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schultz pushed a commit to branch 9.0.x
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The following commit(s) were added to refs/heads/9.0.x by this push:
new b75ee12 Fix https://bz.apache.org/bugzilla/show_bug.cgi?id=62723
b75ee12 is described below
commit b75ee12a4ed6724c21f1a670b5a569ff5e043e52
Author: Christopher Schultz <[email protected]>
AuthorDate: Tue Aug 4 16:59:34 2020 -0400
Fix https://bz.apache.org/bugzilla/show_bug.cgi?id=62723
Clarify the effects of some cluster channelSendOptions.
Patch provided by Mitch Claborn.
---
webapps/docs/changelog.xml | 4 ++++
webapps/docs/cluster-howto.xml | 2 ++
webapps/docs/config/cluster.xml | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 40 insertions(+)
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index 95ddadf..1806b15 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -105,6 +105,10 @@
Clean-up / standardize the XSL files used to generate the
documentation.
PR provided by John Bampton. (markt)
</fix>
+ <fix>
+ <bug>62723</bug>: Clarify the effects of some options for cluster
+ <code>channelSendOptions</code>. Patch provided by Mitch Claborn.
+ (schultz)
</changelog>
</subsection>
<subsection name="Other">
diff --git a/webapps/docs/cluster-howto.xml b/webapps/docs/cluster-howto.xml
index cfbfc2f..09cdb2c 100644
--- a/webapps/docs/cluster-howto.xml
+++ b/webapps/docs/cluster-howto.xml
@@ -218,6 +218,8 @@ should be completed:</p>
Synchronous vs. asynchronous is configured using the
<code>channelSendOptions</code>
flag and is an integer value. The default value for the
<code>SimpleTcpCluster/DeltaManager</code> combo is
8, which is asynchronous.
+ See the <a
href="config/cluster.html#SimpleTcpCluster_Attributes">configuration
reference</a>
+ for more discussion on the various <code>channelSendOptions</code> values.
</p>
<p>
For convenience, <code>channelSendOptions</code> can be set by name(s)
rather than integer,
diff --git a/webapps/docs/config/cluster.xml b/webapps/docs/config/cluster.xml
index 91e8328..12434a8 100644
--- a/webapps/docs/config/cluster.xml
+++ b/webapps/docs/config/cluster.xml
@@ -146,6 +146,40 @@ Tomcat cluster. These include:</p>
to the order in which they were sent.
</p>
<p>
+ The various <code>channelSendOptions</code> values offer a tradeoff
+ between throughput on the sending node and the reliability of
+ replication should the sending or receiving node(s) fail. Here are
+ some common options. "Message" could be any message sent between nodes,
+ but only session-change messages are considered, here.
+ </p>
+ <p>
+ <code>channelSendOptions="8"</code> /
<code>channelSendOptions="async"</code>
+ As far as the sender is concerned, the message is "sent"
+ as soon as it has been placed in the queue on the sender for
+ transmission to the other nodes. The message may not reach any or all
+ of the recipient nodes and may not be successfully processed on any
+ nodes that it does reach. This option offers the highest throughput on
+ the sender but the least reliability, as the triggering request will
+ complete without any knowledge of the success/failure of the session
+ replication.
+ </p>
+ <p>
+ <code>channelSendOptions="2"</code> /
<code>channelSendOptions="use_ack"</code>
+ The sender will block the completion of the current request until all
+ of the receiving nodes have acknowledged that they have received the
+ message, but have not necessarily processed that message. This option
+ will result in lower throughput on the sending node, because the
message
+ must be transmitted and the acknowledgement received, but the
+ reliability is greater than the asynchronous model.
+ </p>
+ <p>
+ <code>channelSendOptions="6"</code> /
<code>channelSendOptions="sync,use_ack"</code>
+ The sender will block the completion of the current request until
+ all of the receiving nodes have acknowledged that they have received
+ <u>and</u> processed the message. This option will have the lowest
+ throughput (of these three) but the greatest reliability.
+ </p>
+ <p>
You may also set these options as a comma separated string, e.g. "async,
multicast", which
will be translated into <code>Channel.SEND_OPTIONS_ASYNCHRONOUS |
Channel.SEND_OPTIONS_MULTICAST</code>
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