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memlogd: use kmsg format for reading the logs

Browse Source 
Switch to a more formally-specified `kmsg`-style format for reading
the logs.

- update the spec in docs/logging.md
- check for bad names in pkg/memlogd with unit test

Signed-off-by: David Scott <dave.scott@docker.com>
This commit is contained in:
David Scott 2018-07-05 14:24:37 +01:00
parent fe64f33430
commit a07ecf60d5
3 changed files with 131 additions and 43 deletions
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54
docs/logging.md
View File

@ -42,32 +42,40 @@ network service, a service should be added to the yaml which connects to
`memlogd` and streams the logs. The example program `logread` in the `memlogd` `memlogd` and streams the logs. The example program `logread` in the `memlogd`
package demonstrates how to do this. package demonstrates how to do this.
Usage examples: ### Message format
The format used to read logs is similar to [kmsg](https://www.kernel.org/doc/Documentation/ABI/testing/dev-kmsg):
```
<timestamp>,<log>;<body>
```
where `<timestamp>` is an RFC3339-formatted timestamp, `<log>` is the name of
the log (e.g. `docker-ce.out`) and `<body>` is the output. The `<log>` must
not contain the character `;`.
### Usage examples
``` ```
/ # logread -f / # logread -f
2017-04-15T15:37:37Z memlogd memlogd started 2018-07-05T13:22:32Z,memlogd;memlogd started
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: waiting for carrier 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: waiting for carrier
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: carrier acquired 2018-07-05T13:22:32Z,onboot.001-dhcpcd.err;eth0: could not detect a useable init
2017-04-15T15:37:37Z 002-dhcpcd.stdout DUID 00:01:00:01:20:84:fa:c1:02:50:00:00:00:24 system
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: IAID 00:00:00:24 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: carrier acquired
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding address fe80::84e3:ca52:2590:fe80 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;DUID 00:01:00:01:22:d0:d8:18:02:50:00:00:00:02
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: soliciting an IPv6 router 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: IAID 00:00:00:02
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: soliciting a DHCP lease 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding address fe80::d33a:3936:
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: offered 192.168.65.37 from 192.168.65.1 `vpnkit' 2ee4:5c8c
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: leased 192.168.65.37 for 7199 seconds 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: soliciting an IPv6 router
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding route to 192.168.65.0/24 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: soliciting a DHCP lease
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding default route via 192.168.65.1 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: offered 192.168.65.4 from 192.1
2017-04-15T15:37:37Z 002-dhcpcd.stdout exiting due to oneshot 68.65.1 `vpnkit'
2017-04-15T15:37:37Z 002-dhcpcd.stdout dhcpcd exited 2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: leased 192.168.65.4 for 7200 se
2017-04-15T15:37:37Z rngd.stderr Unable to open file: /dev/tpm0 conds
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding route to 192.168.65.0/24
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding default route via 192.16
8.65.1
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;exiting due to oneshot
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;dhcpcd exited
^C ^C
/ # logwrite echo testing123
testing123
/ # logread | tail -n1
2017-04-15T15:37:45Z echo.stdout testing123
/ # echo -en "GET / HTTP/1.0\n\n" | nc localhost 80 > /dev/null
/ # logread | grep nginx
2017-04-15T15:42:40Z nginx.stdout 127.0.0.1 - - [15/Apr/2017:15:42:40 +0000] "GET / HTTP/1.0" 200 612 "-" "-" "-"
``` ```
Current issues and limitations: Current issues and limitations:

29
pkg/memlogd/cmd/memlogd/main.go
View File

@ -66,7 +66,7 @@ func logQueryHandler(l *connListener) {
} }
func (msg *logEntry) String() string { func (msg *logEntry) String() string {
return fmt.Sprintf("%s %s %s", msg.time.Format(time.RFC3339), msg.source, msg.msg) return fmt.Sprintf("%s,%s;%s", msg.time.Format(time.RFC3339), msg.source, msg.msg)
} }
func ringBufferHandler(ringSize, chanSize int, logCh chan logEntry, queryMsgChan chan queryMessage) { func ringBufferHandler(ringSize, chanSize int, logCh chan logEntry, queryMsgChan chan queryMessage) {
@ -220,6 +220,23 @@ func readLogFromFd(maxLineLen int, fd int, source string, logCh chan logEntry) {
} }
} }
func loggingRequestHandler(lineMaxLength int, logCh chan logEntry, fdMsgChan chan fdMessage) {
for true {
select {
case msg := <-fdMsgChan: // incoming fd
if strings.Contains(msg.name, ";") {
// The log message spec bans ";" in the log names
doLog(logCh, fmt.Sprintf("ERROR: cannot register log with name '%s' as it contains ;", msg.name))
if err := syscall.Close(msg.fd); err != nil {
doLog(logCh, fmt.Sprintf("ERROR: failed to close fd: %s", err))
}
continue
}
go readLogFromFd(lineMaxLength, msg.fd, msg.name, logCh)
}
}
}
func main() { func main() {
var err error var err error
@ -304,16 +321,14 @@ func main() {
fdMsgChan := make(chan fdMessage) fdMsgChan := make(chan fdMessage)
queryMsgChan := make(chan queryMessage) queryMsgChan := make(chan queryMessage)
// receive fds from the logging Unix domain socket and send on fdMsgChan
go receiveFdHandler(connLogFd, logCh, fdMsgChan) go receiveFdHandler(connLogFd, logCh, fdMsgChan)
// receive fds from the querying Unix domain socket and send on queryMsgChan
go receiveQueryHandler(connQuery, logCh, queryMsgChan) go receiveQueryHandler(connQuery, logCh, queryMsgChan)
// process both log messages and queries
go ringBufferHandler(linesInBuffer, linesInBuffer, logCh, queryMsgChan) go ringBufferHandler(linesInBuffer, linesInBuffer, logCh, queryMsgChan)
doLog(logCh, "memlogd started") doLog(logCh, "memlogd started")
for true { loggingRequestHandler(lineMaxLength, logCh, fdMsgChan)
select {
case msg := <-fdMsgChan: // incoming fd
go readLogFromFd(lineMaxLength, msg.fd, msg.name, logCh)
}
}
} }

