From 40f0707cd9d105203c2b8b97a955b57aca426f13 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Tue, 19 Jan 2010 15:00:56 -0800
Subject: [PATCH] daemon: Make --monitor process change its process title.

When --monitor is used, administrators sometimes become confused about the
presence of two copies of each process.  This commit attempts to clarify
the situation by making the monitoring process change its process name, as
seen in /proc/$pid/cmdline and in "ps", to clearly indicate what is going
on.

CC: Dan Wendlandt <dan@nicira.com>
---
 extras/ezio/ezio-term.c    |   1 +
 extras/ezio/ovs-switchui.c |   1 +
 lib/command-line.c         | 111 ++++++++++++++++++++++++++++++++++++-
 lib/command-line.h         |   7 ++-
 lib/daemon.c               |  23 +++++---
 ovsdb/ovsdb-client.c       |   1 +
 ovsdb/ovsdb-server.c       |   1 +
 tests/test-jsonrpc.c       |   3 +-
 tests/test-timeval.c       |   2 +
 utilities/ovs-controller.c |   1 +
 utilities/ovs-discover.c   |   1 +
 utilities/ovs-openflowd.c  |   1 +
 vswitchd/ovs-brcompatd.c   |   1 +
 vswitchd/ovs-vswitchd.c    |   1 +
 14 files changed, 144 insertions(+), 11 deletions(-)

diff --git a/extras/ezio/ezio-term.c b/extras/ezio/ezio-term.c
index 8f12a7bc..cedc5c96 100644
--- a/extras/ezio/ezio-term.c
+++ b/extras/ezio/ezio-term.c
@@ -96,6 +96,7 @@ main(int argc, char *argv[])
     int retval;
     int i;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/extras/ezio/ovs-switchui.c b/extras/ezio/ovs-switchui.c
index 864e34c1..31e37f68 100644
--- a/extras/ezio/ovs-switchui.c
+++ b/extras/ezio/ovs-switchui.c
@@ -144,6 +144,7 @@ main(int argc, char *argv[])
     long long int last_key_time = 0;
     int repeat_count = 0;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/lib/command-line.c b/lib/command-line.c
index a2a43a1c..2f997984 100644
--- a/lib/command-line.c
+++ b/lib/command-line.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,6 @@
 #include <limits.h>
 #include <stdlib.h>
 #include "util.h"
-#include "vlog.h"
 
 /* Given the GNU-style long options in 'options', returns a string that may be
  * passed to getopt() with the corresponding short options.  The caller is
@@ -87,3 +86,111 @@ run_command(int argc, char *argv[], const struct command commands[])
 
