added ability to specify flow control mode for imuxsock

3 files changed, 51 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index ce359720..f707deec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 ---------------------------------------------------------------------------
 Version 3.21.3  [DEVEL] (rgerhards), 2008-08-??
+- added ability to specify flow control mode for imuxsock
 - added ability to execute actions only after the n-th call of the action
   This also lead to the addition of two new config directives:
   $ActionExecOnlyEveryNthTime and $ActionExecOnlyEveryNthTimeTimeout
diff --git a/doc/imuxsock.html b/doc/imuxsock.html
index 3beabe94..77491992 100644
--- a/doc/imuxsock.html
+++ b/doc/imuxsock.html
@@ -9,23 +9,41 @@
 <p><b>Author: </b>Rainer Gerhards
 &lt;rgerhards@adiscon.com&gt;</p>
 <p><b>Description</b>:</p>
-<p>Provides the ability to accept syslog messages via local Unix
+<p><b>Provides the ability to accept syslog messages via local Unix
 sockets. Most importantly, this is the mechanism by which the syslog(3)
-call delivers syslog messages to rsyslogd. So you need to have this
+call delivers syslog messages to rsyslogd.</b> So you need to have this
 module loaded to read the system log socket and be able to process log
-messages from applications running on the local system.</p><p>Application-provided
-timestamps are ignored by default. This is needed, as some programs
-(e.g. sshd)&nbsp;log with inconsistent timezone information, what
+messages from applications running on the local system.</p>
+<p><b>Application-provided
+timestamps are ignored by default.</b> This is needed, as some programs
+(e.g. sshd) log with inconsistent timezone information, what
 messes up the local logs (which by default don't even contain time zone
 information). This seems to be consistent with what sysklogd did for
 the past four years. Alternate behaviour may be desirable if
 gateway-like processes send messages via the local log slot - in this
 case, it can be enabled via the
-$InputUnixListenSocketIgnoreMsgTimestamp and $SystemLogSocketIgnoreMsgTimestamp config directives</p><p><b>Configuration Directives</b>:</p>
+$InputUnixListenSocketIgnoreMsgTimestamp and $SystemLogSocketIgnoreMsgTimestamp config directives</p>
+<p><b>Unix log sockets can be flow-controlled.</b> That is, if processing queues fill up,
+the unix socket reader is blocked for a short while. This may be useful to prevent overruning
+the queues (which may cause exessive disk-io where it actually would not be needed). However,
+flow-controlling a log socket (and especially the system log socket) can lead to a very
+unresponsive system. As such, flow control is disabled by default. That means any log records
+are places as quickly as possible into the processing queues. If you would like to have
+flow control, you need to enable it via the $SystemLogSocketFlowControl and
+$InputUnixListenSocketFlowControl config directives. Just make sure you thought about
+the implications. Note that for many systems, turning on flow control does not hurt.
+<p><b>Configuration Directives</b>:</p>
 <ul>
