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PEN(1) General Commands Manual PEN(1) NAME pen - Load balancer for udp and tcp based protocols SYNOPSIS pen [-b sec] [-c N] [-e host:port] [-t sec] [-x N] [-j dir] [-u user] [-F cfgfile] [-l logfile] [-p file ] [-w file] [-C port|/path/to/socket] [-T sec] [-UHWXadfhrs] [-o option] [-E certfile] [-K keyfile] [-G cacertfile] [-A cacertdir] [-Z] [-R] [-L protocol] [host:]port|/path/to/socket h1[:p1[:maxc1[:hard1[:weight1[:prio1]]]]] [h2[:p2[:maxc2[:hard2[:weight2[:prio2]]]]]] ... Windows only: pen -i service_name pen -u service_name EXAMPLE pen 80 www1:8000:10 www2:80:10 www3 Here three servers cooperate in a web server farm. Host www1 runs its web server on port 8000 and accepts a maximum of 10 simultaneous connections. Host www2 runs on port 80 and accepts 10 connections. Finally, www3 runs its web server on port 80 and allows an unlimited number of simultaneous connections. DESCRIPTION Pen is a load balancer for udp and tcp based protocols such as dns, http or smtp. It allows several servers to appear as one to the outside and auto- matically detects servers that are down and distributes clients among the available servers. This gives high availability and scalable performance. The load balancing algorithm keeps track of clients and will try to send them back to the server they visited the last time. The client table has a number of slots (default 2048, settable through command-line arguments). When the table is full, the least recently used one will be thrown out to make room for the new one. This is superior to a simple round-robin algorithm, which sends a client that connects repeatedly to different servers. Doing so breaks applications that maintain state between connections in the server, including most mod- ern web applications. When pen detects that a server is unavailable, it scans for another start- ing with the server after the most recently used one. That way we get load balancing and "fair" failover for free. Correctly configured, pen can ensure that a server farm is always avail- able, even when individual servers are brought down for maintenance or re- configuration. The final single point of failure, pen itself, can be elimi- nated by running pen on several servers, using vrrp to decide which is ac- tive. Sending pen a USR1 signal will make it print some useful statistics on stderr, even if debugging is disabled. If pen is running in the background (i.e. without the -f option), syslog is used rather than stderr. If the -w option is used, the statistics is saved in HTML format in the given file. Sending pen a HUP signal will make it close and reopen the logfile, if log- ging is enabled, and reload the configuration file. Rotate the log like this (assuming pen.log is the name of the logfile): mv pen.log pen.log.1 kill -HUP `cat <pidfile>` where <pidfile> is the file containing pen's process id, as written by the -p option. Sending pen a TERM signal will make it exit cleanly, closing the log file and all open sockets. OPTIONS -C port|/path/to/socket Specifies a control port where the load balancer listens for com- mands. See penctl.1 for a list of the commands available. The proto- col is unauthenticated and the administrator is expected to restrict access using an access control list (for connections over a network) or Unix file permissions (for a Unix domain socket). Pen will nor- mally refuse to open the control port if running as root; see -u op- tion. If you still insist that you want to run pen as root with a control port, use "-u root". -F cfgfile Names a configuration file with commands in penctl format (see penctl.1). The file is read after processing all command line argu- ments, and also after receiving a HUP signal. -H Adds X-Forwarded-For header to http requests. -U Use udp protocol support -O command Allows most penctl commands to be used on the Pen command line. -P Use poll() for event notification. -W Use weight for server selection. -X Adds an exit command to the control interface. -a Used in conjunction with -dd to get communication dumps in ascii rather than hexadecimal format. -b sec Servers that do not respond are blacklisted, i.e. excluded from the server selection algorithm, for the specified number of seconds (de- fault 30). -T sec Clients are tracked for the specified number of seconds so they can be sent to the same server as the last time (default 0 = never ex- pire clients). -c N Max number of clients (default 2048). -d Debugging (repeat -d for more). The output goes to stderr if we are running in the foreground (see -f) and to syslog (facility user, priority debug) otherwise. -e host:port host:port specifies the emergency server to contact if all regular servers become unavailable. -f Stay in foreground. -h Use a hash on the client IP address for the initial server selec- tion. This makes it more predictable where clients will be con- nected. -i service_name Windows only. Install pen as a service. -j dir Run in a chroot environment. -l file Turn on logging. -m multi_accept Accept up to multi_accept incoming connections at a time. -p file Write the pid of the running daemon to file. -q backlog Allow the queue of pending incoming connections to grow up to a max- imum of backlog entries. -r Go straight into round-robin server selection without looking up which server a client used the last time. -s Stubborn server selection: if the initial choice is unavailable, the client connection is closed without trying another server. -t sec Connect timeout in seconds (default 5). -u user Posix only. Run as a different user. -u service_name Windows only. Uninstall the service. -x N Max number of simultaneous connections (default 500). -w file File for status reports in HTML format. -o option Use option in penctl format. -E certfile Use the given certificate in PEM format. -K keyfile Use the given key in PEM format (may be contained in cert). -G cacertfile File containing the CA's certificate. -A cacertdir Directory containing CA certificates in hashed format. -Z Use SSL compatibility mode. -R Require valid peer certificate. -L protocol ssl23 (default), ssl3 or tls1. [host:]port OR /path/to/socket The local address and port pen listens to. By default pen listens to all local addresses. Pen can also use a Unix domain socket as the local listening address. h1:p1:soft:hard:weight:prio The address, port and maximum number of simultaneous connections for a remote server. By default, the port is the same as the local port, and the soft limit on the number of connections is unlimited. The hard limit is used for clients which have accessed the server be- fore. The weight and prio are used for the weight- and priority- based server selection algorithms. LIMITATIONS Pen runs in a single process, and opens two sockets for each connection. Depending on kernel configuration, pen can run out of file descriptors. SSL support is available if pen was built with the --with-ssl option. GeoIP support is available if pen was built with the --with-geoip option. SEE ALSO penctl(1), dwatch(1), mergelogs(1), webresolve(1) AUTHOR Copyright (C) 2001-2016 Ulric Eriksson, <ulric@siag.nu>. ACKNOWLEDGEMENTS In part inspired by balance by Thomas Obermair. LOCAL PEN(1)
NAME | SYNOPSIS | EXAMPLE | DESCRIPTION | OPTIONS | LIMITATIONS | SEE ALSO | AUTHOR | ACKNOWLEDGEMENTS
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