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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE document [
<!ENTITY project SYSTEM "project.xml">
]>
<document url="ajp.html">
&project;
<properties>
<author email="yoavs@apache.org">Yoav Shapira</author>
<author email="arjaquith@mindspring.com">Andrew R. Jaquith</author>
<title>The AJP Connector</title>
</properties>
<body>
<section name="Table of Contents">
<toc/>
</section>
<section name="Introduction">
<p>The <strong>AJP Connector</strong> element represents a
<strong>Connector</strong> component that communicates with a web
connector via the <code>AJP</code> protocol. This is used for cases
where you wish to invisibly integrate Tomcat into an existing (or new)
Apache installation, and you want Apache to handle the static content
contained in the web application, and/or utilize Apache's SSL
processing.</p>
<p>Use of the AJP protocol requires additional security considerations because
it allows greater direct manipulation of Tomcat's internal data structures
than the HTTP connectors. Particular attention should be paid to the values
used for the <code>address</code>, <code>secret</code>,
<code>secretRequired</code> and <code>allowedRequestAttributesPattern</code>
attributes.</p>
<p>This connector supports load balancing when used in conjunction with
the <code>jvmRoute</code> attribute of the
<a href="engine.html">Engine</a>.</p>
<p>The native connectors supported with this Tomcat release are:</p>
<ul>
<li>JK 1.2.x with any of the supported servers. See
<a href="https://tomcat.apache.org/connectors-doc/">the JK docs</a>
for details.</li>
<li>mod_proxy on Apache httpd 2.x (included by default in Apache HTTP
Server 2.2), with AJP enabled: see
<a href="https://httpd.apache.org/docs/2.2/mod/mod_proxy_ajp.html">the
httpd docs</a> for details.</li>
</ul>
<p><b>Other native connectors supporting AJP may work, but are no longer
supported.</b></p>
</section>
<section name="Attributes">
<subsection name="Common Attributes">
<p>All implementations of <strong>Connector</strong>
support the following attributes:</p>
<attributes>
<attribute name="ajpFlush" required="false">
<p>A boolean value which can be used to enable or disable sending
AJP flush messages to the fronting proxy whenever an explicit
flush happens. The default value is <code>true</code>.<br/>
An AJP flush message is a SEND_BODY_CHUNK packet with no body content.
Proxy implementations like mod_jk or mod_proxy_ajp will flush the
data buffered in the web server to the client when they receive
such a packet. Setting this to <code>false</code> can reduce
AJP packet traffic but might delay sending packets to the client.
At the end of the response, AJP does always flush to the client.</p>
</attribute>
<attribute name="allowTrace" required="false">
<p>A boolean value which can be used to enable or disable the TRACE
HTTP method. If not specified, this attribute is set to false.</p>
</attribute>
<attribute name="asyncTimeout" required="false">
<p>The default timeout for asynchronous requests in milliseconds. If not
specified, this attribute is set to the Servlet specification default of
30000 (30 seconds).</p>
</attribute>
<attribute name="enableLookups" required="false">
<p>Set to <code>true</code> if you want calls to
<code>request.getRemoteHost()</code> to perform DNS lookups in
order to return the actual host name of the remote client. Set
to <code>false</code> to skip the DNS lookup and return the IP
address in String form instead (thereby improving performance).
By default, DNS lookups are disabled.</p>
</attribute>
<attribute name="maxHeaderCount" required="false">
<p>The maximum number of headers in a request that are allowed by the
container. A request that contains more headers than the specified limit
will be rejected. A value of less than 0 means no limit.
If not specified, a default of 100 is used.</p>
</attribute>
<attribute name="maxParameterCount" required="false">
<p>The maximum number of parameter and value pairs (GET plus POST) which
will be automatically parsed by the container. Parameter and value pairs
beyond this limit will be ignored. A value of less than 0 means no limit.
