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Add a container monitor process

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Signed-off-by: Mrunal Patel <mrunalp@gmail.com>
This commit is contained in:
Mrunal Patel 2016-08-26 14:00:30 -07:00
parent 4ee041a1c1
commit 530a258376
1 changed files with 98 additions and 0 deletions
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98
conmon/conmon.c Normal file
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#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <errno.h>
#include <glib.h>
#define pexit(fmt, ...) \
do { \
fprintf(stderr, "conmon: " fmt " %m\n", ##__VA_ARGS__); \
exit(EXIT_FAILURE); \
} while (0)
#define nexit(fmt, ...) \
do { \
fprintf(stderr, "conmon: " fmt "\n", ##__VA_ARGS__); \
exit(EXIT_FAILURE); \
} while (0)
#define nexit(fmt, ...) \
do { \
fprintf(stderr, "conmon: " fmt "\n", ##__VA_ARGS__); \
exit(EXIT_FAILURE); \
} while (0)
#define _cleanup_(x) __attribute__((cleanup(x)))
static inline void freep(void *p) {
free(*(void**) p);
}
#define _cleanup_free_ _cleanup_(freep)
int main(int argc, char *argv[])
{
int ret;
const char *cid;
char cmd[128];
GError *err = NULL;
gchar *contents;
int cpid = -1;
int status;
pid_t pid;
if (argc < 2) {
nexit("Run as: conmon <id>");
}
// Get the container id
cid = argv[1];
// Set self as subreaper so we can wait for container process
// and return its exit code.
ret = prctl(PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0);
if (ret != 0) {
pexit("Failed to set as subreaper");
}
snprintf(cmd, 128, "runc create %s --pid-file pidfile", cid);
ret = system(cmd);
if (ret != 0) {
nexit("Failed to create container");
}
// Read the pid so we can wait for the process to exit
g_file_get_contents("pidfile", &contents, NULL, &err);
if (err) {
fprintf(stderr, "Failed to read pidfile: %s\n", err->message);
g_error_free(err);
exit(1);
}
cpid = atoi(contents);
printf("container PID: %d\n", cpid);
while ((pid = waitpid(-1, &status, 0)) > 0) {
printf("PID %d exited\n", pid);
if (pid == cpid) {
_cleanup_free_ char *status_str = NULL;
ret = asprintf(&status_str, "%d", status);
if (ret < 0) {
pexit("Failed to allocate memory for status");
}
g_file_set_contents("exit", status_str, strlen(status_str), &err);
if (err) {
fprintf(stderr, "Failed to write %s to exit file: %s\n", status_str, err->message);
g_error_free(err);
exit(1);
}
break;
}
}
return EXIT_SUCCESS;
}