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From kotamrajuyashasvi <kotamrajuyasha...@gmail.com>
Subject Implementing custom affinity logic
Date Mon, 23 Jul 2018 10:24:35 GMT

I m working on an ignite project where I want to have certain records to be
collocated based 
on a custom calculated value which is obtained from the fields of the
primary key object.

For example the Primary key pojos have fields a,b,c. I want all records
having same value of (a+b)/c 
collocated on same node/partition. 
I have gone through the ignite documentation and found that custom
AffinityKeyMapper is the 
one that can be used. Also there is an option to use custom Affinity
function but extra logic has to be added for partition to node mapping etc..

1. How can I achieve my above requirement? What are the correct options and
where can
    I get a working example of custom AffinityKeyMapper or AffinityFunction

2. Once after achieving custom affinity how to test if all records are
getting collocated as expected. One
    option that I found was to use scan query and scan a particular
partition and test each record if it 
    should actually belong to the scanned partition. But if there are huge
number of records I'm facing 
    OOM while running scan query for a partition. So I would like to know
how to achieve this/ test to 
    confirm for sure the collocation is as expected.

3. What is the performance impact of using custom affinity logic when
compared to using no affinity and 
    using @AffinityKeyMapped annotation to achieve affinity where the
scenario is to collocate based on 
    a single field.

4. When using @AffinityKeyMapped or no affinity is used, is 
is used as default 
    AffinityKeyMapper ? or there is any other default module that is used
for calculating affinity ?

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