+1 (non-binding)
------------------ ???????? ------------------
??????:
"dev"
<mattisonc...@gmail.com>;
????????: 2022??1??14??(??????) ????11:23
??????: "dev"<dev@pulsar.apache.org>;
????: Re: [VOTE] PIP-129: Introduce intermediate state for ledger deletion
+1 (non-binding)
Best,
Mattison
On Fri, 14 Jan 2022 at 11:19, Hang Chen <chenh...@apache.org> wrote:
> +1 (binding)
>
> Best,
> Hang
>
> Zhanpeng Wu <wuzhanpeng.w...@gmail.com> ??2022??1??14?????? 10:37??????
> >
> > This is the voting thread for PIP-129. It will stay open for at least
48
> > hours. Pasted below for quoting convenience.
> >
> > ----
> >
> > 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
>
