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public interface GroupHandle
Provides a handle to the interact with the membership group. Using this interface, applications can send messages to the group, to individual members or a list of members, and also to specific components within the target member or group. Provides a reference to the DistributedStateCache, and APIs for FailureFencing.
Method Summary | |
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void |
announceWatchdogObservedFailure(String serverToken)
GMS WATCHDOG member reports serverToken has been observed to have failed to this GMS group. |
List<String> |
getAllCurrentMembers()
returns a List of strings containing the current group membership including spectator members. |
List<String> |
getAllCurrentMembersWithStartTimes()
returns a List of strings containing the current group membership including spectator members. |
List<String> |
getCurrentAliveOrReadyMembers()
* returns only the members that are in ALIVE or READY state |
List<String> |
getCurrentCoreMembers()
returns a List of strings containing the current core members in the group |
List<String> |
getCurrentCoreMembersWithStartTimes()
returns a List of strings containing the current core members in the group. |
List<GMSMember> |
getCurrentView()
Return a snapshot of members in current view. |
DistributedStateCache |
getDistributedStateCache()
returns a DistributedStateCache object that provides the ability to set and retrieve CachedStates. |
String |
getGroupLeader()
Return the leader of the group |
MemberStates |
getMemberState(String member)
API for giving the state of the member Calls #getMemberState(String, long, long) with implementation default values for threshold and timeout . |
MemberStates |
getMemberState(String member,
long threshold,
long timeout)
Returns the state of the member. |
List<GMSMember> |
getPreviousView()
Return snapshot of members in previous view. |
boolean |
isFenced(String componentName,
String memberToken)
Provides the status of a member component's fence, if any. |
boolean |
isGroupLeader()
This is a check to find out if this peer is a group leader. |
boolean |
isMemberAlive(String memberToken)
Checks if a member is alive |
void |
lowerFence(String componentName,
String failedMemberToken)
Enables the caller to lower a logical fence that was earlier raised on a target member component. |
void |
raiseFence(String componentName,
String failedMemberToken)
Enables the caller to raise a logical fence on a specified target member token's component. |
void |
sendMessage(List<String> targetServerTokens,
String targetComponentName,
byte[] message)
Sends a message to a list of members in the group. |
void |
sendMessage(String targetComponentName,
byte[] message)
Sends a message to all members of the Group. |
void |
sendMessage(String targetServerToken,
String targetComponentName,
byte[] message)
Sends a message to a single member of the group Expects a targetServerToken representing the recipient member's id, the target component name in the target recipient member, and a byte array as parameter carrying the payload. |
Method Detail |
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void sendMessage(String targetComponentName, byte[] message) throws GMSException
targetComponentName
- target namemessage
- the message to send
GMSException
- - any exception while sending message wrapped into GMSExceptionvoid sendMessage(String targetServerToken, String targetComponentName, byte[] message) throws GMSException
targetServerToken
- targetServerToken representing the recipient member's idtargetComponentName
- target namemessage
- the message to send
GMSException
- - any exception while sending message wrapped into GMSExceptionvoid sendMessage(List<String> targetServerTokens, String targetComponentName, byte[] message) throws GMSException
targetServerTokens
- List of target server tokenstargetComponentName
- a component in the target members to which message is addressed.message
- - the payload
GMSException
- - any exception while sending message wrapped into GMSExceptionDistributedStateCache getDistributedStateCache()
DistributedStateCache
List<String> getCurrentCoreMembers()
List<String> getCurrentAliveOrReadyMembers()
MemberStates getMemberState(String member)
threshold
and timeout
.
member
- the group member
member
.MemberStates getMemberState(String member, long threshold, long timeout)
threshold
and timeout
enable the caller to tune this
lookup between accuracy and time it will take to complete the call. It is lowest cost to just return
the local computed concept for a member's state. threshold
parameter controls this.
If the local state is stale, then the timeout
parameter enables one to control how
long they are willing to wait for more accurate state information from the member itself.
member
- the group memberthreshold
- allows caller to specify how up-to-date the member state information has to be.
The larger this value, the better chance that this method just returns the local concept of this member's state.
The smaller this value, the better chance that the local state is not fresh enough and the method will find out directly
from the instance what its current state is.timeout
- is the time for which the caller instance should wait to get the state from the concerned member
via a network call.
if timeout and threshold are both 0, then the default values are used
if threshold is 0, then a network call is made to get the state of the member
if timeout is 0, then the caller instance checks for the state of the member stored with it within the
given threshold
List<String> getAllCurrentMembers()
List<String> getCurrentCoreMembersWithStartTimes()
List<String> getAllCurrentMembersWithStartTimes()
void raiseFence(String componentName, String failedMemberToken) throws GMSException
Failure Fencing is a group-wide protocol that, on one hand, requires members to update a shared/distributed datastructure if any of their components need to perform operations on another members' corresponding component. On the other hand, the group-wide protocol requires members to observe "Netiquette" during their startup so as to check if any of their components are being operated upon by other group members. Typically this check is performed by the respective components themselves. See the isFenced() method below for this check. When the operation is completed by the remote member component, it removes the entry from the shared datastructure. See the lowerFence() method below.
Raising the fence, places an entry into a distributed datastructure that is accessed by other members during their startup
Direct calls to this method is meant only for self-recovering clients. For clients that perform recovery as a surrogate for a failed instance, the FailureRecoverySignal's acquire() method should be called. That method has the effect of raising the fence and performing any other state management operation that may be added in future.
componentName
- the component channel namefailedMemberToken
- the failed member
GMSException
- if an error occursvoid lowerFence(String componentName, String failedMemberToken) throws GMSException
Direct calls to this method is meant only for self-recovering clients. For clients that perform recovery as a surrogate for a failed instance, the FailureRecoverySignal's release() method should be called. That method has the effect of lowering the fence and performing any other state management operation that may be added in future.
componentName
- the component channel namefailedMemberToken
- the failed member
GMSException
- if an error occursboolean isFenced(String componentName, String memberToken)
This check is mandatorily done at the time a member component is in the process of starting(note that at this point we assume that this member failed in its previous lifetime).
The boolean value returned would indicate if this member component is being recovered by any other member. The criteria for returning a boolean "true" is that this componentName-memberToken combo is present as a value for any key in the GMS DistributedStateCache. If a true is returned, for instance, this could mean that the client component should continue its startup without attempting to perform its own recovery operations.
The criteria for returning a boolean "false" is that the componentId-memberTokenId combo is not present in the list of values in the DistributedStateCache.If a boolean "false" is returned, this could mean that the client component can continue with its lifecycle startup per its normal startup policies.
componentName
- the component channel namememberToken
- the member
boolean isMemberAlive(String memberToken)
memberToken
- the member
String getGroupLeader()
boolean isGroupLeader()
void announceWatchdogObservedFailure(String serverToken) throws GMSException
serverToken
has been observed to have failed to this GMS group.
This is merely a hint and the GMS system validates that the GMS member has truely failed using
the same verification algorithm used when GMS heartbeat reports a member is INDOUBT and SUSPECTED of
failure.
Allows for enhanced GMS failure detection by external control entities (one example is NodeAgent of Glassfish Application Server.)
Only a GMS MemberType of WATCHDOG is allowed to broadcast to all members of a group that this serverToken
has likely failed.
serverToken
- failed member
GMSException
- if called by a member that is not a WATCHDOG member or if serverToken is not currently running in group.List<GMSMember> getCurrentView()
Note: returns an empty list if no current view.
List<GMSMember> getPreviousView()
Note: returns an empty list if no previous view.
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