5 Managing and Monitoring Server Processes

This chapter describes how to manage and monitor Oracle HTTP Server. It discusses the procedures and tools to manage OHS in your environment.

This chapter includes the following sections:

Section 5.1, "Oracle HTTP Server Processing Model"
Section 5.2, "Monitoring Oracle HTTP Server Performance"
Section 5.3, "Configuring Oracle HTTP Server Performance Directives"
Section 5.4, "Understanding Process Security"

5.1 Oracle HTTP Server Processing Model

The following sections explain the processing model for Oracle HTTP Server.

5.1.1 Request Process Model

After Oracle HTTP Server is started, it is ready to listen for and respond to HTTP(S) requests. The request processing model on Microsoft Windows systems differs from that on UNIX systems.

On Microsoft Windows, there is a single parent process and a single child process. The child process creates threads that are responsible for handling client requests. The number of created threads is static and can be configured for performance.
On UNIX, there is a single parent process that manages multiple child processes. The child processes are responsible for handling requests. The parent process brings up additional child processes as necessary, based on configuration. Although the server has the ability to dynamically bring up additional child processes, it is best to configure the server to start enough child processes initially so that requests can be handled without having to spawn more child processes.

5.1.2 Single Unit Process Model

Oracle HTTP Server provides functionality that allows it to terminate as a single unit if the parent process fails. The parent process is responsible for starting and stopping all the child processes for an Oracle HTTP Server instance. The failure of the parent process without first shutting down the child processes leaves Oracle HTTP Server in an inconsistent state that can only be fixed by manually shutting down all the orphaned child processes. Until all the child processes are closed, a new Oracle HTTP Server instance cannot be started because the orphaned child processes still occupy the ports the new Oracle HTTP Server instance needs to access.

To prevent this from occurring, the DMS instrumentation layer in child processes on UNIX and monitor functionality within WinNT MPM on Windows monitor the parent process. If they detect that the parent process has failed, then all of the remaining child processes are shut down.

5.2 Monitoring Oracle HTTP Server Performance

Oracle Fusion Middleware automatically and continuously measures run-time performance for Oracle HTTP Server. The performance metrics are automatically enabled; you do not need to set options or perform any extra configuration to collect them. If you encounter a problem, such as an application that is running slowly or is hanging, you can view particular metrics to find out more information about the problem.

Note that Fusion Middleware Control provides real-time data. If you are interested in viewing historical data, consider using Grid Control.

5.2.1 Viewing Oracle HTTP Server Performance Metrics

You can view metrics from the Oracle HTTP Server home menu of Fusion Middleware Control:

Select the Oracle HTTP Server that you want to monitor.

The Oracle HTTP Server home page is displayed.
From the Oracle HTTP Server menu, choose Monitoring, and then select Performance Summary.

The Performance Summary page is displayed. It shows performance metrics, and information about response time and request processing time for the Oracle HTTP Server instance.
To see additional metrics, click Show Metric Palette and expand the metric categories.

Tip:
Oracle HTTP Server port usage information is also available from the Oracle HTTP Server home menu.

The following figure shows the Oracle HTTP Server Performance Summary page with the Metric Palette displayed:

Description of the illustration perf_summary.gif
Select additional metrics to add them to the Performance Summary.

5.2.2 Understanding Oracle HTTP Server Performance Metrics

This section lists some most commonly-used metrics that can help you analyze Oracle HTTP Server performance.

OHS Server Metrics

The OHS Server Metrics folder contains performance metric options for Oracle HTTP Server. The following table describes the metrics in the OHS Server Metrics folder:

Element	Description
CPU Usage	CPU usage and idle times
Memory Usage	Memory usage and free memory, in MB
Processes	Busy and idle process metrics
Request Throughput	Request throughput, as measured by requests per second
Request Processing Time	Request processing time, in seconds
Response Data Throughput	Response data throughput, in KB per second
Response Data Processed	Response data processed, in KB per response
Active HTTP Connections	Number of active HTTP connections
Connection Duration	Length of time for connections
HTTP Errors	Number of HTTP 4xx and 5xx errors

OHS Virtual Host Metrics

The OHS Virtual Host Metrics folder contains performance metric options for virtual hosts, also known as access points. The following table describes the metrics in the OHS Virtual Host Metrics folder:

Element	Description
Request Throughput for a Virtual Host	Number of requests per second for each virtual host
Request Processing Time for a Virtual Host	Time to process each request for each virtual host
Response Data Throughput for a Virtual Host	Amount of data being sent for each virtual host
Response Data Processed for a Virtual Host	Amount of data being processed for each virtual host

OHS Module Metrics

The OHS Module Metrics folder contains performance metric option for modules. The following table describes the metrics in the OHS Module Metrics folder.

Element	Description
Request Handling Throughput	Request handling throughput for a module, in requests per second
Request Handling Time	Request handling time for a module, in seconds
Module Metrics	Modules including active requests, throughput, and time for each module

5.3 Configuring Oracle HTTP Server Performance Directives

Oracle HTTP Server uses directives in httpd.conf. This configuration file specifies the maximum number of HTTP requests that can be processed simultaneously, logging details, and certain limits and timeouts. Oracle HTTP Server supports and ships with the following three Multi-Processing Modules (MPMs) which are responsible for binding to network ports on the machine, accepting requests, and dispatching children to handle the requests:

Worker: This is the default MPM for Oracle HTTP Server on UNIX/Linux platforms. This MPM implements a hybrid multi-process multi-threaded server. By using threads to serve requests, it is able to serve a large number of requests with fewer system resources than a process-based server. However, it retains much of the stability of a process-based server by keeping multiple processes available, each with many threads.
WinNT: This is the default MPM for Oracle HTTP Server on Windows platforms. It uses a single control process which launches a single child process which in turn creates threads to handle requests.
Prefork: This MPM implements a non-threaded, pre-forking server that handles requests in a manner similar to Apache 1.3. It is appropriate for sites that need to avoid threading for compatibility with non-thread-safe libraries. It is also the best MPM for isolating each request, so that a problem with a single request will not affect any other.

