ZenPacks

WebScale ZenPack

The WebScale ZenPack enhances Web-based performance of Zenoss.

Support

This ZenPack is included with commercial versions of Zenoss and enterprise support for this ZenPack is provided to Zenoss customers with an active subscription.

Background

The ZenPacks.zenoss.WebScale ZenPack adds the zenwebserver daemon, to deploy and manage multiple Zope instances.


With this ZenPack, Zenoss platform replaces zopectl with the nginx load balancer.

Prerequisites

PrerequisiteRestriction
ProductZenoss platform 4.1.1
Required ZenPacksZenPacks.zenoss.WebScale

Installation notes

  • The installation process replaces zopectl in the startup script (or in the $ZENHOME/etc/daemons.txt file) with zenwebserver. Use zenwebserver to manage the application server.
  • If you have multiple Zope instances deployed behind a custom load balancer, installing this ZenPack will not install zenwebserver as your control script. You must install it manually after determining and executing your migration strategy.

Usage

zenwebserver Command (Option) Target

Command

  • run - Starts Zope in the foreground, on the port normally used by the load balancer. Neither the load balancer nor other Zope servers are used.
  • start - Starts the load balancer and Zope servers. If any are running already, they are ignored.
  • stop - Stops the load balancer and Zope servers. If any are stopped already, they are ignored.
  • restart - Stops and then restarts the load balancer and Zope servers. To minimize downtime, the load balancer is restarted first, and then each Zope server in turn. This ensures that the Zope server pool is never empty.
  • status - Provides status information. It prints the status of the load balancer, including its PID.
  • deploy - Creates or destroys Zope instances. It adds or removes instances from the server pool and updates the load balancer to reference the altered server pool. If the load balancer is running already, then its configuration is reloaded without stopping it.
  • reload - Reloads the load balancer configuration. For example, if you make a change to the nginx configuration to listen at a different port, reload it to use the new port without restarting.
  • attach - Returns a detached Zope server to the server pool and updates the load balancer.
  • detach - Removes a Zope server from the server pool and updates the load balancer. (Zope continues to run, but does not get traffic from the load balancer.)
  • debug - Deploys a Zope server without adding it to the server pool, starting it immediately in the foreground. This server can only be accessed directly. The server is automatically destroyed upon exiting the process.
  • help - Returns command usage information.
  • configure - Generates a new nginx.conf file, based on properties in $ZENHOME/etc/zenwebserver.conf. The properties and their defaults are shown in the following table.
     PropertyDefault Value Description 
    httpPort8080Specifies the port to accept the HTTP request.
    useSSLFalseSpecifies whether SSL config should be used. Set to a value of True to enable.
    sslPort443Specifies the port to use if useSSL is set.
    sslCertZENHOME/etc/ssl/zenoss.crtSpecifies the path to the SSL certificate if useSSL is set.
    sslKeyZENHOME/etc/ssl/zenoss.keySpecifies the path to the SSL key if useSSL is set.


    The generated configuration should not be edited. Use the properties in $ZENHOME/etc/zenwebserver.conf to customize generation of the nginx.conf file.

    After running zenwebserver configure, you must reload (zenwebserver reload) or restart (zenwebserver restart) for the new configuration to take effect.

Option

  • -v - Prints more information, including the status of each Zope server, the ports at which the processes are listening, and the servers currently detached from the server pool.

Target

Several commands accept one or more targets against which the command should be executed. If you do not specify a target, the command runs the action against all targets.

  • loadbalancer - Load balancer. Alternatively, you can specify:
    ngnix
  • servers - All Zope servers.
  • servern - Specific Zope server, where n is the server number. Alternatively, you can specify just a server number or numbers. For example, both of the following commands stop Zope servers 2 and 3:
    zenwebserver stop server2 server3
    zenwebserver stop 2 3

Examples

Status

zenwebserver status [-v]

Start, Stop, and Restart

zenwebserver {stop|start|restart} [-v] [Targets]

Manage the Number of Zope Servers

zenwebserver deploy {n|-n|+n}


Examples:

  • zenwebserver deploy 5 # Ensures that exactly 5 Zope servers are running.
  • zenwebserver deploy +1 # Deploys one additional Zope server, regardless of the current number.
  • zenwebserver deploy -3 # Destroys up to 3 Zope servers (as long as the minimum of 1 is maintained).

Manage the Server Pool

zenwebserver {attach|detach} Targets

Detaching a target is useful when you want to isolate a Zope server and access it via its direct port to ensure that your requests are the only ones being handled by that server.

Start an Independent Instance

zenwebserver debug

Configuring the Load Balancer

The load balancer configuration file (nginx.conf) is generated from the template in $ZENHOME/etc/nginx.conf.template. This template includes a number of variables that can be substituted by providing values in the zenwebserver.conf file.

Custom configurations also can be included in the http and server blocks of the nginx configuration. By default, configuration files in $ZENHOME/etc are included if they match one of these patterns:

  • nginx-custom-http-*.conf
  • nginx-custom-server-*.conf

Values that can be substituted are:

  • Number of worker_processes for nginx to use
    #worker_processes 4
  • Paths for nginx var directories
    #proxy_cache_path $ZENHOME/var/nginx/cache
    #proxy_temp_path $ZENHOME/var/nginx/tmp/proxy
    #client_body_temp_path $ZENHOME/var/nginx/tmp/client_body
  • Custom includes, which include any configuration files that match the pattern.
    • customHttpInclude allows configurations to be added to the http block in the nginx configuration:
      #customHttpInclude $ZENHOME/etc/nginx-custom-http-*.conf
    • customServerInclude allows configurations to be added to the server block in the nginx configuration:
      #customServerInclude $ZENHOME/etc/nginx-custom-server-*.conf
  • Default error log level
    #error_log_level warn

Installation

Normal Installation (packaged egg)

  1. Download the appropriate egg file for the version of Zenoss you are running.
  2. Ensure you are logged in as the zenoss user:
    $ sudo su - zenoss
  3. Install the ZenPack:
    $ zenpack --install ZenPacks.zenoss.WebScale-*.egg
  4. Restart these services:
    $ zenoss restart

Commercial

This ZenPack is developed and supported by Zenoss Inc. Commercial ZenPacks are available to Zenoss commercial customers only. Contact Zenoss to request more information regarding this or any other ZenPacks. Click here to view all available Zenoss Commercial ZenPacks.

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