add LogCollector interface, docker, mock log collectors

connector/collector/docker_logs.go

@@ -0,0 +1,60 @@
+package collector
+
+import (
+	"bufio"
+	"context"
+	"io"
+
+	api "github.com/fsouza/go-dockerclient"
+)
+
+type DockerLogs struct {
+	id     string
+	client *api.Client
+	done   chan bool
+}
+
+func (l *DockerLogs) Stream() chan string {
+	r, w := io.Pipe()
+	logCh := make(chan string)
+	ctx, cancel := context.WithCancel(context.Background())
+
+	opts := api.LogsOptions{
+		Context:      ctx,
+		Container:    l.id,
+		OutputStream: w,
+		ErrorStream:  w,
+		Stdout:       true,
+		Stderr:       true,
+		Tail:         "10",
+		Follow:       true,
+		Timestamps:   true,
+	}
+
+	// read io pipe into channel
+	go func() {
+		scanner := bufio.NewScanner(r)
+		for scanner.Scan() {
+			logCh <- scanner.Text()
+		}
+	}()
+
+	// connect to container log stream
+	go func() {
+		err := l.client.Logs(opts)
+		if err != nil {
+			log.Errorf("error reading container logs: %s", err)
+		}
+	}()
+
+	go func() {
+		select {
+		case <-l.done:
+			cancel()
+		}
+	}()
+
+	return logCh
+}
+
+func (l *DockerLogs) Stop() { l.done <- true }