Apache Tomcat Configuration ReferenceThe HTTP Connector |  |
| Introduction |
The HTTP Connector element represents a
Connector component that supports the HTTP/1.1 protocol.
It enables Catalina to function as a stand-alone web server, in addition
to its ability to execute servlets and JSP pages. A particular instance
of this component listens for connections on a specific TCP port number
on the server. One or more such Connectors can be
configured as part of a single Service, each
forwarding to the associated Engine to perform
request processing and create the response.
If you wish to configure the Connector that is used
for connections to web servers using the AJP protocol (such as the
mod_jk 1.2.x connector for Apache 1.3), see
here instead.
Each incoming request requires
a thread for the duration of that request. If more simultaneous requests
are received than can be handled by the currently available request
processing threads, additional threads will be created up to the
configured maximum (the value of the maxThreads attribute).
If still more simultaneous requests are received, they are stacked up
inside the server socket created by the Connector, up to
the configured maximum (the value of the acceptCount
attribute. Any further simultaneous requests will receive "connection
refused" errors, until resources are available to process them.
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| Attributes |
| Common Attributes |
All implementations of Connector
support the following attributes:
| Attribute | Description |
|---|
allowTrace |
A boolean value which can be used to enable or disable the TRACE
HTTP method. If not specified, this attribute is set to false.
| emptySessionPath |
If set to true, all paths for session cookies will be set
to /. This can be useful for portlet specification implementations.
If not specified, this attribute is set to false.
| enableLookups |
Set to true if you want calls to
request.getRemoteHost() to perform DNS lookups in
order to return the actual host name of the remote client. Set
to false to skip the DNS lookup and return the IP
address in String form instead (thereby improving performance).
By default, DNS lookups are enabled.
| maxPostSize |
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 or equal to 0.
If not specified, this attribute is set to 2097152 (2 megabytes).
| maxSavePostSize |
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).
| protocol |
Sets the protocol to handle incoming traffic.
The default value is HTTP/1.1 and configures the
org.apache.coyote.http11.Http11Protocol. This is the blocking Java connector.
If the PATH(Windows) or LD_LIBRARY_PATH(on most unix system)
environment variables contain the Tomcat native library, the APR connector
will automatically be configured. Please be advised that the APR connector has different
settings for HTTPS than the default Java connector.
Other values for this attribute are, but not limited to:
org.apache.coyote.http11.Http11Protocol - same as HTTP/1.1
org.apache.coyote.http11.Http11NioProtocol - non blocking Java connector
org.apache.coyote.http11.Http11AprProtocol - the APR connector.
Take a look at our Connector Comparison chart.
The configuration for both Java connectors are identical, both for http and https.
For more information on the APR connector and APR specific SSL settings please
visit the APR documentation
| proxyName |
If this Connector is being used in a proxy
configuration, configure this attribute to specify the server name
to be returned for calls to request.getServerName().
See Proxy Support for more
information.
| proxyPort |
If this Connector is being used in a proxy
configuration, configure this attribute to specify the server port
to be returned for calls to request.getServerPort().
See Proxy Support for more
information.
| redirectPort |
If this Connector is supporting non-SSL
requests, and a request is received for which a matching
<security-constraint> requires SSL transport,
Catalina will automatically redirect the request to the port
number specified here.
| SSLEnabled |
Use this attribute to enable SSL traffic on a connector.
To turn on SSL handshake/encryption/decryption on a connector
set this value to true.
The default value is false.
When turning this value true you will want to set the
scheme and the secure attributes as well
to pass the correct request.getScheme() and
request.isSecure() values to the servlets
See SSL Support for more information.
| scheme |
Set this attribute to the name of the protocol you wish to have
returned by calls to request.getScheme(). For
example, you would set this attribute to "https"
for an SSL Connector. The default value is "http".
| secure |
Set this attribute to true if you wish to have
calls to request.isSecure() to return true
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, a SSL appliance or even a webserver.
