making the signal handler almost a no-op.
Fix the killing code to actually be smart instead of the
pseudo-random mess.
Get rid of the silly fixed array of children and make
max-connections dynamic and configurable in the process.
Make git-daemon a proper syslogging citizen with PID-info.
Simplify the overzealous double buffering in the logroutine,
remove the artificial maximum logline length in the process.
Signed-off-by: Stephen R. van den Berg <srb@xxxxxxx>
---
I actually only wanted to fix the signal handler, so that it works
on SysV/Solaris systems (see previous patch).
Then again, once I started looking at the code, it's amazing how
much functionality and robustness can be *improved* by actually
removing more and more code.
Documentation/git-daemon.txt | 8 +
daemon.c | 277 +++++++++++++++---------------------------
2 files changed, 108 insertions(+), 177 deletions(-)
diff --git a/Documentation/git-daemon.txt b/Documentation/git-daemon.txt
index 4ba4b75..48bcc25 100644
--- a/Documentation/git-daemon.txt
+++ b/Documentation/git-daemon.txt
@@ -9,8 +9,9 @@ SYNOPSIS
--------
[verse]
'git daemon' [--verbose] [--syslog] [--export-all]
- [--timeout=n] [--init-timeout=n] [--strict-paths]
- [--base-path=path] [--user-path | --user-path=path]
+ [--timeout=n] [--init-timeout=n] [--max-connections=n]
+ [--strict-paths] [--base-path=path] [--base-path-relaxed]
+ [--user-path | --user-path=path]
[--interpolated-path=pathtemplate]
[--reuseaddr] [--detach] [--pid-file=file]
[--enable=service] [--disable=service]
@@ -99,6 +100,9 @@ OPTIONS
it takes for the server to process the sub-request and time spent
waiting for next client's request.
+--max-connections::
+ Maximum number of concurrent clients, defaults to 32.
+
--syslog::
Log to syslog instead of stderr. Note that this option does not imply
--verbose, thus by default only error conditions will be logged.
diff --git a/daemon.c b/daemon.c
index 1c00305..8e67747 100644
--- a/daemon.c
+++ b/daemon.c
@@ -16,12 +16,11 @@
static int log_syslog;
static int verbose;
static int reuseaddr;
-static int child_handler_pipe[2];
static const char daemon_usage[] =
"git daemon [--verbose] [--syslog] [--export-all]\n"
-" [--timeout=n] [--init-timeout=n] [--strict-paths]\n"
-" [--base-path=path] [--base-path-relaxed]\n"
+" [--timeout=n] [--init-timeout=n] [--max-connections=n]\n"
+" [--strict-paths] [--base-path=path] [--base-path-relaxed]\n"
" [--user-path | --user-path=path]\n"
" [--interpolated-path=path]\n"
" [--reuseaddr] [--detach] [--pid-file=file]\n"
@@ -78,38 +77,16 @@ static struct interp interp_table[] = {
static void logreport(int priority, const char *err, va_list params)
{
- /* We should do a single write so that it is atomic and output
- * of several processes do not get intermingled. */
- char buf[1024];
- int buflen;
- int maxlen, msglen;
-
- /* sizeof(buf) should be big enough for "[pid] \n" */
- buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());
-
- maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
- msglen = vsnprintf(buf + buflen, maxlen, err, params);
-
- if (log_syslog) {
- syslog(priority, "%s", buf);
- return;
+ if (log_syslog)
+ vsyslog(priority, err, params);
+ else {
+ /* Since stderr is set to linebuffered mode, the
+ * logging of different processes will not overlap
+ */
+ fprintf(stderr, "[%d] ", (int)getpid());
+ vfprintf(stderr, err, params);
+ fputc('\n', stderr);
}
-
- /* maxlen counted our own LF but also counts space given to
- * vsnprintf for the terminating NUL. We want to make sure that
- * we have space for our own LF and NUL after the "meat" of the
- * message, so truncate it at maxlen - 1.
- */
- if (msglen > maxlen - 1)
- msglen = maxlen - 1;
- else if (msglen < 0)
- msglen = 0; /* Protect against weird return values. */
- buflen += msglen;
-
- buf[buflen++] = '\n';
- buf[buflen] = '\0';
-
- write_in_full(2, buf, buflen);
}
static void logerror(const char *err, ...)
@@ -605,39 +582,38 @@ static int execute(struct sockaddr *addr)
}
-/*
- * We count spawned/reaped separately, just to avoid any
- * races when updating them from signals. The SIGCHLD handler
- * will only update children_reaped, and the fork logic will
- * only update children_spawned.
- *
- * MAX_CHILDREN should be a power-of-two to make the modulus
- * operation cheap. It should also be at least twice
- * the maximum number of connections we will ever allow.
