Apache Http Server Configuration

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Using Web Server Plug-Ins with WebLogic Server

The following sections describe how to install and configure the Apache HTTP Server Plug-In:

The Apache HTTP Server Plug-In proxies requests from an Apache HTTP Server to a WebLogic Server cluster or instance. The plug-in enhances an Apache installation by enabling WebLogic Server to handle load-balancing or requests that require the dynamic functionality of WebLogic Server. You target a WebLogic Server instance using the WebLogicHost and WebLogicPort parameters in the plug-in configuration file. You target a WebLogic Server cluster or group of non-clustered servers using the WebLogicCluster parameter. For information about setting plug-in parameters, see Parameters for Web Server Plug-Ins.

The plug-in is intended for use in an environment where an Apache Server serves static pages, and another part of the document tree (dynamic pages best generated by HTTP Servlets or JavaServer Pages) is delegated to WebLogic Server, which may be operating in a different process, possibly on a different host. To the end user—the browser—the HTTP requests delegated to WebLogic Server still appear to be coming from the same source.

HTTP-tunneling, a technique that gives HTTP requests and responses access through a company's firewall, can operate through the plug-in. See Editing the httpd.conf File.

The Apache HTTP Server Plug-In operates as an Apache module within an Apache HTTP Server. An Apache module is loaded by Apache Server at startup, and then certain HTTP requests are delegated to it. Apache modules are similar to HTTP servlets, except that an Apache module is written in code native to the platform.

Limitations in Apache Version 1.3.x

Version 1.3x of the Apache HTTP Server has several limitations that affect the WebLogic Server plug-in. These limitations do not exist in later versions.

Keep-Alive Connections Not Supported

Version 1.3.x of the Apache HTTP Server Plug-In creates a socket for each request and closes the socket after reading the response. Because Apache HTTP Server is multiprocessed, connection pooling and keep-alive connections between WebLogic Server and the Apache HTTP Server Plug-In cannot be supported.

Apache Http Server Configuration

Inconsistent States

The Apache HTTP Server has a multi-process architecture, and the state of the plug-in cannot be synchronized across multiple child processes. The following types of problems may occur:

  • In a clustered environment, a plug-in may dispatch requests to an unavailable WebLogic Server instance because the DynamicServerList is not current in all plug-in processes.

    • DynamicServerList=ON works with a single Apache server (httpd daemon process), but for more than one server, such as StartServers=5, the dynamic server list will not be updated across all httpd instances until they have all tried to contact a WebLogic Server instance. This is because they are separate processes. This delay in updating the dynamic server list could allow an Apache httpd process to contact a server that another httpd process has marked as dead. Only after such an attempt will the server list will be updated within the proxy. One possible solution if this is undesirable is to set the DynamicServerList to OFF.

  • In a non-clustered environment, a plug-in may lose the stickiness of a session created after restarting WebLogic Server instances, because some plug-in processes do not have the new JVMID of those restarted servers, and treat them as unknown JVMIDs.

To temporarily correct inconsistencies of this type, restart or send a HUP signal (kill -HUP) to the Apache server to refresh all plug-in processes.

To avoid these issues, upgrade to Apache 2.0.x and configure Apache to use the multi-threaded and single-process model, mpm_worker_module. An example httpd.conf configuration for this module:

For information about this module, see Apache MPM worker.

Keep-Alive Connections Supported in Apache Version 2.0

Version 2.0 of the Apache HTTP Server Plug-In improves performance by using a reusable pool of connections from the plug-in to WebLogic Server. The plug-in implements HTTP 1.1 keep-alive connections between the plug-in and WebLogic Server by reusing the same connection in the pool for subsequent requests from the same client. If the connection is inactive for more than 30 seconds, (or a user-defined amount of time) the connection is closed and returned to the pool. You can disable this feature if desired.

Certifications

The Apache HTTP Server Plug-In is supported on the Linux, Solaris, AIX, Windows, and HPUX11 platforms. Plug-ins are not supported on all operating systems for all releases. For information on platform support for specific versions of Apache, see Platform Support for WebLogic Server Plug-ins and Web Servers in Supported Configurations for WebLogic Server 8.1.