The default value is false.
| URIEncoding |
This specifies the character encoding used to decode the URI bytes,
after %xx decoding the URL. If not specified, ISO-8859-1 will be used.
| useBodyEncodingForURI |
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 explicitely set using
Request.setCharacterEncoding method was also used for the parameters from
the URL. The default value is false.
| useIPVHosts |
Set this attribute to true to cause Tomcat to use
the IP address that the request was recieved on to determine the Host
to send the request to. The default value is false.
| xpoweredBy |
Set this attribute to true to cause Tomcat to advertise
support for the Servlet specification using the header recommended in the
specification. The default value is false.
|
|
| Standard Implementation |
HTTP supports the following additional attributes (in addition to the
common attributes listed above):
| Attribute | Description |
|---|
acceptCount |
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 10.
| address |
For servers with more than one IP address, this attribute
specifies which address will be used for listening on the specified
port. By default, this port will be used on all IP addresses
associated with the server.
| bufferSize |
The size (in bytes) of the buffer to be provided for input
streams created by this connector. By default, buffers of
2048 bytes will be provided.
| compressableMimeType |
The value is a comma separated list of MIME types for which HTTP
compression may be used.
The default value is text/html,text/xml,text/plain.
| compression |
The Connector may use HTTP/1.1 GZIP compression in
an attempt to save server bandwidth. The acceptable values for the
parameter is "off" (disable compression), "on" (allow compression, which
causes text data to be compressed), "force" (forces compression in all
cases), or a numerical integer value (which is equivalent to "on", but
specifies the minimum amount of data before the output is compressed). If
the content-length is not known and compression is set to "on" or more
aggressive, the output will also be compressed. If not specified, this
attribute is set to "off".
| connectionLinger |
The number of milliseconds during which the sockets used by this
Connector will linger when they are closed.
The default value is -1 (socket linger is disabled).
| connectionTimeout |
The number of milliseconds this Connector will wait,
after accepting a connection, for the request URI line to be
presented. The default value is 60000 (i.e. 60 seconds).
| executor |
A reference to the name in an Executor element.
If this attribute is enabled, and the named executor exists, the connector will
use the executor, and all the other thread attributes will be ignored.
| keepAliveTimeout |
The number of milliseconds this Connector will wait for
another HTTP request before closing the connection.
The default value is to use the value that has been set for the
connectionTimeout attribute.
| disableUploadTimeout |
This flag allows the servlet container to use a different, longer
connection timeout while a servlet is being executed, which in the end
allows either the servlet a longer amount of time to complete its
execution, or a longer timeout during data upload. If not specified,
this attribute is set to "true".
| maxHttpHeaderSize |
The maximum size of the request and response HTTP header, specified
in bytes.
If not specified, this attribute is set to 4096 (4 KB).
| maxKeepAliveRequests |
The maximum number of HTTP requests which can be pipelined until
the connection is closed by the server. Setting this attribute to 1 will
disable HTTP/1.0 keep-alive, as well as HTTP/1.1 keep-alive and
pipelining. Setting this to -1 will allow an unlimited amount of
pipelined or keep-alive HTTP requests.
If not specified, this attribute is set to 100.
| maxThreads |
The maximum number of request processing threads to be created
by this Connector, which therefore determines the
maximum number of simultaneous requests that can be handled. If
not specified, this attribute is set to 40. 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.
| noCompressionUserAgents |
The value is a comma separated list of regular expressions matching
user-agents of HTTP clients for which compression should not be used,
because these clients, although they do advertise support for the
feature, have a broken implementation.
The default value is an empty String (regexp matching disabled).
| port |
The TCP port number on which this Connector
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.
| restrictedUserAgents |
The value is a comma separated list of regular expressions matching
user-agents of HTTP clients for which HTTP/1.1 or HTTP/1.0 keep alive
should not be used, even if the clients advertise support for these
features.
The default value is an empty String (regexp matching disabled).
| server |
The Server header for the http response.
Unless you are paranoid, you won't need this feature.
| socketBuffer |
The size (in bytes) of the buffer to be provided for socket
output buffering. -1 can be specified to disable the use of a buffer.
By default, a buffers of 9000 bytes will be used.
| tcpNoDelay |
If set to true, the TCP_NO_DELAY option will be
set on the server socket, which improves performance under most
circumstances. This is set to true by default.
| threadPriority |
The priority of the request processing threads within the JVM.
The default value is java.lang.Thread#NORM_PRIORITY.
See the JavaDoc for the java.lang.Thread class for more details on
what this priority means.
|
|
| Nio Implementation |
The NIO connector exposes all the low level socket properties that can be used to tune the connector.
Most of these attributes are directly linked to the socket implementation in the JDK so you can find out
about the actual meaning in the JDK API documentation.
NoteOn some JDK versions, setTrafficClass causes a problem, a work around for this is to add
the -Djava.net.preferIPv4Stack=true value to your command line
| Attribute | Description |
|---|
useSendfile |
(bool)Use this attribute to enable or disable sendfile capability.
