Sorry for the previous mail. Accidentally hit the send button :(
As per the offline discussion with Imesh and Lahiru, we have decided to
have three partition selection algorithms.
1. Round-Robin : Always next partition will be selected, this is will
not ensure that instances are equally distributed to partitions.
2. Weighted-Round-Robin : It will distribute the instances equally among
partitions.
3. One-After-Another : It will select the next partition only if the
current partition is full.
We will implement Round-Robin by persisting the current partition index.
Thanks.
On Wed, Mar 4, 2015 at 11:21 AM, Rajkumar Rajaratnam <rajkum...@wso2.com>
wrote:
> As per the offline discussion with Imesh and Lahiru, we have decided to
> have three partition selection algorithms.
>
> - Round-Robin : The next partition will be selected
>
>
> On Wed, Mar 4, 2015 at 11:14 AM, Gayan Gunarathne <gay...@wso2.com> wrote:
>
>> Yeah IMO also we need to keep track of the selected index no of the
>> partition.I think we may need to persist the selected index to get the RR
>> algorithm works correctly.
>>
>> IMO in the scale up we will increment the selected index up to max index
>> no while in scale down it will decrease the selected index until it comes
>> to min index no and continue with round robin.
>>
>> Thanks,
>> Gayan
>>
>>
>>
>> On Wed, Mar 4, 2015 at 9:42 AM, Rajkumar Rajaratnam <rajkum...@wso2.com>
>> wrote:
>>
>>> Hi Reka,
>>>
>>> On Wed, Mar 4, 2015 at 1:03 AM, Reka Thirunavukkarasu <r...@wso2.com>
>>> wrote:
>>>
>>>> I think that there is small issue in applying the same RR logic for
>>>> scale up and scale down. if it sclaes up, then
>>>>
>>>> p1 -1, p2-1, p3-1, p1-2, p2-2
>>>>
>>>> Then, if we are to continuously scale down, then which partition will
>>>> we choose next? Will it be p3? In that way, it won't be equally
>>>> distributed..In order to equally distributed, we should choose the
>>>> partition in the reverse order in the scale down p2, p1, p3, p2, p1.
>>>>
>>>> Then as you mentioned, we will need another algorithm specially when
>>>> scaling down. We can apply forward RR in scale up and backward RR in
>>>> scaling down in order to equally distributed the instances.
>>>>
>>>
>>> Again , if we don't persist current partition index, this logic is also
>>> not a pure RR.
>>>
>>> Current logic is working perfectly according to "equally distribute to
>>> partitions" concept in both scale up/down scenarios. But I agree its not a
>>> pure RR.
>>>
>>> IMHO, as Lahiru mentioned, intention of having RR is to equally
>>> distribute instances among partitions. So can we stick to this logic for
>>> now? If we find any issues, we can improve it later.
>>>
>>> WDYT?
>>>
>>>>
>>>> Thanks,
>>>> Reka
>>>>
>>>>
>>>>
>>>> On Tue, Mar 3, 2015 at 12:24 PM, Rajkumar Rajaratnam <
>>>> rajkum...@wso2.com> wrote:
>>>>
>>>>> What I meant in the previous reply is the following scenario.
>>>>>
>>>>> For eg:
>>>>>
>>>>> p1, p2 , p3
>>>>>
>>>>> If the iteration goes as below:
>>>>> selectedIndex = -1
>>>>>
>>>>> since all the partitions has 0 instances, choose the first partition
>>>>> as the selectedIndex = 1
>>>>>
>>>>> p1 - 1 selectedIndex = 1
>>>>> p2 - 1 selectedIndex = 2
>>>>> p3 - 1 selectedIndex = 3
>>>>> p1 - 2 selectedIndex = 1
>>>>>
>>>>> scale down happens, instance will be removed from p1
>>>>> p1 = 1, p2 = 1, p3 = 1
>>>>>
>>>>> stratos restart
>>>>> selectedIndex = -1
>>>>>
>>>>> p1 = 2, p2=1, p3=1 choose the first lower instances partition which
>>>>> will be p1.
