10g (9.0.4) for Linux x86
Part Number B12261-03
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| Oracle® Application Server 10g Release Notes 10g (9.0.4) for Linux x86 Part Number B12261-03 |
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This chapter describes the issues associated with OracleAS Web Cache. It includes the following topics:
This section describes general issues and their workarounds for OracleAS Web Cache. It includes the following topics:
When you configure OracleAS Web Cache to cache Web pages other users can access these pages if they know the URLs. For this reason, do not create cache secure content.
When you enable compression, some browser bugs effect compression and the output HTML. You may have to perform additional configuration to use compression for certain browsers types, or you may have to disable compression for specific browsers with bugs.
End-user performance monitoring creates an additional cookie and inserts JavaScript into pages. If this behavior causes a problem for an application, then disable this feature in the End-User Performance Monitoring page (Logging and Diagnostics > End-User Performance Monitoring) of OracleAS Web Cache Manager.
Because OracleAS Web Cache is an in-memory cache, it is best to deploy OracleAS Web Cache on a dedicated computer. Unless the computer is dedicated to run OracleAS Web Cache, ensure the maximum cache size does not exceed 20 percent of the total memory.
If peaks in time taken to cache or invalidate objects occur, check if the computer is paging. If paging occurs on the computer on which OracleAS Web Cache is installed, performance can be severely degraded. To configure OracleAS Web Cache to work efficiently on a computer with paging, either deploy OracleAS Web Cache on a dedicated computer or reduce the maximum cache size and maximum cached object size.
If the amount of memory used by OracleAS Web Cache is greater than the maximum cache size, the growth in memory usage may be caused by numerous simultaneous requests for documents that are larger than the maximum cached object size. In this situation, because the documents are not cached, OracleAS Web Cache uses more memory processing the requests and forwarding them to the origin server than it would to cache the documents. Review access logs to determine if many simultaneous requests for large documents have been made and adjust the size of the maximum cached object size so that those documents are cached. In addition, check to be sure that a caching rule or response header specifies that the documents be cached.
To modify the maximum cache size or the maximum cached object size, set new limits for the Maximum Cache Size and Maximum Cached Object Size in the Resource Limits page (Properties > Resource Limits) of OracleAS Web Cache Manager.
A system without enough disk space can cause OracleAS Web Cache to fail. Ensure there is sufficient space on the partition that contains the log files.
When OracleAS Web Cache is added to an existing application Web server environment, HTTP traffic changes effect the following aspects of the application:
To ensure traffic is directed through OracleAS Web Cache, configure all absolute URLs to use the protocol, host name, and port number of OracleAS Web Cache. Also, ensure the Port directive in the Oracle HTTP Server httpd.conf file specifies the OracleAS Web Cache listening port.
Change certificate management from the origin server to OracleAS Web Cache.
For compressed pages or pages that requires processing, OracleAS Web Cache waits for an entire page from the origin server before it sends it to the browser.
OracleAS Web Cache transparently performs the following:
Content-Length response header instead of chunked encoding for the initial request.
Content-Length response-header field whenever it is different from what the origin server sent. This feature ensures browsers receive full page content.
In previous releases, when OracleAS Web Cache received a request for a multi-part document with an HTTP Range request-header field and that document was not already cached, OracleAS Web Cache requested the entire document from the origin server and served it to the client. If the document was already cached, OracleAS Web Cache served only the part that the client requested.
In this release, when OracleAS Web Cache receives a request for a multi-part document with an HTTP Range request-header field and that document is not already cached, OracleAS Web Cache now requests the partial document from the origin server. OracleAS Web Cache correctly returns the response (which could be an entire or partial document depending on what it received from the origin server) to the client.
However, OracleAS Web Cache caches only responses that are entire documents; it does not cache responses that are range responses. This caching behavior will be fixed in a future release.
