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authorMattias Andrée <maandree@operamail.com>2015-11-29 11:21:25 +0100
committerMattias Andrée <maandree@operamail.com>2015-11-29 11:21:25 +0100
commitc7134e3735771ddf406001c8a01101131ca899ab (patch)
tree00666ba29100b8f43f95927ab866fc0a3c8a084a /doc/info/bus.texinfo
parentwhitespace (diff)
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info: add last example
Signed-off-by: Mattias Andrée <maandree@operamail.com>
Diffstat (limited to 'doc/info/bus.texinfo')
-rw-r--r--doc/info/bus.texinfo635
1 files changed, 631 insertions, 4 deletions
diff --git a/doc/info/bus.texinfo b/doc/info/bus.texinfo
index 4c9bf51..b358ab0 100644
--- a/doc/info/bus.texinfo
+++ b/doc/info/bus.texinfo
@@ -904,8 +904,6 @@ int main()
#include <stdlib.h>
#include <string.h>
-#define t(stmt) if (stmt) goto fail
-
static size_t pauser_count = 0;
static size_t pausers_size = 0;
static char* pausers = NULL;
@@ -1119,7 +1117,7 @@ int main()
t (bus_open(&bus, "/tmp/example-bus", BUS_RDONLY));
t (bus_poll_start(&bus));
for (;;) @{
- t(clock_gettime(CLOCK_MONOTONIC, &timeout));
+ t (clock_gettime(CLOCK_MONOTONIC, &timeout));
timeout.tv_sec += 1;
message = bus_poll_timed(&bus, &timeout, CLOCK_MONOTONIC);
if (message == NULL) @{
@@ -1419,7 +1417,636 @@ fail:
@node Daemon-dependencies
@section Daemon-dependencies
-TODO
+This example shows how bus can be used in an init system
+to provide ``aggressivly'' parallel startup of daemons.
+
+First of, run make to build this example.
+
+To start the example run @command{./init}. It will print in
+red export-statement you may want to run i other terminals.
+You will need to select at least one daemon, for example
+you can run @code{./init d-ntp}. The available pretend
+daemons are: @command{d-network}, @command{d-ntp}, and
+@command{d-ssh}.
+
+When you are done run @command{./cleanup} with @env{BUS_INIT}
+exported with the value printed by @command{./init}.
+
+
+@subsubheading @file{./Makefile}
+@example
+COMMANDS = announce await-ready await-started cleanup \
+ init require start-daemon test-daemon
+
+all: $@{COMMANDS@}
+%: %.c
+ $@{CC@} -Wall -Wextra -pedantic -std=c99 -lbus -o $@@ $<
+clean:
+ -rm $@{COMMANDS@}
+ -rm -r run
+
+.PHONY: all clean
+@end example
+
+
+@subsubheading @file{./announce.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#define t(stmt) if (stmt) goto fail
+
+static char arg[4098];
+
+int main(int argc, char *argv[])
+@{
+ bus_t bus;
+ if (argc < 3)
+ return fprintf(stderr, "USAGE: %s state daemon", *argv), 2;
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY));
+ sprintf(arg, "%ji %s %s", (intmax_t)getppid(), argv[1], argv[2]);
+ t (bus_write(&bus, arg, 0));
+ t (bus_close(&bus));
+ return 0;
+
+fail:
+ perror("announce");
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./await-ready.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/wait.h>
+
+#define t(stmt) if (stmt) goto fail
+
+static char arg[4098];
+static int argc;
+static char **argv;
+static int remaining = 0;
+static char *started = NULL;
+static char msg[BUS_MEMORY_SIZE];
+
+static void announce_wait(pid_t pid)
+@{
+ bus_t bus;
+ int i;
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY));
+ for (i = 1; i < argc; i++) @{
+ if (!started[i]) @{
+ sprintf(arg, "%ji awaiting-ready %s", (intmax_t)pid, argv[i]);
+ t (bus_write(&bus, arg, 0));
+ @}
+ @}
+ t (bus_close(&bus));
+ return;
