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Clean up journald logger

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We clean up the journald logger with these four changes.

1. Make field array static
2. Make function name more appropriate
3. Initialize the file descriptors only once
4. Avoid copying the journald cursor

Point 4 is the most significant change: instead of treating the journald
cursor like a Go string we use it as a raw C.char pointer. That way we
avoid the copying by the C.CString and C.GoString functions.

Signed-off-by: Silvan Jegen <s.jegen@gmail.com>
This commit is contained in:
Silvan Jegen 2016-10-15 16:12:15 +02:00
parent a70b1d74a0
commit d359daaa48
1 changed files with 29 additions and 27 deletions
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44
daemon/logger/journald/read.go
View file

@ -56,7 +56,7 @@ package journald
//} //}
//static int is_attribute_field(const char *msg, size_t length) //static int is_attribute_field(const char *msg, size_t length)
//{ //{
// const struct known_field { // static const struct known_field {
// const char *name; // const char *name;
// size_t length; // size_t length;
// } fields[] = { // } fields[] = {
@ -101,14 +101,14 @@ package journald
// } // }
// return rc; // return rc;
//} //}
//static int wait_for_data_or_close(sd_journal *j, int pipefd) //static int wait_for_data_cancelable(sd_journal *j, int pipefd)
//{ //{
// struct pollfd fds[2]; // struct pollfd fds[2];
// uint64_t when = 0; // uint64_t when = 0;
// int timeout, jevents, i; // int timeout, jevents, i;
// struct timespec ts; // struct timespec ts;
// uint64_t now; // uint64_t now;
// do { //
// memset(&fds, 0, sizeof(fds)); // memset(&fds, 0, sizeof(fds));
// fds[0].fd = pipefd; // fds[0].fd = pipefd;
// fds[0].events = POLLHUP; // fds[0].events = POLLHUP;
@ -116,6 +116,8 @@ package journald
// if (fds[1].fd < 0) { // if (fds[1].fd < 0) {
// return fds[1].fd; // return fds[1].fd;
// } // }
//
// do {
// jevents = sd_journal_get_events(j); // jevents = sd_journal_get_events(j);
// if (jevents < 0) { // if (jevents < 0) {
// return jevents; // return jevents;
@ -167,7 +169,7 @@ func (s *journald) Close() error {
return nil return nil
} }
func (s *journald) drainJournal(logWatcher *logger.LogWatcher, config logger.ReadConfig, j *C.sd_journal, oldCursor string) string { func (s *journald) drainJournal(logWatcher *logger.LogWatcher, config logger.ReadConfig, j *C.sd_journal, oldCursor *C.char) *C.char {
var msg, data, cursor *C.char var msg, data, cursor *C.char
var length C.size_t var length C.size_t
var stamp C.uint64_t var stamp C.uint64_t
@ -177,10 +179,8 @@ func (s *journald) drainJournal(logWatcher *logger.LogWatcher, config logger.Rea
drain: drain:
for { for {
// Try not to send a given entry twice. // Try not to send a given entry twice.
if oldCursor != "" { if oldCursor != nil {
ccursor := C.CString(oldCursor) for C.sd_journal_test_cursor(j, oldCursor) > 0 {
defer C.free(unsafe.Pointer(ccursor))
for C.sd_journal_test_cursor(j, ccursor) > 0 {
if C.sd_journal_next(j) <= 0 { if C.sd_journal_next(j) <= 0 {
break drain break drain
} }
@ -234,25 +234,24 @@ drain:
break break
} }
} }
retCursor := ""
if C.sd_journal_get_cursor(j, &cursor) == 0 { // free(NULL) is safe
retCursor = C.GoString(cursor) C.free(unsafe.Pointer(oldCursor))
C.free(unsafe.Pointer(cursor)) C.sd_journal_get_cursor(j, &cursor)
} return cursor
return retCursor
} }
func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.ReadConfig, j *C.sd_journal, pfd [2]C.int, cursor string) { func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.ReadConfig, j *C.sd_journal, pfd [2]C.int, cursor *C.char) *C.char {
s.readers.mu.Lock() s.readers.mu.Lock()
s.readers.readers[logWatcher] = logWatcher s.readers.readers[logWatcher] = logWatcher
s.readers.mu.Unlock() s.readers.mu.Unlock()
go func() { go func() {
// Keep copying journal data out until we're notified to stop // Keep copying journal data out until we're notified to stop
// or we hit an error. // or we hit an error.
status := C.wait_for_data_or_close(j, pfd[0]) status := C.wait_for_data_cancelable(j, pfd[0])
for status == 1 { for status == 1 {
cursor = s.drainJournal(logWatcher, config, j, cursor) cursor = s.drainJournal(logWatcher, config, j, cursor)
status = C.wait_for_data_or_close(j, pfd[0]) status = C.wait_for_data_cancelable(j, pfd[0])
} }
if status < 0 { if status < 0 {
cerrstr := C.strerror(C.int(-status)) cerrstr := C.strerror(C.int(-status))
@ -274,15 +273,16 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.Re
// Notify the other goroutine that its work is done. // Notify the other goroutine that its work is done.
C.close(pfd[1]) C.close(pfd[1])
} }
return cursor
} }
func (s *journald) readLogs(logWatcher *logger.LogWatcher, config logger.ReadConfig) { func (s *journald) readLogs(logWatcher *logger.LogWatcher, config logger.ReadConfig) {
var j *C.sd_journal var j *C.sd_journal
var cmatch *C.char var cmatch, cursor *C.char
var stamp C.uint64_t var stamp C.uint64_t
var sinceUnixMicro uint64 var sinceUnixMicro uint64
var pipes [2]C.int var pipes [2]C.int
cursor := ""
// Get a handle to the journal. // Get a handle to the journal.
rc := C.sd_journal_open(&j, C.int(0)) rc := C.sd_journal_open(&j, C.int(0))
@ -370,7 +370,7 @@ func (s *journald) readLogs(logWatcher *logger.LogWatcher, config logger.ReadCon
return return
} }
} }
cursor = s.drainJournal(logWatcher, config, j, "") cursor = s.drainJournal(logWatcher, config, j, nil)
if config.Follow { if config.Follow {
// Allocate a descriptor for following the journal, if we'll // Allocate a descriptor for following the journal, if we'll
// need one. Do it here so that we can report if it fails. // need one. Do it here so that we can report if it fails.
@ -382,13 +382,15 @@ func (s *journald) readLogs(logWatcher *logger.LogWatcher, config logger.ReadCon
if C.pipe(&pipes[0]) == C.int(-1) { if C.pipe(&pipes[0]) == C.int(-1) {
logWatcher.Err <- fmt.Errorf("error opening journald close notification pipe") logWatcher.Err <- fmt.Errorf("error opening journald close notification pipe")
} else { } else {
s.followJournal(logWatcher, config, j, pipes, cursor) cursor = s.followJournal(logWatcher, config, j, pipes, cursor)
// Let followJournal handle freeing the journal context // Let followJournal handle freeing the journal context
// object and closing the channel. // object and closing the channel.
following = true following = true
} }
} }
} }
C.free(unsafe.Pointer(cursor))
return return
} }