Hi Shreedhar,
Thank you for your helpful info.
In my test, I didn't configure ServiceProviderConfigurationKeys.DISCOVERY_TIMEOUT. I tried to set the waiting time to 5s before, but the master discovery process didn't finished. Then I set to 7s, and the process finished. So I set the waiting time to 10s (>7s) in my test. That is how the 10s comes out.
In my test, I didn't see that master discovery is not completed even after 10 seconds. I have tried to run 3 test instances.
Best regards!
leehui
2008-06-01
发件人： Shreedhar Ganapathy
发送时间： 2008-06-01 00:32:41
收件人： dev_at_shoal.dev.java.net
抄送： carryel
主题： Re: [Shoal-Dev] GroupLeader Test
Hi Leehui
Thanks for digging deeper on this.
In your test, are you seeing that master discovery is not completed with a assigned master even after 10 seconds? Are you just using two members and seeing this ?
The Master discovery timeout can be customized by specifying the ServiceProviderConfigurationKeys.DISCOVERY_TIMEOUT as the key and a timeout value in milliseconds.
Passing in this key value pair through a Properties object when starting the GMS module will cause the MasterNode object to be instantiated with this discovery timeout.
By default, the ClusterManager uses 5 seconds as the discovery timeout for master node assignment. Look in ClusterManager's constructor and this method in ClusterManager:
private long getDiscoveryTimeout(Map props) {
long discTimeout = 5000;
if (props != null && !props.isEmpty()) {
Object dt = props.get(JxtaConfigConstants.DISCOVERY_TIMEOUT.toString());
if (dt != null) {
discTimeout = Long.parseLong((String) dt);
}
}
return discTimeout;
}
There is certainly scope to make incremental improvements to the master node state management, for example, notifying when discovery is finished.
Thanks
Shreedhar
leehui wrote:
Hi Bongjae Chang,
Thank you for your reply.
I modified the code for com.sun.enterprise.shoal.groupleadertest.GroupLeaderTest. I set the thread sleep time to 10s , then run the test code. The results is the same as what you said. I have the same opinion with you about the group leader test. You can see GroupLeaderTest. Just because I set the thread sleep time to 2s, I didn't get true from the second invocation of groupHandle.isGroupLeader(). So I said that the second invocation of groupHandle.isGroupLeader() should return true in master node.
I have another question about group leader. Can shoal or jxta provide a notification to notify the application that the MasterDiscovery process had finished? Waiting 10 or more seconds for finishing MasterDiscovery process maybe not good.
Best regards!
--
leehui
2008-05-31
-------------------------------------------------------------
发件人：Bongjae Chang
发送日期：2008-05-30 22:24:22
收件人：dev_at_shoal.dev.java.net
抄送：
主题：Re: [Shoal-Dev] GroupLeader Test
Hi. leehui. This is old issue. But I have another opinion about this. I am sorry for replying too late.
first,
--------------------------
Shreedhar Ganapathy wrote:
The join() call is a blocking call in that it returns only after group
join has occurred. So you should be able to call GroupHandle's apis
without any waiting.
--------------------------
--> I could not agree Shreedhar Ganapathy's comment. When join() is called, MasterDiscovery's logic is executed at new thread. So GroupHandle.isGroupLeader() and GroupHandle.getGroupLeader() API is not safe.
--------------------------
leehui wrote:
"Why isGroupLeader() returns false? I think it should return true"
--------------------------
--> I think GroupHandle.isGroupLeader() have meaning when all members agree or after finishing MasterDiscovery.
Before finishing MasterDiscovery, We can not know who is group leader. So, I think isGroupLeader() can return false before finishing MasterDiscovery.
At the following sample code, GroupHandler.isGroupLeader() returns false for a while. But after finishing MasterDiscovery (MasterAssigned == true, "every group member first elects himself as group leader"), GroupHandler.isGroupLeader() returns true if there is only one member.
...
while( true ) {
System.out.println(groupHandle.isGroupLeader());
System.out.println(groupHandle.getGroupLeader());
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
...
GroupHandle.isGroupLeader() will call ClusterManager.isMaster() finally. see following code.
--------------------------
ClusterManager.java
...
public boolean isMaster() {
return clusterViewManager.isMaster() && masterNode.isMasterAssigned();
}
--------------------------
I think GroupHandler.getGroupLeader() is strange instead.
I think if master is not assigned(e.g. before finishing MasterDiscovery, masterNode.isMasterAssigned() == false), GroupHandler.getGroupLeader() must not return own name. e.g. return unknown state?
Thanks.