>>>>> selectedIndex=1 now, hence not a pure RR.
>>>>>
>>>>> I guess, it is impossible to implement a pure RR without persisting
>>>>> current partition index.
>>>>>
>>>>> Thanks.
>>>>>
>>>>> On Wed, Mar 4, 2015 at 12:29 AM, Rajkumar Rajaratnam <
>>>>> rajkum...@wso2.com> wrote:
>>>>>
>>>>>> Hi Reka,
>>>>>>
>>>>>> There is small issue in the way you suggested above. If you consider
>>>>>> scale down scenario, you can't actually say p2 will have min number
>>>>>> instances. It can be p1, if scale down happened from p1. So if we restart
>>>>>> the stratos, RR will select p1 as next partition right? This is not a
>>>>>> pure
>>>>>> RR right?
>>>>>>
>>>>>> Thanks.
>>>>>>
>>>>>> On Wed, Mar 4, 2015 at 12:24 AM, Reka Thirunavukkarasu <r...@wso2.com
>>>>>> > wrote:
>>>>>>
>>>>>>> Hi Raj,
>>>>>>>
>>>>>>> I don't think that we will need another algorithm. If we implement
>>>>>>> RR in the way that i explained, then it will even make sure to
>>>>>>> distribute
>>>>>>> the members equally.
>>>>>>>
>>>>>>> For eg:
>>>>>>>
>>>>>>> p1, p2 , p3
>>>>>>>
>>>>>>> If the iteration goes as below:
>>>>>>> selectedIndex = -1
>>>>>>>
>>>>>>> since all the partitions has 0 instances, choose the first partition
>>>>>>> as the selectedIndex = 1
>>>>>>>
>>>>>>> p1 - 1 selectedIndex = 1
>>>>>>> p2 - 1 selectedIndex = 2
>>>>>>> p3 - 1 selectedIndex = 3
>>>>>>> p1 - 2 selectedIndex = 1
>>>>>>>
>>>>>>> stratos restart
>>>>>>> selectedIndex = -1
>>>>>>>
>>>>>>> p1 = 2, p2=1, p3=1 choose the first lower instances partition which
>>>>>>> will be p2. (sorry i missed this point earlier)
>>>>>>> selectedIndex=2 now
>>>>>>>
>>>>>>> then iteration can start from where it stops before the restart.
>>>>>>>
>>>>>>> p2 - 2 selectedIndex = 2
>>>>>>> p3 - 2 selectedIndex = 3
>>>>>>> p1 - 3 selectedIndex = 1
>>>>>>> p2 - 3 selectedIndex = 2
>>>>>>> p3 - 3 selectedIndex = 3
>>>>>>>
>>>>>>> If we implement RR in this way, the instances will be equally
>>>>>>> distributed as well.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Reka
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Reka
>>>>>>>
>>>>>>> On Tue, Mar 3, 2015 at 11:43 AM, Rajkumar Rajaratnam <
>>>>>>> rajkum...@wso2.com> wrote:
>>>>>>>
>>>>>>>> So I guess we have three algorithms :)
>>>>>>>>
>>>>>>>> 1. one-after-another (It will go to next partition only if the
>>>>>>>> current partition is full)
>>>>>>>> 2. round-robin (if we implement as Reka explained above. It will
>>>>>>>> always select the next partition)
>>>>>>>> 3. name-should-be-decided (this will work as Lahiru explained
>>>>>>>> above. It will always distribute the members in the partitions equally)
>>>>>>>>
>>>>>>>> WDYT?
>>>>>>>>
>>>>>>>> Thanks.
