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diff --git a/doc/rsyslog_reliable_forwarding.html b/doc/rsyslog_reliable_forwarding.html deleted file mode 100644 index d04d9ea..0000000 --- a/doc/rsyslog_reliable_forwarding.html +++ /dev/null @@ -1,152 +0,0 @@ -<html><head> -<title>Reliable Forwarding of syslog Messages (via plain TCP syslog)</title> -</head> -<body> -<h1>Reliable Forwarding of syslog Messages with Rsyslog</h1> - <P><small><i>Written by - <a href="http://www.gerhards.net/rainer">Rainer - Gerhards</a> (2008-06-27)</i></small></P> -<h2>Abstract</h2> -<p><i><b>In this paper, I describe how to forward -<a href="http://www.monitorware.com/en/topics/syslog/">syslog</a> - - messages (quite) reliable to a central rsyslog server.</b> -This depends on rsyslog being installed on the client system and -it is recommended to have it installed on the server system. Please note -that industry-standard -<a href="http://blog.gerhards.net/2008/04/on-unreliability-of-plain-tcp-syslog.html">plain TCP syslog protocol is not fully reliable</a> -(thus the "quite reliable"). If you need a truely reliable solution, you need -to look into RELP (natively supported by rsyslog).</i></p> - -<h2>The Intention</h2> -<p>Whenever two systems talk over a network, something can go wrong. -For example, the communications link may go down, or a client or server may abort. -Even in regular cases, the server may be offline for a short period of time -because of routine maintenance. -<p>A logging system should be capable of avoiding message loss in situations where the -server is not reachable. To do so, unsent data needs to be buffered at the client while the -server is offline. Then, once the server is up again, this data is to be sent. -<p>This can easily be acomplished by rsyslog. In rsyslog, every action runs on its own queue -and each queue can be set to buffer data if the action is not ready. Of course, -you must be able to detect that "the action is not ready", which means the remote -server is offline. This can be detected with plain TCP syslog and RELP, but not with UDP. -So you need to use either of the two. In this howto, we use plain TCP syslog. -<p>Please note that we are using rsyslog-specific features. The are required on the -client, but not on the server. So the client system must run rsyslog (at least version 3.12.0), while on the -server another syslogd may be running, as long as it supports plain tcp syslog. -<p><b>The rsyslog queueing subsystem tries to buffer to memory. So even if the -remote server goes -offline, no disk file is generated.</b> File on disk are created only if there is -need to, for example if rsyslog runs out of (configured) memory queue space or needs -to shutdown (and thus persist yet unsent messages). Using main memory and going to the -disk when needed is a huge performance benefit. You do not need to care about it, -because, all of it is handled automatically and transparently by rsyslog.</p> -<h2>How To Setup</h2> -<p>First, you need to create a working directory for rsyslog. This is where it -stores its queue files (should need arise). You may use any location on your -local system. -<p>Next, you need to do is instruct rsyslog to use a -disk queue and then configure your action. There is nothing else to do. With the -following simple config file, you forward anything you receive to a remote server -and have buffering applied automatically when it goes down. This must be done on the -client machine.</p> -<textarea rows="9" cols="80"> -$ModLoad imuxsock # local message reception - -$WorkDirectory /rsyslog/work # default location for work (spool) files - -$ActionQueueType LinkedList # use asynchronous processing -$ActionQueueFileName srvrfwd # set file name, also enables disk mode -$ActionResumeRetryCount -1 # infinite retries on insert failure -$ActionQueueSaveOnShutdown on # save in-memory data if rsyslog shuts down -*.