     ovs_fatal(0, "unknown command '%s'; use --help for help", argv[0]);
 }
+
+/* Process title. */
+
+#ifdef __linux__
+static char *argv_start;       /* Start of command-line arguments in memory. */
+static size_t argv_size;       /* Number of bytes of command-line arguments. */
+static char *saved_proctitle;  /* Saved command-line arguments. */
+
+/* Prepares the process so that proctitle_set() can later succeed.
+ *
+ * This modifies the argv[] array so that it no longer points into the memory
+ * that it originally does.  Later, proctitle_set() might overwrite that
+ * memory.  That means that this function should be called before anything else
+ * that accesses the process's argv[] array.  Ideally, it should be called
+ * before anything else, period, at the very beginning of program
+ * execution.  */
+void
+proctitle_init(int argc, char **argv)
+{
+    int i;
+
+    if (!argc || !argv[0]) {
+        /* This situation should never occur, but... */
+        return;
+    }
+
+    /* Specialized version of first loop iteration below. */
+    argv_start = argv[0];
+    argv_size = strlen(argv[0]) + 1;
+    argv[0] = xstrdup(argv[0]);
+
+    for (i = 1; i < argc; i++) {
+        size_t size = strlen(argv[i]) + 1;
+
+        /* Add (argv[i], strlen(argv[i])+1) to (argv_start, argv_size). */
+        if (argv[i] + size == argv_start) {
+            /* Arguments grow downward in memory. */
+            argv_start -= size;
+            argv_size += size;
+        } else if (argv[i] == argv_start + argv_size) {
+            /* Arguments grow upward in memory. */
+            argv_size += size;
+        } else {
+            /* Arguments not contiguous.  (Is this really Linux?) */
+        }
+
+        /* Copy out the old argument so we can reuse the space. */
+        argv[i] = xstrdup(argv[i]);
+    }
+}
+
+/* Changes the name of the process, as shown by "ps", to 'format', which is
+ * formatted as if by printf(). */
+void
+proctitle_set(const char *format, ...)
+{
+    va_list args;
+    int n;
+
+    if (!argv_start || argv_size < 8) {
+        return;
+    }
+
+    if (!saved_proctitle) {
+        saved_proctitle = xmemdup(argv_start, argv_size);
+    }
+
+    va_start(args, format);
+    n = vsnprintf(argv_start, argv_size, format, args);
+    if (n >= argv_size) {
+        /* The name is too long, so add an ellipsis at the end. */
+        strcpy(&argv_start[argv_size - 4], "...");
+    } else {
+        /* Fill the extra space with null bytes, so that trailing bytes don't
+         * show up in the command line. */
+        memset(&argv_start[n], '\0', argv_size - n);
+    }
+    va_end(args);
+}
+
+/* Restores the process's original command line, as seen by "ps". */
+void
+proctitle_restore(void)
+{
+    if (saved_proctitle) {
+        memcpy(argv_start, saved_proctitle, argv_size);
+        free(saved_proctitle);
+        saved_proctitle = NULL;
+    }
+}
+#else  /* !__linux__ */
+/* Stubs that don't do anything on non-Linux systems. */
+
+void
+proctitle_init(int argc UNUSED, char **argv UNUSED)
+{
+}
+
+void
+proctitle_set(const char *format UNUSED, ...)
+{
+}
+
+void
+proctitle_restore(void)
+{
+}
+#endif  /* !__linux__ */
diff --git a/lib/command-line.h b/lib/command-line.h
index bc2071ef..1c880033 100644
--- a/lib/command-line.h
+++ b/lib/command-line.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,4 +33,9 @@ struct command {
 char *long_options_to_short_options(const struct option *options);
 void run_command(int argc, char *argv[], const struct command[]);
 
+void proctitle_init(int argc, char **argv);
+void proctitle_set(const char *, ...)
+    PRINTF_FORMAT(1, 2);
+void proctitle_restore(void);
+
 #endif /* command-line.h */
diff --git a/lib/daemon.c b/lib/daemon.c
index 86291146..140e0f72 100644
--- a/lib/daemon.c
+++ b/lib/daemon.c
@@ -22,6 +22,7 @@
 #include <string.h>
 #include <sys/wait.h>
 #include <unistd.h>
+#include "command-line.h"
 #include "fatal-signal.h"
 #include "dirs.h"
 #include "lockfile.h"
@@ -325,13 +326,19 @@ monitor_daemon(pid_t daemon_pid)
     /* XXX Should limit the rate at which we restart the daemon. */
     /* XXX Should log daemon's stderr output at startup time. */
     const char *saved_program_name;
+    char *status_msg;
 
     saved_program_name = program_name;
     program_name = xasprintf("monitor(%s)", program_name);
+    status_msg = xstrdup("healthy");
     for (;;) {
         int retval;
         int status;
 
+        proctitle_set("%s: monitoring pid %lu (%s)",
+                      saved_program_name, (unsigned long int) daemon_pid,
+                      status_msg);
+
         do {
             retval = waitpid(daemon_pid, &status, 0);
         } while (retval == -1 && errno == EINTR);
@@ -339,25 +346,27 @@ monitor_daemon(pid_t daemon_pid)
         if (retval == -1) {
             ovs_fatal(errno, "waitpid failed");
         } else if (retval == daemon_pid) {
-            char *status_msg = process_status_msg(status);
-            if (should_restart(status)) {
-                VLOG_ERR("%s daemon died unexpectedly (%s), restarting",
-                         saved_program_name, status_msg);
-                free(status_msg);
+            char *s = process_status_msg(status);
+            free(status_msg);
+            status_msg = xasprintf("pid %lu died, %s",
+                                   (unsigned long int) daemon_pid, s);
+            free(s);
 
