+1 Good Job. Looking forward to this feature. Best, Hang
PengHui Li <peng...@apache.org> 于2022年1月12日周三 10:54写道： > > +1 It's a nice approach for making sure the ledger can be deleted correctly. > > Regards, > Penghui > > On Wed, Jan 12, 2022 at 10:23 AM Zhanpeng Wu <wuzhanpeng.w...@gmail.com> > wrote: > > > https://github.com/apache/pulsar/issues/13526 > > > > ---- > > > > ## Motivation > > > > Under the current ledger-trimming design in > > `org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl#internalTrimLedgers`, > > we need to collect those ledgers that need to be deleted first, and then > > perform the asynchronous deletion of the ledger concurrently, but we do not > > continue to pay attention to whether the deletion operation is completed. > > If the meta-information update has been successfully completed but an error > > occurs during the asynchronous deletion, the ledger may not be deleted, but > > at the logical level we think that the deletion has been completed, which > > will make this part of the data remain in the storage layer forever (such > > as bk). As the usage time of the cluster becomes longer, the residual data > > that cannot be deleted will gradually increase. > > > > In order to achieve this goal, we can separate the logic of > > meta-information update and ledger deletion. In the trimming process, we > > can first mark which ledgers are deletable, and update the results to the > > metadatastore. We can perform the deletion of marked ledgers asynchronously > > in the callback of updating the meta information, so that the original > > logic can be retained seamlessly. Therefore, when we are rolling upgrade or > > rollback, the only difference is whether the deleted ledger is marked for > > deletion. > > > > To be more specific: > > 1. for upgrade, only the marker information of ledger has been added, and > > the logical sequence of deletion has not changed. > > 2. for rollback, some ledgers that have been marked for deletion may not be > > deleted due to the restart of the broker. This behavior is consistent with > > the original version. > > > > In addition, if the ledger that has been marked is not deleted > > successfully, the marker will not be removed. So for this part of ledgers, > > every time trimming is triggered, it will be deleted again, which is > > equivalent to a check and retry mechanism. > > > > ## Goal > > > > We need to modify some logic in > > `org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl#internalTrimLedgers` > > so that the ledger deletion logic in ledger-trimming is split into two > > stages, marking and deleting. Once the marker information is updated to the > > metadatastore, every trimming will try to trigger the ledger deletion until > > all the deleteable ledgers are successfully deleted. > > > > ## Implementation > > > > This proposal aims to separate the deletion logic in ledger-trimming, so > > that `ManagedLedgerImpl#internalTrimLedgers` is responsible for marking the > > deletable ledgers and then perform actual ledger deletion according to the > > metadatastore. > > > > Therefore, the entire trimming process is broken down into the following > > steps: > > > > 1. mark deletable ledgers and update ledger metadata. > > 2. do acutual ledger deletion after metadata is updated. > > > > For step 1, we can store the marker of deletable information in > > `org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl#propertiesMap`. When > > retrieving the deleted ledger information, we can directly query by > > iterating `propertiesMap`. If this solution is not accepted, maybe we can > > create a new znode to store these information, but this approach will not > > be able to reuse the current design. > > > > For step 2, we can perform the deletion of marked ledgers asynchronously in > > the callback of updating the meta information. And every trimming will > > trigger the check and delete for those deleteable ledgers. > > > > Related PR: https://github.com/apache/pulsar/pull/13575 > >
