Fix DynamoDBLeaseTaker logging of available leases
#846
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rtyley
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DynamoDBLeaseTaker logging of available leases
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Although the Travis CI build is failing for this small change, it looks like this is probably due to some kind of flakiness in the build, rather than a problem with the PR: https://github.com/awslabs/amazon-kinesis-client/pull/846/checks?check_run_id=3266235711
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When `DynamoDBLeaseTaker` is deciding what leases to take to satisfy the target lease-count of it's worker, it can either take *expired* leases that haven't been updated by any other worker for a while, or failing that, 'steal' a limited number (by default, 1) of leases from other workers, in order to ensure its worker is gradually getting closer to it's target. It turns out that the log message it prints out when taking expired leases is misleading. For instance, in this message - the leases weren't stolen, they were taken from the available 'expired' leases: ``` Worker xxxxxx saw 68 total leases, 0 available leases, 6 workers. Target is 12 leases, I have 2 leases, I will take 10 leases ``` ...yet the message says there were 0 available leases, so how is that possible? The truth is, there were 10 available expired leases, but the log message was printing out the value of `expiredLeases.size()` - and `expiredLeases` has been mutated over the course of the method, with entries removed and added to `leasesToTake`: https://github.com/awslabs/amazon-kinesis-client/blob/0c5042dadf794fe988438436252a5a8fe70b6b0b/amazon-kinesis-client/src/main/java/software/amazon/kinesis/leases/dynamodb/DynamoDBLeaseTaker.java#L421 The fix to logging in this commit just records `numAvailableLeases` at the start of the method, so we can give an accurate log message: ``` Worker xxxxxx saw 68 total leases, 10 available leases, 6 workers. Target is 12 leases, I have 2 leases, I will take 10 leases ```
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LGTM. Thanks for the fix. |
joshua-kim
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Oct 4, 2021
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When
DynamoDBLeaseTakeris deciding what leases to take to satisfy the target lease-count of it's worker, it can take either expired leases that haven't been updated by any other worker for a while, or failing that, 'steal' a limited number (by default, 1) of leases from other workers, in order to ensure its worker is gradually getting closer to its target number.It turns out that the log message it prints out when taking expired leases is misleading. For instance, in this message - the leases weren't stolen, they were taken from the available 'expired' leases:
...yet the message says there were 0 available leases, so how is that possible? The truth is, there were 10 available expired leases, but the log message was printing out the value of
expiredLeases.size()- andexpiredLeaseswas mutated over the course of the method, with entries removed and added toleasesToTake:amazon-kinesis-client/amazon-kinesis-client/src/main/java/software/amazon/kinesis/leases/dynamodb/DynamoDBLeaseTaker.java
Line 421 in 0c5042d
The fix to logging in this commit just records
numAvailableLeasesat the start of the method, so we can give an accurate log message:While I was investigating #845 I found the broken log messaging quite confusing!
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