You install the Apache HTTP Server Plug-In as an Apache module in your Apache HTTP Server installation. There are two ways that this module can be compiled and linked to Apache—as a statically linked module (available only for Apache version 1.3.x), or as a Dynamic Shared Object (DSO).

Keep the following in mind when selecting which type of module to use:

Server
  • Statically linking a plug-in module requires recompiling Apache, which may be inconvenient.
  • A Dynamic Shared Object is compiled as a library that is dynamically loaded by the server at run time, and can be installed without recompiling Apache.

Installing the Apache HTTP Server Plug-In as a Dynamic Shared Object

The Apache plug-in is distributed as a shared object (.so) for Solaris, Linux, Windows, AIX and HPUX11 platforms. WebLogic supplies versions of shared object files that vary according to platform, to whether or not SSL is to be used between the client and Apache, and to the SSL encryption strength (128-bit versions are only installed if you install the 128-bit version of WebLogic Server).

Table 2-1 shows the directories of your WebLogic Server installation that contain shared object files for various platforms (where WL_HOME is the top-level installation directory for the WebLogic platform).

Table 2-2 identifies the WebLogic Server Apache Plug-In modules for different versions of Apache HTTP Server and different encryption strengths.

Table 2-1 Locations of Plug-In Shared Object Files

Operating System

Shared Object Location

Solaris

WL_HOME/server/lib/solaris

Linux

WL_HOME/server/lib/linux/i686
WL_HOME/server/lib/linux/ia64
WL_HOME/server/lib/linux/s390

Windows

WL_HOMEserverbin

AIX

WL_HOME/server/lib/aix

HPUX11

WL_HOME/server/lib/hpux11

Warning: If you are running Apache 2.0.x server on HP-UX11, set the environment variables specified below before you build the Apache server. Because of a problem with the order in which linked libraries are loaded on HP-UX, a core dump can result if the load order is not preset as an environment variable before building. Set the following environment variables before proceeding with the Apache configure, make, and make install steps, (described in Apache HTTP Server documentation at http://httpd.apache.org/docs-2.1/install.html#configure):


Choose the appropriate version of the plug-in shared object from the following table.

Table 2-2 Apache Plug-In Shared Object File Versions

Apache Version

Regular Strength Encryption

128-bit Encryption

Standard Apache Version 1.x

mod_wl.so

mod_wl128.so

Apache w/ SSL/EAPI
Version 1.x

(Stronghold,
modssl etc.)

mod_wl_ssl.so

mod_wl128_ssl.so

Apache + Raven SSL
Version 1.x

Required because Raven SSL applies frontpage patches that makes the plug-in incompatible with the standard shared object

mod_wl_ssl_raven.so

mod_wl128_ssl_raven.so

Standard Apache Version 2.0.x

mod_wl_20.so

mod_wl28_20.so


To install the Apache HTTP Server Plug-In as a dynamic shared object:

  1. In your WebLogic Server installation, locate the shared object directory for your platform using Table 2-1.
  2. Identify the plug-in shared object file for your version of Apache in Table 2-2.
  3. Verify that the WebLogic Server Apache HTTP Server Plug-In mod_so.c module is enabled.

    4. The Apache HTTP Server Plug-In will be installed in your Apache HTTP Server installation as an Apache Dynamic Shared Object (DSO). DSO support in Apache is based on a module mod_so.c, which must be enabled before mod_wl.so is loaded. If you installed Apache HTTP Server using the script supplied by Apache, mod_so.c is already enabled. Verify that mod_so.c is enabled by executing the following command:

    (Where APACHE_HOME is the directory containing your Apache HTTP Server installation.)

    This command lists all enabled modules. If mod_so.c is not listed, you must rebuild your Apache HTTP Server, making sure that the following options are configured:

    ...
    --enable-module=so
    --enable-rule=SHARED_CORE
    ...

    See Apache 1.3 Shared Object (DSO) Support at http://httpd.apache.org/docs/dso.html.

