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retry.c
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retry.c
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/**
* Copyright (C) 2020 Graham Leggett <[email protected]>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <getopt.h>
#include <signal.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sysexits.h>
#include <poll.h>
#include <sys/uio.h>
#include <ctype.h>
#include "config.h"
#define DEFAULT_DELAY "10"
#define DEFAULT_TIMES -1
#define STDIN_FD 0
#define STDOUT_FD 1
#define STDERR_FD 2
#define READ_FD 0
#define WRITE_FD 1
#define OFFSET(X, Y) (X * 2 + Y)
#define PUMPS 2
#define BUFFER_SIZE (100 * 1024)
static struct option long_options[] =
{
{"delay", required_argument, NULL, 'd'},
{"message", required_argument, NULL, 'm'},
{"until", required_argument, NULL, 'u'},
{"while", required_argument, NULL, 'w'},
{"times", required_argument, NULL, 't'},
{"help", no_argument, NULL, 'h'},
{"version", no_argument, NULL, 'v'},
{NULL, 0, NULL, 0}
};
typedef struct pump_t {
struct pollfd *rpollfd;
struct pollfd *wpollfd;
void *base;
size_t len;
off_t offset;
int rfd;
int wfd;
int read_closed:1;
int write_closed:1;
int exit_on_close:1;
int no_close:1;
int send_eof:1;
} pump_t;
static int help(const char *name, const char *msg, int code)
{
const char *n;
n = strrchr(name, '/');
if (!n) {
n = name;
}
else {
n++;
}
fprintf(code ? stderr : stdout,
"%s\n"
"\n"
"NAME\n"
" %s - Repeat command until a criteria is met, usually success.\n"
"\n"
"SYNOPSIS\n"
" %s [-v] [-h] [-u until] [-w while] command ...\n"
"\n"
"DESCRIPTION\n"
"\n"
" The tool repeats the given command until the command is successful,\n"
" backing off with a configurable delay between each attempt.\n"
"\n"
" Retry captures stdin into memory as the data is passed to the repeated\n"
" command, and this captured stdin is then replayed should the command\n"
" be repeated. This makes it possible to embed the retry tool into shell\n"
" pipelines.\n"
"\n"
" Retry captures stdout into memory, and if the command was successful\n"
" stdout is passed on to stdout as normal, while if the command was\n"
" repeated stdout is passed to stderr instead. This ensures that output\n"
" is passed to stdout once and once only.\n"
"\n"
"OPTIONS\n"
" -d seconds, --delay=seconds The number of seconds to back off\n"
" after each attempt. Multiple comma separated\n"
" delays allow subsequent delays to be different,\n"
" with the last delay repeated.\n"
"\n"
" -m message, --message=message A message to include in the notification\n"
" when repeat has backed off. Defaults to the\n"
" command name.\n"
"\n"
" -t times, --times=times The number of times to retry\n"
" the command. By default we try forever.\n"
"\n"
" -u criteria, --until=criteria Keep repeating the command until any one\n"
" of the comma separated criteria is met.\n"
" Options include 'success', 'true', 'fail',\n"
" 'false', an integer or a range of integers.\n"
" Default is 'success'.\n"
"\n"
" -w criteria, --while=criteria Keep repeating the command while any one\n"
" of the comma separated criteria is met.\n"
" Options include 'success', 'true', 'fail',\n"
" 'false', an integer or a range of integers.\n"
"\n"
" -h, --help Display this help message.\n"
"\n"
