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Posted to user@zookeeper.apache.org by Todd Nine <to...@spidertracks.co.nz> on 2010/08/27 02:58:31 UTC
Receiving create events for self with synchronous create
Hi all,
I'm running into a strange issue I could use a hand with. I've
implemented leader election, and this is working well. I'm now
implementing a follower queue with ephemeral nodes. I have an interface
IClusterManager which simply has the api "clusterChanged". I don't care
if nodes are added or deleted, I always want to fire this event. I have
the following basic algorithm.
init
Create a path with "/follower/"+mynode name
fire the clusterChangedEvent
Watch set the event watcher on the path "/follower".
watch:
reset the watch on "/follower"
if event is not a NodeDeleted or NodeCreated, ignore
fire the clustermanager event
this seems pretty straightforward. Here is what I'm expecting
1. Create my node path
2. fire the clusterChanged event
3. Set watch on "/follower"
4. Receive watch events for changes from any other nodes.
What's actually happening
1. Create my node path
2. fire the clusterChanged event
3. Set Watch on "/follower"
4. Receive watch event for node created in step 1
5. Receive future watch events for changes from any other nodes.
Here is my code. Since I set the watch after I create the node, I'm not
expecting to receive the event for it. Am I doing something incorrectly
in creating my watch? Here is my code.
http://pastebin.com/zDXgLagd
Thanks,
Todd
Re: Receiving create events for self with synchronous create
Posted by Patrick Hunt <ph...@apache.org>.
On line 64 are you ensuring that the ZooKeeper session is active before
executing that sequence?
zookeeper = new ZooKeeper(...) is async - it returns before you're actually
connected to the server (you get notified of this in your watcher). If you
execute this sequence quickly enough your zk.create operation is queued
until the zookeeper session is actually established.
Patrick
On Thu, Aug 26, 2010 at 8:09 PM, Todd Nine <to...@spidertracks.co.nz> wrote:
> Sure thing. The FollowerWatcher class is instantiated by the
> IClusterManager implementation. It then performs the following
>
> FollowerWatcher.init() which is intended to do the following.
>
> 1. Create our follower node so that other nodes know we exist at path
> "/com/spidertracks/aviator/cluster/follower/10.0.1.1" where the last
> node is an ephemeral node with the internal IP address of the node.
> These are lines 67 through 72.
> 2. Signal to the clusterManager that the cluster has changed (line 79).
> Ultimately the clusterManager will perform a barrier for partitioning
> data ( a separate watcher)
> 3. Register a watcher to receive all future events on the follower path
> "/com/spidertracks/aviator/cluster/follower/" line 81.
>
>
> Then we have the following characteristics in the watcher
>
> 1. If a node has been added or deleted from the children of
> "/com/spidertracks/aviator/cluster/follower" then continue. Otherwise,
> ignore the event. Lines 33 through 44
> 2. If this was an event we should process our cluster has changed,
> signal to the CusterManager that a node has either been added or
> removed. line 51.
>
>
> I'm trying to encapsulate the detection of additions and deletions of
> child nodes within this Watcher. All other events that occur due to a
> node being added or deleted should be handled externally by the
> clustermanager.
>
> Thanks,
> Todd
>
>
> On Thu, 2010-08-26 at 19:26 -0700, Mahadev Konar wrote:
>
> > Hi Todd,
> > The code that you point to, I am not able to make out the sequence
> > of steps.
> > Can you be more clear on what you are trying to do in terms of
> > zookeeper api?
> >
> > Thanks
> > mahadev
> > On 8/26/10 5:58 PM, "Todd Nine" <to...@spidertracks.co.nz> wrote:
> >
> >
> > Hi all,
> > I'm running into a strange issue I could use a hand with.
> > I've
> > implemented leader election, and this is working well. I'm
> > now
> > implementing a follower queue with ephemeral nodes. I have an
> > interface
> > IClusterManager which simply has the api "clusterChanged". I
> > don't care
> > if nodes are added or deleted, I always want to fire this
> > event. I have
> > the following basic algorithm.
> >
> >
> > init
> >
> > Create a path with "/follower/"+mynode name
> >
> > fire the clusterChangedEvent
> >
> > Watch set the event watcher on the path "/follower".
