changeset 30409:0852161588c6

osutil: implement setprocname to set process title for some platforms This patch adds a simple setprocname method to osutil. The operation is not defined by any standard and is platform-specific, the current implementation tries to cover some major platforms (ex. Linux, OS X, FreeBSD) that is relatively easy to support. Other platforms (Windows [4], other BSDs, ...) can be added in the future. The current implementation supports two methods to change process title: a. setproctitle if available (works in FreeBSD). b. rewrite argv in place (works in Linux [1] and Mac OS X). [2] [3] [1]: Linux has "prctl(PR_SET_NAME, ...)" but 1) it has 16-byte limit, which is too small; 2) it is not quite equivalent to what we want - it changes "/proc/self/comm", not "/proc/self/cmdline" - "comm" change won't show up in "ps" output unless "-o comm" is used. [2]: The implementation does not rewrite the **environ buffer like some other implementations do, just to make the code simpler and safer. However, this also means the buffer size we can rewrite is significantly shorter. If we are really greedy and want the "environ" space, we can change the implementation later. [3]: It requires a CPython private API: Py_GetArgcArgv to get the original argv. Unfortunately Python 3 makes a copy of argv and returns the wchar_t version, so it is not supported for now. (if we really want to, we could count backwards from "char **environ", given known argc and argv, not sure if that's a good idea - probably not) [4]: The feature is aimed to make it easier for forked command server processes to show what they are doing. Since Windows does not support fork(), despite it's a major platform, its support is not added in this patch.
author Jun Wu <quark@fb.com>
date Fri, 11 Nov 2016 21:11:17 +0000
parents ce9a3033c118
children 7a5d6e2fd2d5
files mercurial/osutil.c
diffstat 1 files changed, 61 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/mercurial/osutil.c	Fri Nov 11 20:45:40 2016 +0000
+++ b/mercurial/osutil.c	Fri Nov 11 21:11:17 2016 +0000
@@ -727,6 +727,63 @@
 }
 
 #endif /* CMSG_LEN */
+
+#if defined(HAVE_SETPROCTITLE)
+/* setproctitle is the first choice - available in FreeBSD */
+#define SETPROCNAME_USE_SETPROCTITLE
+#elif (defined(__linux__) || defined(__APPLE__)) && PY_MAJOR_VERSION == 2
+/* rewrite the argv buffer in place - works in Linux and OS X. Py_GetArgcArgv
+ * in Python 3 returns the copied wchar_t **argv, thus unsupported. */
+#define SETPROCNAME_USE_ARGVREWRITE
+#else
+#define SETPROCNAME_USE_NONE
+#endif
+
+#ifndef SETPROCNAME_USE_NONE
+static PyObject *setprocname(PyObject *self, PyObject *args)
+{
+	const char *name = NULL;
+	if (!PyArg_ParseTuple(args, "s", &name))
+		return NULL;
+
+#if defined(SETPROCNAME_USE_SETPROCTITLE)
+	setproctitle("%s", name);
+#elif defined(SETPROCNAME_USE_ARGVREWRITE)
+	{
+		static char *argvstart = NULL;
+		static size_t argvsize = 0;
+		if (argvstart == NULL) {
+			int argc = 0, i;
+			char **argv = NULL;
+			char *argvend;
+			extern void Py_GetArgcArgv(int *argc, char ***argv);
+			Py_GetArgcArgv(&argc, &argv);
+
+			/* Check the memory we can use. Typically, argv[i] and
+			 * argv[i + 1] are continuous. */
+			argvend = argvstart = argv[0];
+			for (i = 0; i < argc; ++i) {
+				if (argv[i] > argvend || argv[i] < argvstart)
+					break; /* not continuous */
+				size_t len = strlen(argv[i]);
+				argvend = argv[i] + len + 1 /* '\0' */;
+			}
+			if (argvend > argvstart) /* sanity check */
+				argvsize = argvend - argvstart;
+		}
+
+		if (argvstart && argvsize > 1) {
+			int n = snprintf(argvstart, argvsize, "%s", name);
+			if (n >= 0 && (size_t)n < argvsize)
+				memset(argvstart + n, 0, argvsize - n);
+		}
+	}
+#endif
+
+	Py_RETURN_NONE;
+}
+#endif /* ndef SETPROCNAME_USE_NONE */
+
 #endif /* ndef _WIN32 */
 
 static PyObject *listdir(PyObject *self, PyObject *args, PyObject *kwargs)
@@ -899,7 +956,11 @@
 	{"recvfds", (PyCFunction)recvfds, METH_VARARGS,
 	 "receive list of file descriptors via socket\n"},
 #endif
+#ifndef SETPROCNAME_USE_NONE
+	{"setprocname", (PyCFunction)setprocname, METH_VARARGS,
+	 "set process title (best-effort)\n"},
 #endif
+#endif /* ndef _WIN32 */
 #ifdef __APPLE__
 	{
 		"isgui", (PyCFunction)isgui, METH_NOARGS,