Fix messages to stdout/stderr getting truncated

The maximum zlog message length is 1024 including timestamp et cetera.

With very long messages over 1024 characters, these get wrapped into multiple chunks correctly, but then the "WARNING: child blah said into blah" gets added and the zlog call truncates the messages using "..." at the end, resulting in a couple dozen bytes getting lost.

This change calculates the length at which wrapping needs to occur correctly.

Author: dzuelke

sapi/fpm/fpm/fpm_stdio.c

@@ -119,6 +119,8 @@ static void fpm_stdio_child_said(struct fpm_event_s *ev, short which, void *arg)
 	int is_last_message = 0;
 	int in_buf = 0;
 	int res;
+	char fmt_buf[max_buf_size];
+	int fmt_len = 0;
 
 	if (!arg) {
 		return;
@@ -130,10 +132,15 @@ static void fpm_stdio_child_said(struct fpm_event_s *ev, short which, void *arg)
 	} else {
 		event = &child->ev_stderr;
 	}
+	
+	/* calculate how long the "child 123 said into ..." prefix is so we can subtract its length from max_buf_size */
+	fmt_len = snprintf(fmt_buf, max_buf_size, "[pool %s] child %d said into %s: \"%%s\"%%s", child->wp->config->name, (int) child->pid, is_stdout ? "stdout" : "stderr");
+	/* subtract two characters each for the two "%s", then add character counts for "WARNING: " added by zlog and "[11-Feb-2015 15:58:20] " added by zlog; we're ignoring the potential extra length in log_level=DEBUG */
+	fmt_len = fmt_len - 2 - 2 + 9 + 23; 
 
 	while (fifo_in || fifo_out) {
 		if (fifo_in) {
-			res = read(fd, buf + in_buf, max_buf_size - 1 - in_buf);
+			res = read(fd, buf + in_buf, max_buf_size - fmt_len - 1 - in_buf);
 			if (res <= 0) { /* no data */
 				fifo_in = 0;
 				if (res < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
@@ -171,7 +178,7 @@ static void fpm_stdio_child_said(struct fpm_event_s *ev, short which, void *arg)
 				/* FIXME: there might be binary data */
 
 				/* we should print if no more space in the buffer */
-				if (in_buf == max_buf_size - 1) {
+				if (in_buf == max_buf_size - fmt_len - 1) {
 					should_print = 1;
 				}
 
@@ -187,8 +194,7 @@ static void fpm_stdio_child_said(struct fpm_event_s *ev, short which, void *arg)
 						*nl = '\0';
 					}
 
-					zlog(ZLOG_WARNING, "[pool %s] child %d said into %s: \"%s\"%s", child->wp->config->name,
-					  (int) child->pid, is_stdout ? "stdout" : "stderr", buf, is_last_message ? ", pipe is closed" : "");
+					zlog(ZLOG_WARNING, fmt_buf, buf, is_last_message ? ", pipe is closed" : "");
 
 					if (nl) {
 						int out_buf = 1 + nl - buf;