    • For Apache 1.x, use a command shell to navigate to the directory in your WebLogic Server installation that contains the shared object for your platform and activate the weblogic_module by issuing this command (note that you must have Perl installed to run this Perl script):

      • This command copies the mod_wl.so file to the APACHE_HOMElibexec directory. It also adds two lines of instructionsfor weblogic_module to the httpd.conf file and activates the module. Make sure that the following lines were added to your APACHE_HOME/conf/httpd.conf file in your Apache 1.x server installation:

      For information about the Apache utility apxs (APache eXtenSion) see http://httpd.apache.org/docs/programs/apxs.html).

    • For Apache 2.0.x, install the plug-in by copying the mod_wl_20.so file to the APACHE_HOMEmodules directory and adding the following line to your APACHE_HOME/conf/httpd.conf file manually:
  4. In httpd.conf, define any additional parameters for the Apache HTTP Server Plug-In as described in Configuring the Apache HTTP Server Plug-In.

    5. The Apache HTTP Server Plug-In recognizes the parameters listed in General Parameters for Web Server Plug-Ins.

  5. Start (or restart if you have changed the configuration) Apache HTTP Server.
  6. Test the plug-in by opening a browser and setting the URL to the Apache Server + '/weblogic/', which should bring up the default WebLogic Server HTML page, welcome file, or default servlet, as defined for the default Web Application on WebLogic Server. For example:

Apache Http Server Configuration File

Installing the Apache HTTP Server Plug-In as a Statically Linked Module

To install the Apache HTTP Server Plug-In as a statically linked module:

  1. Unpack the Apache Plug-In distribution using the following command:
  2. Within the unpacked distribution switch to the src/modules directory.
  3. Locate the linked library file for your platform.

    4. Each library file is distributed as a separate version, depending on the platform and the encryption strength for SSL (128-bit versions are only installed if you install the 128-bit version of WebLogic Server). The library files are located in the following directories of your WebLogic Server installation.

    Table 2-3 Locations of Plug-In Files

    Operating System

    Shared Object Location

    Solaris

    WL_HOME/Server/lib/solaris

    Linux

    WL_HOME/Server/lib/linux

    Note: You also need to set the following environment variable:
    LDFLAGS = '-lpthread'

    HPUX11

    WL_HOME/Server/lib/hpux11

    Warning: If you are running Apache 2.0.x server on HP-UX11, set the environment variables specified below before you build the Apache server. Because of a problem with the order in which linked libraries are loaded on HP-UX, a core dump can result if the load order is not preset as an environment variable before building. Set the following environment variables before proceeding with the Apache configure, make, and make install steps, (described in Apache HTTP Server documentation at http://httpd.apache.org/docs-2.1/install.html#configure):


    Choose the appropriate shared object from the following table.

    Table 2-4 Statically Linked Modules for Different Levels of Encryption

    Apache Version

    Regular Strength Encryption

    128-bit
    Encryption

    Standard Apache Version 1.3.x

    libweblogic.a

    libweblogic128.a

    If you are using the Gnu C Compiler (gcc), gcc 2.95.x is the recommended version.

  4. Copy Makefile.libdir, Makefile.tmpl from the lib directory of your WebLogic Server installation to srcmodulesweblogic.
  5. Copy libweblogic.a (use libweblogic128.a instead, if you are using 128 bit security.) from the same directory containing the linked library file to srcmodulesweblogic.
  6. If you are using regular (such as 56-bit or 40-bit) 56-bit or 40-bit, execute the following command from the Apache 1.3 home directory:

    7. If you are using 128-bit encryption, execute the following command (on a single line) from the Apache 1.3 home directory:

  7. Execute the following command:
  8. Define parameters for the Apache HTTP Server Plug-In as described in Configuring the Apache HTTP Server Plug-In.

After installing the plug-in in the Apache HTTP Server, configure the WebLogic Server Apache Plug-In and configure the Apache server to use the plug-in. This section explains how to edit the Apache httpd.conf file to instruct the Apache server to load the WebLogic Server library for the plug-in as an Apache module, and to specify the application requests that should be handled by the module.

Editing the httpd.conf File

Edit the httpd.conf file in your Apache HTTP server installation to configure the Apache HTTP Server Plug-In.

