---
title: "Custom Instrumentation"
url: https://docs.sentry.io/platforms/unreal/tracing/trace-propagation/custom-instrumentation/
---

# Custom Instrumentation | Sentry for Unreal Engine

On this page you will learn how to manually propagate trace information into and out of your Unreal Engine game.

Continuing a trace from an upstream service requires using `ContinueTrace()`, which will create a transaction context with the provided `sentry-trace` header. This transaction starts with the transaction context will contain everything needed to continue the trace.

```cpp
// Get incoming tracing information
const FString inTrace = ...
TArray<FString> inBaggage = ...

USentryTransactionContext* transactionContext =
    SentrySubsystem->ContinueTrace(inTrace, inBaggage);

USentryTransaction* transaction =
    SentrySubsystem->StartTransactionWithContext(transactionContext);
```

To obtain trace header from a transaction or span, use `GetTrace()`. Pass the returned value to the downstream service. If communication happens over HTTP, we recommend you attach this header to the outgoing HTTP request.

The format of the `sentry-trace` header should follow the one defined in [the telemetry docs](https://develop.sentry.dev/sdk/telemetry/traces/#header-sentry-trace). It should consist of a 32 character hexadecimal string for the `traceId`, followed by a 16 character hexadecimal string for the `spanId` and an optional single character for the `sampled` flag. If the given string doesn't match this format, the update is ignored and the values in the transaction context will remain unchanged.