" -v, --version Display the version number.\n"
"\n"
"RETURN VALUE\n"
" The retry tool returns the return code from the\n"
" command being executed, once the criteria is reached.\n"
"\n"
" If the command was interrupted with a signal, the return\n"
" code is the signal number plus 128.\n"
"\n"
" If the command could not be executed, or if the options\n"
" are invalid, the status 1 is returned.\n"
"\n"
"EXAMPLES\n"
" In this basic example, we repeat the command forever.\n"
"\n"
"\t~$ retry --until=success -- false\n"
"\tretry: 'false' returned 1, backing off for 10 seconds and trying again...\n"
"\tretry: 'false' returned 1, backing off for 10 seconds and trying again...\n"
"\tretry: 'false' returned 1, backing off for 10 seconds and trying again...\n"
"\t^C\n"
"\n"
" In this more complex example, each invocation of curl is\n"
" retried until curl succeeds, at which point stdout is\n"
" passed once and once only to the next element in the\n"
" pipeline.\n"
"\n"
"\t~$ retry -- curl --fail http://localhost/entities | \\\\ \n"
"\tjq ... | \\\\ \n"
"\tretry -- curl --fail -X POST http://localhost/resource | \\\\ \n"
"\tlogger -t resource-init\n"
"\n"
" In this example, we stagger each delay exponentially\n"
" until 64 seconds, which is then repeated until\n"
" interrupted.\n"
"\n"
"\t~$ retry --until=success --delay \"1,2,4,8,16,32,64\" -- false\n"
"\tretry: false returned 1, backing off for 1 second and trying again...\n"
"\tretry: false returned 1, backing off for 2 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 4 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 8 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 16 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 32 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 64 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 64 seconds and trying again...\n"
"\tretry: false returned 1, backing off for 64 seconds and trying again...\n"
"\t^C\n"
"\n"
"AUTHOR\n"
" Graham Leggett <[email protected]>\n"
"", msg ? msg : "", n, n);
return code;
}
static int version()
{
printf(PACKAGE_STRING "\n");
return 0;
}
static int status_match(int status, const char *criteria)
{
int len;
while (criteria) {
const char *next;
char *endptr;
long r1, r2;
next = strchr(criteria, ',');
if (next) {
len = next - criteria;
}
else {
len = strlen(criteria);
}
if (!strncmp(criteria, "success", len) ||
!strncmp(criteria, "true", len)) {
return ((status == 0));
}
if (!strncmp(criteria, "fail", len) ||
!strncmp(criteria, "false", len)) {
return ((status != 0));
}
if (!isdigit(*criteria)) {
return -1;
}
r1 = strtol(criteria, &endptr, 10);
if (!endptr || !*endptr || *endptr == ',') {
return ((status == r1));
}
if (*endptr++ != '-') {
return -1;
}
if (!isdigit(*endptr)) {
return -1;
}
r2 = strtol(endptr, &endptr, 10);
if (!endptr || !*endptr || *endptr == ',') {
return ((status >= r1 && status <= r2));
}
if (endptr && *endptr && *endptr != ',') {
return -1;
}
criteria = next;
}
return 1;
}
static int pump(const char *name, pump_t *pumps)
{
int i;
while (1) {
nfds_t nfds = 0;
struct pollfd fds[PUMPS * 2] = { 0 };
for (i = 0; i < PUMPS; i++) {
pumps[i].rpollfd = NULL;
pumps[i].wpollfd = NULL;
if (!pumps[i].read_closed) {
pumps[i].rpollfd = fds + nfds;
fds[nfds].events = POLLIN;