This section explains how to locate and edit the httpd.conf file, to configure the Apache server to use the WebLogic Server Apache Plug-In, to proxy requests by path or by MIME type, to enable HTTP tunneling, and to use other WebLogic Server plug-in parameters.

    The file is located at APACHE_HOMEconfhttpd.conf (where APACHE_HOME is the root directory of your Apache HTTP server installation). See a sample httpd.conf file at Template for the Apache HTTP Server httpd.conf File.

  1. Ensure that the WebLogic Server modules are included.
    • For Apache 1.x, verify that the following two lines were added to the httpd.conf file when you ran the apxs utility, or add them manually:
    • For Apache 2.0.x, manually add the following line to the httpd.conf file:
  2. Add an IfModule block that defines one of the following:

    3. For a non-clustered WebLogic Server instance:

    The WebLogicHost and WebLogicPort parameters.

    For a cluster of WebLogic Servers instances:

    The WebLogicCluster parameter.

    For example:

  3. To proxy requests by MIME type, add a MatchExpression line to the IfModule block. Note that if both MIME type and proxying by path are enabled, proxying by path takes precedence over proxying by MIME type.

    4. For example, the following IfModule block for a non-clustered WebLogic Server specifies that all files with MIME type .jsp are proxied:

    You can also use multiple MatchExpressions, for example:

    If you are proxying requests by MIME type to a cluster of WebLogic Servers, use the WebLogicCluster parameter instead of the WebLogicHost and WebLogicPort parameters. For example:

  4. To proxy requests by path, use the Location block and the SetHandler statement. SetHandler specifies the handler for the Apache HTTP Server Plug-In module. For example the following Location block proxies all requests containing /weblogic in the URL:

    5. The PathTrim parameter specifies a string trimmed from the beginning of the URL before the request is passed to the WebLogic Server instance (see General Parameters for Web Server Plug-Ins).

  5. Optionally, enable HTTP tunneling for t3 or IIOP.
    1. To enable HTTP tunneling if you are using the t3 protocol and weblogic.jar, add the following Location block to the httpd.conf file:
    2. To enable HTTP tunneling if you are using IIOP, the only protocol used by the WebLogic Server thin client, wlclient.jar, add the following Location block to the httpd.conf file:
  6. Define any additional parameters for the Apache HTTP Server Plug-In.

    7. The Apache HTTP Server Plug-In recognizes the parameters listed in General Parameters for Web Server Plug-Ins. To modify the behavior of your Apache HTTP Server Plug-In, define these parameters either:

    • In a Location block, for parameters that apply to proxying by path, or
    • In an IfModule block, for parameters that apply to proxying by MIME type.
  7. Verify the syntax of the APACHE_HOMEconfhttpd.conf file with the following commands:

    8. The output of this command reports any errors in your httpd.conf file or returns:

  8. Start (or restart if you have changed the configuration) Apache HTTP Server.
  9. Test the plug-in by opening a browser and setting the URL to the Apache Server + '/weblogic/', which should bring up the default WebLogic Server HTML page, welcome file, or default servlet, as defined for the default Web Application on WebLogic Server. For example:

Including a weblogic.conf File in the httpd.conf File

If you want to keep several separate configuration files so that you can quickly switch among different stored configurations, you can define parameters in a separate configuration file called weblogic.conf file, and invoke specific weblogic.conf files by using the Apache Include directive in an IfModule block in the httpd.conf file:

The syntax of weblogic.conf files is the same as that for the httpd.conf file.

This section describes how to create weblogic.conf files, and includes sample weblogic.conf files.

Creating weblogic.conf Files

Be aware of the following when constructing a weblogic.conf file.

