CONFIGURING MULTICAST IN HYDRA TESTS

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How to:  enable multicast for a distributed system and use multicast for discovery
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Add the following to .conf or local.conf:

  hydra.GemFirePrms-enableMcast = true;   

Hydra selects appropriate unique mcast-port and mcast-address.
Use GemFirePrms to set multicast properties.   

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How to:  enable multicast for a distributed system and use locator for discovery
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Add the following to .conf or local.conf:

  hydra.GemFirePrms-enableMcast = true;   
  hydra.GemFirePrms-useLocator = true;

Per CongoMulticast.doc (see gemfireSpecs repository) it is recommended to use 
multicast and locators in the Congo release.

Locator and Multicast section below describes how Hydra configures locator(s)
when multicast is enabled.

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How to:  use multicast for distribution (configurable per region)
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In addition to setting GemFirePrms-enableMcast = true, you must also set the region attribute:
multicastEnabled = true (the default is false).

If using RegionDefinition include the following in the RegionDefPrms-regionSpecs:
multicastEnabled = true

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How to: specify multicast setting for distribution should match multicast setting for the distributed system
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Set hydra.GemFirePrms-enableMcast = true; 

If using RegionDefinition include the following in the RegionDefPrms-regionSpecs:
useDsMulticastSetting = true

Note:  This ensures region attributes will be consistent when ONEOF is used for enableMcast in the conf file.

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How to:  enable multicast for the distributed system, but use unicast for distribution
======================================================================================
Set hydra.GemFirePrms-enableMcast = true; 

If using RegionDefinition include the following in the RegionDefPrms-regionSpecs:
useDsMulticastSetting = false
multicastEnabled = false


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Locators and Multicast
======================
For each distributed system in a test which uses locators: 
1. Hydra creates a locator system directory (for system log and stat archive) 
2. configures and starts a Locator using distributed system 
   properties from GemFireDescription (including mcast port and address).

The locator system directory is named locator_<distributed system name>_<pid> 
and is in the user dir (the directory in which the test runs).  
The locatoragent log is also in the user dir.

