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https://issues.apache.org/jira/browse/CLOUDSTACK-10132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16358117#comment-16358117
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ASF GitHub Bot commented on CLOUDSTACK-10132:
---------------------------------------------

nvazquez opened a new pull request #2309: CLOUDSTACK-10132: Multiple Management 
Servers Support for agents
URL: https://github.com/apache/cloudstack/pull/2309
 
 
   JIRA Ticket: https://issues.apache.org/jira/browse/CLOUDSTACK-10132
   
   Functional Specification: 
https://cwiki.apache.org/confluence/display/CLOUDSTACK/Multiple+Management+Servers+Support+on+agents
   
   This feature allows the direct agents to support multiple management 
servers. With this feature, a load balancer may no longer be necessary. The 
CloudStack administrator is responsible for setting a list of management 
servers and an algorithm in which to sort them, to the management server, using 
global configurations. The management server is responsible for applying 
algorithm to the management server list and propagate it to the agents. 
   
   ### Overview
   A new global configuration is added: 'direct.agent.lb.algorithm'. Possible 
values of this global configuration are: 'static', 'roundrobin' and 'shuffle', 
corresponding to the algorithm that would be applied to the list of comma 
separated hosts defined on 'host' global configuration before sending them to 
the agents.
   - 'static': No modification is made to the original 'host' list
   - 'roundrobin': Rotate items one by one once the list is read
   - 'shuffle': Randomly sort the list
   
   A central utility is reading values from both global configurations on 
management server startup and is responsible of propagating list to each agent. 
In propagated list, the first element acts as the main host. Load balancing 
takes place by prepending the management server each agent should connect to, 
to the propagated actual list.
   
   Once agents connect to management server, they receive a comma separated 
string of management servers. This value is compared to their actual 'host' 
configuration, and in case they differ, 'host' property is updated and 
persisted on 'agent.properties' file with the newly received string.
   
   Reconnection logic between agent and management server is refactored as 
well. If agent is not able to establish a connection to its actual management 
server after some timeout interval, it attempts connection to the next element 
on its 'host' list.
   
   Also, a background task is added to the agents to attempt reconnection to 
their main management server in pursuit of balancing. The interval of this 
background task is set on 'hosts.lb.background.interval' property on 
'agent.properties' file. It can be optionally disabled, by setting property to 0
   
   ### Example
   Supposing an environment in which there are 3 management servers: A, B and C 
and 3 KVM agents.
   Setting 'host' = 'A,B,C', agents will receive lists depending on 
'direct.agent.lb' value:
   - 'static': Each agent will receive the list: 'A,B,C'
   - 'roundrobin': First agent receives: 'A,B,C', second agent receives: 
'B,C,A', third agent receives: 'C,B,A'
   - 'shuffle': Each agent will receive a list in random order.

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> Multiple Management Servers Support for agents
> ----------------------------------------------
>
>                 Key: CLOUDSTACK-10132
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-10132
>             Project: CloudStack
>          Issue Type: Improvement
>      Security Level: Public(Anyone can view this level - this is the 
> default.) 
>    Affects Versions: 4.11.0.0
>            Reporter: Nicolas Vazquez
>            Assignee: Nicolas Vazquez
>            Priority: Major
>
> Multiple Management Servers Support for agents



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