Set Up Tracing

Learn how to enable tracing in your app and discover valuable performance insights of your application.

With tracing, 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.

If you’re adopting Tracing in a high-throughput environment, we recommend testing prior to deployment to ensure that your service’s performance characteristics maintain expectations.

First, enable tracing and configure the sample rate for transactions. Set the sample rate for your transactions by either:

  • 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.)
  • 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.

    'dsn' => '',
    // Specify a fixed sample rate:
    'traces_sample_rate' => 0.2,
    // Or provide a custom sampler:
    'traces_sampler' => function (\Sentry\Tracing\SamplingContext $context): float {
        // return a number between 0 and 1

Learn more about tracing options, how to use the traces_sampler function, or how to sample 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.

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

This is due to the nature of PHP, where requests are usually sent as part of the process in which you serve your users' response. This affects the time it takes to send a request to Sentry because it's added to your servers' response time.

To offset this and make the addition close to zero, 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.

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