+            if (should_restart(status)) {
+                VLOG_ERR("%s, restarting", status_msg);
                 daemon_pid = fork_and_wait_for_startup(&daemonize_fd);
                 if (!daemon_pid) {
                     break;
                 }
             } else {
-                VLOG_INFO("%s daemon exited normally (%s), exiting",
-                          saved_program_name, status_msg);
+                VLOG_INFO("%s, exiting", status_msg);
                 exit(0);
             }
         }
     }
 
     /* Running in new daemon process. */
+    proctitle_restore();
     free((char *) program_name);
     program_name = saved_program_name;
 }
diff --git a/ovsdb/ovsdb-client.c b/ovsdb/ovsdb-client.c
index baf525d4..02946df6 100644
--- a/ovsdb/ovsdb-client.c
+++ b/ovsdb/ovsdb-client.c
@@ -67,6 +67,7 @@ static void parse_options(int argc, char *argv[]);
 int
 main(int argc, char *argv[])
 {
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/ovsdb/ovsdb-server.c b/ovsdb/ovsdb-server.c
index e3740a36..900f4ecc 100644
--- a/ovsdb/ovsdb-server.c
+++ b/ovsdb/ovsdb-server.c
@@ -71,6 +71,7 @@ main(int argc, char *argv[])
     bool exiting;
     int retval;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/tests/test-jsonrpc.c b/tests/test-jsonrpc.c
index da92cec9..570ae11a 100644
--- a/tests/test-jsonrpc.c
+++ b/tests/test-jsonrpc.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009 Nicira Networks.
+ * Copyright (c) 2009, 2010 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,6 +42,7 @@ static void parse_options(int argc, char *argv[]);
 int
 main(int argc, char *argv[])
 {
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/tests/test-timeval.c b/tests/test-timeval.c
index 7aa6867a..3b39b411 100644
--- a/tests/test-timeval.c
+++ b/tests/test-timeval.c
@@ -24,6 +24,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include "command-line.h"
 #include "daemon.h"
 #include "util.h"
 
@@ -83,6 +84,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
 
diff --git a/utilities/ovs-controller.c b/utilities/ovs-controller.c
index 34198b5a..0497d9a4 100644
--- a/utilities/ovs-controller.c
+++ b/utilities/ovs-controller.c
@@ -82,6 +82,7 @@ main(int argc, char *argv[])
     int retval;
     int i;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/utilities/ovs-discover.c b/utilities/ovs-discover.c
index 8f46b992..dbdd741a 100644
--- a/utilities/ovs-discover.c
+++ b/utilities/ovs-discover.c
@@ -75,6 +75,7 @@ main(int argc, char *argv[])
     int retval;
     int i;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/utilities/ovs-openflowd.c b/utilities/ovs-openflowd.c
index 43cbd6e0..e0cfdc95 100644
--- a/utilities/ovs-openflowd.c
+++ b/utilities/ovs-openflowd.c
@@ -112,6 +112,7 @@ main(int argc, char *argv[])
     int error;
     struct netflow_options nf_options;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/vswitchd/ovs-brcompatd.c b/vswitchd/ovs-brcompatd.c
index 04ee2c06..585ab2c7 100644
--- a/vswitchd/ovs-brcompatd.c
+++ b/vswitchd/ovs-brcompatd.c
@@ -1144,6 +1144,7 @@ main(int argc, char *argv[])
     struct ovsdb_idl *idl;
     int retval;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
diff --git a/vswitchd/ovs-vswitchd.c b/vswitchd/ovs-vswitchd.c
index d9086dc9..ea997b0e 100644
--- a/vswitchd/ovs-vswitchd.c
+++ b/vswitchd/ovs-vswitchd.c
@@ -62,6 +62,7 @@ main(int argc, char *argv[])
     unsigned int idl_seqno;
     int retval;
 
+    proctitle_init(argc, argv);
     set_program_name(argv[0]);
     time_init();
     vlog_init();
-- 
2.30.2