Keep the log fd, don't re-open logfile in every logs

src/config.c

@@ -561,17 +561,12 @@ void loadServerConfigFromString(char *config) {
         argv = NULL;
     }
 
-    if (server.logfile[0] != '\0') {
-        FILE *logfp;
-
+    serverLogOpen();
+    if (server.log_fd == -1) {
         /* Test if we are able to open the file. The server will not
          * be able to abort just for this problem later... */
-        logfp = fopen(server.logfile, "a");
-        if (logfp == NULL) {
-            err = sdscatprintf(sdsempty(), "Can't open the log file: %s", strerror(errno));
-            goto loaderr;
-        }
-        fclose(logfp);
+        err = sdscatprintf(sdsempty(), "Can't open the log file: %s", strerror(errno));
+        goto loaderr;
     }
 
     /* Sanity checks. */
@@ -2713,6 +2708,7 @@ static int setConfigDirOption(standardConfig *config, sds *argv, int argc, const
         *err = strerror(errno);
         return 0;
     }
+    if (server.logfile[0] != '\0') serverLogOpen();
     return 1;
 }
 

src/debug.c

@@ -1607,15 +1607,12 @@ void logRegisters(ucontext_t *uc) {
  *
  * Close it with closeDirectLogFiledes(). */
 int openDirectLogFiledes(void) {
-    int log_to_stdout = server.logfile[0] == '\0';
-    int fd = log_to_stdout ? STDOUT_FILENO : open(server.logfile, O_APPEND | O_CREAT | O_WRONLY, 0644);
-    return fd;
+    return server.log_fd;
 }
 
 /* Used to close what closeDirectLogFiledes() returns. */
 void closeDirectLogFiledes(int fd) {
-    int log_to_stdout = server.logfile[0] == '\0';
-    if (!log_to_stdout) close(fd);
+    UNUSED(fd);
 }
 
 #if defined(HAVE_BACKTRACE) && defined(__linux__)

src/server.c

@@ -108,26 +108,34 @@ const char *replstateToString(int replstate);
  * function of the server may be called from other threads. */
 void nolocks_localtime(struct tm *tmp, time_t t, time_t tz, int dst);
 
+void serverLogOpen(void) {
+    if (server.log_fd != -1 && server.log_fd != STDOUT_FILENO) close(server.log_fd);
+
+    if (server.logfile[0] != '\0') {
+        server.log_fd = open(server.logfile, O_APPEND | O_CREAT | O_WRONLY, 0644);
+    } else {
+        server.log_fd = STDOUT_FILENO;
+    }
+}
+
 /* Low level logging. To use only for very big messages, otherwise
  * serverLog() is to prefer. */
 void serverLogRaw(int level, const char *msg) {
     const int syslogLevelMap[] = {LOG_DEBUG, LOG_INFO, LOG_NOTICE, LOG_WARNING};
     const char *c = ".-*#";
-    FILE *fp;
     char buf[64];
     int rawmode = (level & LL_RAW);
-    int log_to_stdout = server.logfile[0] == '\0';
 
     level &= 0xff; /* clear flags */
     if (level < server.verbosity) return;
 
-    fp = log_to_stdout ? stdout : fopen(server.logfile, "a");
-    if (!fp) return;
+    if (server.log_fd == -1) serverLogOpen();
+    if (server.log_fd == -1) return;
 
