[jira] [Updated] (CASSANALYTICS-184) CdcState.ReplicaCountSerializer map-size overflow corrupts persisted CDC state

["Josh McKenzie (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANALYTICS-184?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Josh McKenzie updated CASSANALYTICS-184:
----------------------------------------
    Reviewers: Josh McKenzie

> CdcState.ReplicaCountSerializer map-size overflow corrupts persisted CDC state
> ------------------------------------------------------------------------------
>
>                 Key: CASSANALYTICS-184
>                 URL: https://issues.apache.org/jira/browse/CASSANALYTICS-184
>             Project: Apache Cassandra Analytics
>          Issue Type: Bug
>            Reporter: Jyothsna Konisa
>            Priority: Normal
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> CdcState.ReplicaCountSerializer serializes the number of entries in the CDC watermarker's replica-count map (numUpdates — the count of distinct mutations awaiting sufficient replica acknowledgment) using a signed short (max 32,767), this silently overflows once the map grows past that sizeOnce corrupted. The bad size gets persisted to Cassandra via SidecarStatePersister and re-read on every subsequent restart, causing a permanent crash loop.
> message="Failed to start CDC consumers, cleaning up resources"
>   exception=java.lang.IllegalArgumentException: Illegal initial capacity: -4366
>       at java.util.HashMap.<init>
>       at org.apache.cassandra.cdc.state.CdcState$ReplicaCountSerializer.read(CdcState.java:404)
>       at org.apache.cassandra.cdc.state.CdcState$Serializer.read(CdcState.java:380)
>       at org.apache.cassandra.cdc.Cdc.start(Cdc.java:137)
> -4366 is the short-overflow wraparound of a map size that grew past 32,767 under sustained backpressure (CDC write-rejection storms inflating the watermarker as mutations piled up waiting for replica quorum). The corrupted size persists indefinitely — each restart re-reads the same broken state and crashes identically, with no self-heal.



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