If not specified, a default of 10000 is used. Note that
<code>FailedRequestFilter</code> <a href="filter.html">filter</a> can be
used to reject requests that hit the limit.</p>
</attribute>
<attribute name="maxPostSize" required="false">
<p>The maximum size in bytes of the POST which will be handled by
the container FORM URL parameter parsing. The limit can be disabled by
setting this attribute to a value less than zero. If not specified, this
attribute is set to 2097152 (2 megabytes). Note that the
<a href="filter.html#Failed_Request_Filter"><code>FailedRequestFilter</code></a>
can be used to reject requests that exceed this limit.</p>
</attribute>
<attribute name="maxSavePostSize" required="false">
<p>The maximum size in bytes of the POST which will be saved/buffered by
the container during FORM or CLIENT-CERT authentication. For both types
of authentication, the POST will be saved/buffered before the user is
authenticated. For CLIENT-CERT authentication, the POST is buffered for
the duration of the SSL handshake and the buffer emptied when the request
is processed. For FORM authentication the POST is saved whilst the user
is re-directed to the login form and is retained until the user
successfully authenticates or the session associated with the
authentication request expires. The limit can be disabled by setting this
attribute to -1. Setting the attribute to zero will disable the saving of
POST data during authentication. If not specified, this attribute is set
to 4096 (4 kilobytes).</p>
</attribute>
<attribute name="parseBodyMethods" required="false">
<p>A comma-separated list of HTTP methods for which request
bodies using <code>application/x-www-form-urlencoded</code> will be parsed
for request parameters identically to POST. This is useful in RESTful
applications that want to support POST-style semantics for PUT requests.
Note that any setting other than <code>POST</code> causes Tomcat
to behave in a way that goes against the intent of the servlet
specification.
The HTTP method TRACE is specifically forbidden here in accordance
with the HTTP specification.
The default is <code>POST</code></p>
</attribute>
<attribute name="port" required="true">
<p>The TCP port number on which this <strong>Connector</strong>
will create a server socket and await incoming connections. Your
operating system will allow only one server application to listen
to a particular port number on a particular IP address. If the special
value of 0 (zero) is used, then Tomcat will select a free port at random
to use for this connector. This is typically only useful in embedded and
testing applications.</p>
</attribute>
<attribute name="protocol" required="false">
<p>Sets the protocol to handle incoming traffic. To configure an AJP
connector this must be specified. If no value for protocol is provided,
an <a href="http.html">HTTP connector</a> rather than an AJP connector
will be configured.<br/>
The standard protocol value for an AJP connector is <code>AJP/1.3</code>
which uses an auto-switching mechanism to select either a Java NIO based
connector or an APR/native based connector. If the
<code>PATH</code> (Windows) or <code>LD_LIBRARY_PATH</code> (on most unix
systems) environment variables contain the Tomcat native library, the
native/APR connector will be used. If the native library cannot be
found, the Java NIO based connector will be used.<br/>
To use an explicit protocol rather than rely on the auto-switching
mechanism described above, the following values may be used:<br/>
<code>org.apache.coyote.ajp.AjpNioProtocol</code>
- non blocking Java NIO connector.<br/>
<code>org.apache.coyote.ajp.AjpNio2Protocol</code>
- non blocking Java NIO2 connector.<br/>
<code>org.apache.coyote.ajp.AjpAprProtocol</code>
- the APR/native connector.<br/>
Custom implementations may also be used.<br/>
Take a look at our <a href="#Connector_Comparison">Connector
Comparison</a> chart.
</p>
</attribute>
<attribute name="proxyName" required="false">
<p>If this <strong>Connector</strong> is being used in a proxy
configuration, configure this attribute to specify the server name
to be returned for calls to <code>request.getServerName()</code>.
See <a href="#Proxy_Support">Proxy Support</a> for more
information.</p>
</attribute>
<attribute name="proxyPort" required="false">
<p>If this <strong>Connector</strong> is being used in a proxy
configuration, configure this attribute to specify the server port
to be returned for calls to <code>request.getServerPort()</code>.
See <a href="#Proxy_Support">Proxy Support</a> for more
information.</p>
</attribute>
<attribute name="redirectPort" required="false">
<p>If this <strong>Connector</strong> is supporting non-SSL
requests, and a request is received for which a matching
<code>&lt;security-constraint&gt;</code> requires SSL transport,
Catalina will automatically redirect the request to the port
number specified here.</p>
</attribute>
<attribute name="scheme" required="false">
<p>Set this attribute to the name of the protocol you wish to have
returned by calls to <code>request.getScheme()</code>. For
example, you would set this attribute to "<code>https</code>"
for an SSL Connector. The default value is "<code>http</code>".