- */
-#define MAX_CHILDREN 128
-
-static int max_connections = 25;
-
-/* These are updated by the signal handler */
-static volatile unsigned int children_reaped;
-static pid_t dead_child[MAX_CHILDREN];
+static int max_connections = 32;
-/* These are updated by the main loop */
-static unsigned int children_spawned;
-static unsigned int children_deleted;
+static unsigned int live_children;
static struct child {
+ struct child*next;
pid_t pid;
- int addrlen;
struct sockaddr_storage address;
-} live_child[MAX_CHILDREN];
+} *firstborn;
-static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
+static void add_child(pid_t pid, struct sockaddr *addr, int addrlen)
{
- live_child[idx].pid = pid;
- live_child[idx].addrlen = addrlen;
- memcpy(&live_child[idx].address, addr, addrlen);
+ struct child*newborn;
+ newborn = xmalloc(sizeof *newborn);
+ if (newborn) {
+ struct child**cradle,*blanket;
+
+ live_children++;
+ newborn->pid = pid;
+ memcpy(memset(&newborn->address, 0, sizeof newborn->address),
+ addr, addrlen);
+ for (cradle = &firstborn;
+ (blanket = *cradle);
+ cradle = &blanket->next)
+ if (!memcmp(&blanket->address, &newborn->address,
+ sizeof newborn->address))
+ break;
+ newborn->next = blanket;
+ *cradle = newborn;
+ }
+ else
+ logerror("Out of memory spawning new child");
}
/*
@@ -646,107 +622,74 @@ static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
* We move everything up by one, since the new "deleted" will
* be one higher.
*/
-static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
+static void remove_child(pid_t pid)
{
- struct child n;
-
- deleted %= MAX_CHILDREN;
- spawned %= MAX_CHILDREN;
- if (live_child[deleted].pid == pid) {
- live_child[deleted].pid = -1;
- return;
- }
- n = live_child[deleted];
- for (;;) {
- struct child m;
- deleted = (deleted + 1) % MAX_CHILDREN;
- if (deleted == spawned)
- die("could not find dead child %d\n", pid);
- m = live_child[deleted];
- live_child[deleted] = n;
- if (m.pid == pid)
- return;
- n = m;
- }
+ struct child**cradle,*blanket;
+
+ for (cradle = &firstborn;
+ (blanket = *cradle);
+ cradle = &blanket->next)
+ if (blanket->pid == pid) {
+ *cradle = blanket->next;
+ live_children--;
+ free(blanket);
+ break;
+ }
}
/*
* This gets called if the number of connections grows
* past "max_connections".
*
- * We _should_ start off by searching for connections
- * from the same IP, and if there is some address wth
- * multiple connections, we should kill that first.
- *
- * As it is, we just "randomly" kill 25% of the connections,
- * and our pseudo-random generator sucks too. I have no
- * shame.
- *
- * Really, this is just a place-holder for a _real_ algorithm.
+ * We kill the newest connection from a duplicate IP first.
+ * If there are no duplicates, then the newest connection is killed,
+ * in order to allow long running clones to actually complete.
*/
-static void kill_some_children(int signo, unsigned start, unsigned stop)
+static void kill_some_child(int signo)
{
- start %= MAX_CHILDREN;
- stop %= MAX_CHILDREN;
- while (start != stop) {
- if (!(start & 3))
- kill(live_child[start].pid, signo);
- start = (start + 1) % MAX_CHILDREN;
+ const struct child *blanket;
+
+ if ((blanket = firstborn)) {
+ const struct child *next;
+
+ for (; (next = blanket->next); blanket = next)
+ if (!memcmp(&blanket->address, &next->address,
+ sizeof next->address))
+ break;
+
+ kill(blanket->pid, signo);
}
}
static void check_dead_children(void)
{
- unsigned spawned, reaped, deleted;
-
- spawned = children_spawned;
- reaped = children_reaped;
- deleted = children_deleted;
-
- while (deleted < reaped) {
- pid_t pid = dead_child[deleted % MAX_CHILDREN];
- const char *dead = pid < 0 ? " (with error)" : "";
-
- if (pid < 0)
- pid = -pid;
+ int status;
+ pid_t pid;
- /* XXX: Custom logging, since we don't wanna getpid() */
- if (verbose) {
- if (log_syslog)
- syslog(LOG_INFO, "[%d] Disconnected%s",
- pid, dead);
- else
- fprintf(stderr, "[%d] Disconnected%s\n",
- pid, dead);
- }
