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memlogd: use kmsg format for reading the logs
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
parent
fe64f33430
commit
a07ecf60d5
@ -42,32 +42,40 @@ network service, a service should be added to the yaml which connects to
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`memlogd` and streams the logs. The example program `logread` in the `memlogd`
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package demonstrates how to do this.
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Usage examples:
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### Message format
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The format used to read logs is similar to [kmsg](https://www.kernel.org/doc/Documentation/ABI/testing/dev-kmsg):
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```
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<timestamp>,<log>;<body>
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```
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where `<timestamp>` is an RFC3339-formatted timestamp, `<log>` is the name of
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the log (e.g. `docker-ce.out`) and `<body>` is the output. The `<log>` must
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not contain the character `;`.
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### Usage examples
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```
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/ # logread -f
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2017-04-15T15:37:37Z memlogd memlogd started
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: waiting for carrier
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: carrier acquired
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2017-04-15T15:37:37Z 002-dhcpcd.stdout DUID 00:01:00:01:20:84:fa:c1:02:50:00:00:00:24
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: IAID 00:00:00:24
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding address fe80::84e3:ca52:2590:fe80
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: soliciting an IPv6 router
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: soliciting a DHCP lease
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: offered 192.168.65.37 from 192.168.65.1 `vpnkit'
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: leased 192.168.65.37 for 7199 seconds
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding route to 192.168.65.0/24
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2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding default route via 192.168.65.1
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2017-04-15T15:37:37Z 002-dhcpcd.stdout exiting due to oneshot
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2017-04-15T15:37:37Z 002-dhcpcd.stdout dhcpcd exited
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2017-04-15T15:37:37Z rngd.stderr Unable to open file: /dev/tpm0
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2018-07-05T13:22:32Z,memlogd;memlogd started
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: waiting for carrier
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.err;eth0: could not detect a useable init
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system
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: carrier acquired
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;DUID 00:01:00:01:22:d0:d8:18:02:50:00:00:00:02
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: IAID 00:00:00:02
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding address fe80::d33a:3936:
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2ee4:5c8c
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: soliciting an IPv6 router
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: soliciting a DHCP lease
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: offered 192.168.65.4 from 192.1
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68.65.1 `vpnkit'
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: leased 192.168.65.4 for 7200 se
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conds
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding route to 192.168.65.0/24
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding default route via 192.16
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8.65.1
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;exiting due to oneshot
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2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;dhcpcd exited
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^C
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/ # logwrite echo testing123
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testing123
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/ # logread | tail -n1
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2017-04-15T15:37:45Z echo.stdout testing123
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/ # echo -en "GET / HTTP/1.0\n\n" | nc localhost 80 > /dev/null
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/ # logread | grep nginx
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2017-04-15T15:42:40Z nginx.stdout 127.0.0.1 - - [15/Apr/2017:15:42:40 +0000] "GET / HTTP/1.0" 200 612 "-" "-" "-"
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```
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Current issues and limitations:
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@ -66,7 +66,7 @@ func logQueryHandler(l *connListener) {
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}
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func (msg *logEntry) String() string {
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return fmt.Sprintf("%s %s %s", msg.time.Format(time.RFC3339), msg.source, msg.msg)
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return fmt.Sprintf("%s,%s;%s", msg.time.Format(time.RFC3339), msg.source, msg.msg)
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}
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func ringBufferHandler(ringSize, chanSize int, logCh chan logEntry, queryMsgChan chan queryMessage) {
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@ -220,6 +220,23 @@ func readLogFromFd(maxLineLen int, fd int, source string, logCh chan logEntry) {
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}
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}
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func loggingRequestHandler(lineMaxLength int, logCh chan logEntry, fdMsgChan chan fdMessage) {
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for true {
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select {
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case msg := <-fdMsgChan: // incoming fd
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if strings.Contains(msg.name, ";") {
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// The log message spec bans ";" in the log names
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doLog(logCh, fmt.Sprintf("ERROR: cannot register log with name '%s' as it contains ;", msg.name))
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if err := syscall.Close(msg.fd); err != nil {
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doLog(logCh, fmt.Sprintf("ERROR: failed to close fd: %s", err))
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}
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continue
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}
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go readLogFromFd(lineMaxLength, msg.fd, msg.name, logCh)
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}
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}
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}
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func main() {
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var err error
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@ -304,16 +321,14 @@ func main() {
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fdMsgChan := make(chan fdMessage)
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queryMsgChan := make(chan queryMessage)
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// receive fds from the logging Unix domain socket and send on fdMsgChan
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go receiveFdHandler(connLogFd, logCh, fdMsgChan)
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// receive fds from the querying Unix domain socket and send on queryMsgChan
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go receiveQueryHandler(connQuery, logCh, queryMsgChan)
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// process both log messages and queries
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go ringBufferHandler(linesInBuffer, linesInBuffer, logCh, queryMsgChan)
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doLog(logCh, "memlogd started")
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for true {
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select {
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case msg := <-fdMsgChan: // incoming fd
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go readLogFromFd(lineMaxLength, msg.fd, msg.name, logCh)
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}
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}
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loggingRequestHandler(lineMaxLength, logCh, fdMsgChan)
