KBEC-00201 - Installing multiple web servers for Flow on the same machine

Summary

Is it possible to install more than one instance of the Flow server and/or web server on the same machine?

Use case as described by the customer:

Today we have a single Flow server that is front-ended by a set of Flow web servers spread around the world. We are contemplating adding a second Flow server to the mix and would like to run multiple Flow web servers on the same machines that are running a single Flow web server today because those machines are very lightly utilized (as compared to the Flow server itself).

Put another way, this is a scalability issue. We need to add a new Flow server due to the utilization of the current one. But deploying new machines for the Flow web servers appears to be "way overkill" due to their current utilization.

Solution

If you launch the installer from the command-line with the flag --parallelInstallName=Alternate, then you can run a second instance of Flow on a given machine. Some details/limitations:

  • You can still use the GUI installer, but launch it from the command line with --parallelInstallName set.
  • On Windows, if you use a parallel install name, it will not be registered in the registry, hence there will be no uninstall entry.
  • Upgrades will not work.
    This should not be a big issue for a web server-only installation though because it is easy to uninstall/reinstall.
  • The parallel install name will be embedded in the service name on Windows and the name of the init.d script on Linux so there is no collision in that name space.

How to perform the install:

  • Install a Flow agent only on the machine
  • For each desired web server, run a procedure that prompts for the following:
    • parallelName - should be unique for each installation
    • httpPort - the HTTP port for the web server
    • httpsPort - the HTTPS port for the web server
    • installerPath - a path to the installer being run
    • serverName - the host for the remote Flow server
  • The procedure must run as root (using impersonation)
  • The procedure should have a step whose command is similar to the following shell script on Linux (see example below).
    Writing a Windows version should be similar.

Examples

Adjust parameters as needed, for example, note the hard-coded user and group.

unset COMMANDER_SERVER
unset COMMANDER_SESSIONFILE
unset COMMANDER_SESSIONID
unset COMMANDER_JOBSTEPID
unset COMMANDER_HTTP_PROXY
 
if [ -e /opt/electriccloud/electriccommander-$[parallelName]/uninstall ] ; then
    /opt/electriccloud/electriccommander-$[parallelName]/uninstall --mode silent
    rm -rf /opt/electriccloud/electriccommander-$[parallelName]
fi
 
$[installerPath] --mode silent \
    --parallelInstallName $[parallelName] \
    --installWeb \
    --installDirectory "/opt/electriccloud/electriccommander-$[parallelName]" \
    --dataDirectory "/opt/electriccloud/electriccommander-$[parallelName]" \
    --webHttpPort $[httpPort] \
    --webHttpsPort $[httpsPort] \
    --unixServerUser build \
    --unixServerGroup build \
    --remoteServer $[serverName] \
    --overwrite

 Because the uninstaller is run if it exists, this same procedure can be run again to upgrade the web servers.

It may be worth having a wrapper procedure that calls this procedure multiple times, once for each web server that must be installed across all of the designated machines.

See Also

KBEC-00046 - Installing multiple ElectricCommander agents on the same machine

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