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/**
* Syslog wrapper that does not block
*
* Lon Hohberger, 2009
*/
#include "config.h"
#include <pthread.h>
#include <unistd.h>
#include <sys/syslog.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdarg.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/time.h>
#include <errno.h>
#include "list.h"
struct log_entry {
list_head();
char *message;
int sev;
int bufsz;
};
#define MAX_QUEUE_LENGTH 10
#define LOGLEN 256
static struct log_entry *_log_entries = NULL;
static pthread_mutex_t log_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t log_cond = PTHREAD_COND_INITIALIZER;
static int log_size = 0;
static int dropped = 0;
static pthread_t thread_id = 0;
void __real_syslog(int severity, const char *fmt, ...);
void __wrap_syslog(int severity, const char *fmt, ...);
void __wrap_closelog(void);
static void *
_log_thread(void *arg)
{
struct timeval tv;
struct timespec ts;
struct log_entry *entry;
do {
gettimeofday(&tv, NULL);
ts.tv_sec = tv.tv_sec + 10;
ts.tv_nsec = tv.tv_usec;
pthread_mutex_lock(&log_mutex);
while (!(entry = _log_entries)) {
if (pthread_cond_timedwait(&log_cond,
&log_mutex,
&ts) == ETIMEDOUT)
goto out;
}
list_remove(&_log_entries, entry);
--log_size;
if (log_size < 0)
raise(SIGSEGV);
pthread_mutex_unlock(&log_mutex);
__real_syslog(entry->sev, entry->message);
free(entry->message);
free(entry);
} while (1);
out:
thread_id = (pthread_t)0;
pthread_mutex_unlock(&log_mutex);
return NULL;
}
static int
insert_entry(int sev, char *buf, int bufsz)
{
struct log_entry *lent;
pthread_attr_t attrs;
lent = malloc(sizeof(*lent));
if (!lent)
return -1;
lent->sev = sev;
lent->message = buf;
lent->bufsz = bufsz;
pthread_mutex_lock(&log_mutex);
if (log_size >= MAX_QUEUE_LENGTH) {
free(lent->message);
free(lent);
++dropped;
lent = (struct log_entry *)(le(_log_entries)->le_prev);
lent->sev = LOG_WARNING;
snprintf(lent->message, lent->bufsz,
"%d message(s) lost due to syslog load\n",
dropped + 1);
/* Dropped +1 because we overwrote a message to
* give the 'dropped' message */
} else {
++log_size;
dropped = 0;
list_insert(&_log_entries, lent);
}
if (!thread_id) {
pthread_attr_init(&attrs);
pthread_attr_setinheritsched(&attrs, PTHREAD_INHERIT_SCHED);
if (pthread_create(&thread_id, &attrs, _log_thread, NULL) < 0)
thread_id = 0;
pthread_mutex_unlock(&log_mutex);
} else {
pthread_mutex_unlock(&log_mutex);
pthread_cond_signal(&log_cond);
}
return 0;
}
__attribute__((__format__ (__printf__, 2, 0)))
void
__wrap_syslog(int severity, const char *fmt, ...)
{
va_list args;
char *logmsg;
logmsg = malloc(LOGLEN);
if (!logmsg)
return;
memset(logmsg, 0, LOGLEN);
va_start(args, fmt);
vsnprintf(logmsg + strlen(logmsg), LOGLEN - strlen(logmsg),
fmt, args);
va_end(args);
insert_entry(severity, logmsg, LOGLEN);
return;
}
void __real_closelog(void);
void
__wrap_closelog(void)
{
struct log_entry *lent;
#ifdef DEBUG
int lost = 0;
#endif
if (thread_id != 0) {
pthread_cancel(thread_id);
pthread_join(thread_id, NULL);
thread_id = 0;
}
__real_closelog();
while (_log_entries) {
#ifdef DEBUG
++lost;
#endif
lent = _log_entries;
list_remove(&_log_entries, lent);
free(lent->message);
free(lent);
}
#ifdef DEBUG
printf("%d lost\n", lost);
#endif
}
#ifdef STANDALONE
int
main(int argc, char**argv)
{
int x;
for (x = 0; x < 100; x++) {
syslog(1, "Yo %d\n", x);
}
sleep(1);
closelog();
return 0;
}
#endif
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