment seen by the transaction tracer.

As spans are sampled, the PHP agent will prioritize spans related to external calls above other spans, which are then recorded in descending order of their duration.

If you find that there are too many unimportant spans being reported for PHP function calls, you can reduce the detail of the transaction tracer by setting newrelic.transaction_tracer.detail to 0. You may then use the newrelic.transaction_tracer.custom configuration setting or the newrelic_add_custom_tracer API method to add trace segments and spans for the specific PHP function or methods you want to add to your traces.

Manually instrument applications and services with PHP agent API

newrelic_create_distributed_trace_payload()
newrelic_accept_distributed_trace_payload($payload)

newrelic_insert_distributed_trace_headers($outbound_headers)
newrelic_accept_distributed_trace_headers($inbound_headers)

If you're using an unsupported library, or have a non-HTTP based distributed system component (such as messaging queues), you can use the PHP agent API to manually identify transactions to be included in a distributed trace. This is a two step process:

1. Modify your service or application to create or insert the distributed tracing data
2. Modify your service or application to accept distributed trace data created by other transactions or requests.

The following example uses a generic message/job queue. While the actual details will vary depending on what sort of system you're trying to add to a distributed trace, the core concepts are the same. Also, while we've used a job queue as an example, you can use these methods with any distributed system component.

For more information about using manual instrumentation to get more detail or to see connections between services, see the documentation about distributed tracing APIs.

Header API

// create a job object
$job = new \Generic\Queue\Job;

// set the information needed to run the queue job
$job->setData('info', $info);

// save the job
$job->save();

$outbound_headers = array();
if (newrelic_insert_distributed_trace_headers($outbound_headers)) {

    // create a job object
    $job = new \Generic\Queue\Job;

    // set the information needed to run the queue job
    $job->setData('info', $info);

    // add the headers to the job data
    $job->setData('nr_dt_headers', $outbound_headers);

    // save the job
    $job->save();
} else {
    echo "Unable to obtain distributed tracing headers";
}

// create the job runner
$jobRunner = \Generic\Queue\Runner;

// grab jobs until there aren't any
while($job = $jobRunner->next()) {
    // run the job
    $job->run();
}

// create the job runner
$jobRunner = \Generic\Queue\Runner;

while($job = $jobRunner->next()) {
    $inbound_headers = $job->getData('nr_dt_headers');
    if($inbound_headers) {
        newrelic_accept_distributed_trace_headers($inbound_headers);
    }
    $job->run();
}

Payload API (deprecated)

// create a job object
$job = new \Generic\Queue\Job;

// set the information needed to run the queue job
$job->setData('info', $info);

// save the job
$job->save();

$payload = newrelic_create_distributed_trace_payload();

// create a job object
$job = new \Generic\Queue\Job;

// set the information needed to run the queue job
$job->setData('info', $info);

// add the payload data to the job data as a text json string
$job->setData('dt_payload', $payload->Text());

// save the job
$job->save();

// create the job runner
$jobRunner = \Generic\Queue\Runner;

// grab jobs until there aren't any
while($job = $jobRunner->next()) {
    // run the job
    $job->run();
}

// create the job runner
$jobRunner = \Generic\Queue\Runner;

while($job = $jobRunner->next()) {
    $payload = $job->getData('dt_payload');
    if($payload) {
        newrelic_accept_distributed_trace_payload($payload);
    }
    $job->run();
}

// create the HTTP safe payload string 
$payload = newrelic_create_distributed_trace_payload();
$httpSafePayload = $payload->httpSafe();

// ...

// accept the HTTP safe payload string
newrelic_accept_distributed_trace_payload_httpsafe($httpSafePayload);

Command line PHP programs

PHP programs run from the PHP command line are always sampled by the agent's distributed tracer. Depending on the programs you run, these processes could see an over-representation in your collection of distributed traces. In these situations, you can opt to disable command line instrumentation by using the per-directory newrelic.enabled setting in your newrelic.ini files.