- remove_child(pid, deleted, spawned);
- deleted++;
+ while ((pid = waitpid(-1, &status, WNOHANG))>0) {
+ const char *dead = "";
+ remove_child(pid);
+ if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
+ dead = " (with error)";
+ loginfo("[%d] Disconnected%s", (int)pid, dead);
}
- children_deleted = deleted;
}
static void check_max_connections(void)
{
for (;;) {
- int active;
- unsigned spawned, deleted;
-
check_dead_children();
-
- spawned = children_spawned;
- deleted = children_deleted;
-
- active = spawned - deleted;
- if (active <= max_connections)
+ if (live_children <= max_connections)
break;
/* Kill some unstarted connections with SIGTERM */
- kill_some_children(SIGTERM, deleted, spawned);
- if (active <= max_connections << 1)
+ kill_some_child(SIGTERM);
+ check_dead_children();
+ if (live_children <= max_connections << 1)
break;
/* If the SIGTERM thing isn't helping use SIGKILL */
- kill_some_children(SIGKILL, deleted, spawned);
+ kill_some_child(SIGKILL);
sleep(1);
}
}
@@ -756,16 +699,13 @@ static void handle(int incoming, struct sockaddr *addr, int addrlen)
pid_t pid = fork();
if (pid) {
- unsigned idx;
-
close(incoming);
- if (pid < 0)
+ if (pid < 0) {
+ logerror("Couldn't fork %s", strerror(errno));
return;
+ }
- idx = children_spawned % MAX_CHILDREN;
- children_spawned++;
- add_child(idx, pid, addr, addrlen);
-
+ add_child(pid, addr, addrlen);
check_max_connections();
return;
}
@@ -779,21 +719,10 @@ static void handle(int incoming, struct sockaddr *addr, int addrlen)
static void child_handler(int signo)
{
- for (;;) {
- int status;
- pid_t pid = waitpid(-1, &status, WNOHANG);
-
- if (pid > 0) {
- unsigned reaped = children_reaped;
- if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
- pid = -pid;
- dead_child[reaped % MAX_CHILDREN] = pid;
- children_reaped = reaped + 1;
- write(child_handler_pipe[1], &status, 1);
- continue;
- }
- break;
- }
+ /* Otherwise empty handler because systemcalls will get interrupted
+ * upon signal receipt
+ * SysV needs the handler to be reinstated
+ */
signal(SIGCHLD, child_handler);
}
@@ -936,35 +865,30 @@ static int service_loop(int socknum, int *socklist)
struct pollfd *pfd;
int i;
- if (pipe(child_handler_pipe) < 0)
- die ("Could not set up pipe for child handler");
-
- pfd = xcalloc(socknum + 1, sizeof(struct pollfd));
+ pfd = xcalloc(socknum, sizeof(struct pollfd));
for (i = 0; i < socknum; i++) {
pfd[i].fd = socklist[i];
pfd[i].events = POLLIN;
}
- pfd[socknum].fd = child_handler_pipe[0];
- pfd[socknum].events = POLLIN;
-
- child_handler(0);
for (;;) {
int i;
+ int olderrno;
+
+ i = poll(pfd, socknum, -1);
+ olderrno = errno;
- if (poll(pfd, socknum + 1, -1) < 0) {
- if (errno != EINTR) {
+ check_dead_children();
+
+ if (i < 0) {
+ if (olderrno != EINTR) {
error("poll failed, resuming: %s",
- strerror(errno));
+ strerror(olderrno));
sleep(1);
}
continue;
}
- if (pfd[socknum].revents & POLLIN) {
- read(child_handler_pipe[0], &i, 1);
- check_dead_children();
- }
for (i = 0; i < socknum; i++) {
if (pfd[i].revents & POLLIN) {
@@ -1055,10 +979,7 @@ int main(int argc, char **argv)
gid_t gid = 0;
int i;
- /* Without this we cannot rely on waitpid() to tell
- * what happened to our children.
- */
- signal(SIGCHLD, SIG_DFL);
+ child_handler(0);
for (i = 1; i < argc; i++) {
char *arg = argv[i];
@@ -1105,6 +1026,10 @@ int main(int argc, char **argv)
init_timeout = atoi(arg+15);
continue;
}
+ if (!prefixcmp(arg, "--max-connections=")) {
+ max_connections = atoi(arg+18);
+ continue;
+ }
if (!strcmp(arg, "--strict-paths")) {
strict_paths = 1;
continue;
@@ -1178,9 +1103,11 @@ int main(int argc, char **argv)
}
if (log_syslog) {
- openlog("git-daemon", 0, LOG_DAEMON);
+ openlog("git-daemon", LOG_PID, LOG_DAEMON);
set_die_routine(daemon_die);
}
+ else /* so that logging into a file is atomic */
+ setlinebuf(stderr);
if (inetd_mode && (group_name || user_name))
die("--user and --group are incompatible with --inetd");
--
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