>>>>>>>>
>>>>>>>> On Wed, Mar 4, 2015 at 12:01 AM, Reka Thirunavukkarasu <
>>>>>>>> r...@wso2.com> wrote:
>>>>>>>>
>>>>>>>>> I think that if the selectedIndex is initial value as -1, then RR
>>>>>>>>> should traverse through all the partitions and find out who has the
>>>>>>>>> minimum
>>>>>>>>> instances and choose that partition as the selectedIndex in the first
>>>>>>>>> iteration(may be we can exc). Then from the second iteration onwards,
>>>>>>>>> it
>>>>>>>>> can increase the selectedIndex by 1 to choose the next adjacent
>>>>>>>>> partition.
>>>>>>>>> This will help in the stratos restart as we don't persist the
>>>>>>>>> selectedIndex. WDYT?
>>>>>>>>>
>>>>>>>>> On Tue, Mar 3, 2015 at 10:53 AM, Lahiru Sandaruwan <
>>>>>>>>> lahi...@wso2.com> wrote:
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Tue, Mar 3, 2015 at 11:15 PM, Rajkumar Rajaratnam <
>>>>>>>>>> rajkum...@wso2.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> Problem is lowestInstanceCount is initially taking 0. Instead it
>>>>>>>>>>> should take the non terminated member count of 1st partition.
>>>>>>>>>>>
>>>>>>>>>>> To Fix,
>>>>>>>>>>>
>>>>>>>>>>> int selectedIndex = 0;
>>>>>>>>>>> int lowestInstanceCount =
>>>>>>>>>>> partitionContexts[0].getNonTerminatedMemberCount();
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>> +1. I was thinking the same. We can start with first partition
>>>>>>>>>> count.
>>>>>>>>>>
>>>>>>>>>> Thanks.
>>>>>>>>>>
>>>>>>>>>>> wdyt?
>>>>>>>>>>>
>>>>>>>>>>> Thanks.
>>>>>>>>>>>
>>>>>>>>>>> On Tue, Mar 3, 2015 at 10:57 PM, Rajkumar Rajaratnam <
>>>>>>>>>>> rajkum...@wso2.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi Lahiru,
>>>>>>>>>>>>
>>>>>>>>>>>> Actually, current logic is not working as your example. This
>>>>>>>>>>>> logic only uses the first partition. This will never use any other
>>>>>>>>>>>> partitions. See my comments within the following code.
>>>>>>>>>>>>
>>>>>>>>>>>> public PartitionContext
>>>>>>>>>>>> getNextScaleUpPartitionContext(PartitionContext[]
>>>>>>>>>>>> partitionContexts) {
>>>>>>>>>>>>
>>>>>>>>>>>> int selectedIndex = 0;
>>>>>>>>>>>> int lowestInstanceCount = 0;
>>>>>>>>>>>>
>>>>>>>>>>>> for(int partitionIndex = 0; partitionIndex <
>>>>>>>>>>>> partitionContexts.length - 1; partitionIndex++) {
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> if(partitionContexts[partitionIndex].getNonTerminatedMemberCount()
>>>>>>>>>>>> <
>>>>>>>>>>>> lowestInstanceCount) {
>>>>>>>>>>>>
>>>>>>>>>>>> *// this if condition is always false, because non terminated
>>>>>>>>>>>> count is always >=0*
>>>>>>>>>>>>
>>>>>>>>>>>> lowestInstanceCount =
>>>>>>>>>>>> partitionContexts[partitionIndex].getNonTerminatedMemberCount();
>>>>>>>>>>>> selectedIndex = partitionIndex;
>>>>>>>>>>>> }
>>>>>>>>>>>> }
>>>>>>>>>>>>
>>>>>>>>>>>> *// selected index is 0 always, so round-robin will always use
>>>>>>>>>>>> first partition*
>>>>>>>>>>>>
>>>>>>>>>>>> if(partitionContexts[selectedIndex].getNonTerminatedMemberCount() <
>>>>>>>>>>>> partitionContexts[selectedIndex].getMax()) {
>>>>>>>>>>>>
>>>>>>>>>>>> if(log.isDebugEnabled()){
>>>>>>>>>>>> log.debug(String.format("[round-robin
>>>>>>>>>>>> algorithm] [scale-up] [partition] %s has space to create members.