</p>
</attribute>
<attribute name="secure" required="false">
<p>Set this attribute to <code>true</code> if you wish to have
calls to <code>request.isSecure()</code> to return <code>true</code>
for requests received by this Connector. You would want this on an
SSL Connector or a non SSL connector that is receiving data from a
SSL accelerator, like a crypto card, an SSL appliance or even a webserver.
The default value is <code>false</code>.</p>
</attribute>
<attribute name="sendReasonPhrase" required="false">
<p>Set this attribute to <code>true</code> if you wish to have
a reason phrase in the response.
The default value is <code>false</code>.</p>
<p><strong>Note:</strong> This option is deprecated and will be removed
in Tomcat 9. The reason phrase will not be sent.</p>
</attribute>
<attribute name="URIEncoding" required="false">
<p>This specifies the character encoding used to decode the URI bytes,
after %xx decoding the URL. If not specified, UTF-8 will be used unless
the <code>org.apache.catalina.STRICT_SERVLET_COMPLIANCE</code>
<a href="systemprops.html">system property</a> is set to <code>true</code>
in which case ISO-8859-1 will be used.</p>
</attribute>
<attribute name="useBodyEncodingForURI" required="false">
<p>This specifies if the encoding specified in contentType should be used
for URI query parameters, instead of using the URIEncoding. This
setting is present for compatibility with Tomcat 4.1.x, where the
encoding specified in the contentType, or explicitly set using
Request.setCharacterEncoding method was also used for the parameters from
the URL. The default value is <code>false</code>.
</p>
<p><em>Notes:</em> See notes on this attribute in
<a href="http.html">HTTP Connector</a> documentation.</p>
</attribute>
<attribute name="useIPVHosts" required="false">
<p>Set this attribute to <code>true</code> to cause Tomcat to use
the IP address passed by the native web server to determine the Host
to send the request to. The default value is <code>false</code>.</p>
</attribute>
<attribute name="xpoweredBy" required="false">
<p>Set this attribute to <code>true</code> to cause Tomcat to advertise
support for the Servlet specification using the header recommended in the
specification. The default value is <code>false</code>.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Standard Implementations">
<p>To use AJP, you must specify the protocol attribute (see above).</p>
<p>The standard AJP connectors (NIO, NIO2 and APR/native) all support the
following attributes in addition to the common Connector attributes listed
above.</p>
<attributes>
<attribute name="acceptCount" required="false">
<p>The maximum queue length for incoming connection requests when
all possible request processing threads are in use. Any requests
received when the queue is full will be refused. The default
value is 100.</p>
</attribute>
<attribute name="acceptorThreadCount" required="false">
<p>The number of threads to be used to accept connections. Increase this
value on a multi CPU machine, although you would never really need more
than <code>2</code>. Also, with a lot of non keep alive connections, you
might want to increase this value as well. Default value is
<code>1</code>.</p>
</attribute>
<attribute name="acceptorThreadPriority" required="false">
<p>The priority of the acceptor threads. The threads used to accept
new connections. The default value is <code>5</code> (the value of the
<code>java.lang.Thread.NORM_PRIORITY</code> constant). See the JavaDoc
for the <code>java.lang.Thread</code> class for more details on what
this priority means.</p>
</attribute>
<attribute name="address" required="false">
<p>For servers with more than one IP address, this attribute
specifies which address will be used for listening on the specified
port. By default, the loopback address will be used.</p>
</attribute>
<attribute name="allowedRequestAttributesPattern" required="false">
<p>The AJP protocol passes some information from the reverse proxy to the
AJP connector using request attributes. These attributes are:</p>
<ul>
<li>javax.servlet.request.cipher_suite</li>
<li>javax.servlet.request.key_size</li>
<li>javax.servlet.request.ssl_session</li>
<li>javax.servlet.request.X509Certificate</li>
<li>AJP_LOCAL_ADDR</li>
<li>AJP_REMOTE_PORT</li>
<li>AJP_SSL_PROTOCOL</li>
<li>JK_LB_ACTIVATION</li>
</ul>
<p>The AJP protocol supports the passing of arbitrary request attributes.