--
Bongjae Chang
----- Original Message -----
From: "leehui" <leehui70_at_gmail.com>
To: "dev" <dev_at_shoal.dev.java.net>
Sent: Wednesday, April 30, 2008 3:55 PM
Subject: [Shoal-Dev] GroupLeader Test
Hi,
I write a simple class to test shoal's GroupLeader functions. The codes like this:
import java.util.UUID;
import com.sun.enterprise.ee.cms.core.GMSException;
import com.sun.enterprise.ee.cms.core.GMSFactory;
import com.sun.enterprise.ee.cms.core.GroupHandle;
import com.sun.enterprise.ee.cms.core.GroupManagementService;
import com.sun.enterprise.ee.cms.core.GroupManagementService.MemberType;
public class SimpleTest {
/**
* @param args
*/
public static void main(String[] args) {
String serverToken = UUID.randomUUID().toString();
GroupManagementService gms = (GroupManagementService) GMSFactory.startGMSModule(serverToken, "DemoGroup", MemberType.CORE, null);
try {
gms.join();
} catch (GMSException e) {
e.printStackTrace();
}
GroupHandle groupHandle = gms.getGroupHandle();
System.out.println(groupHandle.isGroupLeader());
System.out.println(groupHandle.getGroupLeader());
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(groupHandle.isGroupLeader());
System.out.println(groupHandle.getGroupLeader());
}
}
When I run it, the console prints:
false
e2fed556-ff76-4a38-9645-c1f6160dc07f
2008-4-30 14:29:33 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow getMemberTokens
信息: GMS View Change Received for group DemoGroup : Members in view for (before change analysis) are :
1: MemberId: e2fed556-ff76-4a38-9645-c1f6160dc07f, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49AE78AB5C0E6B94A499134E1DEA803497203
2008-4-30 14:29:33 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow newViewObserved
信息: Analyzing new membership snapshot received as part of event : MASTER_CHANGE_EVENT
false
e2fed556-ff76-4a38-9645-c1f6160dc07f
(1) Why isGroupLeader() returns false? I think it should return true.
Then, I start another instance of SimpleTest, the console prints:
false
836f3c91-a20a-4edf-a13c-326028990a8e
2008-4-30 14:29:46 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow getMemberTokens
信息: GMS View Change Received for group DemoGroup : Members in view for (before change analysis) are :
1: MemberId: 836f3c91-a20a-4edf-a13c-326028990a8e, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49A428F46CA05A349DBA7A9B02FEBDB344803
2008-4-30 14:29:47 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow newViewObserved
信息: Analyzing new membership snapshot received as part of event : MASTER_CHANGE_EVENT
2008-4-30 14:29:47 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow getMemberTokens
信息: GMS View Change Received for group DemoGroup : Members in view for (before change analysis) are :
1: MemberId: 836f3c91-a20a-4edf-a13c-326028990a8e, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49A428F46CA05A349DBA7A9B02FEBDB344803
2: MemberId: e2fed556-ff76-4a38-9645-c1f6160dc07f, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49AE78AB5C0E6B94A499134E1DEA803497203
2008-4-30 14:29:47 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow newViewObserved
信息: Analyzing new membership snapshot received as part of event : MASTER_CHANGE_EVENT
2008-4-30 14:29:47 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow getMemberTokens
信息: GMS View Change Received for group DemoGroup : Members in view for (before change analysis) are :
1: MemberId: 836f3c91-a20a-4edf-a13c-326028990a8e, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49A428F46CA05A349DBA7A9B02FEBDB344803
2: MemberId: e2fed556-ff76-4a38-9645-c1f6160dc07f, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49AE78AB5C0E6B94A499134E1DEA803497203
2008-4-30 14:29:47 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow newViewObserved
信息: Analyzing new membership snapshot received as part of event : ADD_EVENT
false
e2fed556-ff76-4a38-9645-c1f6160dc07f
(2) The first isGroupLeader() prints false. I think it should be true. Just like my question (1).
(3) Form above console's info, it seems that every group member first elects himself as group leader, then communicate others to update group leader' info.
As there is no change notification of group leader, I think it may be better to return the true group leader after gms.join(). Otherwise, the shoal should
provide some callbacks. Am I right?
When you run SimpleTest serveral times, the console may prints:
false
Exception in thread "main" java.lang.NullPointerException
at com.sun.enterprise.ee.cms.impl.jxta.GroupCommunicationProviderImpl.getGroupLeader(GroupCommunicationProviderImpl.java:281)
at com.sun.enterprise.ee.cms.impl.jxta.GroupHandleImpl.getGroupLeader(GroupHandleImpl.java:398)
at SimpleTest.main(SimpleTest.java:28)
2008-4-30 14:51:16 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow getMemberTokens
信息: GMS View Change Received for group DemoGroup : Members in view for (before change analysis) are :
1: MemberId: ab6418c9-84bc-49a8-af4c-d6e5b6127de4, MemberType: CORE, Address: urn:jxta:uuid-289CBAB1836A4A009242B36E1509E49A1B75978AE67A4B04A022C83142739EC103
2008-4-30 14:51:16 com.sun.enterprise.ee.cms.impl.jxta.ViewWindow newViewObserved
信息: Analyzing new membership snapshot received as part of event : MASTER_CHANGE_EVENT
(4) This exception occurs occasionally. But I don't know when and why it occurs. How to handle it?
(5) Does shoal plan to expose MASTER_CHANGE_EVENT callback in future?
Thank you in advance for your reply.
--------------
leehui
2008-04-30