03-18-2006
FreeBSD, fork() and zombies
i'm writing small http proxy server (accept client -> connect to remote proxy server -> recv client's request -> send to remote proxy server -> get responce from remote proxy server -> send answer to client -> close connection to client and to remote proxy server) and having problems with fork(). when connections come to local port, i'm forking them to process the request. but when there are many (100+) simaltenious connections, childs become to work slower and die in 2-20 seconds. i have no limits for simaltenious incoming connections. when child dies it sends SIGCHLD signal to the parent application, which has a handler:
static void sig_chld(int no) {
while (waitpid(-1, NULL, WNOHANG) > 0);
}
and a set up function:
static void install_sig_handlers(void) {
struct sigaction sig_act;
sig_act.sa_handler = sig_chld;
sig_act.sa_flags = 0;
sigfillset(&sig_act.sa_mask);
sigaction(SIGCHLD, &sig_act, NULL);
sig_act.sa_handler = SIG_IGN;
sig_act.sa_flags = 0;
sigemptyset(&sig_act.sa_mask);
sigaction(SIGPIPE, &sig_act, NULL);
}
this works fine on my FreeBSD 4.4 server for 1-100 simaltenious connections from clients. but it becomes wierd when 100+ connections come: zombies start leaving in memory and their number grows. after several minutes of work with 100+ connections server goes down with about 10000 zombies in memory and 0% cpu idle, and at the same time none of my processes (parent or childs) loads the server (by `ps -awx` results) - neither cpu, nor memory.
please help me to find correct decision for this problem. Thanx.
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LEARN ABOUT XFREE86
systemd-socket-proxyd
SYSTEMD-SOCKET-PROXYD(8) systemd-socket-proxyd SYSTEMD-SOCKET-PROXYD(8)
NAME
systemd-socket-proxyd - Bidirectionally proxy local sockets to another (possibly remote) socket.
SYNOPSIS
systemd-socket-proxyd [OPTIONS...] HOST:PORT
systemd-socket-proxyd [OPTIONS...] UNIX-DOMAIN-SOCKET-PATH
DESCRIPTION
systemd-socket-proxyd is a generic socket-activated network socket forwarder proxy daemon for IPv4, IPv6 and UNIX stream sockets. It may be
used to bi-directionally forward traffic from a local listening socket to a local or remote destination socket.
One use of this tool is to provide socket activation support for services that do not natively support socket activation. On behalf of the
service to activate, the proxy inherits the socket from systemd, accepts each client connection, opens a connection to a configured server
for each client, and then bidirectionally forwards data between the two.
This utility's behavior is similar to socat(1). The main differences for systemd-socket-proxyd are support for socket activation with
"Accept=false" and an event-driven design that scales better with the number of connections.
OPTIONS
The following options are understood:
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
--connections-max=, -c
Sets the maximum number of simultaneous connections, defaults to 256. If the limit of concurrent connections is reached further
connections will be refused.
EXIT STATUS
On success, 0 is returned, a non-zero failure code otherwise.
EXAMPLES
Simple Example
Use two services with a dependency and no namespace isolation.
Example 1. proxy-to-nginx.socket
[Socket]
ListenStream=80
[Install]
WantedBy=sockets.target
Example 2. proxy-to-nginx.service
[Unit]
Requires=nginx.service
After=nginx.service
Requires=proxy-to-nginx.socket
After=proxy-to-nginx.socket
[Service]
ExecStart=/lib/systemd/systemd-socket-proxyd /tmp/nginx.sock
PrivateTmp=yes
PrivateNetwork=yes
Example 3. nginx.conf
[...]
server {
listen unix:/tmp/nginx.sock;
[...]
Example 4. Enabling the proxy
# systemctl enable --now proxy-to-nginx.socket
$ curl http://localhost:80/
Namespace Example
Similar as above, but runs the socket proxy and the main service in the same private namespace, assuming that nginx.service has PrivateTmp=
and PrivateNetwork= set, too.
Example 5. proxy-to-nginx.socket
[Socket]
ListenStream=80
[Install]
WantedBy=sockets.target
Example 6. proxy-to-nginx.service
[Unit]
Requires=nginx.service
After=nginx.service
Requires=proxy-to-nginx.socket
After=proxy-to-nginx.socket
JoinsNamespaceOf=nginx.service
[Service]
ExecStart=/lib/systemd/systemd-socket-proxyd 127.0.0.1:8080
PrivateTmp=yes
PrivateNetwork=yes
Example 7. nginx.conf
[...]
server {
listen 8080;
[...]
Example 8. Enabling the proxy
# systemctl enable --now proxy-to-nginx.socket
$ curl http://localhost:80/
SEE ALSO
systemd(1), systemd.socket(5), systemd.service(5), systemctl(1), socat(1), nginx(1), curl(1)
systemd 237 SYSTEMD-SOCKET-PROXYD(8)