+
+fail:
+ perror("await-ready");
+@}
+
+static int callback(const char *message, void *user_data)
+@{
+ int i;
+ char *arg2;
+ char *arg3;
+ pid_t pid;
+ pid_t ppid;
+
+ if (!message) @{
+ ppid = getppid();
+ pid = fork();
+ if (pid == 0) @{
+ if (fork() == 0)
+ announce_wait(ppid);
+ exit(0);
+ @} else @{
+ (void) waitpid(pid, NULL, 0);
+ /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */
+ @}
+ return 1;
+ @}
+
+ strncpy(msg, message, BUS_MEMORY_SIZE - 1);
+ msg[BUS_MEMORY_SIZE - 1] = 0;
+
+ arg2 = strchr(msg, ' ');
+ if (!arg2)
+ return 1;
+ arg3 = strchr(++arg2, ' ');
+ if (!arg3)
+ return 1;
+ *arg3++ = 0;
+
+ if (strcmp(arg2, "ready"))
+ return 1;
+
+ for (i = 1; i < argc; i++)
+ if (!started[i] && !strcmp(argv[i], arg3))
+ started[i] = 1, remaining--;
+
+ return !!remaining;
+ (void) user_data;
+@}
+
+int main(int argc_, char *argv_[])
+@{
+ bus_t bus;
+ int i;
+
+ argc = argc_;
+ argv = argv_;
+
+ if (argc < 2)
+ return fprintf(stderr, "USAGE: %s daemon...", *argv), 2;
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_RDONLY));
+ started = calloc(argc, sizeof(char));
+ t (started == NULL);
+
+ started[0] = 1;
+ for (i = 1; i < argc; i++) @{
+ sprintf(arg, "grep '^%s$'"
+ " <\"$@{XDG_RUNTIME_DIR@}/ready-daemons\""
+ " >/dev/null",
+ argv[i]);
+ if (!WEXITSTATUS(system(arg)))
+ started[i] = 1;
+ else
+ remaining++;
+ @}
+
+ if (remaining)
+ bus_read(&bus, callback, NULL);
+
+ bus_close(&bus);
+ free(started);
+ return 0;
+
+fail:
+ perror("await-ready");
+ bus_close(&bus);
+ free(started);
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./await-started.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/wait.h>
+
+#define t(stmt) if (stmt) goto fail
+
+static char arg[4098];
+static int argc;
+static char **argv;
+static int remaining = 0;
+static char *started = NULL;
+static char msg[BUS_MEMORY_SIZE];
+
+static void announce_wait(pid_t pid)
+@{
+ bus_t bus;
+ int i;
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY));
+ for (i = 1; i < argc; i++) @{
+ if (!started[i]) @{
+ sprintf(arg, "%ji awaiting-started %s", (intmax_t)pid, argv[i]);
+ t (bus_write(&bus, arg, 0));
+ @}
+ @}
+ t (bus_close(&bus));
+ return;
+
+fail:
+ perror("await-started");
+@}
+
+static int callback(const char *message, void *user_data)
+@{
+ int i;
+ char *arg2;
+ char *arg3;
+ pid_t pid;
+ pid_t ppid;
+
+ if (!message) @{
+ ppid = getppid();
+ pid = fork();
+ if (pid == 0) @{
+ if (fork() == 0)
+ announce_wait(ppid);
+ exit(0);
+ @} else @{
+ (void) waitpid(pid, NULL, 0);
+ /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */
+ @}
+ return 1;
+ @}
+
+ strncpy(msg, message, BUS_MEMORY_SIZE - 1);
+ msg[BUS_MEMORY_SIZE - 1] = 0;
+
+ arg2 = strchr(msg, ' ');
+ if (!arg2)
+ return 1;
+ arg3 = strchr(++arg2, ' ');
+ if (!arg3)
+ return 1;
+ *arg3++ = 0;
+
+ if (strcmp(arg2, "started") && strcmp(arg2, "ready"))
+ return 1;
+
+ for (i = 1; i < argc; i++)
+ if (!started[i] && !strcmp(argv[i], arg3))
+ started[i] = 1, remaining--;
+
+ return !!remaining;
+ (void) user_data;
+@}
+
+int main(int argc_, char *argv_[])
+@{
+ bus_t bus;
+ int i;
+
+ argc = argc_;
+ argv = argv_;
+
+ if (argc < 2)
+ return fprintf(stderr, "USAGE: %s daemon...", *argv), 2;
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_RDONLY));
+ started = calloc(argc, sizeof(char));
+ t (started == NULL);
+
+ started[0] = 1;
+ for (i = 1; i < argc; i++) @{