  • If you are using SSL between the Apache HTTP Server Plug-In and WebLogic Server, you cannot define parameters in a file accessed, as the weblogic.conf file is, through the Apache Include directive. Thus you can not use both SSL and weblogic.conf files.
  • Enter each parameter on a new line. Do not put `=' between a parameter and its value. For example:
  • If a request matches both a MIME type specified in a MatchExpression in an IfModule block and a path specified in a Location block, the behavior specified by the Location block takes precedence.
  • If you define the CookieName parameter , you must define it in an IfModule block.
  • If you use an Apache HTTP Server <VirtualHost> block, you must include all configuration parameters (MatchExpression, for example) for the virtual host within the <VirtualHost> block (see Apache Virtual Host documentation).
  • If you want to have only one log file for all the virtual hosts configured in your environment, you can achieve it using global properties. Instead of specifying the same Debug, WLLogFile and WLTempDir properties in each virtual host you can specify them just once in the <IfModule> tag
  • Sample httpd.conf file:
  • All the requests which match /jurl/* will have Debug Level set to ALL and log messages will be logged to c:/tmp/global_proxy.log file. All the requests which match /web/* will have Debug Level set to OFF and no log messages will be logged. All the requests which match /foo/* will have Debug Level set to ERR and log messages will be logged to c:/tmp/foo_proxy.log file
  • BEA recommends that you use the MatchExpression statement instead of the <files> block.

Sample weblogic.conf Configuration Files

The following examples of weblogic.conf files may be used as templates that you can modify to suit your environment and server. Lines beginning with # are comments.

Example Using WebLogic Clusters

Example Using Multiple WebLogic Clusters

In this example, the MatchExpression parameter syntax for expressing the filename pattern, the WebLogic Server host to which HTTP requests should be forwarded, and various other parameters is as follows:

The first MatchExpression parameter below specifies the filename pattern *.jsp, and then names the single WebLogicHost. The paramName=value combinations following the pipe symbol specify the port at which WebLogic Server is listening for connection requests, and also activate the Debug option. The second MatchExpression specifies the filename pattern *.http and identifies the WebLogicCluster hosts and their ports. The paramName=value combination following the pipe symbol specifies the error page for the cluster.

Example Without WebLogic Clusters

Example Configuring Multiple Name-Based Virtual Hosts

You must define a unique value for 'ServerName'or some Plug-In parameters will not work as expected.

Server

Template for the Apache HTTP Server httpd.conf File

This section contains a sample httpd.conf file for Apache 1.3. You can use this sample as a template and modify it to suit your environment and server. Lines beginning with # are comments.

Http

Note that Apache HTTP Server is not case sensitive.

Use perimeter authentication to secure WebLogic Server applications that are accessed via the Apache Plug-In.

A WebLogic Identity Assertion Provider authenticates tokens from outside systems that access your WebLogic Server application, including users who access your WebLogic Server application through the Apache HTTP Server Plug-In. Create an Identity Assertion Provider that will safely secure your Plug-In as follows:

  1. Create a custom Identity Assertion Provider for your WebLogic Server application. See How to Develop a Custom Identity Assertion Provider in Developing Security Providers for WebLogic Server.
  2. Configure the custom Identity Assertion Provider to support the Cert token type and make Cert the active token type. See How to Create New Token Types in Developing Security Providers for WebLogic Server.

Set clientCertProxy to True in the web.xml deployment descriptor file for the Web application (or, if using a cluster, optionally set the Client Cert Proxy Enabled attribute to true for the whole cluster in the Administration Console). This parameter can be used with a third party proxy server such as a load balancer or an SSL accelerator to enable 2-way SSL authentication. For more information about the clientCertProxy attribute, see context-param in Developing Web Applications for WebLogic Server.

  1. Once you have set clientCertProxy, be sure to use a connection filter to ensure that WebLogic Server accepts connections only from the machine on which the Apache Plug-In is running. See Using Network Connection Filters in Programming WebLogic Security.

See Identity Assertion Providers in Developing Security Providers for WebLogic Server.

You can use the Secure Sockets Layer (SSL) protocol to protect the connection between the Apache HTTP Server Plug-In and WebLogic Server. The SSL protocol provides confidentiality and integrity to the data passed between the Apache HTTP Server Plug-In and WebLogic Server. If you use weblogic.conf files, you cannot use SSL (see Including a weblogic.conf File in the httpd.conf File).

The Apache HTTP Server Plug-In does not use the transport protocol (http or https) specified in the HTTP request (usually by the browser) to determine whether or not the SSL protocol is used to protect the connection between the Apache HTTP Server Plug-In and WebLogic Server.

