Actions due to dependency

Online/Offline of the group is performed from bottom to top according to the dependency in case of online, and from top to bottom in case of offline.
Following are a few examples how MCCS manages the resources after dependency link among the resources when a resource is failed. Attributes and state of resources are defined as the figure below.

[Figure] Resource State Information Charts

Action by dependency attribute

• OnlineDependency

[Figure] Example of bring bringing online of resource r1(OnlineDependency attribute of D1 between r1 and r2 is STRONG, OnlineDependency attribute of D2 between r1 and r3 is WEAK.) 

1. MCCS check checks the Online Dependency attribute linked to r1.
2. When you initiate resource online of r1, Child resources, r4 -> r2 -> r1, are brought online in order to hierarchy when initiate resource online of r1 due to through the hierarchy as the attribute of D1 is STRONG.
   (r3 isn't brought online due to as the attribute of D2 is WEAK.)

• OfflineDependency
  

[Figure] Example of take offline of resource r4.(D1의 OfflineDependency attribute of D1 between r2 and r4 is STRONG, OfflineDependency attribute of D2 between r3 and r4 is WEAK.) 

1. MCCS checks OfflineDependency attribute linked to r4.
2. When you initiate resource online of r4, Parents resources, r1 -> r2 -> r4, are taken offline in order to hierarchy when initiate resource offline of r4 due to through the hierarchy as the attribute of D1 is D1 STRONG.
   (r3 isn't taken offline due to attribute as the attribute of D2 is WEAK.)

Resource Critical Attributes

• Failure occurs from a resource on which critical resource depend.
  
  

[Figure] Example of Failure Occur 1

1. As a failure is occurred at resource r2, resource r1 will be taken offline. (Since resource r1 depends on resource r2 which is failed, resource r1 may cannot be online properly.)
2. Since resource r1 has critical attribute, resource r3 and r4 will be taken offline in order to failover the group.
3. As a result, resource r2 is considered as failure and all resources in the group will be taken offline

• Non-critical Resources

[Figure] Example of Failure Occur 2

1. Resource r1 which is not critical is online status.
2. When resource r2 get failed, resource r1 will be taken offline because it dependent on resource r2.
3. As r1 resource is not critical, group failover will be not performed. Therefore, the group will be partial online status.

RestartLimit Attribute

RestartLimit is an attribute of the resource type. This value determines how many times the recovery will be attempted until it is finally confirmed that it is failure. 
(Please refer to "7. Resource" for more details.)

[Figure] Example of Failure Occur 3

1. On the assumption that the value of RestartLimit is 1 for resource r2, the first failure has occurred.
2. MCCS will bring online resource r2 again as the value of RestartLimit. 
   At this time, resource r1 which depends on resource r2 will be taken offline.
3. resource r2 restart.
4. resource r1 online.
5. When another failure occurs on resource r2, all of the resource will be taken offline from resource r1 to r3 by order.
6. Resource r3 will be taken offline.
7. As a result, resource r2 is considered as failure and all resources in the group is offline status in the node.

※ 장애로 인한 리소스 재시작 시에는 의존성의 OfflineDependency 속성값에 따라 상위 리소스를 오프라인 하고 재시작합니다.
    재시작 후에는 오프라인 한 리소스들에 대해서 다시 온라인 합니다When it restart bring online of a group in a node due to failure, parent resources are taken offline first based on OfflineDependency attribute in the failure node. And then, bring online resources through the hierarchy.