-<li><span style="font-weight: bold;">$InputUnixListenSocketIgnoreMsgTimestamp</span> [<span style="font-weight: bold;">on</span>/off]<strong></strong><br>Ignore timestamps included in the message. Applies to the next socket being added.</li><li><span style="font-weight: bold;">$SystemLogSocketIgnoreMsgTimestamp</span> [<span style="font-weight: bold;">on</span>/off]<br>Ignore timestamps included in the messages, applies to messages received via the system log socket.</li><li><span style="font-weight: bold;">$OmitLocalLogging</span> (imuxsock) [on/<b>off</b>] --
-former -o option</li><li><span style="font-weight: bold;">$SystemLogSocketName</span> &lt;name-of-socket&gt; --
-former -p option</li>
+<li><b>$InputUnixListenSocketIgnoreMsgTimestamp</b> [<b>on</b>/off]
+<br>Ignore timestamps included in the message. Applies to the next socket being added.</li>
+<li><b>$InputUnixListenSocketFlowControl</b> [on/<b>off</b>] - specifies if flow control should be applied
+to the next socket.</li>
+<li><b>$SystemLogSocketIgnoreMsgTimestamp</b> [<b>on</b>/off]<br>
+Ignore timestamps included in the messages, applies to messages received via the system log socket.</li>
+<li><b>$OmitLocalLogging</b> (imuxsock) [on/<b>off</b>] -- former -o option</li>
+<li><b>$SystemLogSocketName</b> &lt;name-of-socket&gt; -- former -p option</li>
+<li><b>$SystemLogFlowControl</b> [on/<b>off</b>] - specifies if flow control should be applied
+to the system log socket.</li>
 <li><b>$AddUnixListenSocket</b> &lt;name-of-socket&gt; adds additional unix socket, default none -- former -a option</li>
 <li><b>$InputUnixListenSocketHostName</b> &lt;hostname&gt; permits to override the hostname that
 shall be used inside messages taken from the <b>next</b> $AddUnixListenSocket socket. Note that
@@ -39,7 +57,8 @@ This documentation is sparse and incomplete.
 <p><b>Sample:</b></p>
 <p>The following sample is the minimum setup required to accept syslog messages from applications running on the local system.<br>
 </p>
-<textarea rows="2" cols="60">$ModLoad imuxsock # needs to be done just once
+<textarea rows="2" cols="70">$ModLoad imuxsock # needs to be done just once
+$SystemLogSocketFlowControl on # enable flow control (use if needed)
 </textarea>
 <p>The following sample is a configuration where rsyslogd pulls logs from two
 jails, and assigns different hostnames to each of the jails: </p>
diff --git a/plugins/imuxsock/imuxsock.c b/plugins/imuxsock/imuxsock.c
index 9d2ab8a1..4f1fcea4 100644
--- a/plugins/imuxsock/imuxsock.c
+++ b/plugins/imuxsock/imuxsock.c
@@ -74,6 +74,7 @@ static int funixParseHost[MAXFUNIX] = { 0, }; /* should parser parse host name?
 static int funixFlags[MAXFUNIX] = { ADDDATE, }; /* should parser parse host name?  read-only after startup */
 static uchar *funixn[MAXFUNIX] = { (uchar*) _PATH_LOG }; /* read-only after startup */
 static uchar *funixHName[MAXFUNIX] = { NULL, }; /* host-name override - if set, use this instead of actual name */
+static int funixFlowCtl[MAXFUNIX] = { eFLOWCTL_NO_DELAY, }; /* flow control settings for this socket */
 static int funix[MAXFUNIX] = { -1, }; /* read-only after startup */
 static int nfunix = 1; /* number of Unix sockets open / read-only after startup */
 