Requests containing arbitrary request attributes will be rejected with a
403 response unless the entire attribute name matches this regular
expression. If not specified, the default value is <code>null</code>.</p>
</attribute>
<attribute name="bindOnInit" required="false">
<p>Controls when the socket used by the connector is bound. By default it
is bound when the connector is initiated and unbound when the connector is
destroyed. If set to <code>false</code>, the socket will be bound when the
connector is started and unbound when it is stopped.</p>
</attribute>
<attribute name="clientCertProvider" required="false">
<p>When client certificate information is presented in a form other than
instances of <code>java.security.cert.X509Certificate</code> it needs to
be converted before it can be used and this property controls which JSSE
provider is used to perform the conversion. For example it is used with
the AJP connectors, the <a href="http.html">HTTP APR connector</a> and
with the <a href="valve.html#SSL_Authenticator_Valve">
org.apache.catalina.valves.SSLValve</a>.If not specified, the default
provider will be used.</p>
</attribute>
<attribute name="connectionLinger" required="false">
<p>The number of seconds during which the sockets used by this
<strong>Connector</strong> will linger when they are closed. The default
value is <code>-1</code> which disables socket linger.</p>
</attribute>
<attribute name="connectionTimeout" required="false">
<p>The number of milliseconds this <strong>Connector</strong> will wait,
after accepting a connection, for the request URI line to be
presented. The default value for AJP protocol connectors
is <code>-1</code> (i.e. infinite).</p>
</attribute>
<attribute name="executor" required="false">
<p>A reference to the name in an <a href="executor.html">Executor</a>
element. If this attribute is set, and the named executor exists, the
connector will use the executor, and all the other thread attributes will
be ignored. Note that if a shared executor is not specified for a
connector then the connector will use a private, internal executor to
provide the thread pool.</p>
</attribute>
<attribute name="executorTerminationTimeoutMillis" required="false">
<p>The time that the private internal executor will wait for request
processing threads to terminate before continuing with the process of
stopping the connector. If not set, the default is <code>5000</code> (5
seconds).</p>
</attribute>
<attribute name="keepAliveTimeout" required="false">
<p>The number of milliseconds this <strong>Connector</strong> will wait for
another AJP request before closing the connection.
The default value is to use the value that has been set for the
connectionTimeout attribute.</p>
</attribute>
<attribute name="maxConnections" required="false">
<p>The maximum number of connections that the server will accept and
process at any given time. When this number has been reached, the server
will accept, but not process, one further connection. This additional
connection be blocked until the number of connections being processed
falls below <strong>maxConnections</strong> at which point the server will
start accepting and processing new connections again. Note that once the
limit has been reached, the operating system may still accept connections
based on the <code>acceptCount</code> setting. The default value varies by
connector type. For NIO and NIO2 the default is <code>10000</code>.
For APR/native, the default is <code>8192</code>.</p>
<p>For NIO/NIO2 only, setting the value to -1, will disable the
maxConnections feature and connections will not be counted.</p>
</attribute>
<attribute name="maxCookieCount" required="false">
<p>The maximum number of cookies that are permitted for a request. A value
of less than zero means no limit. If not specified, a default value of 200
will be used.</p>
</attribute>
<attribute name="maxThreads" required="false">
<p>The maximum number of request processing threads to be created
by this <strong>Connector</strong>, which therefore determines the
maximum number of simultaneous requests that can be handled. If
not specified, this attribute is set to 200. If an executor is associated
with this connector, this attribute is ignored as the connector will
execute tasks using the executor rather than an internal thread pool. Note
that if an executor is configured any value set for this attribute will be
recorded correctly but it will be reported (e.g. via JMX) as
<code>-1</code> to make clear that it is not used.</p>
</attribute>
<attribute name="minSpareThreads" required="false">
<p>The minimum number of threads always kept running. This includes both
active and idle threads. If not specified, the default of <code>10</code>
is used. If an executor is associated with this connector, this attribute
is ignored as the connector will execute tasks using the executor rather
than an internal thread pool. Note that if an executor is configured any
value set for this attribute will be recorded correctly but it will be
reported (e.g. via JMX) as <code>-1</code> to make clear that it is not
used.</p>
</attribute>
<attribute name="packetSize" required="false">
<p>This attribute sets the maximum AJP packet size in Bytes. The maximum
value is 65536. It should be the same as the <code>max_packet_size</code>
directive configured for mod_jk. Normally it is not necessary to change
the maximum packet size. Problems with the default value have been
reported when sending certificates or certificate chains. The default
value is 8192. If set to less than 8192 then the setting will ignored and
the default value of 8192 used.</p>
</attribute>
<attribute name="processorCache" required="false">
<p>The protocol handler caches Processor objects to speed up performance.
