ZDU - Distributed Installation

Setting up a distributed installation for the Zero Downtime Upgrade is the best practice in order to have a base and a target version system ready to upgrade and test properly.

Notes

In the documents pertaining to the ZDU, all references to base and target system also mean base and target version.

Two special modes exist for this upgrade function, the compatibility mode and the parallel mode.

• Compatibility mode: This mode is started as soon as you choose the option Run System Upgrade Wizard in the wizard's System Upgrade page. In this mode, which is in effect until you click the option Next in the final seventh step of the wizard, certain system optimization functions are not available. Also system performance will be reduced noticeably.
• Parallel mode: A mode during the upgrade when base and target version processes are active at the same time.

Whenever you upgrade your system, Automic strongly recommends using a test system for extensive testing before installing upgrades on your production system.

General

In order to be able to seamlessly upgrade the Automation Engine without any downtime, using the ZDU Upgrade Process, you have to set up a distributed installation. It serves to ensure that a base and target version system are available for conducting the upgrade and testing the proper running of tasks and jobs in the target version.

As base and target version CPs / WPs will be active in the parallel mode, you have to set up two separate installations in separate bin directories, one instance of the version you want to upgrade from (base), another of the version you want to upgrade to (target).

These may be two installations on:

1. the same host (recommended)
2. two separate hosts

You can use 1. or 2. with a Proxy, details you find below.

The two alternatives can be realized using either two AE installations or an existing AE installation by duplicating or splitting it.

You have to use the same ucsrv.ini for base and target version, located in one directory only.

Split an Existing Installation

In most cases this will be the solution of choice.

1. Use two separate bin directories.
2. Split an existing installation:
   1. In this case you use already configured and known ports.
   2. You would shut down half the system, that is, shut down half the number of all existing WPs and CPs. After upgrading the shut down ones to the target version, you would start them again.

Advantage:

• Less time needed for configuring ports, as no additional ports are necessary.

Disadvantages:

• Shutting down CPs results in agents and users connected to those CPs being disconnected.
• System performance will be reduced to half of its usual amount.

Distributed Installation

In rare cases, where the number of agents in a system are tens of thousands, this setup is advisable. In case of doubt consult Automic support.

1. Set up two installations of the AE system you want to upgrade (base version).
   1. Use either the same host and set up two separate installations.
   2. Alternatively use two separate hosts and separate installations.
2. You have to configure double the amount of ports than are usually necessary for the correct working of an AE system.
   1. These ports have to be known to any clients that are going to connect to a CP, therefore enter them either in the INI or the config file.
      This is necessary, because at some point during the upgrade base and target version CPs have to be active in a parallel mode at the same time.
      
3. You also have to create double the amount of MQ1CPnnn and MQ2CPnnnn in the database.

Advantages:

• Using this kind of setup lets users continue their work without being disconnected.
• Agents can be phased out successively and connect to the new CPs.

Disadvantages:

• Setting up the system this way requires a little more preparation time at first.
• Additional ports are necessary, which have to be configured in Firewall and existing Proxies.
• All ports have to be known by all existing clients before you start the upgrade.

Combine with a Proxy

You can execute the ZDU by using the most hassle-free solution and run a Proxy.

The Proxy combines and reroutes CP connections, while agents just connect to the Proxy, using the ports or port ranges configured in it.

1. You have to set up one of the environment variants explained above, use a distributed installation or split your existing environment.
2. Configure the second system in the Proxy accordingly.
3. The Proxy will then reroute connections to either the base or target version CPs, as necessary.

Advantages:

• You do not have to configure any additional ports, either in the distributed installation or the split system environment.
• The connections will be taken care of by the Proxy so that agents will be connected to whatever system and CPs are active and in use, be it base or target system.

See also:

Upgrade Process