Although two-way SSL can be used between the HTTP client and Apache HTTP server, note that one-way SSL is used between Apache HTTP Server and WebLogic Server.

Note: Using the <Location> tag in Red Hat Apache 2.0.x, results in a core dump. Instead, use the MATCH expression to proxy requests by path or MIME type.

Configuring SSL Between the Apache HTTP Server Plug-In and WebLogic Server

To use the SSL protocol between Apache HTTP Server Plug-In and WebLogic Server:

  1. Configure WebLogic Server for SSL. For more information, see Configuring the SSL Protocol.
  2. Configure the WebLogic Server SSL listen port. For more information, see Configuring the SSL Protocol.
  3. In the Apache Server, set the WebLogicPort parameter in the httpd.conf file to the WebLogic Server SSL listen port configured in step 2.
  4. In the Apache Server, set the SecureProxy parameter in the httpd.conf file to ON.
  5. Set any additional parameters in the httpd.conf file that define information about the SSL connection. For a complete list of the SSL parameters that you can configure for the plug-in, see SSL Parameters for Web Server Plug-Ins.
  6. Web server plug-ins require a trusted Certificate Authority file in order to use SSL between the plug-in and WebLogic Server. Use Sun Microsystems' keytool utility to export a trusted Certificate Authority file from the DemoTrust.jks keystore file that resides in BEA_HOME/weblogic81/server/lib.
    1. To extract the wlsdemoca file, for example, use the command:

      2. Change the alias name to obtain a different trusted CA file from the keystore.

      To look at all of the keystore's trusted CA files, use:

      Press enter if prompted for password.

    2. To convert the Certificate Authority file to pem format:

Issues with SSL-Apache Configuration

The following are known issues that may arise when you configure the Apache plug-in to use SSL.

  • To prepare the plugin configuration, double click the lock and go to the certificates path:

    • * Select the root CA (at the top)

    * Display it

    * Detail and then copy this certificate to a file using the Coded 'Base

    64 X509' option

    * Save the file, for example, to ýMyWeblogicCAToTrust.cerý (which is also a

    PEM file)

  • The PathTrim parameter (see General Parameters for Web Server Plug-Ins) must be configured inside the <Location> tag.

    • The following configuration is incorrect:

    The following configuration is the correct setup:

  • The Include directive does not work with Apache SSL. You must configure all parameters directly in the httpd.conf file. Do not use the following configuration when using SSL:
  • If you use precompiled OpenSSL from Sunfreeware.com, failover may not work properly when the plug-in tries to connect to a backend instance of WebLogic Server. If you encounter such a failure, rebuild OpenSSL and modssl and Apache using the following configuration settings.
    • For building OpenSSL:
    • For building modssl and Apache:
  • The current implementation of the WebLogic Server Apache Plug-In does not support the use of multiple certificate files with Apache SSL.

When the Apache HTTP Server Plug-In attempts to connect to WebLogic Server, the plug-in uses several configuration parameters to determine how long to wait for connections to the WebLogic Server host and, after a connection is established, how long the plug-in waits for a response. If the plug-in cannot connect or does not receive a response, the plug-in attempts to connect and send the request to other WebLogic Server instances in the cluster. If the connection fails or there is no response from any WebLogic Server in the cluster, an error message is sent.

Figure 2-1 demonstrates how the plug-in handles failover.

Possible Causes of Connection Failures

Failure of the WebLogic Server host to respond to a connection request could indicate the following problems:

  • Physical problems with the host machine
  • Network problems
  • Other server failures

Failure of all WebLogic Server instances to respond could indicate the following problems:

  • WebLogic Server is not running or is unavailable
  • A hung server
  • A database problem
  • An application-specific failure

Tuning to Reduce Connection_Refused Errors

Under load, an Apache plug-in may receive CONNECTION_REFUSED errors from a back-end WebLogic Server instance. Follow these tuning tips to reduce CONNECTION_REFUSED errors:

  • Increase the AcceptBackLog setting in the configuration of your WebLogic Server domain. See Tuning Connection Backlog Buffering.
  • On Apache 2.0.x, set the KeepAlive directive in the httpd.conf file to On. For example:

    • See Apache HTTP Server 2.0 documentation at http://httpd.apache.org/docs-project/.