The default value is true
| useExecutor |
(bool)Set to true to use the NIO thread pool executor. The default value is true.
If set to false, it uses a thread pool based on a stack for its execution.
Generally, using the executor yields a little bit slower performance, but yields a better
fairness for processing connections in a high load environment as the traffic gets queued through a
FIFO queue. If set to true(default) then the max pool size is the maxThreads attribute
and the core pool size is the minSpareThreads.
This value is ignored if the executor attribute is present and points to a valid shared thread pool.
| acceptorThreadCount |
(int)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 2. Also, with a lot of non keep alive connections,
you might want to increase this value as well. Default value is 1.
| pollerThreadCount |
(int)The number of threads to be used to run for the polling events. Default value is 1.
Can't see a reason to go above that. But experiment and find your own results.
| pollerThreadPriority |
(int)The priority of the poller threads.
The default value is java.lang.Thread#NORM_PRIORITY.
See the JavaDoc for the java.lang.Thread class for more details on
what this priority means.
| acceptorThreadPriority |
(int)The priority of the acceptor threads. The threads used to accept new connections.
The default value is java.lang.Thread#NORM_PRIORITY.
See the JavaDoc for the java.lang.Thread class for more details on
what this priority means.
| selectorTimeout |
(int)The time in milliseconds to timeout on a select() for the poller.
This value is important, since connection clean up is done on the same thread, so dont set this
value to an extremely high one. The default value is 1000 milliseconds.
| useComet |
(bool)Whether to allow comet servlets or not, Default value is true.
| processCache |
(int)The protocol handler caches Http11NioProcessor objects to speed up performance.
This setting dictates how many of these objects get cached.
-1 means unlimited, default is 200. Set this value somewhere close to your maxThreads value.
| socket.directBuffer |
(bool)Boolean value, whether to use direct ByteBuffers or java mapped ByteBuffers. Default is false
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 -XX:MaxDirectMemorySize=256m
| socket.rxBufSize |
(int)The socket receive buffer (SO_RCVBUF) size in bytes. Default value is 25188
| socket.txBufSize |
(int)The socket send buffer (SO_SNDBUF) size in bytes. Default value is 43800
| socket.appReadBufSize |
(int)Each connection that is opened up in Tomcat get associated with a read and a write ByteBuffer
This attribute controls the size of these buffers. By default this read buffer is sized at 8192 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.
| socket.appWriteBufSize |
(int)Each connection that is opened up in Tomcat get associated with a read and a write ByteBuffer
This attribute controls the size of these buffers. By default this write buffer is sized at 8192 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.
The default value here is pretty low, you should up it if you are not dealing with tens of thousands
concurrent connections.
| socket.bufferPool |
(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 500, and represents that the cache will hold 500 NioChannel objects.
Other values are -1. unlimited cache, and 0, no cache.
| socket.bufferPoolSize |
(int)The NioChannel pool can also be size based, not used object based. The size is calculated as follows:
NioChannel buffer size = read buffer size + write buffer size
SecureNioChannel buffer size = application read buffer size + application write buffer size + network read buffer size + network write buffer size
The value is in bytes, the default value is 1024*1024*100 (100MB)
| socket.processorCache |
(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 500.
Other values are -1. unlimited cache, and 0, no cache.
| socket.keyCache |
(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 500.
Other values are -1. unlimited cache, and 0, no cache.
| socket.eventCache |
(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 500.
Other values are -1. unlimited cache, and 0, no cache.
| socket.tcpNoDelay |
(bool)same as the standard setting tcpNoDelay. Default value is false
| socket.soKeepAlive |
(bool)Boolean value for the socket's keep alive setting (SO_KEEPALIVE). Default is false.
| socket.ooBInline |
(bool)Boolean value for the socket OOBINLINE setting. Default value is true
| socket.soReuseAddress |
(bool)Boolean value for the sockets reuse address option (SO_REUSEADDR). Default value is true
| socket.soLingerOn |
(bool)Boolean value for the sockets so linger option (SO_LINGER). Default value is true.
This option is paired with the soLingerTime value.
| socket.soLingerTime |
(bool)Value in seconds for the sockets so linger option (SO_LINGER). Default value is 25 seconds.