+ sprintf(arg, "grep '^%s$'"
+ " <\"$@{XDG_RUNTIME_DIR@}/started-daemons\""
+ " >/dev/null",
+ argv[i]);
+ if (!WEXITSTATUS(system(arg))) @{
+ started[i] = 1;
+ @} else @{
+ sprintf(arg, "grep '^%s$'"
+ " <\"$@{XDG_RUNTIME_DIR@}/ready-daemons\""
+ " >/dev/null",
+ argv[i]);
+ if (!WEXITSTATUS(system(arg)))
+ started[i] = 1;
+ else
+ remaining++;
+ @}
+ @}
+
+ if (remaining)
+ bus_read(&bus, callback, NULL);
+
+ bus_close(&bus);
+ free(started);
+ return 0;
+
+fail:
+ perror("await-started");
+ bus_close(&bus);
+ free(started);
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./cleanup.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define t(stmt) if (stmt) goto fail
+
+int main()
+@{
+ char *bus_address = getenv("BUS_INIT");
+ if (!bus_address || !*bus_address) @{
+ fprintf(stderr, "$BUS_INIT has not been set, its export statement "
+ "should have been printed in bold red by ./init\n");
+ return 1;
+ @}
+ t (bus_unlink(bus_address));
+ return 0;
+
+fail:
+ perror("cleanup");
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./d-network}
+@example
+#!/bin/sh
+PATH=.:$PATH
+d=d-network
+
+echo $d: starting
+sleep 2
+echo $d: ready
+announce ready $d
+@end example
+
+
+@subsubheading @file{./d-ntp}
+@example
+#!/bin/sh
+PATH=.:$PATH
+d=d-ntp
+
+require d-network
+echo $d: started
+announce started $d
+await-ready d-network
+echo $d: ready
+announce ready $d
+@end example
+
+
+@subsubheading @file{./d-ssh}
+@example
+#!/bin/sh
+PATH=.:$PATH
+d=d-ssh
+
+require d-network
+echo $d: starting
+sleep 1
+echo $d: started
+announce started $d
+sleep 1
+echo $d: ready
+announce ready $d
+@end example
+
+
+@subsubheading @file{./init.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+#define t(stmt) if (stmt) goto fail
+#define _2(...) __VA_ARGS__, __VA_ARGS__
+
+static char msg[BUS_MEMORY_SIZE];
+static int argc;
+static char **argv;
+static char arg[4098];
+
+static void start_daemons()
+@{
+ int i;
+ for (i = 1; i < argc; i++)
+ if (fork() == 0)
+ execl("./start-daemon", "./start-daemon", argv[i], NULL);
+@}
+
+static int callback(const char *message, void *user_data)
+@{
+ pid_t pid;
+ char *arg2;
+ char *arg3;
+ if (!message) @{
+ pid = fork();
+ t (pid == -1);
+ if (pid == 0) @{
+ if (fork() == 0) @{
+ start_daemons();
+ @}
+ exit(0);
+ @} else @{
+ (void) waitpid(pid, NULL, 0);
+ /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */
+ @}
+ return 1;
+ @}
+
+ strncpy(msg, message, BUS_MEMORY_SIZE - 1);
+ msg[BUS_MEMORY_SIZE - 1] = 0;
+
+ pid = fork();
+ t (pid == -1);
+
+ if (pid == 0) @{
+ if (fork() == 0) @{
+ arg2 = strchr(msg, ' ');
+ if (arg2 == NULL)
+ exit(0);
+ arg3 = strchr(++arg2, ' ');
+ if (arg3 == NULL)
+ exit(0);
+ *arg3++ = 0;
+ if (!strcmp(arg2, "require")) @{
+ execl(_2("./start-daemon"), arg3, NULL);
+ @} else if (!strcmp(arg2, "awaiting-started")) @{
+ execl(_2("./test-daemon"), arg3, "started", NULL);
+ @} else if (!strcmp(arg2, "awaiting-ready") ||
+ !strcmp(arg2, "awaiting")) @{
+ execl(_2("./test-daemon"), arg3, "ready", NULL);
+ @} else if (!strcmp(arg2, "started")) @{
+ sprintf(arg,
+ "grep '^%s\\$' < \"%s\" >/dev/null || echo %s >> \"%s\"",
+ _2(arg3, "$@{XDG_RUNTIME_DIR@}/started-daemons"));
+ execlp(_2("sh"), "-c", arg, NULL);
+ @} else if (!strcmp(arg2, "ready")) @{
+ sprintf(arg,
+ "grep '^%s\\$' < \"%s\" >/dev/null || echo %s >> \"%s\"",
+ _2(arg3, "$@{XDG_RUNTIME_DIR@}/ready-daemons"));
+ execlp(_2("sh"), "-c", arg, NULL);