> >
> >
> > watch:
> >
> > reset the watch on "/follower"
> >
> > if event is not a NodeDeleted or NodeCreated, ignore
> >
> > fire the clustermanager event
> >
> >
> > this seems pretty straightforward. Here is what I'm expecting
> >
> >
> > 1. Create my node path
> > 2. fire the clusterChanged event
> > 3. Set watch on "/follower"
> > 4. Receive watch events for changes from any other nodes.
> >
> > What's actually happening
> >
> > 1. Create my node path
> > 2. fire the clusterChanged event
> > 3. Set Watch on "/follower"
> > 4. Receive watch event for node created in step 1
> > 5. Receive future watch events for changes from any other
> > nodes.
> >
> >
> > Here is my code. Since I set the watch after I create the
> > node, I'm not
> > expecting to receive the event for it. Am I doing something
> > incorrectly
> > in creating my watch? Here is my code.
> >
> > http://pastebin.com/zDXgLagd
> >
> > Thanks,
> > Todd
> >
> >
> >
> >
> >
>
Re: Receiving create events for self with synchronous create
Posted by Mahadev Konar <ma...@yahoo-inc.com>.
Hi Todd,
Sorry for my late response. I had marked this email to respond but couldn't find the time :). Did you figure this out? It mostly looks like that as soon as you set a watch on /follower, some other node instantly creates another child of /follower? Could that be the case?
Thanks
mahadev
On 8/26/10 8:09 PM, "Todd Nine" <to...@spidertracks.co.nz> wrote:
Sure thing. The FollowerWatcher class is instantiated by the IClusterManager implementation. It then performs the following
FollowerWatcher.init() which is intended to do the following.
1. Create our follower node so that other nodes know we exist at path "/com/spidertracks/aviator/cluster/follower/10.0.1.1" where the last node is an ephemeral node with the internal IP address of the node. These are lines 67 through 72.
2. Signal to the clusterManager that the cluster has changed (line 79). Ultimately the clusterManager will perform a barrier for partitioning data ( a separate watcher)
3. Register a watcher to receive all future events on the follower path "/com/spidertracks/aviator/cluster/follower/" line 81.
Then we have the following characteristics in the watcher
1. If a node has been added or deleted from the children of "/com/spidertracks/aviator/cluster/follower" then continue. Otherwise, ignore the event. Lines 33 through 44
2. If this was an event we should process our cluster has changed, signal to the CusterManager that a node has either been added or removed. line 51.
I'm trying to encapsulate the detection of additions and deletions of child nodes within this Watcher. All other events that occur due to a node being added or deleted should be handled externally by the clustermanager.
Thanks,
Todd
On Thu, 2010-08-26 at 19:26 -0700, Mahadev Konar wrote:
Hi Todd,
The code that you point to, I am not able to make out the sequence of steps.
Can you be more clear on what you are trying to do in terms of zookeeper api?
Thanks
mahadev
On 8/26/10 5:58 PM, "Todd Nine" <to...@spidertracks.co.nz> wrote:
Hi all,
I'm running into a strange issue I could use a hand with. I've
implemented leader election, and this is working well. I'm now
implementing a follower queue with ephemeral nodes. I have an interface
IClusterManager which simply has the api "clusterChanged". I don't care
if nodes are added or deleted, I always want to fire this event. I have
the following basic algorithm.
init
Create a path with "/follower/"+mynode name
fire the clusterChangedEvent
Watch set the event watcher on the path "/follower".
watch:
reset the watch on "/follower"
if event is not a NodeDeleted or NodeCreated, ignore
fire the clustermanager event
this seems pretty straightforward. Here is what I'm expecting
1. Create my node path
2. fire the clusterChanged event
3. Set watch on "/follower"
4. Receive watch events for changes from any other nodes.
What's actually happening
1. Create my node path
2. fire the clusterChanged event
3. Set Watch on "/follower"
4. Receive watch event for node created in step 1
5. Receive future watch events for changes from any other nodes.
Here is my code. Since I set the watch after I create the node, I'm not
expecting to receive the event for it. Am I doing something incorrectly
in creating my watch? Here is my code.
http://pastebin.com/zDXgLagd
Thanks,
Todd
Re: Receiving create events for self with synchronous create
Posted by Todd Nine <to...@spidertracks.co.nz>.
Sure thing. The FollowerWatcher class is instantiated by the
IClusterManager implementation. It then performs the following
FollowerWatcher.init() which is intended to do the following.
