Support Go execd plugins with shim (#7283)

plugins/inputs/execd/shim/shim_posix_test.go

@@ -0,0 +1,76 @@
+// +build !windows
+
+package shim
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"runtime"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestShimUSR1SignalingWorks(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip()
+		return
+	}
+	stdoutBytes := bytes.NewBufferString("")
+	stdout = stdoutBytes
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	wait := runInputPlugin(t, 40*time.Second)
+
+	// sleep a bit to avoid a race condition where the input hasn't loaded yet.
+	time.Sleep(10 * time.Millisecond)
+
+	// signal USR1 to yourself.
+	pid := os.Getpid()
+	process, err := os.FindProcess(pid)
+	require.NoError(t, err)
+
+	go func() {
+		// On slow machines this signal can fire before the service comes up.
+		// rather than depend on accurate sleep times, we'll just retry sending
+		// the signal every so often until it goes through.
+		for {
+			select {
+			case <-ctx.Done():
+				return // test is done
+			default:
+				// test isn't done, keep going.
+				process.Signal(syscall.SIGUSR1)
+				time.Sleep(200 * time.Millisecond)
+			}
+		}
+	}()
+
+	timeout := time.NewTimer(10 * time.Second)
+
+	select {
+	case <-wait:
+	case <-timeout.C:
+		require.Fail(t, "Timeout waiting for metric to arrive")
+	}
+
+	for stdoutBytes.Len() == 0 {
+		select {
+		case <-timeout.C:
+			require.Fail(t, "Timeout waiting to read metric from stdout")
+			return
+		default:
+			time.Sleep(10 * time.Millisecond)
+		}
+	}
+
+	out := string(stdoutBytes.Bytes())
+	require.Contains(t, out, "\n")
+	metricLine := strings.Split(out, "\n")[0]
+	require.Equal(t, "measurement,tag=tag field=1i 1234000005678", metricLine)
+}