This setting dictates how many of these objects get cached.
<code>-1</code> means unlimited, default is <code>200</code>. If not using
Servlet 3.0 asynchronous processing, a good default is to use the same as
the maxThreads setting. If using Servlet 3.0 asynchronous processing, a
good default is to use the larger of maxThreads and the maximum number of
expected concurrent requests (synchronous and asynchronous).</p>
</attribute>
<attribute name="secret" required="false">
<p>Only requests from workers with this secret keyword will be accepted.
The default value is <code>null</code>. This attrbute must be specified
with a non-null, non-zero length value unless
<strong>secretRequired</strong> is explicitly configured to be
<code>false</code>.</p>
</attribute>
<attribute name="secretRequired" required="false">
<p>If this attribute is <code>true</code>, the AJP Connector will only
start if the <strong>secret</strong> attribute is configured with a
non-null, non-zero length value. The default value is <code>true</code>.
This attributue should only be set to <code>false</code> when the
Connector is used on a trusted network.</p>
</attribute>
<attribute name="tcpNoDelay" required="false">
<p>If set to <code>true</code>, the TCP_NO_DELAY option will be
set on the server socket, which improves performance under most
circumstances. This is set to <code>true</code> by default.</p>
</attribute>
<attribute name="threadPriority" required="false">
<p>The priority of the request processing threads within the JVM.
The default value is <code>5</code> (the value of the
<code>java.lang.Thread.NORM_PRIORITY</code> constant). See the JavaDoc
for the <code>java.lang.Thread</code> class for more details on what
this priority means.If an executor is associated
with this connector, this attribute is ignored as the connector will
execute tasks using the executor rather than an internal thread pool. Note
that if an executor is configured any value set for this attribute will be
recorded correctly but it will be reported (e.g. via JMX) as
<code>-1</code> to make clear that it is not used.</p>
</attribute>
<attribute name="tomcatAuthentication" required="false">
<p>If set to <code>true</code>, the authentication will be done in Tomcat.
Otherwise, the authenticated principal will be propagated from the native
webserver and used for authorization in Tomcat. Note that this principal
will have no roles associated with it.
The default value is <code>true</code>. If
<code>tomcatAuthorization</code> is set to <code>true</code> this
attribute has no effect.</p>
</attribute>
<attribute name="tomcatAuthorization" required="false">
<p>If set to <code>true</code>, the authenticated principal will be
propagated from the native webserver and considered already authenticated
in Tomcat. If the web application has one or more security constraints,
authorization will then be performed by Tomcat and roles assigned to the
authenticated principal. If the appropriate Tomcat Realm for the request
does not recognise the provided user name, a Principal will be still be
created but it will have no roles. The default value is
<code>false</code>.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Java TCP socket attributes">
<p>The NIO and NIO2 implementation support the following Java TCP socket
attributes in addition to the common Connector and HTTP attributes listed
above.</p>
<attributes>
<attribute name="socket.rxBufSize" required="false">
<p>(int)The socket receive buffer (SO_RCVBUF) size in bytes. JVM default
used if not set.</p>
</attribute>
<attribute name="socket.txBufSize" required="false">
<p>(int)The socket send buffer (SO_SNDBUF) size in bytes. JVM default
used if not set. Care should be taken if explicitly setting this value.
