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Move DNS cache settings to important configuration 

This commit moves the DNS cache settings for the JVM to the important
settings section of the docs.

Relates #27592
This commit is contained in:
Jason Tedor 2017-11-29 18:02:26 -05:00 committed by GitHub
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commit ff3c19ed13
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2 changed files with 25 additions and 10 deletions
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16
docs/reference/modules/discovery/zen.asciidoc
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@ -22,16 +22,12 @@ other nodes.
[[unicast]] [[unicast]]
===== Unicast ===== Unicast
Unicast discovery requires a list of hosts to use that will act as gossip routers. These hosts can be specified as Unicast discovery requires a list of hosts to use that will act as gossip
hostnames or IP addresses; hosts specified as hostnames are resolved to IP addresses during each round of pinging. Note routers. These hosts can be specified as hostnames or IP addresses; hosts
that with the Java security manager in place, the JVM defaults to caching positive hostname resolutions indefinitely. specified as hostnames are resolved to IP addresses during each round of
This can be modified by adding pinging. Note that if you are in an environment where DNS resolutions vary with
http://docs.oracle.com/javase/8/docs/technotes/guides/net/properties.html[`networkaddress.cache.ttl=<timeout>`] to your time, you might need to adjust your <<networkaddress-cache-ttl,JVM security
http://docs.oracle.com/javase/8/docs/technotes/guides/security/PolicyFiles.html[Java security policy]. Any hosts that settings>>.
fail to resolve will be logged. Note also that with the Java security manager in place, the JVM defaults to caching
negative hostname resolutions for ten seconds. This can be modified by adding
http://docs.oracle.com/javase/8/docs/technotes/guides/net/properties.html[`networkaddress.cache.negative.ttl=<timeout>`]
to your http://docs.oracle.com/javase/8/docs/technotes/guides/security/PolicyFiles.html[Java security policy].
It is recommended that the unicast hosts list be maintained as the list of It is recommended that the unicast hosts list be maintained as the list of
master-eligible nodes in the cluster. master-eligible nodes in the cluster.

19
docs/reference/setup/important-settings.asciidoc
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@ -201,3 +201,22 @@ the Elasticsearch process. If you wish to configure a heap dump path, you should
modify the entry `#-XX:HeapDumpPath=/heap/dump/path` in modify the entry `#-XX:HeapDumpPath=/heap/dump/path` in
<<jvm-options,`jvm.options`>> to remove the comment marker `#` and to specify an <<jvm-options,`jvm.options`>> to remove the comment marker `#` and to specify an
actual path. actual path.
[float]
[[networkaddress-cache-ttl]]
Elasticsearch runs with a security manager in place. With a security manager in
place, the JVM defaults to caching positive hostname resolutions
indefinitely. If your Elasticsearch nodes rely on DNS in an environment where
DNS resolutions vary with time (e.g., for node-to-node discovery) then you might
want to modify the default JVM behavior. This can be modified by adding
http://docs.oracle.com/javase/8/docs/technotes/guides/net/properties.html[`networkaddress.cache.ttl=<timeout>`]
to your
http://docs.oracle.com/javase/8/docs/technotes/guides/security/PolicyFiles.html[Java
security policy]. Any hosts that fail to resolve will be logged. Note also that
with the Java security manager in place, the JVM defaults to caching negative
hostname resolutions for ten seconds. This can be modified by adding
http://docs.oracle.com/javase/8/docs/technotes/guides/net/properties.html[`networkaddress.cache.negative.ttl=<timeout>`]
to your
http://docs.oracle.com/javase/8/docs/technotes/guides/security/PolicyFiles.html[Java
security policy].