avoid runaway memory consumtion on unlimited open file limits

Usually ulimit -n is has sane values somewhere between 1000 and 10000. Some
container managers like docker set higher values, so naemon might end up
with ulimit of millions which just wastes memory.
If a single worker hits the open file limit, simply start more worker.

Author: sni

lib/iobroker.c

@@ -140,6 +140,10 @@ struct iobroker_set *iobroker_create(void)
 	}
 
 	iobs->max_fds = iobroker_max_usable_fds();
+	/* add sane max limit, if ulimit is set to unlimited or a very high value we
+	 * don't want to waste memory for nothing */
+	if (iobs->max_fds > MAX_FD_LIMIT)
+		iobs->max_fds = MAX_FD_LIMIT;
 	iobs->iobroker_fds = calloc(iobs->max_fds, sizeof(iobroker_fd *));
 	if (!iobs->iobroker_fds) {
 		goto error_out;

lib/lnae-utils.h

@@ -88,6 +88,11 @@
 # define veclen ARRAY_SIZE
 #endif
 
+/* sets a limit for max open files if ulimit is set to unlimited or a unusual high value */
+#ifndef MAX_FD_LIMIT
+#define MAX_FD_LIMIT 100000
+#endif
+
 #ifndef offsetof
 /** standard offsetof macro */
 # define offsetof(t, f) ((unsigned long)&((t *)0)->f)

lib/runcmd.c

@@ -69,7 +69,6 @@ static int maxfd = 0;
 # endif /* _SC_OPEN_MAX */
 #endif /* OPEN_MAX */
 
-
 const char *runcmd_strerror(int code)
 {
 	switch (code) {
@@ -424,6 +423,11 @@ void runcmd_init(void)
 	}
 #endif
 
+	/* add sane max limit, if ulimit is set to unlimited or a very high value we
+	 * don't want to waste memory for nothing */
+	if (maxfd > MAX_FD_LIMIT)
+		maxfd = MAX_FD_LIMIT;
+
 	/* reset pipe handling so child processes can use shell pipes */
 	signal(SIGPIPE, SIG_DFL);