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.

Automatic instrumentation for monitoring the performance of your application is currently in preview. You can also use custom instrumentation to capture transactions.

Configure

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

• Setting a uniform sample rate for all transactions using the tracesSampleRate option in your SDK config to a number between 0 and 1. (For example, to send 20% of transactions, set tracesSampleRate 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 tracesSampler config option.

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

import Sentry

SentrySDK.start { options in
    options.dsn = "https://examplePublicKey@o0.ingest.sentry.io/0"

    // Example uniform sample rate: capture 100% of transactions
    // In Production you will probably want a smaller number such as 0.5 for 50%
    options.tracesSampleRate = 1.0

    // OR if you prefer, determine traces sample rate based on the
    // sampling context
    options.tracesSampler = { context in
         // Don't miss any transactions for VIP users
        if context?["vip"] as? Bool == true {
            return 1.0
        } else {
            return 0.25 // 25% for everything else
        }
    }
}

Learn more about performance monitoring options, how to use the tracesSampler function, or how to sample transactions.

Verify

Verify that performance monitoring is working correctly by using our automatic instrumentation or by starting and finishing a transaction using custom instrumentation.

Test out tracing by starting and finishing a transaction, which you must do so transactions can be sent to Sentry. Learn how in our Custom Instrumentation content.

While you're testing, set tracesSampleRate 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 tracesSampleRate value, or switch to using tracesSampler to selectively sample and filter your transactions, based on contextual data.

Next Steps