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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Fri, 24 May 2013 19:17:18 -0000
Message-ID: <20130524191718.52068.54933@eos.apache.org>
Subject: 
 =?utf-8?q?=5BSolr_Wiki=5D_Update_of_=22SolrLogging=22_by_ShawnHeisey?=
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The "SolrLogging" page has been changed by ShawnHeisey:
http://wiki.apache.org/solr/SolrLogging?action=3Ddiff&rev1=3D30&rev2=3D31

Comment:
added section about intercept jars, other minor edits.

  =

  =3D Solr's Logging Mechanism =3D
  =

- Starting with Solr 1.4, the Solr Code base compiles against the "SLF4J" A=
PI.
+ Starting with Solr 1.4, the Solr Code base compiles against the [[http://=
www.slf4j.org|SLF4J]] API.
  =

  The Solr Admin console has a [[http://localhost:8983/solr/admin/logging.j=
sp|screen for changing the logging level globally]].  This is a transient s=
etting good for doing diagnostic work, but does not persist after restart.
  =

  =3D=3D Solr 4.3 and above =3D=3D
  =

+ =3D=3D=3D What changed =3D=3D=3D
- These versions do not include any logging jars in the WAR file.  They mus=
t be provided separately.  The Solr example for these versions includes jar=
s (in the jetty lib/ext directory) that set up SLF4J with a binding to the =
Apache log4j library.  By changing the jar files, you can easily switch to =
an alternate logging mechanism (like logback) or use upgraded versions of t=
he logging components.
+ These versions do not include any logging jars in the WAR file.  They mus=
t be provided separately.  The Solr example for these versions includes jar=
s (in the jetty lib/ext directory) that set up SLF4J with a binding to the =
Apache log4j library.
  =

+ =3D=3D=3D Why did it change? =3D=3D=3D
+ The logging setup was changed for increased flexibility.  With older vers=
ions, changing your logging mechanism required either building a special ta=
rget from the source code or doing surgery on the WAR file.  Now anyone can=
 change to another logging mechanism or upgrade to newer component versions=
 simply by changing jar files.
+ =

+ =3D=3D=3D A note about SLF4J intercept jars =3D=3D=3D
+ Some of the third-party software components in Solr do not use the SLF4J =
library for their logging, they use one of the other logging frameworks dir=
ectly.  SLF4J includes various 'intercept' jars that grab the output of the=
se direct calls and send them through SLF4J so that all your logs end up ha=
ndled by the same configuration.  The logging frameworks that must be dealt=
 with are java.util.logging (JUL), java.commons.logging (JCL), and log4j.
+ =

+ The default SLF4J logging destination for the 4.3 example is log4j, so th=
e example does not need to intercept calls for that framework.  They will b=
e handled by the real log4j jar.  It only needs to intercept JUL and JCL, a=
s described above.  This is why the jul-to-slf4j and jcl-over-slf4j jars ar=
e included in the 4.3 example.  If you change your logging framework from l=
og4j to JUL, then you must remove the intercept jar for JUL and add the int=
ercept jar for log4j, which is named log4j-over-slf4j.  If you use an entir=
ely different logging mechanism like logback, then you must have intercepts=
 for all three - JUL, JCL, and log4j.
+ =

+ =3D=3D=3D Using the example logging setup in containers other than Jetty =
=3D=3D=3D
- To get the same logging setup in e.g. Tomcat as with the example Jetty se=
rver, you need to do the following
+ To get the same logging setup in another container (Tomcat for example) a=
s with the example Jetty server, you need to do the following
   1. Copy the jars from {{{solr/example/lib/ext}}} into {{{tomcat/lib}}} t=
o setup SLF4J
-  2. Copy the logging config from {{{solr/example/resources/log4j.properti=
es}}} into some location, e.g. {{{tomcat/lib}}} and edit the file for you p=
referred log destination
+  1. Copy the logging config from {{{solr/example/resources/log4j.properti=
es}}} into a location on the classpath.  Usually you can use the same locat=
ion as the jar files above.  Edit the configuration file for your preferred=
 log destination.
-  3. Optionally, if you did not place {{{log4j.properties}}}=C2=A0on the c=
lasspath, set java option {{{-Dlog4j.configuration=3Dfile:///path/to/log4j.=
properties}}}
+  1. Optionally, if you did not place {{{log4j.properties}}}=C2=A0on the c=
lasspath, set java option {{{-Dlog4j.configuration=3Dfile:///path/to/log4j.=
properties}}}
  =

- If the system cannot find your logging configuration, you may get erros l=
ike this:
+ If the system cannot find your logging configuration, you may get errors =
like this:
  {{{
  log4j:WARN No appenders could be found for logger (org.apache.solr.servle=
t.SolrDispatchFilter).
  log4j:WARN Please initialize the log4j system properly.
@@ -27, +37 @@

  It might help to start the server with {{{-Dlog4j.debug=3Dtrue}}} to see =
more details.
  =

  =3D=3D=3D Switching from Log4J logging back to Java-util logging =3D=3D=
=3D
- If you want to stick to the old-style logging, here's what to do (assumin=
g solr4.3 - note that SLF4J version may be different for newer versions)
+ If you want to stick to the old-style logging, here's what to do.  This a=
ssumes that the slf4j version is 1.6.6, which comes with [[Solr4.3]].  Newe=
r versions may use a different slf4j version.  All slf4j components in your=
 classpath must be the same version.
   1. Download slf4j version 1.6.6 (the version used in Solr4.3.x). http://=
www.slf4j.org/dist/slf4j-1.6.6.zip
-  2. Unpack, and pull out the file slf4j-jdk14-1.6.6.jar (This is the JUL =
logger impl)
+  2. Unpack the slf4j archive.
   3. Delete these JARs from your lib folder: slf4j-log4j12-1.6.6.jar, jul-=
to-slf4j-1.6.6.jar, log4j-1.2.16.jar
   4. Add these JARs to your lib folder (from slf4j zip): slf4j-jdk14-1.6.6=
.jar, log4j-over-slf4j-1.6.6.jar
   5. Use your old logging.properties