    Apache 1.3.x does not support this feature.

  • Decrease the time wait interval. This setting varies according to the operating system you are using. For example:
    • On Windows NT, set the TcpTimedWaitDelay on the proxy and WebLogic Server servers to a lower value. Set the TIME_WAIT interval in Windows NT by editing the registry key under HKEY_LOCAL_MACHINE:

      • If this key does not exist you can create it as a DWORD value. The numeric value is the number of seconds to wait and may be set to any value between 30 and 240. If not set, Windows NT defaults to 240 seconds for TIME_WAIT.

    • On Windows 2000, lower the value of the TcpTimedWaitDelay by editing the registry key under HKEY_LOCAL_MACHINE:
    • On Solaris, reduce the setting tcp_time_wait_interval to one second (for both the WebLogic Server machine and the Apache machine, if possible):
  • Increase the open file descriptor limit on your machine. This limit varies by operating system. Using the limit (.csh) or ulimit (.sh) directives, you can make a script to increase the limit. For example:
  • On Solaris, increase the values of the following tunables on the WebLogic Server machine:
    • tcp_conn_req_max_q
    • tcp_conn_req_max_q0

Failover with a Single, Non-Clustered WebLogic Server

If you are running only a single WebLogic Server instance the plug-in only attempts to connect to the server defined with the WebLogicHost parameter. If the attempt fails, an HTTP 503 error message is returned. The plug-in continues trying to connect to that same WebLogic Server instance until ConnectTimeoutSecs is exceeded.

The Dynamic Server List

When you use the WebLogicCluster parameter in your httpd.conf or weblogic.conf file to specify a list of WebLogic Servers, the plug-in uses that list as a starting point for load balancing among the members of the cluster. After the first request is routed to one of these servers, a dynamic server list is returned containing an updated list of servers in the cluster. The updated list adds any new servers in the cluster and deletes any that are no longer part of the cluster or that have failed to respond to requests. This list is updated automatically with the HTTP response when a change in the cluster occurs.

Failover, Cookies, and HTTP Sessions

When a request contains session information stored in a cookie or in the POST data, or encoded in a URL, the session ID contains a reference to the specific server instance in which the session was originally established (called the primary server) and a reference to an additional server where the original session is replicated (called the secondary server). A request containing a cookie attempts to connect to the primary server. If that attempt fails, the request is routed to the secondary server. If both the primary and secondary servers fail, the session is lost and the plug-in attempts to make a fresh connection to another server in the dynamic cluster list. See Figure 2-1Connection Failover.

Apache Httpd Ssl Configuration

Note: If the POST data is larger than 64K, the plug-in will not parse the POST data to obtain the session ID. Therefore, if you store the session ID in the POST data, the plug-in cannot route the request to the correct primary or secondary server, resulting in possible loss of session data.

Figure 2-1 Connection Failover


Server

Notes:

The HTTP error code thrown by the plug-in depends on the situation. Plug-in will return the HTTP error code 500 in the following conditions:

  • Neither WebLogicCluster nor WebLogicPort was specified in the httpd.conf file.
  • Unable to resolve the WebLogicHost parameter specified in the httpd.conf file.
  • Port number specified by WebLogicPort, in the httpd.conf file, exceeds 65535.
  • Unsuccessful in parsing the request while applying the PathTrim property.
  • The request header is of type Unknown Transfer-Encoding.
  • Failed to read the chunked request.
  • Encounetered an error reading POST data from client.
  • Failed to open a temporary(temp) file.
  • Failed to write POST data to the temp file.
  • Encounetered an error reading POST data from the temp file.
  • POST timed out.
  • SSL was specified without the parameter trustedCAFile.

On the other hand, the HTTP error code 503 is returned when:

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  • The maximum number of retries is exceeded. This value is computed by dividing ConnectTimeoutSecs by ConnectRetrySecs.
  • Idempotent is OFF.

Apache Http Server Configuration Linux