This section describes issues with client-side certificate handling. It includes the following topics:
The Oracle Application Server does not support Microsoft Server Gated Cryptography Certificates (SGC) or VeriSign Global Server IDs. This cryptography enables export version browsers to transparently upgrade to strong 128-bit encryption from weaker 40-bit encryption when communicating with an application server. Without this cryptography, browsers with the weaker 40-bit encryption cannot negotiate a secure connection to the Oracle Application Server. In a future release of the Oracle Application Server, Oracle plans to support SGC and Global Server IDs.
OracleAS Web Cache does not support the use of client-side certificates in distributed cache hierarchies.
In an ESI cache hierarchy, a provider cache must be able to accept the client-side certificate information in HTTP headers from the subscriber cache. However, with this configuration, the provider caches could inadvertently accept the certificate information in a header from a bogus entity. To prevent this, you must secure the provider caches, by methods such as installing them behind a firewall.
This section describes configuration issues and their workarounds for OracleAS Web Cache. It includes the following topics:
Use OracleAS Web Cache Manager to configure OracleAS Web Cache. Once configuration is complete, you can use the Application Server Control to start, stop, or restart the cache, as well as monitor cache and origin server status.
To use OracleAS Web Cache Manager:
opmnctl startproc ias-component=WebCache
http://web_cache_hostname:portno/webcacheadmin
ias_admin, or the OracleAS Web Cache administrator user name, administrator, for the user name. If you supplied a password during the installation, enter that password.
OracleAS Web Cache uses two configuration files: webcache.xml and internal.xml. The OracleAS Web Cache Manager writes its configuration information to the webcache.xml file. OracleAS Web Cache uses internal.xml file. These files are located in the $ORACLE_HOME/webcache directory on UNIX and ORACLE_HOME\webcache directory on Windows. Do not edit these configuration files manually, except in the cases described in these Release Notes, or when directed to do so by Oracle Support Services. Improper editing of these configuration files may cause problems in OracleAS Web Cache.
Common configuration mistakes include:
*
"Configuring OracleAS Web Cache Listen Port and Logical Site Ports" for additional configuration advice
See Also:
When configuring the Ping URL field in the Origin Server page (Origin Servers, Sites, and Load Balancing > Origin Servers), how you enter the URL depends on the origin server. For an application Web Server, enter either a relative or fully-qualified URL that includes the domain name, or site name, representing the virtual host of the application Web server. For a proxy server, enter a fully-qualified URL that includes the domain name, or site name, representing the virtual host of the origin server behind the proxy server. Ensure the URL is cached.
webcached with root privilege
You must configure webcached to run with root privilege when privileged port numbers less than 1024, there are more than 1,024 file descriptors, or the current opmnctl or webcachectl user does not match the configured user in the Process Identity page (Properties > Process Identity) of OracleAS Web Cache Manager.
By default, OracleAS Web Cache is configured to use the following default HTTP ports:
If these ports are in use, then the installation procedure attempts to assign other port numbers from a range of possible port numbers.
The Oracle HTTP Server is configured to use the following default ports:
At the end of installation, OracleAS Web Cache attempts to start. If there are port conflicts, then OracleAS Web Cache may fail to start.
To specify a maximum cached object size, go to the Resource Limits page (Properties > Resource Limits) of OracleAS Web Cache Manager.
If you specify a maximum cached object size, only documents that are not larger than a specified size and that match the caching rules will be stored in the cache. Objects larger than the specified size will not be cached, even if they meet other caching rules. The default is 100 KB for 9.0.4 installations. For upgraded caches, the default is that no limit is specified. If you want to apply the default to upgraded caches, modify the entry for Maximum Cached Object Size in the Resource Limits page.
If you have documents that are larger than the maximum cached object size and those documents are requested frequently, consider increasing the maximum cached object size limit.
The setting for the maximum cached object size is ignored if no Content-Length header is present in the response.
If the definition of Oracle home in the webcache.xml configuration file is different than the definition of Oracle home in your environment, OracleAS Web Cache may fail to start.
On UNIX, you may see the following alert message in the event log:
No matchingCACHEelement found inwebcache.xmlfor current host name (webcache-host) andORACLE_HOME(Oracle_home).