Very poor performance has been observed on some JVMs with values less
than ~8k.</p>
</attribute>
<attribute name="socket.tcpNoDelay" required="false">
<p>(bool)This is equivalent to standard attribute
<strong>tcpNoDelay</strong>.</p>
</attribute>
<attribute name="socket.soKeepAlive" required="false">
<p>(bool)Boolean value for the socket's keep alive setting
(SO_KEEPALIVE). JVM default used if not set.</p>
</attribute>
<attribute name="socket.ooBInline" required="false">
<p>(bool)Boolean value for the socket OOBINLINE setting. JVM default
used if not set.</p>
</attribute>
<attribute name="socket.soReuseAddress" required="false">
<p>(bool)Boolean value for the sockets reuse address option
(SO_REUSEADDR). JVM default used if not set.</p>
</attribute>
<attribute name="socket.soLingerOn" required="false">
<p>(bool)Boolean value for the sockets so linger option (SO_LINGER).
A value for the standard attribute <strong>connectionLinger</strong>
that is &gt;=0 is equivalent to setting this to <code>true</code>.
A value for the standard attribute <strong>connectionLinger</strong>
that is &lt;0 is equivalent to setting this to <code>false</code>.
Both this attribute and <code>soLingerTime</code> must be set else the
JVM defaults will be used for both.</p>
</attribute>
<attribute name="socket.soLingerTime" required="false">
<p>(int)Value in seconds for the sockets so linger option (SO_LINGER).
This is equivalent to standard attribute
<strong>connectionLinger</strong>.
Both this attribute and <code>soLingerOn</code> must be set else the
JVM defaults will be used for both.</p>
</attribute>
<attribute name="socket.soTimeout" required="false">
<p>This is equivalent to standard attribute
<strong>connectionTimeout</strong>.</p>
</attribute>
<attribute name="socket.performanceConnectionTime" required="false">
<p>(int)The first value for the performance settings. See
<a href="http://docs.oracle.com/javase/6/docs/api/java/net/Socket.html#setPerformancePreferences(int,%20int,%20int)">Socket Performance Options</a>
All three performance attributes must be set else the JVM defaults will
be used for all three.</p>
</attribute>
<attribute name="socket.performanceLatency" required="false">
<p>(int)The second value for the performance settings. See
<a href="http://docs.oracle.com/javase/6/docs/api/java/net/Socket.html#setPerformancePreferences(int,%20int,%20int)">Socket Performance Options</a>
All three performance attributes must be set else the JVM defaults will
be used for all three.</p>
</attribute>
<attribute name="socket.performanceBandwidth" required="false">
<p>(int)The third value for the performance settings. See
<a href="http://docs.oracle.com/javase/6/docs/api/java/net/Socket.html#setPerformancePreferences(int,%20int,%20int)">Socket Performance Options</a>
All three performance attributes must be set else the JVM defaults will
be used for all three.</p>
</attribute>
<attribute name="socket.unlockTimeout" required="false">
<p>(int) The timeout for a socket unlock. When a connector is stopped, it will try to release the acceptor thread by opening a connector to itself.
The default value is <code>250</code> and the value is in milliseconds</p>
</attribute>
</attributes>
</subsection>
<subsection name="NIO specific configuration">
<p>The following attributes are specific to the NIO connector.</p>
<attributes>
<attribute name="socket.directBuffer" required="false">
<p>(bool)Boolean value, whether to use direct ByteBuffers or java mapped
ByteBuffers. Default is <code>false</code>.<br/>
When you are using direct buffers, make sure you allocate the
appropriate amount of memory for the direct memory space. On Sun's JDK
that would be something like <code>-XX:MaxDirectMemorySize=256m</code>.