The discussion and recommendations in this section are based on the use of Worker or WinNT MPM, which uses threads. The thread-related directives listed below are not applicable if you are using the Prefork MPM.

The Performance Directives page enables you to tune performance-related directives for Oracle HTTP Server, as illustrated in the following figure:

Description of the illustration directive2.gif

Performance directives management consists of three areas: request configuration, connection configuration, and process configuration. You can set these configurations using the Performance Directive page of Fusion Middleware Control and by following the instructions in the following sections:

Using Fusion Middleware Control to Set the Request Configuration
Using Fusion Middleware Control to Set the Connection Configuration
Using Fusion Middleware Control to Set the Process Configuration

5.3.1 Using Fusion Middleware Control to Set the Request Configuration

To specify the Oracle HTTP Server request configuration using Fusion Middleware Control, do the following:

Select Administration from the Oracle HTTP Server menu.
Select Performance Directives from the Administration menu. The Performance Directives page appears.
Enter the maximum number of requests in the Maximum Requests field (MaxClients directive). This setting limits the number of requests that can be dealt with at one time. The default and recommended value is 150. This is applicable for all Linux/UNIX platforms.
Set the maximum requests per child process in the Maximum Request per Child Process field (MaxRequestPerChild directive). You can choose to have no limit, or a maximum number. If you choose to have a limit, enter the maximum number in the field.
Enter the request timeout value in the Request Timeout (seconds) field (Timeout directive). This value sets the maximum time, in seconds, Oracle HTTP Server waits to receive a GET request, the amount of time between receipt of TCP packets on a POST or PUT request, and the amount of time between ACKs on transmissions of TCP packets in responses.
Review the settings. If the settings are correct, click Apply to apply the changes. If the settings are incorrect, or you decide to not apply the changes, click Revert to return to the original settings.
Restart Oracle HTTP Server. See Section 4.3.4.

The request configuration settings are saved, and shown on the Performance Directives page.

5.3.2 Using Fusion Middleware Control to Set the Connection Configuration

To specify the connection configuration using Fusion Middleware Control, do the following:

Select Administration from the Oracle HTTP Server menu.
Select Performance Directives from the Administration menu. The Performance Directives page appears.
Enter the maximum connection queue length in the Maximum Connection Queue Length field (ListenBacklog directive). This is the queue for pending connections. This is useful if the server is experiencing a TCP SYN overload, which causes numerous new connections to open up, but without completing the pending task.
Set the Multiple Requests per Connection field (KeepAlive directive) to indicate whether to allow multiple connections. If you choose to allow multiple connections, enter the number of seconds for timeout in the Allow With Connection Timeout field.

The Allow With Connection Timeout value sets the number of seconds the server waits for a subsequent request before closing the connection. Once a request has been received, the specified value applies. The default is 15 seconds.
Review the settings. If the settings are correct, click Apply to apply the changes. If the settings are incorrect, or you decide to not apply the changes, click Revert to return to the original settings.
Restart Oracle HTTP Server. See Section 4.3.4.

The connection configuration settings are saved, and shown on the Performance Directives page.

5.3.3 Using Fusion Middleware Control to Set the Process Configuration

The child process and configuration settings impact the ability of the server to process requests. You may need to modify the settings as the number of requests increase or decrease to maintain a well-performing server.

For UNIX, the default number of child server processes is 2. For Microsoft Windows, the default number of threads to handle requests is 150.

To specify the process configuration using Fusion Middleware Control, do the following:

Select Administration from the Oracle HTTP Server menu.
Select Performance Directives from the Administration menu. The Performance Directives page appears.
Enter the number for the initial child server processes in the Initial Child Server Processes field (StartServers directive). This is the number of child server processes created when Oracle HTTP Server is started. The default is 2. This is for UNIX only.
Enter the number for the maximum idle threads in the Maximum Idle Threads field (MaxSpareThreads directive). An idle thread is a process that is running, but not handling a request.
Enter the number for the minimum idle threads in the Minimum Idle Threads field (MinSpareThreads directive).
Enter the number for the threads per child server process in the Threads per Child Server Process field (ThreadsPerChild directive).
Review the settings. If the settings are correct, click Apply to apply the changes. If the settings are incorrect, or you decide to not apply the changes, click Revert to return to the original settings.
Restart Oracle HTTP Server. See Section 4.3.4, "Restarting Oracle HTTP Server Instances".

The process configuration settings are saved, and shown on the Performance Directives page.

5.4 Understanding Process Security

By default, Oracle HTTP Server is not able to bind to ports on UNIX in the reserved range (typically less than 1024). To enable Oracle HTTP Server to listen on ports in the reserved range (for example, port 80 and port 443) on UNIX, see Section 4.3.2.4, "Starting Oracle HTTP Server Instances on a Privileged Port (UNIX Only)".

If your PL/SQL application is using the file system caching functionality in mod_plsql, then Oracle HTTP server should have read and write privileges to the cache directory, specified through the parameter PlsqlCacheDirectory in DOMAIN_HOME/config/fmwconfig/components/OHS/componentName/mod_plsql/cache.conf. By default, this parameter points to DOMAIN_HOME/servers/componentName.

Finally, given that the cached content might contain sensitive data, the contents of the file system cache should be protected. So, access to the system as this user should be well-protected.