Instrument Go transactions

Monitor your New Relic for Go application or microservice by creating transactions associated with specific app server activities, such as HTTP responses or background tasks. You can then view your app's performance in the New Relic, including the APM Transactions page.

Identify web and non-web transactions

Unlike many other languages, Go applications run from a compiled, native binary file. This means that setting up New Relic for your Golang app requires you to manually add New Relic methods to your source code.

In APM, transactions are identified as web transactions or non-web transactions.

• When you instrument or wrap a transaction that has an HTTP request and response writer, New Relic treats it as a web transaction.
• When you instrument or wrap a transaction that does not have HTTP data, New Relic treats it as a non-web transaction.

Segments are the functions and calls that make up a transaction. You can also use New Relic for Go to add segment-level detail to your transactions.

Monitor a transaction

To monitor a transaction: Place the following code immediately after the start of the function you want to monitor. For example:

txn := app.StartTransaction("transaction_name")
defer txn.End()

In this code example:

• app refers to the variable assigned during the New Relic configuration process. For more information, see the Go agent installation procedures.
• The defer statement defers the segment ending until the function closes.

To monitor a web transaction, call the Transaction.SetWebRequest and optionally the Transaction.SetWebResponse APIs:

txn := app.StartTransaction("transaction_name")
defer txn.End()

// req is a *http.Request, this marks the transaction as a web transaction
txn.SetWebRequestHTTP(req)

// writer is a http.ResponseWriter, use the returned writer in place of the original
writer = txn.SetWebResponse(writer)
writer.WriteHeader(500)

func checkout() {
    // function code here
}

func checkout() {
    txn := app.StartTransaction("checkout_transaction")
    defer txn.End()
    // function code here
}

Monitor a transaction with multiple goroutines

To monitor a transaction across multiple goroutines, use Transaction.NewGoroutine(). The NewGoroutine method returns a new reference to the Transaction, which is required by each segment-creating goroutine. It does not matter if you call NewGoroutine before or after the other goroutine starts.

All Transaction methods can be used in any Transaction reference. The Transactionwill end when End() is called in any goroutine.

go func(txn *newrelic.Transaction) {
    defer txn.StartSegment("async").End()
    time.Sleep(100 * time.Millisecond)
}(txn.NewGoroutine())

ch := make(chan *newrelic.Transaction)
go func() {
    txn := <-ch
    defer txn.StartSegment("async").End()
    time.Sleep(100 * time.Millisecond)
}()
ch <- txn.NewGoroutine()

Monitor a transaction by wrapping an HTTP handler

If you are using the standard HTTP library package, you can create transactions by wrapping HTTP requests, as an alternative to instrumenting a function's code.

Here is a before-and-after example of an HTTP handler being wrapped:

Before:

http.HandleFunc("/users", usersHandler)

After:

This automatically starts and ends a transaction with the request and response writer.

http.HandleFunc(newrelic.WrapHandleFunc(app, "/users", usersHandler))

To access the transaction in your handler, use the newrelic.FromContext API. Note this will only work for Go versions 1.7 and newer. For example:

func myHandler(w http.ResponseWriter, r *http.Request) {
    txn := newrelic.FromContext(r.Context())
    txn.NoticeError(errors.New("my error message"))
}

Monitor errors

New Relic for Go captures errors in three different ways:

View logs for your APM and infrastructure data

You can also bring your logs and application's data together to make troubleshooting easier and faster. With logs in context, you can see log messages related to your errors and traces directly in your app's UI.

1. From the Errors page, click on a trace to go to the Error details page.
2. From the error details page, click See logs.
3. To view details related to an individual log message, click directly on the message.

You can also see logs in context of your infrastructure data, such as Kubernetes clusters. No need to switch to another UI.

Additional transaction methods

The Transaction object has several optional methods that can be used for controlling transaction behavior, such as NoticeError, AddAttribute, and Ignore. For a list of transaction methods, see the New Relic for Go transaction methods on Godoc.