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
