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{}
+}

pkg/server/agents/logger.go

@@ -0,0 +1,116 @@
+/*
+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 (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"time"
+
+	"github.com/golang/glog"
+)
+
+const (
+	// delimiter used in CRI logging format.
+	delimiter = ' '
+	// eof is end-of-line.
+	eol = '\n'
+	// timestampFormat is the timestamp format used in CRI logging format.
+	timestampFormat = time.RFC3339Nano
+	// pipeBufSize is the system PIPE_BUF size, on linux it is 4096 bytes.
+	// POSIX.1 says that write less than PIPE_BUF is atmoic.
+	pipeBufSize = 4096
+	// bufSize is the size of the read buffer.
+	bufSize = pipeBufSize - len(timestampFormat) - len(Stdout) - 2 /*2 delimiter*/ - 1 /*eol*/
+)
+
+// sandboxLogger is the log agent used for sandbox.
+// It discards sandbox all output for now.
+type sandboxLogger struct {
+	rc io.ReadCloser
+}
+
+func (*agentFactory) NewSandboxLogger(rc io.ReadCloser) Agent {
+	return &sandboxLogger{rc: rc}
+}
+
+func (s *sandboxLogger) Start() error {
+	go func() {
+		// Discard the output for now.
+		io.Copy(ioutil.Discard, s.rc) // nolint: errcheck
+		s.rc.Close()
+	}()
+	return nil
+}
+
+// containerLogger is the log agent used for container.
+// It redirect container log into CRI log file, and decorate the log
+// line into CRI defined format.
+type containerLogger struct {
+	path   string
+	stream StreamType
+	rc     io.ReadCloser
+}
+
+func (*agentFactory) NewContainerLogger(path string, stream StreamType, rc io.ReadCloser) Agent {
+	return &containerLogger{
+		path:   path,
+		stream: stream,
+		rc:     rc,
+	}
+}
+
+func (c *containerLogger) Start() error {
+	glog.V(4).Infof("Start reading log file %q", c.path)
+	wc, err := os.OpenFile(c.path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0640)
+	if err != nil {
+		return fmt.Errorf("failed to open log file %q: %v", c.path, err)
+	}
+	go c.redirectLogs(wc)
+	return nil
+}
+
+func (c *containerLogger) redirectLogs(wc io.WriteCloser) {
+	defer c.rc.Close()
+	defer wc.Close()
+	streamBytes := []byte(c.stream)
+	delimiterBytes := []byte{delimiter}
+	r := bufio.NewReaderSize(c.rc, bufSize)
+	for {
+		// TODO(random-liu): Better define CRI log format, and escape newline in log.
+		lineBytes, _, err := r.ReadLine()
+		if err == io.EOF {
+			glog.V(4).Infof("Finish redirecting log file %q", c.path)
+			return
+		}
+		if err != nil {
+			glog.Errorf("An error occurred when redirecting log file %q: %v", c.path, err)
+			return
+		}
+		timestampBytes := time.Now().AppendFormat(nil, time.RFC3339Nano)
+		data := bytes.Join([][]byte{timestampBytes, streamBytes, lineBytes}, delimiterBytes)
+		data = append(data, eol)
+		if _, err := wc.Write(data); err != nil {
+			glog.Errorf("Fail to write log line %q: %v", data, err)
+		}
+		// Continue on write error to drain the input.
+	}
+}