Add support for task and arbitrary combo logs

Refactored the API to more easily accept new endpoints. Added REST,
client, and CLI endpoints for getting logs from a specific task. All
that is needed after this commit to enable arbitrary service log
selectors is a REST endpoint and handler.

Task logs can be retrieved by putting in a task ID at the CLI instead of
a service ID.

Signed-off-by: Drew Erny <drew.erny@docker.com>

interface.go

@@ -128,6 +128,7 @@ type ServiceAPIClient interface {
 	ServiceRemove(ctx context.Context, serviceID string) error
 	ServiceUpdate(ctx context.Context, serviceID string, version swarm.Version, service swarm.ServiceSpec, options types.ServiceUpdateOptions) (types.ServiceUpdateResponse, error)
 	ServiceLogs(ctx context.Context, serviceID string, options types.ContainerLogsOptions) (io.ReadCloser, error)
+	TaskLogs(ctx context.Context, taskID string, options types.ContainerLogsOptions) (io.ReadCloser, error)
 	TaskInspectWithRaw(ctx context.Context, taskID string) (swarm.Task, []byte, error)
 	TaskList(ctx context.Context, options types.TaskListOptions) ([]swarm.Task, error)
 }

task_logs.go

@@ -0,0 +1,52 @@
+package client
+
+import (
+	"io"
+	"net/url"
+	"time"
+
+	"golang.org/x/net/context"
+
+	"github.com/docker/docker/api/types"
+	timetypes "github.com/docker/docker/api/types/time"
+)
+
+// TaskLogs returns the logs generated by a task in an io.ReadCloser.
+// It's up to the caller to close the stream.
+func (cli *Client) TaskLogs(ctx context.Context, taskID string, options types.ContainerLogsOptions) (io.ReadCloser, error) {
+	query := url.Values{}
+	if options.ShowStdout {
+		query.Set("stdout", "1")
+	}
+
+	if options.ShowStderr {
+		query.Set("stderr", "1")
+	}
+
+	if options.Since != "" {
+		ts, err := timetypes.GetTimestamp(options.Since, time.Now())
+		if err != nil {
+			return nil, err
+		}
+		query.Set("since", ts)
+	}
+
+	if options.Timestamps {
+		query.Set("timestamps", "1")
+	}
+
+	if options.Details {
+		query.Set("details", "1")
+	}
+
+	if options.Follow {
+		query.Set("follow", "1")
+	}
+	query.Set("tail", options.Tail)
+
+	resp, err := cli.get(ctx, "/tasks/"+taskID+"/logs", query, nil)
+	if err != nil {
+		return nil, err
+	}
+	return resp.body, nil
+}