</p>
</attribute>
<attribute name="socket.appReadBufSize" required="false">
<p>(int)Each connection that is opened up in Tomcat get associated with
a read ByteBuffer. This attribute controls the size of this buffer. By
default this read buffer is sized at <code>8192</code> bytes. For lower
concurrency, you can increase this to buffer more data. For an extreme
amount of keep alive connections, decrease this number or increase your
heap size.</p>
</attribute>
<attribute name="socket.appWriteBufSize" required="false">
<p>(int)Each connection that is opened up in Tomcat get associated with
a write ByteBuffer. This attribute controls the size of this buffer. By
default this write buffer is sized at <code>8192</code> bytes. For low
concurrency you can increase this to buffer more response data. For an
extreme amount of keep alive connections, decrease this number or
increase your heap size.<br/>
The default value here is pretty low, you should up it if you are not
dealing with tens of thousands concurrent connections.</p>
</attribute>
<attribute name="socket.bufferPool" required="false">
<p>(int)The NIO connector uses a class called NioChannel that holds
elements linked to a socket. To reduce garbage collection, the NIO
connector caches these channel objects. This value specifies the size of
this cache. The default value is <code>500</code>, and represents that
the cache will hold 500 NioChannel objects. Other values are
<code>-1</code> for unlimited cache and <code>0</code> for no cache.</p>
</attribute>
<attribute name="socket.bufferPoolSize" required="false">
<p>(int)The NioChannel pool can also be size based, not used object
based. The size is calculated as follows:<br/>
NioChannel
<code>buffer size = read buffer size + write buffer size</code><br/>
SecureNioChannel <code>buffer size = application read buffer size +
application write buffer size + network read buffer size +
network write buffer size</code><br/>
The value is in bytes, the default value is <code>1024*1024*100</code>
(100MB).</p>
</attribute>
<attribute name="socket.processorCache" required="false">
<p>(int)Tomcat will cache SocketProcessor objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is <code>500</code>. Other values are
<code>-1</code> for unlimited cache and <code>0</code> for no cache.</p>
</attribute>
<attribute name="socket.keyCache" required="false">
<p>(int)Tomcat will cache KeyAttachment objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is <code>500</code>. Other values are
<code>-1</code> for unlimited cache and <code>0</code> for no cache.</p>
</attribute>
<attribute name="socket.eventCache" required="false">
<p>(int)Tomcat will cache PollerEvent objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is <code>500</code>. Other values are
<code>-1</code> for unlimited cache and <code>0</code> for no cache.</p>
</attribute>
<attribute name="selectorPool.maxSelectors" required="false">
<p>(int)The max selectors to be used in the pool, to reduce selector
contention. Use this option when the command line
<code>org.apache.tomcat.util.net.NioSelectorShared</code> value is set
to false. Default value is <code>200</code>.</p>
</attribute>
<attribute name="selectorPool.maxSpareSelectors" required="false">
<p>(int)The max spare selectors to be used in the pool, to reduce
selector contention. When a selector is returned to the pool, the system
can decide to keep it or let it be GC'd. Use this option when the
command line <code>org.apache.tomcat.util.net.NioSelectorShared</code>
value is set to false. Default value is <code>-1</code> (unlimited).</p>
</attribute>
<attribute name="command-line-options" required="false">
<p>The following command line options are available for the NIO
connector:<br/>
<code>-Dorg.apache.tomcat.util.net.NioSelectorShared=true|false</code>
- default is <code>true</code>. Set this value to <code>false</code> if you wish to
use a selector for each thread. When you set it to <code>false</code>, you can
control the size of the pool of selectors by using the
<strong>selectorPool.maxSelectors</strong> attribute.</p>
</attribute>
</attributes>
</subsection>
<subsection name="NIO2 specific configuration">
<p>The following attributes are specific to the NIO2 connector.</p>
<attributes>
<attribute name="useCaches" required="false">
<p>(bool)Use this attribute to enable or disable object caching to
reduce the amount of GC objects produced.
The default value is <code>false</code>.</p>
</attribute>
<attribute name="socket.directBuffer" required="false">
<p>(bool)Boolean value, whether to use direct ByteBuffers or java mapped
ByteBuffers. Default is <code>false</code>.<br/>
When you are using direct buffers, make sure you allocate the
appropriate amount of memory for the direct memory space. On Sun's JDK
that would be something like <code>-XX:MaxDirectMemorySize=256m</code>.