+    ssize_t nwritten;
     if (rawmode) {
-        fprintf(fp, "%s", msg);
+        nwritten = write(server.log_fd, msg, strlen(msg));
     } else {
-        int off;
         struct timeval tv;
         int role_char;
         pid_t pid = getpid();
@@ -136,20 +144,28 @@ void serverLogRaw(int level, const char *msg) {
         gettimeofday(&tv, NULL);
         struct tm tm;
         nolocks_localtime(&tm, tv.tv_sec, server.timezone, daylight_active);
-        off = strftime(buf, sizeof(buf), "%d %b %Y %H:%M:%S.", &tm);
-        snprintf(buf + off, sizeof(buf) - off, "%03d", (int)tv.tv_usec / 1000);
+
         if (server.sentinel_mode) {
             role_char = 'X'; /* Sentinel. */
         } else if (pid != server.pid) {
             role_char = 'C'; /* RDB / AOF writing child. */
         } else {
             role_char = (server.primary_host ? 'S' : 'M'); /* replica or Primary. */
         }
-        fprintf(fp, "%d:%c %s %c %s\n", (int)getpid(), role_char, buf, c[level], msg);
+
+        size_t len = snprintf(buf, sizeof(buf), "%d:%c ", (int)pid, role_char);
+        len += strftime(buf + len, sizeof(buf) - len, "%d %b %Y %H:%M:%S.", &tm);
+        len += snprintf(buf + len, sizeof(buf) - len, "%03d %c ", (int)tv.tv_usec / 1000, c[level]);
+
+        char newline[] = "\n";
+
+        struct iovec iov[3] = {{.iov_base = (void *)buf, .iov_len = len},
+                               {.iov_base = (void *)msg, .iov_len = strlen(msg)},
+                               {.iov_base = (void *)newline, strlen(newline)}};
+        nwritten = writev(server.log_fd, iov, 3);
     }
-    fflush(fp);
+    UNUSED(nwritten);
 
-    if (!log_to_stdout) fclose(fp);
     if (server.syslog_enabled) syslog(syslogLevelMap[level], "%s", msg);
 }
 
@@ -171,12 +187,14 @@ void _serverLog(int level, const char *fmt, ...) {
    See serverLogFromHandler. */
 void serverLogRawFromHandler(int level, const char *msg) {
     int fd;
-    int log_to_stdout = server.logfile[0] == '\0';
     char buf[64];
 
-    if ((level & 0xff) < server.verbosity || (log_to_stdout && server.daemonize)) return;
-    fd = log_to_stdout ? STDOUT_FILENO : open(server.logfile, O_APPEND | O_CREAT | O_WRONLY, 0644);
-    if (fd == -1) return;
+    if ((level & 0xff) < server.verbosity || (server.log_fd == STDOUT_FILENO && server.daemonize)) return;
+
+    if (server.log_fd == -1) serverLogOpen();
+    if (server.log_fd == -1) return;
+
+    fd = server.log_fd;
     if (level & LL_RAW) {
         if (write(fd, msg, strlen(msg)) == -1) goto err;
     } else {
@@ -190,7 +208,7 @@ void serverLogRawFromHandler(int level, const char *msg) {
         if (write(fd, "\n", 1) == -1) goto err;
     }
 err:
-    if (!log_to_stdout) close(fd);
+    return;
 }
 
 /* An async-signal-safe version of serverLog. if LL_RAW is not included in level flags,
@@ -1980,6 +1998,7 @@ void initServerConfig(void) {
     server.runid[CONFIG_RUN_ID_SIZE] = '\0';
     changeReplicationId();
     clearReplicationId2();
+    server.log_fd = -1;
     server.hz = CONFIG_DEFAULT_HZ;   /* Initialize it ASAP, even if it may get
                                         updated later after loading the config.
                                         This value may be used before the server
@@ -6863,6 +6882,9 @@ int main(int argc, char **argv) {
     }
     if (server.sentinel_mode) sentinelCheckConfigFile();
 
+    /* Make sure that after the configuration is loaded and before printing the logs. */
+    if (server.logfile[0] == '\0') server.log_fd = STDOUT_FILENO;
+
         /* Do system checks */
 #ifdef __linux__
     linuxMemoryWarnings();

src/server.h

@@ -1967,6 +1967,7 @@ struct valkeyServer {
     int replication_allowed;      /* Are we allowed to replicate? */
     /* Logging */
     char *logfile;         /* Path of log file */
+    int log_fd;            /* File descriptor of currently log file. */
     int syslog_enabled;    /* Is syslog enabled? */
     char *syslog_ident;    /* Syslog ident */
     int syslog_facility;   /* Syslog facility */
@@ -3283,6 +3284,7 @@ void serverLogFromHandler(int level, const char *fmt, ...) __attribute__((format
 void serverLogFromHandler(int level, const char *fmt, ...);
 void _serverLog(int level, const char *fmt, ...);
 #endif
+void serverLogOpen(void);
 void serverLogRaw(int level, const char *msg);
 void serverLogRawFromHandler(int level, const char *msg);
 void usage(void);