+ @}
+ @}
+ exit(0);
+ @} else @{
+ (void) waitpid(pid, NULL, 0);
+ /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */
+ @}
+
+ return 1;
+ (void) user_data;
+
+fail:
+ perror("init");
+ return -1;
+@}
+
+int main(int argc_, char *argv_[])
+@{
+ char *bus_address = NULL;
+ bus_t bus;
+ argv = argv_;
+ argc = argc_;
+ if (argc < 2) @{
+ fprintf(stderr, "USAGE: %s daemon...\n", *argv);
+ return 1;
+ @}
+ t (setenv("XDG_RUNTIME_DIR", "./run", 1));
+ /* @w{@xrm{}Real init systems with not have the period.@xtt{}} */
+ system("mkdir -p -- \"$@{XDG_RUNTIME_DIR@}\"");
+ system("truncate -s 0 -- \"$@{XDG_RUNTIME_DIR@}/started-daemons\"");
+ system("truncate -s 0 -- \"$@{XDG_RUNTIME_DIR@}/ready-daemons\"");
+ t (bus_create(NULL, 1, &bus_address));
+ fprintf(stderr, "\033[00;01;31mexport BUS_INIT=%s\033[00m\n",
+ bus_address);
+ fprintf(stderr, "\033[00;31mexport XDG_RUNTIME_DIR=./run\033[00m\n");
+ t (setenv("BUS_INIT", bus_address, 1));
+ t (bus_open(&bus, bus_address, BUS_RDONLY));
+ t (bus_read(&bus, callback, NULL));
+ bus_close(&bus);
+ free(bus_address);
+ return 0;
+
+fail:
+ perror("init");
+ bus_close(&bus);
+ free(bus_address);
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./require.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#define t(stmt) if (stmt) goto fail
+
+static char arg[4098];
+
+int main(int argc, char *argv[])
+@{
+ bus_t bus;
+ int i;
+ if (argc < 2)
+ return fprintf(stderr, "USAGE: %s daemon...", *argv), 2;
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY));
+
+ for (i = 1; i < argc; i++) @{
+ sprintf(arg, "grep '^%s$' <\"%s\" >/dev/null",
+ argv[i], "$@{XDG_RUNTIME_DIR@}/started-daemons");
+ if (WEXITSTATUS(system(arg))) @{
+ sprintf(arg, "%ji require %s", (intmax_t)getppid(), argv[i]);
+ t (bus_write(&bus, arg, 0));
+ @}
+ @}
+
+ bus_close(&bus);
+ return 0;
+
+fail:
+ perror("require");
+ bus_close(&bus);
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./start-daemon.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static char arg[4098];
+
+int main(int argc, char *argv[])
+@{
+ if (argc != 2) @{
+ fprintf(stderr, "This program should be called from ./init\n");
+ return 2;
+ @}
+
+ sprintf(arg, "grep '^%s$' <\"%s\" >/dev/null",
+ argv[1], "$@{XDG_RUNTIME_DIR@}/started-daemons");
+ if (!WEXITSTATUS(system(arg)))
+ return 0;
+ sprintf(arg, "grep '^%s$' <\"%s\" >/dev/null",
+ argv[1], "$@{XDG_RUNTIME_DIR@}/ready-daemons");
+ if (!WEXITSTATUS(system(arg)))
+ return 0;
+
+ sprintf(arg, "./%s", argv[1]);
+ execlp(arg, arg, NULL);
+ perror("start-daemon");
+ return 1;
+@}
+@end example
+
+
+@subsubheading @file{./test-daemon.c}
+@example
+#include <bus.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define t(stmt) if (stmt) goto fail
+
+static char arg[4098];
+
+int main(int argc, char *argv[])
+@{
+ bus_t bus;
+ if (argc != 3) @{
+ fprintf(stderr, "This program should be called from ./init\n");
+ return 2;
+ @}
+
+retry:
+ sprintf(arg, "grep '^%s$'"
+ " <\"$@{XDG_RUNTIME_DIR@}/%s-daemons\""
+ " >/dev/null",
+ argv[1], argv[2]);
+ if (!WEXITSTATUS(system(arg))) @{
+ t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY));
+ sprintf(arg, "0 %s %s", argv[2], argv[1]);
+ t (bus_write(&bus, arg, 0));
+ bus_close(&bus);
+ @} else if (!strcmp(argv[2], "started")) @{
+ argv[2] = "ready";
+ goto retry;
+ @}
+ return 0;
+
+fail:
+ perror("test-daemon");
+ return 1;
+@}
+@end example