91
pkg/memlogd/cmd/memlogd/main_test.go
View File

@ -6,6 +6,7 @@ import (
"log" "log"
"net" "net"
"os" "os"
"strings"
"syscall" "syscall"
"testing" "testing"
"time" "time"
@ -44,7 +45,7 @@ func TestFinite(t *testing.T) {
for i := 0; i < 2*linesInBuffer; i++ { for i := 0; i < 2*linesInBuffer; i++ {
logCh <- logEntry{time: time.Now(), source: "memlogd", msg: "hello TestFinite"} logCh <- logEntry{time: time.Now(), source: "memlogd", msg: "hello TestFinite"}
} }
a, b := socketpair() a, b := loopback()
defer a.Close() defer a.Close()
defer b.Close() defer b.Close()
queryM := queryMessage{ queryM := queryMessage{
@ -85,7 +86,7 @@ func TestFinite2(t *testing.T) {
logCh <- logEntry{time: time.Now(), source: "memlogd", msg: "hello TestFinite2"} logCh <- logEntry{time: time.Now(), source: "memlogd", msg: "hello TestFinite2"}
} }
a, b := socketpair() a, b := loopback()
defer a.Close() defer a.Close()
defer b.Close() defer b.Close()
queryM := queryMessage{ queryM := queryMessage{
@ -112,22 +113,86 @@ func TestFinite2(t *testing.T) {
} }
} }
func socketpair() (net.Conn, net.Conn) { func TestGoodName(t *testing.T) {
// Test that the source names can't contain ";"
linesInBuffer := 10
logCh := make(chan logEntry)
fdMsgChan := make(chan fdMessage)
queryMsgChan := make(chan queryMessage)
go ringBufferHandler(linesInBuffer, linesInBuffer, logCh, queryMsgChan)
go loggingRequestHandler(80, logCh, fdMsgChan)
fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0) fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)
if err != nil { if err != nil {
log.Fatal("Unable to create socketpair: ", err) log.Fatal("Unable to create socketpair: ", err)
} }
f := os.NewFile(uintptr(fds[0]), "a") a := fdToConn(fds[0])
a, err := net.FileConn(f) b := fdToConn(fds[1])
if err != nil { defer a.Close()
log.Fatal("Unable to create net.Conn from socketpair: ", err) defer b.Close()
// defer close fds
fdMsgChan <- fdMessage{
name: "semi-colons are banned;",
fd: fds[0],
} }
_ = f.Close() // although the fd should be rejected my memlogd the Write should be buffered
f = os.NewFile(uintptr(fds[1]), "b") // by the kernel and not block.
b, err := net.FileConn(f) if _, err := b.Write([]byte("hello\n")); err != nil {
if err != nil { log.Fatalf("Failed to write log message: %s", err)
log.Fatal("Unable to create net.Conn from socketpair: ", err) }
c, d := loopback()
defer c.Close()
defer d.Close()
// this log should not be in the ring because the connection was rejected.
queryM := queryMessage{
conn: c,
mode: logDumpFollow,
}
queryMsgChan <- queryM
// The error log is generated asynchronously. It should be fast. On error time out
// after 5s.
d.SetDeadline(time.Now().Add(5 * time.Second))
r := bufio.NewReader(d)
for {
line, err := r.ReadString('\n')
if err == io.EOF {
break
}
if err != nil {
log.Fatalf("Unexpected error reading from socket: %s", err)
}
if strings.Contains(line, "ERROR: cannot register log") {
return
}
}
t.Fatal("Failed to read error message when registering a log with a ;")
}
// caller must close fd themselves: closing the net.Conn will not close fd.
func fdToConn(fd int) net.Conn {
f := os.NewFile(uintptr(fd), "")
c, err := net.FileConn(f)
if err != nil {
log.Fatal("Unable to create net.Conn from file descriptor: ", err)
}
return c
}
func loopback() (net.Conn, net.Conn) {
fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)
if err != nil {
log.Fatal("Unable to create socketpair: ", err)
}
a := fdToConn(fds[0])
b := fdToConn(fds[1])
// net.Conns are independent of the fds, so we must close the fds now.
if err := syscall.Close(fds[0]); err != nil {
log.Fatal("Unable to close socketpair fd: ", err)
}
if err := syscall.Close(fds[1]); err != nil {
log.Fatal("Unable to close socketpair fd: ", err)
} }
_ = f.Close()
return a, b return a, b
} }