resume waiting for the container to complete

shared/docker/docker.go

@@ -1,9 +1,11 @@
 package docker
 
 import (
+	"errors"
 	"io"
 	"io/ioutil"
 
+	log "github.com/Sirupsen/logrus"
 	"github.com/samalba/dockerclient"
 )
 
@@ -80,24 +82,48 @@ func Wait(client dockerclient.Client, name string) (*dockerclient.ContainerInfo,
 	errc := make(chan error, 1)
 	infoc := make(chan *dockerclient.ContainerInfo, 1)
 	go func() {
-
-		// blocks and waits for the container to finish
-		// by streaming the logs (to /dev/null). Ideally
-		// we could use the `wait` function instead
-		rc, err := client.ContainerLogs(name, LogOptsTail)
-		if err != nil {
-			errc <- err
-			return
+		// options to fetch the stdout and stderr logs
+		// by tailing the output.
+		logOptsTail := &dockerclient.LogOptions{
+			Follow: true,
+			Stdout: true,
+			Stderr: true,
 		}
-		io.Copy(ioutil.Discard, rc)
-		rc.Close()
 
-		info, err := client.InspectContainer(name)
-		if err != nil {
-			errc <- err
-			return
+		for attempts := 0; attempts < 5; attempts++ {
+			if attempts > 0 {
+				// When resuming the stream, only grab the last line when starting
+				// the tailing.
+				logOptsTail.Tail = 1
+			}
+
+			// blocks and waits for the container to finish
+			// by streaming the logs (to /dev/null). Ideally
+			// we could use the `wait` function instead
+			rc, err := client.ContainerLogs(name, logOptsTail)
+			if err != nil {
+				errc <- err
+				return
+			}
+			io.Copy(ioutil.Discard, rc)
+			rc.Close()
+
+			info, err := client.InspectContainer(name)
+			if err != nil {
+				errc <- err
+				return
+			}
+
+			if !info.State.Running {
+				// The container is no longer running, there should be no more logs to tail.
+				infoc <- info
+				return
+			}
+
+			log.Debugf("Attempting to resume log tailing after %d attempts.\n", attempts)
 		}
-		infoc <- info
+
+		errc <- errors.New("Maximum number of attempts made while tailing logs.")
 	}()
 
 	select {