On Windows, you may see the following message:
The description for Event ID ( 1 ) in Source ( Oracle-Web-Cache ) cannot be found. The local computer may not have the necessary registry information or message DLL files to display messages from a remote computer. The following information is part of the event: Cannot open log files because NULL socket indicates problem.
During installation, the Oracle home is written to the ORACLEHOME attribute of the CACHE NAME element. in the webcache.xml file. The Oracle home is specified with the $ORACLE_HOME environment variable on UNIX and the ORACLE_HOME parameter located at HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE in the Windows registry.
If there is a mismatch, modify either the ORACLEHOME attribute in the webcache.xml file or the Oracle home environment setting. (In a cluster environment, there is more than one CACHE NAME element in the webcache.xml file, one for each cluster member. Be sure to modify the correct element.)
By default, peer requests between two members of a cache cluster are not logged in the access log. Only client requests to the cluster are logged. Peer request logging can be enabled for individual cache cluster members by adding the ACCESSLOGIGNOREPEERREQUEST attribute to the MISCELLANEOUS element in the internal.xml configuration file.
The valid values for this attribute are:
The default value is YES.
The following example shows the MISCELLANEOUS element with peer-to-peer logging enabled:
<MISCELLANEOUS ACCESSLOGIGNOREPEERREQUEST="NO"/>
The script chgiphost.sh enables you to change the host name or IP address of a computer. If the computer contains a middle-tier instance that is part of OracleAS Web Cache cluster, remove the instance from the cluster prior to running this script.
If you have a OracleAS Web Cache cluster, you can upgrade one cache cluster member at a time. The caches will continue to respond to requests. However, because other cluster members have a different version of the configuration, the caches will not forward requests to those cache cluster members operating with a different version. Instead, if the requested document is not cached by that cache or by cluster members with the same version of the configuration, OracleAS Web Cache forwards the request to the origin server. In this situation, the Operations page (Operations > Cache Operations) in OracleAS Web Cache Manager indicates that the Operation Needed is Incompatible software version.
When the cache cluster members are not running the same version of OracleAS Web Cache, you can still invalidate documents and you can propagate the invalidation to other cluster members, but the invalidation request must originate with the cache that is operating with the earlier version, such as 9.0.2 or 9.0.3, of OracleAS Web Cache.
In a configuration in which the OracleAS Web Cache listen port is the same as the logical site port, changing the OracleAS Web Cache listen port in the Listen Ports page (Ports > Listen Ports) of OracleAS Web Cache Manager requires you to also change the logical site port in the Site Definitions and Site-to-Server Mapping pages (Origin Servers, Sites, and Load Balancing > Site Definitions or Site-to-Server Mapping).
OracleAS Web Cache Manager does not enforce stringent validation checking. This is especially a problem when the admin server process is shut down after applying invalid configuration changes. In that case, the admin server process will not be able to start up, and the OracleAS Web Cache Manager will become inaccessible. If you suspect a problem, check the event_log file for startup errors or the Event Viewer on Windows.
To solve this problem:
webcache.xml file to Oracle Support Services to troubleshoot the invalid configuration entry.
webcachectl reset command to restore to the previous version of the configuration. The opmnctl utility does not provide a reset command.
To configure OracleAS Web Cache to bind user sessions to an origin server, you associate a site with a session definition name in the Session Binding page (Origin Servers, Sites, and Load Balancing > Session Binding). If you want OracleAS Web Cache to bind user sessions with multiple cookies when any cookie is set, select a session of Any Set Cookie. When selecting Any Set Cookie, in Session Binding Cookie, click Enable to instruct OracleAS Web Cache to include a Set-Cookie response-header in the response.
Prior to running the webcache_setuser.sh script, stop both the cache and admin server processes.
opmnctl stopproc ias-compononent=WebCache.
webcachectl utility command webcachectl stop. Do not use webcachectl stop from an Oracle Application Server home directory.
You cannot use the Restart option in the Cache Operations page to restart the admin server process.
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