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3.x: Add RackAwareRoundRobinPolicy (second version) #227

Merged
merged 3 commits into from
Jul 7, 2023
Merged

3.x: Add RackAwareRoundRobinPolicy (second version) #227

merged 3 commits into from
Jul 7, 2023

Commits on Jul 7, 2023

  1. Add RackAwareRoundRobinPolicy 

    RackAwareRoundRobinPolicy is a modified version of 
DCAwareRoundRobinPolicy. The new policy shares much of the code with
the original policy, but changes the logic of newQueryPlan - it will
return hosts in local rack first, followed by remote racks in local DC, 
followed by remote DC.

In contrast to the approach in scylladb#199, this policy does not change the 
distance() method - it will return LOCAL for both local rack in local DC
and remote racks in local DC. This is a deliberate choice, as many other
places in the driver look at the distance and introducing a new distance
type (e.g. LOCAL_REMOTERACK) would necessitate many changes. One example
of that is PoolingOptions, where the user can specify how many 
connections should be made to LOCAL/REMOTE nodes - adding another type
of distance would force the user to remember to change yet another
configuration parameter.

Integration tests in RackAwareRoundRobinPolicyTest are based on tests
in DCAwareRoundRobinPolicyTest, as much of the behavior should be
the same between the policies. A couple new tests were introduced to
specifically test the rack-aware feature in local DC.
    @avelanarius
    avelanarius committed Jul 7, 2023
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  2. Increase timeout in ScassandraCluster 

    On my local system some Scassandra nodes sometimes take a long time
to shut down and the previous 10 second value was insufficient.
    @avelanarius
    avelanarius committed Jul 7, 2023
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  3. Reduce the number of queries in integration tests 

    Reduce the number of queries that are executed in DCAwareRoundRobinPolicyTest
and RackAwareRoundRobinPolicyTest, as we observed that on GitHub Actions
the test would be flaky, failing with:

<com.datastax.driver.core.exceptions.TransportException: [/127.0.1.1:34153] Connection has been closed>

Unfortunately this error could not be reproduced locally.
    @avelanarius
    avelanarius committed Jul 7, 2023
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