Set Up Performance

With performance monitoring, Sentry tracks your software performance, measuring metrics like throughput and latency, and displaying the impact of errors across multiple systems. Sentry captures distributed traces consisting of transactions and spans, which measure individual services and individual operations within those services. Learn more about our model in Distributed Tracing.

Configure the Sample Rate

First, enable both

tracingThe process of logging the events that took place during a request, often across multiple services.
and configure the sampling rate for transactions. Set the sample rate for your transactions by either:

  1. Setting a uniform sample rate for all transactions using the traces_sample_rate option in your SDK config to a number between 0 and 1. (For example, to send 20% of transactions, set traces_sample_rate to 0.2.)
  2. Controlling the sample rate based on the transaction itself and the context in which it's captured, by providing a function to the traces_sampler config option.

The two options are meant to be mutually exclusive. If you set both, traces_sampler will take precedence.

        # Specify a fixed sample rate:
        traces_sample_rate: 1.0
        # Or provide a custom sampler:
        traces_sampler: 'sentry.callback.traces_sampler'

# Only needed when using the `traces_sampler`
        class: 'App\Service\Sentry'
        factory: [ '@App\Service\Sentry', 'getTracesSampler' ]

The service needed for the traces_sampler option can be implemented as follows:


namespace App\Service;

class Sentry
    public function getTracesSampler(): callable
        return function(\Sentry\Tracing\SamplingContext $context): float {
            // return a number between 0 and 1

Learn more about how the options work in Sampling Transactions.


While you're testing, set traces_sample_rate to 1.0, as that ensures that every transaction will be sent to Sentry.

Once testing is complete, you may want to set a lower traces_sample_rate value, or switch to using traces_sampler to selectively sample and filter your transactions, based on contextual data.

Connecting Services

If you are also using Performance Monitoring for JavaScript, depending on where your request originates, you can connect traces:

  1. For requests that start in your backend, by adding a meta tag in your HTML template that contains
    tracingThe process of logging the events that took place during a request, often across multiple services.
  2. For requests that start in JavaScript, by the SDK setting a header on requests to your backend.

Otherwise, backend services with Performance Monitoring connect automatically.

Improve Response Time

Response time is somewhat impacted when you use the performance capabilities in your PHP application, (depending on the traces_sample_rate you've configured).

If your web server is using FastCGI, our SDK utilizes the kernel.terminate event, which means the response is sent to the user before the performance data is sent to Sentry.

If your web server isn't using FastCGI, you can run Relay locally on the same machine or a local network that can act as a proxy/agent.

Doing this will make the PHP process send requests to your local Relay, which will then forward them to Sentry, instead of sending requests to Sentry directly.

To begin using Relay, check out our docs for getting started. We recommend using Relay in managed mode (which is the default).

Follow the instructions in the Relay docs to send a test event through Relay to Sentry. Don't forget to update your DSN to point to your running Relay instance. After you set up Relay, you should see a dramatic improvement to the impact on your server.

Next Steps:

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