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// Copyright 2020 New Relic Corporation. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
// An application that illustrates Distributed Tracing with custom
// instrumentation.
//
// This application simulates simple inter-process communication between a
// calling and a called process.
//
// Invoked without arguments, the application acts as a calling process;
// invoked with one argument representing a payload, it acts as a called
// process. The calling process creates a payload, starts a called process and
// passes on the payload. The calling process waits until the called process is
// done and then terminates. Thus to start both processes, only a single
// invocation of the application (without any arguments) is needed.
package main
import (
"fmt"
"os"
"os/exec"
"time"
"github.com/newrelic/go-agent"
)
func mustGetEnv(key string) string {
if val := os.Getenv(key); "" != val {
return val
}
panic(fmt.Sprintf("environment variable %s unset", key))
}
func called(app newrelic.Application, payload string) {
txn := app.StartTransaction("called-txn", nil, nil)
defer txn.End()
// Accept the payload that was passed on the command line.
txn.AcceptDistributedTracePayload(newrelic.TransportOther, payload)
time.Sleep(1 * time.Second)
}
func calling(app newrelic.Application) {
txn := app.StartTransaction("calling-txn", nil, nil)
defer txn.End()
// Create a payload, start the called process and pass the payload.
payload := txn.CreateDistributedTracePayload()
cmd := exec.Command(os.Args[0], payload.Text())
cmd.Start()
// Wait until the called process is done, then exit.
cmd.Wait()
time.Sleep(1 * time.Second)
}
func makeApplication(name string) (newrelic.Application, error) {
cfg := newrelic.NewConfig(name, mustGetEnv("NEW_RELIC_LICENSE_KEY"))
cfg.Logger = newrelic.NewDebugLogger(os.Stdout)
// Distributed Tracing and Cross Application Tracing cannot both be
// enabled at the same time.
cfg.DistributedTracer.Enabled = true
app, err := newrelic.NewApplication(cfg)
if nil != err {
return nil, err
}
// Wait for the application to connect.
if err = app.WaitForConnection(5 * time.Second); nil != err {
return nil, err
}
return app, nil
}
func main() {
// Calling processes have no command line arguments, called processes
// have one command line argument (the payload).
isCalled := (len(os.Args) > 1)
// Initialize the application name.
name := "Go Custom Instrumentation"
if isCalled {
name += " Called"
} else {
name += " Calling"
}
// Initialize the application.
app, err := makeApplication(name)
if nil != err {
fmt.Println(err)
os.Exit(1)
}
// Run calling/called routines.
if isCalled {
payload := os.Args[1]
called(app, payload)
} else {
calling(app)
}
// Shut down the application to flush data to New Relic.
app.Shutdown(10 * time.Second)
}
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