github.com/fabiokung/docker@v0.11.2-0.20170222101415-4534dcd49497/daemon/logger/copier.go (about) 1 package logger 2 3 import ( 4 "bytes" 5 "io" 6 "sync" 7 "time" 8 9 "github.com/Sirupsen/logrus" 10 ) 11 12 const ( 13 bufSize = 16 * 1024 14 readSize = 2 * 1024 15 ) 16 17 // Copier can copy logs from specified sources to Logger and attach Timestamp. 18 // Writes are concurrent, so you need implement some sync in your logger. 19 type Copier struct { 20 // srcs is map of name -> reader pairs, for example "stdout", "stderr" 21 srcs map[string]io.Reader 22 dst Logger 23 copyJobs sync.WaitGroup 24 closeOnce sync.Once 25 closed chan struct{} 26 } 27 28 // NewCopier creates a new Copier 29 func NewCopier(srcs map[string]io.Reader, dst Logger) *Copier { 30 return &Copier{ 31 srcs: srcs, 32 dst: dst, 33 closed: make(chan struct{}), 34 } 35 } 36 37 // Run starts logs copying 38 func (c *Copier) Run() { 39 for src, w := range c.srcs { 40 c.copyJobs.Add(1) 41 go c.copySrc(src, w) 42 } 43 } 44 45 func (c *Copier) copySrc(name string, src io.Reader) { 46 defer c.copyJobs.Done() 47 buf := make([]byte, bufSize) 48 n := 0 49 eof := false 50 51 for { 52 select { 53 case <-c.closed: 54 return 55 default: 56 // Work out how much more data we are okay with reading this time. 57 upto := n + readSize 58 if upto > cap(buf) { 59 upto = cap(buf) 60 } 61 // Try to read that data. 62 if upto > n { 63 read, err := src.Read(buf[n:upto]) 64 if err != nil { 65 if err != io.EOF { 66 logrus.Errorf("Error scanning log stream: %s", err) 67 return 68 } 69 eof = true 70 } 71 n += read 72 } 73 // If we have no data to log, and there's no more coming, we're done. 74 if n == 0 && eof { 75 return 76 } 77 // Break up the data that we've buffered up into lines, and log each in turn. 78 p := 0 79 for q := bytes.IndexByte(buf[p:n], '\n'); q >= 0; q = bytes.IndexByte(buf[p:n], '\n') { 80 select { 81 case <-c.closed: 82 return 83 default: 84 msg := NewMessage() 85 msg.Source = name 86 msg.Timestamp = time.Now().UTC() 87 msg.Line = append(msg.Line, buf[p:p+q]...) 88 89 if logErr := c.dst.Log(msg); logErr != nil { 90 logrus.Errorf("Failed to log msg %q for logger %s: %s", msg.Line, c.dst.Name(), logErr) 91 } 92 } 93 p += q + 1 94 } 95 // If there's no more coming, or the buffer is full but 96 // has no newlines, log whatever we haven't logged yet, 97 // noting that it's a partial log line. 98 if eof || (p == 0 && n == len(buf)) { 99 if p < n { 100 msg := NewMessage() 101 msg.Source = name 102 msg.Timestamp = time.Now().UTC() 103 msg.Line = append(msg.Line, buf[p:n]...) 104 msg.Partial = true 105 106 if logErr := c.dst.Log(msg); logErr != nil { 107 logrus.Errorf("Failed to log msg %q for logger %s: %s", msg.Line, c.dst.Name(), logErr) 108 } 109 p = 0 110 n = 0 111 } 112 if eof { 113 return 114 } 115 } 116 // Move any unlogged data to the front of the buffer in preparation for another read. 117 if p > 0 { 118 copy(buf[0:], buf[p:n]) 119 n -= p 120 } 121 } 122 } 123 } 124 125 // Wait waits until all copying is done 126 func (c *Copier) Wait() { 127 c.copyJobs.Wait() 128 } 129 130 // Close closes the copier 131 func (c *Copier) Close() { 132 c.closeOnce.Do(func() { 133 close(c.closed) 134 }) 135 }