</p>
</attribute>
<attribute name="socket.appReadBufSize" required="false">
<p>(int)Each connection that is opened up in Tomcat get associated with
a read ByteBuffer. This attribute controls the size of this buffer. By
default this read buffer is sized at <code>8192</code> bytes. For lower
concurrency, you can increase this to buffer more data. For an extreme
amount of keep alive connections, decrease this number or increase your
heap size.</p>
</attribute>
<attribute name="socket.appWriteBufSize" required="false">
<p>(int)Each connection that is opened up in Tomcat get associated with
a write ByteBuffer. This attribute controls the size of this buffer. By
default this write buffer is sized at <code>8192</code> bytes. For low
concurrency you can increase this to buffer more response data. For an
extreme amount of keep alive connections, decrease this number or
increase your heap size.<br/>
The default value here is pretty low, you should up it if you are not
dealing with tens of thousands concurrent connections.</p>
</attribute>
<attribute name="socket.bufferPoolSize" required="false">
<p>(int)The NIO2 connector uses a class called Nio2Channel that holds
elements linked to a socket. To reduce garbage collection, the NIO
connector caches these channel objects. This value specifies the size of
this cache. The default value is <code>500</code>, and represents that
the cache will hold 500 Nio2Channel objects. Other values are
<code>-1</code> for unlimited cache and <code>0</code> for no cache.</p>
</attribute>
<attribute name="socket.processorCache" required="false">
<p>(int)Tomcat will cache SocketProcessor objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is <code>500</code>. Other values are
<code>-1</code> for unlimited cache and <code>0</code> for no cache.</p>
</attribute>
</attributes>
</subsection>
<subsection name="APR/native specific configuration">
<p>The APR/native implementation supports the following attributes in
addition to the common Connector and AJP attributes listed above.</p>
<attributes>
<attribute name="pollTime" required="false">
<p>Duration of a poll call in microseconds. Lowering this value will
slightly decrease latency of connections being kept alive in some cases
, but will use more CPU as more poll calls are being made. The default
value is 2000 (2ms).
</p>
</attribute>
</attributes>
</subsection>
</section>
<section name="Nested Components">
<p>None at this time.</p>
</section>
<section name="Special Features">
<subsection name="Proxy Support">
<p>The <code>proxyName</code> and <code>proxyPort</code> attributes can
be used when Tomcat is run behind a proxy server. These attributes
modify the values returned to web applications that call the
<code>request.getServerName()</code> and <code>request.getServerPort()</code>
methods, which are often used to construct absolute URLs for redirects.
Without configuring these attributes, the values returned would reflect
the server name and port on which the connection from the proxy server
was received, rather than the server name and port to whom the client
directed the original request.</p>
<p>For more information, see the
<a href="../proxy-howto.html">Proxy Support How-To</a>.</p>
</subsection>
<subsection name="Connector Comparison">
<p>Below is a small chart that shows how the connectors differ.</p>
<table class="defaultTable" style="text-align: center;">
<tr>
<th />
<th style="text-align: center;">Java Nio Connector<br />NIO</th>
<th style="text-align: center;">Java Nio2 Connector<br />NIO2</th>
<th style="text-align: center;">APR/native Connector<br />APR</th>
</tr>
<tr>
<th>Classname</th>
<td><code class="noHighlight">AjpNioProtocol</code></td>
<td><code class="noHighlight">AjpNio2Protocol</code></td>
<td><code class="noHighlight">AjpAprProtocol</code></td>
</tr>
<tr>
<th>Tomcat Version</th>
<td>7.x onwards</td>
<td>8.x onwards</td>
<td>5.5.x onwards</td>
</tr>
<tr>
<th>Support Polling</th>
<td>YES</td>
<td>YES</td>
<td>YES</td>
</tr>
<tr>
<th>Polling Size</th>
<td><code class="noHighlight">maxConnections</code></td>
<td><code class="noHighlight">maxConnections</code></td>
<td><code class="noHighlight">maxConnections</code></td>
</tr>
<tr>
<th>Read Request Headers</th>
<td>Blocking</td>
<td>Blocking</td>
<td>Blocking</td>
</tr>
<tr>
<th>Read Request Body</th>
<td>Blocking</td>
<td>Blocking</td>
<td>Blocking</td>
</tr>
<tr>
<th>Write Response Headers and Body</th>
<td>Blocking</td>
<td>Blocking</td>
<td>Blocking</td>
</tr>
<tr>
<th>Wait for next Request</th>
<td>Non Blocking</td>
<td>Non Blocking</td>
<td>Non Blocking</td>
</tr>
<tr>
<th>Max Connections</th>
<td><code class="noHighlight">maxConnections</code></td>
<td><code class="noHighlight">maxConnections</code></td>
<td><code class="noHighlight">maxConnections</code></td>
</tr>
</table>
</subsection>
</section>
</body>
</document>