>>>>>>>>>>>> " +
>>>>>>>>>>>> "[non terminated count] %s [max] %s"
>>>>>>>>>>>> ,
>>>>>>>>>>>> partitionContexts[selectedIndex].getPartitionId(),
>>>>>>>>>>>>
>>>>>>>>>>>> partitionContexts[selectedIndex].getNonTerminatedMemberCount(),
>>>>>>>>>>>>
>>>>>>>>>>>> partitionContexts[selectedIndex].getMax()));
>>>>>>>>>>>> }
>>>>>>>>>>>> return partitionContexts[selectedIndex];
>>>>>>>>>>>> } else {
>>>>>>>>>>>>
>>>>>>>>>>>> return null;
>>>>>>>>>>>> }
>>>>>>>>>>>> }
>>>>>>>>>>>>
>>>>>>>>>>>> May be I am missing something here.
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks.
>>>>>>>>>>>>
>>>>>>>>>>>> On Tue, Mar 3, 2015 at 10:42 PM, Lahiru Sandaruwan <
>>>>>>>>>>>> lahi...@wso2.com> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Hi Raj,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Earlier in 4.0.0 release, we have been using the partition
>>>>>>>>>>>>> index. If that to be worked correctly we should persist the index
>>>>>>>>>>>>> for each
>>>>>>>>>>>>> cluster.
>>>>>>>>>>>>>
>>>>>>>>>>>>> IMO there is a better way to execute the round-robin method as
>>>>>>>>>>>>> follows,
>>>>>>>>>>>>>
>>>>>>>>>>>>> The intention of round robin algorithm is to distribute the
>>>>>>>>>>>>> members in the partitions equally. Current method works as per the
>>>>>>>>>>>>> following example.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Say we have 3 partitions, p1, p2, and p3 and max of each
>>>>>>>>>>>>> partition is 2.
>>>>>>>>>>>>>
>>>>>>>>>>>>> So according to the algorithm, it will select the first
>>>>>>>>>>>>> partition who has the lowest member count.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Iteration1: It will select p1.
>>>>>>>>>>>>> Iteration2: It will select p2.
>>>>>>>>>>>>> Iteration3: It will select p3.
>>>>>>>>>>>>> Iteration4: It will select p1.
>>>>>>>>>>>>> Iteration5: It will select p2.
>>>>>>>>>>>>> ....
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Tue, Mar 3, 2015 at 10:22 PM, Rajkumar Rajaratnam <
>>>>>>>>>>>>> rajkum...@wso2.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hi Devs,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> It seems to me that there is a bug in round-robin
>>>>>>>>>>>>>> implementation of partition algorithm.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> https://github.com/apache/stratos/blob/0b7734f4c9f1444d064fec93bf9ac59a5883faf2/components/org.apache.stratos.autoscaler/src/main/java/org/apache/stratos/autoscaler/algorithm/RoundRobin.java#L43-L64
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Shouldn't it work based on current partition index? For
>>>>>>>>>>>>>> example, if the most recent instance was spin up in partition-1,
>>>>>>>>>>>>>> the next
>>>>>>>>>>>>>> instance should be spin up in partition-2 and so on. According
>>>>>>>>>>>>>> to current
>>>>>>>>>>>>>> logic what is happening is, all the instance are spin up in
>>>>>>>>>>>>>> partition-1.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Please correct me If I am wrong.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> --
>>>>>>>>>>>>>> Rajkumar Rajaratnam
>>>>>>>>>>>>>> Committer & PMC Member, Apache Stratos
>>>>>>>>>>>>>> Software Engineer, WSO2
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Mobile : +94777568639
