Add container logging support.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/server/agents/agents.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package agents
+
+import "io"
+
+// StreamType is the type of the stream, stdout/stderr.
+type StreamType string
+
+const (
+	// Stdout stream type.
+	Stdout StreamType = "stdout"
+	// Stderr stream type.
+	Stderr StreamType = "stderr"
+)
+
+// Agent is the a running agent perform a specific task, e.g. redirect and
+// decorate log, redirect stream etc.
+type Agent interface {
+	// Start starts the logger.
+	Start() error
+}
+
+// AgentFactory is the factory to create required agents.
+type AgentFactory interface {
+	// NewSandboxLogger creates a sandbox logging agent.
+	NewSandboxLogger(io.ReadCloser) Agent
+	// NewContainerLogger creates a container logging agent.
+	NewContainerLogger(string, StreamType, io.ReadCloser) Agent
+}
+
+type agentFactory struct{}
+
+// NewAgentFactory creates a new agent factory.
+func NewAgentFactory() AgentFactory {
+	return &agentFactory{}
+}