1. Create our follower node so that other nodes know we exist at path
"/com/spidertracks/aviator/cluster/follower/10.0.1.1" where the last
node is an ephemeral node with the internal IP address of the node.
These are lines 67 through 72.
2. Signal to the clusterManager that the cluster has changed (line 79).
Ultimately the clusterManager will perform a barrier for partitioning
data ( a separate watcher)
3. Register a watcher to receive all future events on the follower path
"/com/spidertracks/aviator/cluster/follower/" line 81.
Then we have the following characteristics in the watcher
1. If a node has been added or deleted from the children of
"/com/spidertracks/aviator/cluster/follower" then continue. Otherwise,
ignore the event. Lines 33 through 44
2. If this was an event we should process our cluster has changed,
signal to the CusterManager that a node has either been added or
removed. line 51.
I'm trying to encapsulate the detection of additions and deletions of
child nodes within this Watcher. All other events that occur due to a
node being added or deleted should be handled externally by the
clustermanager.
Thanks,
Todd
On Thu, 2010-08-26 at 19:26 -0700, Mahadev Konar wrote:
> Hi Todd,
> The code that you point to, I am not able to make out the sequence
> of steps.
> Can you be more clear on what you are trying to do in terms of
> zookeeper api?
>
> Thanks
> mahadev
> On 8/26/10 5:58 PM, "Todd Nine" <to...@spidertracks.co.nz> wrote:
>
>
> Hi all,
> I'm running into a strange issue I could use a hand with.
> I've
> implemented leader election, and this is working well. I'm
> now
> implementing a follower queue with ephemeral nodes. I have an
> interface
> IClusterManager which simply has the api "clusterChanged". I
> don't care
> if nodes are added or deleted, I always want to fire this
> event. I have
> the following basic algorithm.
>
>
> init
>
> Create a path with "/follower/"+mynode name
>
> fire the clusterChangedEvent
>
> Watch set the event watcher on the path "/follower".
>
>
> watch:
>
> reset the watch on "/follower"
>
> if event is not a NodeDeleted or NodeCreated, ignore
>
> fire the clustermanager event
>
>
> this seems pretty straightforward. Here is what I'm expecting
>
>
> 1. Create my node path
> 2. fire the clusterChanged event
> 3. Set watch on "/follower"
> 4. Receive watch events for changes from any other nodes.
>
> What's actually happening
>
> 1. Create my node path
> 2. fire the clusterChanged event
> 3. Set Watch on "/follower"
> 4. Receive watch event for node created in step 1
> 5. Receive future watch events for changes from any other
> nodes.
>
>
> Here is my code. Since I set the watch after I create the
> node, I'm not
> expecting to receive the event for it. Am I doing something
> incorrectly
> in creating my watch? Here is my code.
>
> http://pastebin.com/zDXgLagd
>
> Thanks,
> Todd
>
>
>
>
>
Re: Receiving create events for self with synchronous create
Posted by Mahadev Konar <ma...@yahoo-inc.com>.
Hi Todd,
The code that you point to, I am not able to make out the sequence of steps.
Can you be more clear on what you are trying to do in terms of zookeeper api?
Thanks
mahadev
On 8/26/10 5:58 PM, "Todd Nine" <to...@spidertracks.co.nz> wrote:
Hi all,
I'm running into a strange issue I could use a hand with. I've
implemented leader election, and this is working well. I'm now
implementing a follower queue with ephemeral nodes. I have an interface
IClusterManager which simply has the api "clusterChanged". I don't care
if nodes are added or deleted, I always want to fire this event. I have
the following basic algorithm.
init
Create a path with "/follower/"+mynode name
fire the clusterChangedEvent
Watch set the event watcher on the path "/follower".
watch:
reset the watch on "/follower"
if event is not a NodeDeleted or NodeCreated, ignore
fire the clustermanager event
this seems pretty straightforward. Here is what I'm expecting
1. Create my node path
2. fire the clusterChanged event
3. Set watch on "/follower"
4. Receive watch events for changes from any other nodes.
What's actually happening
1. Create my node path
2. fire the clusterChanged event
3. Set Watch on "/follower"
4. Receive watch event for node created in step 1
5. Receive future watch events for changes from any other nodes.
Here is my code. Since I set the watch after I create the node, I'm not
expecting to receive the event for it. Am I doing something incorrectly
in creating my watch? Here is my code.
http://pastebin.com/zDXgLagd
Thanks,
Todd