vlib: add nosyslog unix option

The "nosyslog" option disables syslog just like the "interactive" mode
but can be used together with "nodaemon".

This is useful for when VPP is running under a process supervisor like
runit or daemontools that pipe the stdout/stderr to a dedicated logger
service.

Type: feature

Change-Id: Ic4287338d6836fea9f3eabdcf960dc1f51875dd1
Signed-off-by: Ruslan Babayev <ruslan@babayev.com>

3 files changed, 24 insertions, 3 deletions

diff --git a/docs/gettingstarted/users/configuring/startup.rst b/docs/gettingstarted/users/configuring/startup.rst
index f80d55c03df..69d6ee5e3ea 100644
--- a/docs/gettingstarted/users/configuring/startup.rst
+++ b/docs/gettingstarted/users/configuring/startup.rst
@@ -123,6 +123,18 @@ applications from a process monitor. Set by default in the default
 
    nodaemon
 
+nosyslog
+^^^^^^^^
+
+Disable syslog and log errors to stderr instead. Typical when invoking
+VPP applications from a process monitor like runit or daemontools that
+pipe service's output to a dedicated log service, which will typically
+attach a timestamp and rotate the logs as necessary.
+
+.. code-block:: console
+
+   nosyslog
+
 interactive
 ^^^^^^^^^^^
 
diff --git a/src/vlib/unix/main.c b/src/vlib/unix/main.c
index 90601d7bc41..0f9068c67c3 100755
--- a/src/vlib/unix/main.c
+++ b/src/vlib/unix/main.c
@@ -239,8 +239,8 @@ unix_error_handler (void *arg, u8 * msg, int msg_len)
 {
   unix_main_t *um = arg;
 
-  /* Echo to stderr when interactive. */
-  if (um->flags & UNIX_FLAG_INTERACTIVE)
+  /* Echo to stderr when interactive or syslog is disabled. */
+  if (um->flags & (UNIX_FLAG_INTERACTIVE | UNIX_FLAG_NOSYSLOG))
     {
       CLIB_UNUSED (int r) = write (2, msg, msg_len);
     }
@@ -400,6 +400,8 @@ unix_config (vlib_main_t * vm, unformat_input_t * input)
 	um->flags |= UNIX_FLAG_INTERACTIVE;
       else if (unformat (input, "nodaemon"))
 	um->flags |= UNIX_FLAG_NODAEMON;
+      else if (unformat (input, "nosyslog"))
+	um->flags |= UNIX_FLAG_NOSYSLOG;
       else if (unformat (input, "cli-prompt %s", &cli_prompt))
 	vlib_unix_cli_set_prompt (cli_prompt);
       else
@@ -529,7 +531,7 @@ unix_config (vlib_main_t * vm, unformat_input_t * input)
 	}
     }
 
-  if (!(um->flags & UNIX_FLAG_INTERACTIVE))
+  if (!(um->flags & (UNIX_FLAG_INTERACTIVE | UNIX_FLAG_NOSYSLOG)))
     {
       openlog (vm->name, LOG_CONS | LOG_PERROR | LOG_PID, LOG_DAEMON);
       clib_error_register_handler (unix_error_handler, um);
@@ -569,6 +571,11 @@ unix_config (vlib_main_t * vm, unformat_input_t * input)
  * Do not fork or background the VPP process. Typically used when invoking
  * VPP applications from a process monitor.
  *
+ * @cfgcmd{nosyslog}
+ * Do not send e.g. clib_warning(...) output to syslog. Used
+ * when invoking VPP applications from a process monitor which
+ * pipe stdout/stderr to a dedicated logger service.
+ *
  * @cfgcmd{exec, <filename>}
  * @par <code>startup-config &lt;filename&gt;</code>
  * Read startup operational configuration from @c filename.
diff --git a/src/vlib/unix/unix.h b/src/vlib/unix/unix.h
index e71b0bac6a5..9fa95a0c1d6 100644
--- a/src/vlib/unix/unix.h
+++ b/src/vlib/unix/unix.h
@@ -59,6 +59,8 @@ typedef struct
   /* Run interactively or as daemon (background process). */
 #define UNIX_FLAG_INTERACTIVE (1 << 0)
 #define UNIX_FLAG_NODAEMON (1 << 1)
+#define UNIX_FLAG_NOSYSLOG (1 << 2)
+
 
   /* CLI listen socket. */
   clib_socket_t cli_listen_socket;