fds[nfds].fd = pumps[i].rfd;
fds[nfds].revents = 0;
nfds++;
}
if (!pumps[i].write_closed
&& (pumps[i].send_eof || pumps[i].len > pumps[i].offset)) {
pumps[i].wpollfd = fds + nfds;
fds[nfds].events = POLLOUT;
fds[nfds].fd = pumps[i].wfd;
fds[nfds].revents = 0;
nfds++;
}
if (pumps[i].read_closed && pumps[i].exit_on_close) {
nfds = 0;
break;
}
}
if (!nfds) {
break;
}
if (poll(fds, nfds, -1) < 0) {
fprintf(stderr, "%s: Could not poll, giving up: %s\n", name,
strerror(errno));
return -1;
}
for (i = 0; i < PUMPS; i++) {
if (pumps[i].rpollfd) {
if (pumps[i].rpollfd->revents & POLLIN) {
void *base;
ssize_t num;
base = realloc(pumps[i].base, pumps[i].len + BUFFER_SIZE);
if (!base) {
fprintf(stderr, "%s: Out of memory, giving up.\n",
name);
return -1;
}
pumps[i].base = base;
num = read(pumps[i].rfd, base + pumps[i].len, BUFFER_SIZE);
if (num < 0) {
fprintf(stderr, "%s: Could not read, giving up: %s\n",
name, strerror(errno));
return -1;
} else if (num == 0) {
pumps[i].read_closed = 1;
pumps[i].send_eof = 1;
close(pumps[i].rfd);
} else {
pumps[i].len += num;
}
}
if ((pumps[i].rpollfd->revents & POLLHUP)
|| (pumps[i].rpollfd->revents & POLLERR)
|| (pumps[i].rpollfd->revents & POLLNVAL)) {
pumps[i].read_closed = 1;
pumps[i].send_eof = 1;
close(pumps[i].rfd);
}
}
if (pumps[i].wpollfd) {
if (pumps[i].wpollfd->revents & POLLOUT) {
ssize_t num;
num = write(pumps[i].wfd, pumps[i].base + pumps[i].offset,
pumps[i].len - pumps[i].offset);
if (num < 0) {
fprintf(stderr, "%s: Could not write, giving up: %s\n",
name, strerror(errno));
return -1;
} else {
pumps[i].offset += num;
}
if (pumps[i].read_closed
&& pumps[i].offset == pumps[i].len) {
pumps[i].write_closed = 1;
close(pumps[i].wfd);
}
}
if ((pumps[i].wpollfd->revents & POLLHUP)
|| (pumps[i].wpollfd->revents & POLLERR)
|| (pumps[i].wpollfd->revents & POLLNVAL)) {
pumps[i].write_closed = 1;
close(pumps[i].wfd);
}
}
}
}
return 0;
}
int main (int argc, char **argv)
{
const char *name = argv[0];
const char *repeat_until = "success";
const char *repeat_while = NULL;
const char *message = NULL;
char *delay = DEFAULT_DELAY;
pump_t pumps[PUMPS] = { 0 };
int c, status = 0, i;
long int d = 0;
long int times = DEFAULT_TIMES;
while ((c = getopt_long(argc, argv, "+d:m:t:u:w:hv", long_options, NULL)) != -1) {
switch (c)
{
case 'd':
delay = optarg;
do {
errno = 0;
d = strtol(optarg, &optarg, 10);
if (errno || (optarg[0] && optarg[0] != ',') || d < 0) {
return help(name, "Delay(s) must be bigger or equal to 0.\n", EXIT_FAILURE);
}
} while (optarg++[0] == ',');
break;
case 'm':
message = optarg;
break;
case 't':
errno = 0;
times = strtol(optarg, &optarg, 10);
if (errno || optarg[0] || times < -1) {
return help(name, "Times must be bigger or equal to -1.\n", EXIT_FAILURE);
}
break;
case 'u':
if (status_match(0, optarg) == -1) {
return help(name, "Until must contain comma separated numbers, ranges, 'success/true' or 'fail/false'.\n", EXIT_FAILURE);
}
repeat_until = optarg;
repeat_while = NULL;
break;
case 'w':
if (status_match(0, optarg) == -1) {
return help(name, "While must contain comma separated numbers, ranges, 'success/true' or 'fail/false'.\n", EXIT_FAILURE);
}
repeat_until = NULL;
repeat_while = optarg;
break;
case 'h':
return help(name, NULL, 0);
case 'v':
return version();
default:
return help(name, NULL, EXIT_FAILURE);
