1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
|
/* Copyright (c) 2008, 2011, Oracle and/or its affiliates
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/*
Utility program that encapsulates process creation, monitoring
and bulletproof process cleanup
Usage:
safe_process [options to safe_process] -- progname arg1 ... argn
To safeguard mysqld you would invoke safe_process with a few options
for safe_process itself followed by a double dash to indicate start
of the command line for the program you really want to start
$> safe_process --output=output.log -- mysqld --datadir=var/data1 ...
This would redirect output to output.log and then start mysqld,
once it has done that it will continue to monitor the child as well
as the parent.
The safe_process then checks the follwing things:
1. Child exits, propagate the childs return code to the parent
by exiting with the same return code as the child.
2. Parent dies, immediately kill the child and exit, thus the
parent does not need to properly cleanup any child, it is handled
automatically.
3. Signal's recieced by the process will trigger same action as 2)
*/
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <unistd.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
int verbose= 0;
int terminated= 0;
pid_t child_pid= -1;
char safe_process_name[32]= {0};
static void message(const char* fmt, ...)
{
if (!verbose)
return;
va_list args;
fprintf(stderr, "%s: ", safe_process_name);
va_start(args, fmt);
vfprintf(stderr, fmt, args);
fprintf(stderr, "\n");
va_end(args);
fflush(stderr);
}
static void die(const char* fmt, ...)
{
va_list args;
fprintf(stderr, "%s: FATAL ERROR, ", safe_process_name);
va_start(args, fmt);
vfprintf(stderr, fmt, args);
fprintf(stderr, "\n");
va_end(args);
if (int last_err= errno)
fprintf(stderr, "error: %d, %s\n", last_err, strerror(last_err));
exit(6);
}
static void kill_child(bool was_killed)
{
int status= 0;
message("Killing child: %d", child_pid);
// Terminate whole process group
if (! was_killed)
kill(-child_pid, SIGKILL);
pid_t ret_pid= waitpid(child_pid, &status, 0);
if (ret_pid == child_pid)
{
int exit_code= 1;
if (WIFEXITED(status))
{
// Process has exited, collect return status
exit_code= WEXITSTATUS(status);
message("Child exit: %d", exit_code);
// Exit with exit status of the child
exit(exit_code);
}
if (WIFSIGNALED(status))
message("Child killed by signal: %d", WTERMSIG(status));
exit(exit_code);
}
exit(5);
}
extern "C" void handle_abort(int sig)
{
message("Got signal %d, child_pid: %d, sending ABRT", sig, child_pid);
if (child_pid > 0) {
kill (-child_pid, SIGABRT); // Don't wait for it to terminate
}
}
extern "C" void handle_signal(int sig)
{
message("Got signal %d, child_pid: %d", sig, child_pid);
terminated= 1;
if (child_pid > 0)
kill_child(sig == SIGCHLD);
// Ignore further signals
signal(SIGTERM, SIG_IGN);
signal(SIGINT, SIG_IGN);
// Continune execution, allow the child to be started and
// finally terminated by monitor loop
}
int main(int argc, char* const argv[] )
{
char* const* child_argv= 0;
pid_t own_pid= getpid();
pid_t parent_pid= getppid();
bool nocore = false;
/* Install signal handlers */
signal(SIGTERM, handle_signal);
signal(SIGINT, handle_signal);
signal(SIGCHLD, handle_signal);
signal(SIGABRT, handle_abort);
sprintf(safe_process_name, "safe_process[%ld]", (long) own_pid);
message("Started");
/* Parse arguments */
for (int i= 1; i < argc; i++) {
const char* arg= argv[i];
if (strcmp(arg, "--") == 0 && strlen(arg) == 2) {
/* Got the "--" delimiter */
if (i >= argc)
die("No real args -> nothing to do");
child_argv= &argv[i+1];
break;
} else {
if ( strcmp(arg, "--verbose") == 0 )
verbose++;
else if ( strncmp(arg, "--parent-pid", 12) == 0 )
{
/* Override parent_pid with a value provided by user */
const char* start;
if ((start= strstr(arg, "=")) == NULL)
die("Could not find start of option value in '%s'", arg);
start++; /* Step past = */
if ((parent_pid= atoi(start)) == 0)
die("Invalid value '%s' passed to --parent-id", start);
}
else if ( strcmp(arg, "--nocore") == 0 )
{
nocore = true; // Don't allow the process to dump core
}
else if ( strncmp (arg, "--env ", 6) == 0 )
{
putenv(strdup(arg+6));
}
else
die("Unknown option: %s", arg);
}
}
if (!child_argv || *child_argv == 0)
die("nothing to do");
message("parent_pid: %d", parent_pid);
if (parent_pid == own_pid)
die("parent_pid is equal to own pid!");
char buf;
int pfd[2];
if (pipe(pfd) == -1)
die("Failed to create pipe");
/* Create the child process */
while((child_pid= fork()) == -1)
{
message("fork failed");
sleep(1);
}
if (child_pid == 0)
{
close(pfd[0]); // Close unused read end
// Use default signal handlers in child
signal(SIGTERM, SIG_DFL);
signal(SIGINT, SIG_DFL);
signal(SIGCHLD, SIG_DFL);
// Make this process it's own process group to be able to kill
// it and any childs(that hasn't changed group themself)
setpgid(0, 0);
if (nocore)
{
struct rlimit corelim = { 0, 0 };
if (setrlimit (RLIMIT_CORE, &corelim) < 0)
{
message("setrlimit failed, errno=%d", errno);
}
}
// Signal that child is ready
buf= 37;
if ((write(pfd[1], &buf, 1)) < 1)
die("Failed to signal that child is ready");
// Close write end
close(pfd[1]);
execvp(child_argv[0], child_argv);
die("Failed to exec child");
}
close(pfd[1]); // Close unused write end
// Wait for child to signal it's ready
if ((read(pfd[0], &buf, 1)) < 1)
die("Failed to read signal from child");
if (buf != 37)
die("Didn't get 37 from pipe");
close(pfd[0]); // Close read end
/* Monitor loop */
message("Started child %d, terminated: %d", child_pid, terminated);
while (!terminated)
{
// Check if parent is still alive
if (kill(parent_pid, 0) != 0)
{
message("Parent is not alive anymore");
break;
}
/* Wait for parent or child to die */
sleep(1);
}
kill_child(0);
return 4;
}
|