[improve][pip] PIP-350: Allow to disable the managedLedgerOffloadDele…

…tionLagInMillis (#22688)

pip/pip-350.md

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+# PIP-350: Allow to disable the managedLedgerOffloadDeletionLagInMillis
+
+# Background knowledge
+
+https://pulsar.apache.org/docs/3.2.x/tiered-storage-overview/
+Pulsar provides the ability to offload the data from bookkeeper to the cloud storage with the tiered storage.
+Once the data is offloaded to the cloud storage, the data in the bookkeeper can be deleted after a certain period of time.
+We use the managedLedgerOffloadDeletionLagInMillis to control the deletion lag time for the offloaded data.
+The default value of managedLedgerOffloadDeletionLagInMillis is 4 hours. It means the offloaded data will be deleted after 4 hours by default.
+
+# Motivation
+
+In some test scenarios, we want to disable the deletionLag and never delete the data from the bookkeeper.
+Then when the tiered storage data is broken, we can still read the data from the bookkeeper.
+
+# Goals
+
+## In Scope
+
+Never deletes the bookkeeper data when the managedLedgerOffloadDeletionLagInMillis is set to -1.
+
+# Detailed Design
+
+## Design & Implementation Details
+
+Only need to check the value of managedLedgerOffloadDeletionLagInMillis in the ManagedLedgerImpl when it is going to delete the bookkeeper data.
+https://github.com/apache/pulsar/blob/774a5d42e8342ee50395cf3626b9e7af27da849e/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java#L2579
+
+# Backward & Forward Compatibility
+
+Fully compatible.
+
+# Links
+
+* Mailing List discussion thread: https://lists.apache.org/thread/7tlpkcm2933ddg95kgrb42943r4gq3v9
+* Mailing List voting thread: https://lists.apache.org/thread/c3rh530dlwo6nhrdflpw0mjck85hhfbx