* @@server:port -</textarea> -<p>The port given above is optional. It may not be specified, in which case you only -provide the server name. The "$ActionQueueFileName" is used to create queue files, should need -arise. This value must be unique inside rsyslog.conf. No two rules must use the same queue file. -Also, for obvious reasons, it must only contain those characters that can be used inside a -valid file name. Rsyslog possibly adds some characters in front and/or at the end of that name -when it creates files. So that name should not be at the file size name length limit (which -should not be a problem these days). -<p>Please note that actual spool files are only created if the remote server is down -<b>and</b> there is no more space in the in-memory queue. By default, a short failure -of the remote server will never result in the creation of a disk file as a couple of -hundered messages can be held in memory by default. [These parameters can be fine-tuned. However, -then you need to either fully understand how the queue works -(<a href="http://www.rsyslog.com/doc-queues.html">read elaborate doc</a>) or -use <a href="http://www.rsyslog.com/doc-professional_support.html">professional services</a> -to have it done based on -your specs ;) - what that means is that fine-tuning queue parameters is far from -being trivial...] -<p>If you would like to test if your buffering scenario works, you need to -stop, wait a while and restart you central server. Do <b>not</b> watch for files being created, -as this usually does not happen and never happens immediately. - -<h3>Forwarding to More than One Server</h3> -<p>If you have more than one server you would like to forward to, that's quickly done. -Rsyslog has no limit on the number or type of actions, so you can define as many targets -as you like. What is important to know, however, is that the full set of directives make -up an action. So you can not simply add (just) a second forwarding rule, but need to -duplicate the rule configuration as well. Be careful that you use different queue -file names for the second action, else you will mess up your system. -<p>A sample for forwarding to two hosts looks like this: -<p> -<textarea rows="20" cols="80"> -$ModLoad imuxsock # local message reception - -$WorkDirectory /rsyslog/work # default location for work (spool) files - -# start forwarding rule 1 -$ActionQueueType LinkedList # use asynchronous processing -$ActionQueueFileName srvrfwd1 # set file name, also enables disk mode -$ActionResumeRetryCount -1 # infinite retries on insert failure -$ActionQueueSaveOnShutdown on # save in-memory data if rsyslog shuts down -*.* @@server1:port -# end forwarding rule 1 - -# start forwarding rule 2 -$ActionQueueType LinkedList # use asynchronous processing -$ActionQueueFileName srvrfwd2 # set file name, also enables disk mode -$ActionResumeRetryCount -1 # infinite retries on insert failure -$ActionQueueSaveOnShutdown on # save in-memory data if rsyslog shuts down -*.* @@server2 -# end forwarding rule 2 -</textarea> -<p>Note the filename used for the first rule it is "srvrfwd1" and for the second it -is "srvrfwd2". I have used a server without port name in the second forwarding rule. -This was just to illustrate how this can be done. You can also specify a port there -(or drop the port from server1). -<p>When there are multiple action queues, they all work independently. Thus, if server1 -goes down, server2 still receives data in real-time. The client will <b>not</b> block -and wait for server1 to come back online. Similarily, server1's operation will not -be affected by server2's state. - -<h2>Some Final Words on Reliability ...</h2> -<p>Using plain TCP syslog provides a lot of reliability over UDP syslog. However, -plain TCP syslog is <b>not</b> a fully reliable transport. In order to get full reliability, -you need to use the RELP protocol. -<p>Folow the next link to learn more about -<a href="http://blog.gerhards.net/2008/04/on-unreliability-of-plain-tcp-syslog.html">the -problems you may encounter with plain tcp syslog</a>. -<h3>Feedback requested</h3> -<P>I would appreciate feedback on this tutorial. If you have additional ideas, -comments or find bugs (I *do* bugs - no way... ;)), please -<a href="mailto:rgerhards@adiscon.com">let me know</a>.</P> -<h2>Revision History</h2> -<ul> - <li>2008-06-27 * - <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> * Initial Version created</li> -</ul> -<h2>Copyright</h2> -<p>Copyright (c) 2008 -<a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> and -<a href="http://www.adiscon.com/en/">Adiscon</a>.</p> -<p> Permission is granted to copy, distribute and/or modify this document - under the terms of the GNU Free Documentation License, Version 1.2 - or any later version published by the Free Software Foundation; - with no Invariant Sections, no Front-Cover Texts, and no Back-Cover - Texts. A copy of the license can be viewed at -<a href="http://www.gnu.org/copyleft/fdl.html"> -http://www.gnu.org/copyleft/fdl.html</a>.</p> -</body> -</html> |