[GitHub] [pulsar] wmccarley opened a new issue #5792: Extend autoSkipNonRecoverableData to apply to missing Schemas in Bookkeeper

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wmccarley opened a new issue #5792: Extend autoSkipNonRecoverableData to apply to missing Schemas in Bookkeeper
URL: https://github.com/apache/pulsar/issues/5792
 
 
   **Background**
   Pulsar uses bookkeeper as the storage mechanism for data/cursors. In #1046 a flag was added by  @rdhabalia : _autoSkipNonRecoverableData_ that allows an admin to tell the broker to disregard missing ledgers and skip ahead. This helps in certain scenarios where the ledger is gone and it is unrecoverable (or not worth recovering.)
   
   This flag helps prevent users from getting stuck with NoSuchEntryException/NoLedgerException when the bookkeeper cluster has suffered data loss.
   
   **Is your feature request related to a problem? Please describe.**
   The _autoSkipNonRecoverableData_ flag does not solve the problem where the topic has a schema attached (stored in bookkeeper) and the ledger containing that schema goes missing. In this situation clients will receive NoSuchEntryException/NoLedgerException exceptions. Even if the admin unloads the topic the problem will still continue to occur until the admin deletes the schema
   
   There are two key problems:
   
   If the admin has never seen this issue before they will probably spend time checking stats-internal to see if the ledger is a cursor or if it contains entries. However the referenced ledger will not appear anywhere in stats-internal.
   
   The _autoSkipNonRecoverableData_ ostensibly exists to prevent users from getting stuck with NoSuchEntryException/NoLedgerException when ledgers go missing but it doesn't apply to missing schemas.
   
   **Describe the solution you'd like**
   
   Modify [BookkeeperSchemaStorage](https://github.com/apache/pulsar/blob/master/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/schema/BookkeeperSchemaStorage.java) to check _autoSkipNonRecoverableData_ and behave accordingly.
   
   Add additional output to stats-internal to show schema information including the ledgers that are used for schema storage (if the default BookkeeperSchemaStorage implementation is being used.)
   
   **Describe alternatives you've considered**
   
   Rather than modify BookkeeperSchemaStorage the broker code could be modified to catch the missing ledger exception and hide it if this flag is set.
   
   A different boolean flag could also be used to control this behavior if there is a scenario where the admin wants to skip missing schemas but not missing data (or vice-versa)
   
   
   
   

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