>>>>>>>>>>>>>> Blog : rajkumarr.com
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> --
>>>>>>>>>>>>> --
>>>>>>>>>>>>> Lahiru Sandaruwan
>>>>>>>>>>>>> Committer and PMC member, Apache Stratos,
>>>>>>>>>>>>> Senior Software Engineer,
>>>>>>>>>>>>> WSO2 Inc., http://wso2.com
>>>>>>>>>>>>> lean.enterprise.middleware
>>>>>>>>>>>>>
>>>>>>>>>>>>> email: lahi...@wso2.com blog:
>>>>>>>>>>>>> http://lahiruwrites.blogspot.com/
>>>>>>>>>>>>> linked-in:
>>>>>>>>>>>>> http://lk.linkedin.com/pub/lahiru-sandaruwan/16/153/146
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> --
>>>>>>>>>>>> Rajkumar Rajaratnam
>>>>>>>>>>>> Committer & PMC Member, Apache Stratos
>>>>>>>>>>>> Software Engineer, WSO2
>>>>>>>>>>>>
>>>>>>>>>>>> Mobile : +94777568639
>>>>>>>>>>>> Blog : rajkumarr.com
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> --
>>>>>>>>>>> Rajkumar Rajaratnam
>>>>>>>>>>> Committer & PMC Member, Apache Stratos
>>>>>>>>>>> Software Engineer, WSO2
>>>>>>>>>>>
>>>>>>>>>>> Mobile : +94777568639
>>>>>>>>>>> Blog : rajkumarr.com
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> --
>>>>>>>>>> Lahiru Sandaruwan
>>>>>>>>>> Committer and PMC member, Apache Stratos,
>>>>>>>>>> Senior Software Engineer,
>>>>>>>>>> WSO2 Inc., http://wso2.com
>>>>>>>>>> lean.enterprise.middleware
>>>>>>>>>>
>>>>>>>>>> email: lahi...@wso2.com blog: http://lahiruwrites.blogspot.com/
>>>>>>>>>> linked-in:
>>>>>>>>>> http://lk.linkedin.com/pub/lahiru-sandaruwan/16/153/146
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> Reka Thirunavukkarasu
>>>>>>>>> Senior Software Engineer,
>>>>>>>>> WSO2, Inc.:http://wso2.com,
>>>>>>>>> Mobile: +94776442007
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> Rajkumar Rajaratnam
>>>>>>>> Committer & PMC Member, Apache Stratos
>>>>>>>> Software Engineer, WSO2
>>>>>>>>
>>>>>>>> Mobile : +94777568639
>>>>>>>> Blog : rajkumarr.com
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Reka Thirunavukkarasu
>>>>>>> Senior Software Engineer,
>>>>>>> WSO2, Inc.:http://wso2.com,
>>>>>>> Mobile: +94776442007
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Rajkumar Rajaratnam
>>>>>> Committer & PMC Member, Apache Stratos
>>>>>> Software Engineer, WSO2
>>>>>>
>>>>>> Mobile : +94777568639
>>>>>> Blog : rajkumarr.com
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Rajkumar Rajaratnam
>>>>> Committer & PMC Member, Apache Stratos
>>>>> Software Engineer, WSO2
>>>>>
>>>>> Mobile : +94777568639
>>>>> Blog : rajkumarr.com
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Reka Thirunavukkarasu
>>>> Senior Software Engineer,
>>>> WSO2, Inc.:http://wso2.com,
>>>> Mobile: +94776442007
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Rajkumar Rajaratnam
>>> Committer & PMC Member, Apache Stratos
>>> Software Engineer, WSO2
>>>
>>> Mobile : +94777568639
>>> Blog : rajkumarr.com
>>>
>>
>>
>>
>> --
>>
>> Gayan Gunarathne
>> Technical Lead
>> WSO2 Inc. (http://wso2.com)
>> email : gay...@wso2.com | mobile : +94 766819985
>>
>>
>
>
>
> --
> Rajkumar Rajaratnam
> Committer & PMC Member, Apache Stratos
> Software Engineer, WSO2
>
> Mobile : +94777568639
> Blog : rajkumarr.com
>
--
Rajkumar Rajaratnam
Committer & PMC Member, Apache Stratos
Software Engineer, WSO2
Mobile : +94777568639
Blog : rajkumarr.com