}
}
if (optind == argc) {
return help(name, "No command specified.\n", EXIT_FAILURE);
}
while (times) {
pid_t w, f;
int inpair[2], outpair[2];
if (pipe(inpair) || pipe(outpair)) {
fprintf(stderr, "%s: Could not create pipe, giving up: %s", name,
strerror(errno));
status = EXIT_FAILURE;
break;
}
/* Clear any inherited settings */
signal(SIGCHLD, SIG_DFL);
f = fork();
/* error */
if (f < 0) {
fprintf(stderr, "%s: Could not fork, giving up: %s", name,
strerror(errno));
status = EXIT_FAILURE;
break;
}
/* child */
else if (f == 0) {
dup2(inpair[READ_FD], STDIN_FD);
close(inpair[READ_FD]);
close(inpair[WRITE_FD]);
dup2(outpair[WRITE_FD], STDOUT_FD);
close(outpair[READ_FD]);
close(outpair[WRITE_FD]);
execvp(argv[optind], argv + optind);
fprintf(stderr, "%s: Could not execute '%s', giving up: %s\n", name,
argv[optind], strerror(errno));
status = EXIT_FAILURE;
break;
}
/* parent */
else {
/* handle stdin */
pumps[STDIN_FD].rfd = dup(STDIN_FD);
pumps[STDIN_FD].wfd = inpair[WRITE_FD];
close(inpair[READ_FD]);
/* handle stdout */
pumps[STDOUT_FD].rfd = outpair[READ_FD];
pumps[STDOUT_FD].wfd = dup(STDOUT_FD);
close(outpair[WRITE_FD]);
/* prevent write to stdout, we will handle it later */
pumps[STDOUT_FD].write_closed = 1;
/* if stdout closes, the pump must exit */
pumps[STDOUT_FD].exit_on_close = 1;
/* pump all data */
if (pump(name, pumps)) {
status = EXIT_FAILURE;
break;
}
close(inpair[WRITE_FD]);
close(outpair[READ_FD]);
close(pumps[STDIN_FD].rfd);
close(pumps[STDOUT_FD].wfd);
/* reset stdin in case we repeat the command */
pumps[STDIN_FD].offset = 0;
pumps[STDIN_FD].write_closed = 0;
/* wait for the child process to be done */
do {
w = waitpid(f, &status, 0);
if (w == -1 && errno != EINTR) {
break;
}
} while (w != f);
/* waitpid failed, we give up */
if (w == -1) {
status = EXIT_FAILURE;
fprintf(stderr, "%s: waitpid for '%s' failed, giving up: %s\n", name,
argv[optind], strerror(errno));
break;
}
/* process normal exit, should we try again? */
else if (WIFEXITED(status)) {
status = WEXITSTATUS(status);
if ((repeat_until && status_match(status, repeat_until))
|| (repeat_while && !status_match(status, repeat_while))
|| (!repeat_until && !repeat_while && status)) {
/* success - write stdout to stdout */
fwrite(pumps[STDOUT_FD].base, pumps[STDOUT_FD].len, 1, stdout);
break;
}
/* failure - write stdout to stderr */
fwrite(pumps[STDOUT_FD].base, pumps[STDOUT_FD].len, 1, stderr);
/* reset stdout for a go-around */
free(pumps[STDOUT_FD].base);
memset(&pumps[STDOUT_FD], 0, sizeof(pump_t));
if (delay[0]) {
d = strtol(delay, &delay, 10);
}
if (delay[0] == ',') {
delay++;
}
if (d) {
fprintf(stderr,
"%s: %s returned %d, backing off for %ld second%s and trying again...\n",
name, message ? message : argv[optind], status,
d, d > 1 ? "s" : "");
sleep(d);
}
else {
fprintf(stderr,
"%s: %s returned %d, trying again...\n",
name, message ? message : argv[optind], status);
}
if (times > 0) {
times--;
}
continue;
}
/* process received a signal, we must leave cleanly */
else if (WIFSIGNALED(status)) {
status = WTERMSIG(status) + 128;
break;
}
/* otherwise weirdness, just leave */
else {
status = EX_OSERR;
break;
}
}
}
for (i = 0; i < PUMPS; i++) {
if (pumps[i].base) {
free(pumps[i].base);
pumps[i].base = NULL;
}
}
return status;
}