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}
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@ -6,6 +6,7 @@ import (
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"log"
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"net"
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"os"
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"strings"
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"syscall"
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"testing"
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"time"
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@ -44,7 +45,7 @@ func TestFinite(t *testing.T) {
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for i := 0; i < 2*linesInBuffer; i++ {
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logCh <- logEntry{time: time.Now(), source: "memlogd", msg: "hello TestFinite"}
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}
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a, b := socketpair()
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a, b := loopback()
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defer a.Close()
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defer b.Close()
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queryM := queryMessage{
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@ -85,7 +86,7 @@ func TestFinite2(t *testing.T) {
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logCh <- logEntry{time: time.Now(), source: "memlogd", msg: "hello TestFinite2"}
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}
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a, b := socketpair()
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a, b := loopback()
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defer a.Close()
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defer b.Close()
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queryM := queryMessage{
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@ -112,22 +113,86 @@ func TestFinite2(t *testing.T) {
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}
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}
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func socketpair() (net.Conn, net.Conn) {
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func TestGoodName(t *testing.T) {
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// Test that the source names can't contain ";"
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linesInBuffer := 10
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logCh := make(chan logEntry)
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fdMsgChan := make(chan fdMessage)
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queryMsgChan := make(chan queryMessage)
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go ringBufferHandler(linesInBuffer, linesInBuffer, logCh, queryMsgChan)
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go loggingRequestHandler(80, logCh, fdMsgChan)
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fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)
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if err != nil {
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log.Fatal("Unable to create socketpair: ", err)
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}
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f := os.NewFile(uintptr(fds[0]), "a")
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a, err := net.FileConn(f)
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if err != nil {
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log.Fatal("Unable to create net.Conn from socketpair: ", err)
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a := fdToConn(fds[0])
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b := fdToConn(fds[1])
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defer a.Close()
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defer b.Close()
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// defer close fds
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fdMsgChan <- fdMessage{
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name: "semi-colons are banned;",
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fd: fds[0],
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}
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_ = f.Close()
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f = os.NewFile(uintptr(fds[1]), "b")
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b, err := net.FileConn(f)
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if err != nil {
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log.Fatal("Unable to create net.Conn from socketpair: ", err)
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// although the fd should be rejected my memlogd the Write should be buffered
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// by the kernel and not block.
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if _, err := b.Write([]byte("hello\n")); err != nil {
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log.Fatalf("Failed to write log message: %s", err)
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}
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c, d := loopback()
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defer c.Close()
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defer d.Close()
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// this log should not be in the ring because the connection was rejected.
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queryM := queryMessage{
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conn: c,
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mode: logDumpFollow,
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}
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queryMsgChan <- queryM
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// The error log is generated asynchronously. It should be fast. On error time out
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// after 5s.
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d.SetDeadline(time.Now().Add(5 * time.Second))
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r := bufio.NewReader(d)
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for {
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line, err := r.ReadString('\n')
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if err == io.EOF {
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break
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}
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if err != nil {
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log.Fatalf("Unexpected error reading from socket: %s", err)
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}
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if strings.Contains(line, "ERROR: cannot register log") {
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return
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}
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}
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t.Fatal("Failed to read error message when registering a log with a ;")
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}
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// caller must close fd themselves: closing the net.Conn will not close fd.
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func fdToConn(fd int) net.Conn {
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f := os.NewFile(uintptr(fd), "")
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c, err := net.FileConn(f)
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if err != nil {
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log.Fatal("Unable to create net.Conn from file descriptor: ", err)
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}
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return c
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}
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func loopback() (net.Conn, net.Conn) {
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fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)
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if err != nil {
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log.Fatal("Unable to create socketpair: ", err)
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}
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a := fdToConn(fds[0])
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b := fdToConn(fds[1])
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// net.Conns are independent of the fds, so we must close the fds now.
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if err := syscall.Close(fds[0]); err != nil {
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log.Fatal("Unable to close socketpair fd: ", err)
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}
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if err := syscall.Close(fds[1]); err != nil {
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log.Fatal("Unable to close socketpair fd: ", err)
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}
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_ = f.Close()
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return a, b
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}
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