From: Luca Toscano <elukey@apache.org>
Date: Fri, 28 Jul 2017 09:29:20 +0000 (+0000)
Subject: mod_proxy*.xml: improve connection reuse documentation
X-Git-Tag: 2.4.28~94
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3e057be995f8063e4b211bd8ebe0c46ab68969e5;p=apache

mod_proxy*.xml: improve connection reuse documentation

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1803258 13f79535-47bb-0310-9956-ffa450edef68
---

diff --git a/docs/manual/mod/mod_proxy.xml b/docs/manual/mod/mod_proxy.xml
index 094f1de113..73b2042b1d 100644
--- a/docs/manual/mod/mod_proxy.xml
+++ b/docs/manual/mod/mod_proxy.xml
@@ -201,7 +201,7 @@ ProxyVia On
 
       <p>The two default workers have a fixed configuration
       and will be used if no other worker matches the request.
-      They do not use HTTP Keep-Alive or connection pooling.
+      They do not use HTTP Keep-Alive or connection reuse.
       The TCP connections to the origin server will instead be
       opened and closed for each request.</p>
 
@@ -306,8 +306,8 @@ ProxyPass "/examples" "http://backend.example.com/examples" timeout=10
       <note><title>DNS resolution for origin domains</title>
       <p>DNS resolution happens when the socket to
         the origin domain is created for the first time.
-        When connection pooling is used, each backend domain is resolved 
-        only once per child process, and reused for all further connections 
+        When connection reuse is enabled, each backend domain is resolved 
+        only once per child process, and cached for all further connections 
         until the child is recycled. This information should to be considered 
         while planning DNS maintenance tasks involving backend domains. 
         Please also check <directive module="mod_proxy">ProxyPass</directive>
@@ -871,7 +871,11 @@ expressions</description>
     a local virtual path; <var>url</var> is a partial URL for the
     remote server and cannot include a query string.</p>
 
-    <note><strong>Note: </strong>This directive is not supported within
+    <note>It is strongly suggested to review the concept of a
+    <a href="#workers">Worker</a> before proceeding any further
+    with this section.</note>
+
+    <note>This directive is not supported within
     <directive type="section" module="core">Directory</directive> and
     <directive type="section" module="core">Files</directive> containers.</note>
 
@@ -986,27 +990,29 @@ ProxyPass "/mirror/foo" "http://backend.example.com"
     using  <code>key=value</code> parameters, described in the tables
     below.</p>
 
+    <note type="warning"><title>Maximum connections to the backend</title>
     <p>By default, mod_proxy will allow and retain the maximum number of
     connections that could be used simultaneously by that web server child
     process.  Use the <code>max</code> parameter to reduce the number from
-    the default.  Use the <code>ttl</code> parameter to set an optional
+    the default. The pool of connections is maintained per web server child
+    process, and <code>max</code> and other settings are not coordinated
+    among all child processes, except when only one child process is allowed
+    by configuration or MPM design.</p>
+    </note>
+
+    <p>Use the <code>ttl</code> parameter to set an optional
     time to live; connections which have been unused for at least
     <code>ttl</code> seconds will be closed.  <code>ttl</code> can be used
     to avoid using a connection which is subject to closing because of the
     backend server's keep-alive timeout.</p>
 
-    <p>The pool of connections is maintained per web server child
-    process, and <code>max</code> and other settings are not coordinated
-    among all child processes, except when only one child process is allowed
-    by configuration or MPM design.</p>
-
     <example><title>Example</title>
         <highlight language="config">
         ProxyPass "/example" "http://backend.example.com" max=20 ttl=120 retry=300
         </highlight>
     </example>
 
-    <table border="2"><tr><th>BalancerMember parameters</th></tr></table>
+    <table border="2"><tr><th>Worker|BalancerMember parameters</th></tr></table>
     <table>
     <tr><th>Parameter</th>
         <th>Default</th>
@@ -1057,7 +1063,10 @@ ProxyPass "/mirror/foo" "http://backend.example.com"
     httpd and
     the backend server (regardless of protocol) tends to silently
     drop connections or when backends themselves may be under round-
-    robin DNS. To disable connection pooling reuse,
+    robin DNS.
+    When connection reuse is enabled each backend domain is resolved
+    (with a DNS query) only once per child process and cached for all further
+    connections until the child is recycled. To disable connection reuse,
     set this property value to <code>On</code>.
     </td></tr>
     <tr><td>enablereuse</td>
diff --git a/docs/manual/mod/mod_proxy_fcgi.xml b/docs/manual/mod/mod_proxy_fcgi.xml
index fac574425b..fa1e5cc8f1 100644
--- a/docs/manual/mod/mod_proxy_fcgi.xml
+++ b/docs/manual/mod/mod_proxy_fcgi.xml
@@ -85,7 +85,7 @@ ProxyPass "/myapp/" "fcgi://localhost:4000/" enablereuse=on
     <p> The following example passes the request URI as a filesystem
     path for the PHP-FPM daemon to run. The request URL is implicitly added
     to the 2nd parameter. The hostname and port following fcgi:// are where
-    PHP-FPM is listening.  Connection pooling is enabled.</p>
+    PHP-FPM is listening.  Connection pooling/reuse is enabled.</p>
     <example><title>PHP-FPM</title>
     <highlight language="config">
 ProxyPassMatch "^/myapp/.*\.php(/.*)?$" "fcgi://localhost:9000/var/www/" enablereuse=on
diff --git a/docs/manual/rewrite/flags.xml b/docs/manual/rewrite/flags.xml
index 1ec7ce553a..8f5ac3ec32 100644
--- a/docs/manual/rewrite/flags.xml
+++ b/docs/manual/rewrite/flags.xml
@@ -547,7 +547,7 @@ client undue influence.</p>
 <p>Using this flag triggers the use of <module>mod_proxy</module>, without handling of persistent connections. This
 means the performance of your proxy will be better if you set it up with <directive module="mod_proxy">ProxyPass</directive> or
 <directive module="mod_proxy">ProxyPassMatch</directive></p>
-<p>This is because this flag triggers the use of the default worker, which does not handle connection pooling.</p>
+<p>This is because this flag triggers the use of the default worker, which does not handle connection pooling/reuse.</p>
 <p>Avoid using this flag and prefer those directives, whenever you can.</p>
 </note>