This option is paired with the soLinger value.
| socket.soTimeout |
(int)Value in milliseconds for the sockets read timeout (SO_TIMEOUT). Default value is 5000 milliseconds.
| socket.soTrafficClass |
(byte)Value between 0 and 255 for the traffic class on the socket, 0x04 | 0x08 | 0x010
| socket.performanceConnectionTime |
(int)The first value for the performance settings. Default is 1, see Socket Performance Options
| socket.performanceLatency |
(int)The second value for the performance settings. Default is 0, see Socket Performance Options
| socket.performanceBandwidth |
(int)The third value for the performance settings. Default is 1, see Socket Performance Options
| selectorPool.maxSelectors |
(int)The max selectors to be used in the pool, to reduce selector contention.
Use this option when the command line org.apache.tomcat.util.net.NioSelectorShared value is set to false.
Default value is 200.
| selectorPool.maxSpareSelectors |
(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:ed.
Use this option when the command line org.apache.tomcat.util.net.NioSelectorShared value is set to false.
Default value is -1 (unlimited)
| command-line-options |
The following command line options are available for the NIO connector:
-Dorg.apache.tomcat.util.net.NioSelectorShared=true|false - default is true.
Set this value to false if you wish to use a selector for each thread.
the property. If you do set it to false, you can control the size of the pool of selectors by using the
selectorPool.maxSelectors attribute
| oomParachute |
(int)The NIO connector implements an OutOfMemoryError strategy called parachute.
It holds a chunk of data as a byte array. In case of an OOM,
this chunk of data is released and the error is reported. This will give the VM enough room
to clean up. The oomParachute represent the size in bytes of the parachute(the byte array).
The default value is 1024*1024(1MB).
Please note, this only works for OOM errors regarding the Java Heap space, and there is absolutely no
guarantee that you will be able to recover at all.
If you have an OOM outside of the Java Heap, then this parachute trick will not help.
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| Special Features |
| HTTP/1.1 and HTTP/1.0 Support |
This Connector supports all of the required features
of the HTTP/1.1 protocol, as described in RFC 2616, including persistent
connections, pipelining, expectations and chunked encoding. If the client
(typically a browser) supports only HTTP/1.0, the
Connector will gracefully fall back to supporting this
protocol as well. No special configuration is required to enable this
support. The Connector also supports HTTP/1.0
keep-alive.
RFC 2616 requires that HTTP servers always begin their responses with
the highest HTTP version that they claim to support. Therefore, this
Connector will always return HTTP/1.1 at
the beginning of its responses.
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| Proxy Support |
The proxyName and proxyPort attributes can
be used when Tomcat is run behind a proxy server. These attributes
modify the values returned to web applications that call the
request.getServerName() and request.getServerPort()
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.
For more information, see the
Proxy Support HOW-TO.
|
| SSL Support |
You can enable SSL support for a particular instance of this
Connector by setting the secure attribute to
true. In addition, you may need to configure the following
attributes:
| Attribute | Description |
|---|
algorithm |
The certificate encoding algorithm to be used. This defaults to the Sun
implementation (SunX509). For IBM JVMs you should use the
value IbmX509. For other vendors, consult the JVM
documentation for the correct value.
| clientAuth |
Set to true if you want the SSL stack to require a
valid certificate chain from the client before accepting a connection.
Set to want if you want the SSL stack to request a client
Certificate, but not fail if one isn't presented. A false
value (which is the default) will not require a certificate chain
unless the client requests a resource protected by a security
constraint that uses CLIENT-CERT authentication. See the
SSL HowTo for an example.
| keystoreFile |
The pathname of the keystore file where you have stored the
server certificate to be loaded. By default, the pathname is
the file ".keystore" in the operating system home
directory of the user that is running Tomcat.
| keystorePass |
The password used to access the server certificate from the
specified keystore file. The default value is "changeit".
| keystoreType |
The type of keystore file to be used for the server certificate.
If not specified, the default value is "JKS".
| sslProtocol |
The version of the SSL protocol to use. If not specified,
the default is "TLS".
| ciphers |
A comma seperated list of the encryption ciphers that may be used.
If not specified, then any available cipher may be used.
| keyAlias |
The alias used to for the server certificate in the keystore. If not
specified the first key read in the keystore will be used.
| truststoreFile |
The TrustStore file to use to validate client certificates.
| truststorePass |
The password to access the TrustStore. This defaults to the value
of keystorePass.
| truststoreType |
Add this element if your are using a different format for the
TrustStore then you are using for the KeyStore.
|
For more information, see the
SSL Configuration HOW-TO.
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