libcephfs_proxy: avoid libc buffering for logging

Instead of using printf() for writing loggin information, which gets
buffered by libc when the destination is not a terminal, we use a direct
write to the standard output to avoid this buffering.

Signed-off-by: Xavi Hernandez <xhernandez@gmail.com>

diff --git a/src/libcephfs_proxy/libcephfsd.c b/src/libcephfs_proxy/libcephfsd.c
index b48e88b338b83341a9f5a5ce1ab7e5a2ad9bf68f..2248caca17a60aaeb0651f14fe05d3ea85f65e10 100644 (file)
--- a/src/libcephfs_proxy/libcephfsd.c
+++ b/src/libcephfs_proxy/libcephfsd.c
@@ -2,8 +2,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <sys/uio.h>
 #include <getopt.h>
 #include <endian.h>
+#include <string.h>
+#include <stdarg.h>
 
 #include "include/cephfs/libcephfs.h"
 
@@ -1825,10 +1828,54 @@ static int32_t server_start(proxy_manager_t *manager)
                                 accept_connection, check_stop);
 }
 
+static void log_format(struct iovec *iov, char *buffer, size_t size,
+                      const char *fmt, const char *err, ...)
+{
+       va_list args;
+       int32_t len;
+
+       va_start(args, err);
+       len = vsnprintf(buffer, size, fmt, args);
+       va_end(args);
+
+       if (len < 0) {
+               iov->iov_base = (void *)err;
+               iov->iov_len = strlen(err);
+       } else {
+               if (len >= size) {
+                       memcpy(buffer + size - 6, "[...]", 6);
+                       len = size - 1;
+               }
+
+               iov->iov_base = buffer;
+               iov->iov_len = len;
+       }
+}
+
 static void log_print(proxy_log_handler_t *handler, int32_t level, int32_t err,
                      const char *msg)
 {
-       printf("[%d] %s\n", level, msg);
+       static const char level_chars[] = "CEWID";
+
+       char emsg[256];
+       char header[8];
+       struct iovec iov[3];
+
+       log_format(&iov[0], header, sizeof(header), "[%c] ", "[?] ",
+                  level_chars[level]);
+
+       iov[1].iov_base = (void *)msg;
+       iov[1].iov_len = strlen(msg);
+
+       if (err != 0) {
+               log_format(&iov[2], emsg, sizeof(emsg), " (error %d: %s)\n",
+                          " (error ?)\n", err, strerror(err));
+       } else {
+               iov[2].iov_base = "\n";
+               iov[2].iov_len = 1;
+       }
+
+       writev(STDOUT_FILENO, iov, 3);
 }
 
 static struct option main_opts[] = {