@@ -81,6 +82,7 @@ static int nfunix = 1; /* number of Unix sockets open / read-only after startup
 static int bOmitLocalLogging = 0;
 static uchar *pLogSockName = NULL;
 static uchar *pLogHostName = NULL;	/* host name to use with this socket */
+static int bUseFlowCtl = 0;		/* use flow control or not (if yes, only LIGHT is used! */
 static int bIgnoreTimestamp = 1; /* ignore timestamps present in the incoming message? */
 
 
@@ -95,6 +97,14 @@ static rsRetVal setSystemLogTimestampIgnore(void __attribute__((unused)) *pVal,
 	RETiRet;
 }
 
+/* set flowcontrol for the system log socket
+ */
+static rsRetVal setSystemLogFlowControl(void __attribute__((unused)) *pVal, int iNewVal)
+{
+	DEFiRet;
+	funixFlowCtl[0] = iNewVal ? eFLOWCTL_LIGHT_DELAY : eFLOWCTL_NO_DELAY;
+	RETiRet;
+}
 
 /* add an additional listen socket. Socket names are added
  * until the array is filled up. It is never reset, only at
@@ -115,6 +125,7 @@ static rsRetVal addLstnSocketName(void __attribute__((unused)) *pVal, uchar *pNe
 		}
 		funixHName[nfunix] = pLogHostName;
 		pLogHostName = NULL; /* re-init for next, not freed because funixHName[] now owns it */
+		funixFlowCtl[nfunix] = bUseFlowCtl ? eFLOWCTL_LIGHT_DELAY : eFLOWCTL_NO_DELAY;
 		funixFlags[nfunix] = bIgnoreTimestamp ? ADDDATE : NOFLAG;
 		funixn[nfunix++] = pNewVal;
 	}
@@ -193,7 +204,7 @@ static rsRetVal readSocket(int fd, int iSock)
 	if (iRcvd > 0) {
 		parseAndSubmitMessage(funixHName[iSock] == NULL ? glbl.GetLocalHostName() : funixHName[iSock],
 				      (uchar*)"127.0.0.1", line,
-			 	      iRcvd, funixParseHost[iSock], funixFlags[iSock], eFLOWCTL_LIGHT_DELAY);
+			 	      iRcvd, funixParseHost[iSock], funixFlags[iSock], funixFlowCtl[iSock]);
 	} else if (iRcvd < 0 && errno != EINTR) {
 		char errStr[1024];
 		rs_strerror_r(errno, errStr, sizeof(errStr));
@@ -328,6 +339,7 @@ static rsRetVal resetConfigVariables(uchar __attribute__((unused)) *pp, void __a
 	discardFunixn();
 	nfunix = 1;
 	bIgnoreTimestamp = 1;
+	bUseFlowCtl = 0;
 
 	return RS_RET_OK;
 }
@@ -341,6 +353,8 @@ CODEmodInit_QueryRegCFSLineHdlr
 	CHKiRet(objUse(errmsg, CORE_COMPONENT));
 	CHKiRet(objUse(glbl, CORE_COMPONENT));
 
+	dbgprintf("imuxsock version %s initializing\n", PACKAGE_VERSION);
+
 	/* initialize funixn[] array */
 	for(i = 1 ; i < MAXFUNIX ; ++i) {
 		funixn[i] = NULL;
@@ -356,18 +370,22 @@ CODEmodInit_QueryRegCFSLineHdlr
 		NULL, &pLogSockName, STD_LOADABLE_MODULE_ID));
 	CHKiRet(omsdRegCFSLineHdlr((uchar *)"inputunixlistensockethostname", 0, eCmdHdlrGetWord,
 		NULL, &pLogHostName, STD_LOADABLE_MODULE_ID));
+	CHKiRet(omsdRegCFSLineHdlr((uchar *)"inputunixlistensocketflowcontrol", 0, eCmdHdlrBinary,
+		NULL, &bUseFlowCtl, STD_LOADABLE_MODULE_ID));
 	CHKiRet(omsdRegCFSLineHdlr((uchar *)"addunixlistensocket", 0, eCmdHdlrGetWord,
 		addLstnSocketName, NULL, STD_LOADABLE_MODULE_ID));
 	CHKiRet(omsdRegCFSLineHdlr((uchar *)"resetconfigvariables", 1, eCmdHdlrCustomHandler,
 		resetConfigVariables, NULL, STD_LOADABLE_MODULE_ID));
 	/* the following one is a (dirty) trick: the system log socket is not added via
-	 * an "addUnixListenSocket" config format. As such, the timestamp can not be modified
-	 * via $InputUnixListenSocketIgnoreMsgTimestamp". So we need to add a special directive
+	 * an "addUnixListenSocket" config format. As such, it's properties can not be modified
+	 * via $InputUnixListenSocket*". So we need to add a special directive
 	 * for that. We should revisit all of that once we have the new config format...
 	 * rgerhards, 2008-03-06
 	 */
 	CHKiRet(omsdRegCFSLineHdlr((uchar *)"systemlogsocketignoremsgtimestamp", 0, eCmdHdlrBinary,
 		setSystemLogTimestampIgnore, NULL, STD_LOADABLE_MODULE_ID));
+	CHKiRet(omsdRegCFSLineHdlr((uchar *)"systemlogsocketflowcontrol", 0, eCmdHdlrBinary,
+		setSystemLogFlowControl, NULL, STD_LOADABLE_MODULE_ID));
 ENDmodInit
 /* vim:set ai:
  */