I agree with the point, we should avoid the `clearNamespaceBacklog(String namespace)` to apply to the internal topic or internal cursor. It will introduce abnormal behaviors, e.g. clear a replication cursor backlog, clear a dedup cursor backlog, clear a compaction cursor backlog.
I would suggest letting the `clearNamespaceBacklog(String namespace)` method does not apply to the Pulsar internal topics and cursors. Thanks, Penghui On Thu, Jan 13, 2022 at 4:32 PM 丛搏 <congbobo...@gmail.com> wrote: > Hi : > > issue link : https://github.com/streamnative/support-tickets/issues/408 < > https://github.com/streamnative/support-tickets/issues/408> > > # Background > Now we have many clear namespace backlog interfaces etc. > ``` > clearNamespaceBacklog(String namespace) > > clearNamespaceBacklogAsync(String namespace) > > clearNamespaceBacklogForSubscription(String namespace, String subscription) > > clearNamespaceBacklogForSubscriptionAsync(String namespace, String > subscription) > > clearNamespaceBundleBacklog(String namespace, String bundle) > > clearNamespaceBundleBacklogAsync(String namespace, String bundle) > > clearNamespaceBundleBacklogForSubscription(String namespace, String > bundle, String subscription) > > clearNamespaceBundleBacklogForSubscriptionAsync(String namespace, String > bundle, String subscription) > ``` > There are two types of interfaces: > 1. clear namespace backlog with subscriptionName > 2. clear namespace backlog no subscriptionName > > But there have a problem, users do not know that there are many system > topics in the namespace. > > ``` > > /** > * Local topic name for the namespace events. > */ > public static final String NAMESPACE_EVENTS_LOCAL_NAME = > "__change_events"; > > /** > * Local topic name for the transaction buffer snapshot. > */ > public static final String TRANSACTION_BUFFER_SNAPSHOT = > "__transaction_buffer_snapshot"; > > public static final String SUBSCRIPTION_NAME = > "transaction-buffer-sub"; > ``` > User only want to clear the backlog witch they own created and sub. But > now we have clear the system topic sub backlog when user don't specify > subName and clear system sub with a topic witch user created. It will bring > many problems. etc. > 1. clear `NAMESPACE_EVENTS_LOCAL_NAME` will clear any topic policy in this > namespace, but user don't know and they don't want to be cleared. If the > user does not understand the problems caused by this interface, it will > delete many topic policy configurations and is difficult to recover, which > will lead to unpredictable and disastrous problems. > 2. clear `TRANSACTION_BUFFER_SNAPSHOT` topic backlog will cause > transaction buffer recover incompletely. > 3. clear `transaction-buffer-sub` sub also will cause transaction buffer > recover incompletely. > 4. if add new system topic and system sub, we should think about this > problem. > > # Motivation > We want to solve the above problems, but we can't make users unable to > delete the backlog of system topic and system sub. > So, we should solve types of interface > There are two types of interfaces: > 1. clear namespace backlog with subscriptionName > 2. clear namespace backlog no subscriptionName > > when clear namespace backlog no subscriptionName: > It represents user know the sub name is system subName and really want to > delete it, We should not block the user clear system sub backlog and do not > allow the user to create system sub. If the user uses it, it means that the > user has considered the result of the clear system sub backlog > > when clear namespace backlog with subscriptionName: > Because the user may not consider the existence of system topic and system > sub, and the wrong clear backlog may lead to serious results. Therefore, > this interface cannot delete the backlog of system topic and the backlog of > system sub. If the user really wants to clear backlog, please bring > subscriptionName and use another type of interface with subscriptionName. > > **Clear namespace and clear namespace bundle all need to handle is > logical.** > > # implement > > ``` > class SystemTopicName { > /** > * Local topic name for the namespace events. > */ > public static final String NAMESPACE_EVENTS_LOCAL_NAME = > "__change_events"; > > /** > * Local topic name for the transaction buffer snapshot. > */ > public static final String TRANSACTION_BUFFER_SNAPSHOT = > "__transaction_buffer_snapshot"; > } > ``` > ``` > class SystemSubName { > > public static final String SUBSCRIPTION_NAME = > "transaction-buffer-sub"; > > } > ``` > > 1. In order to make the code easier to maintain and reduce redundancy, we > need to move systemTopic and systemSub to a specific classes to manage. > 2. If the newly added systemTopic and systemSub are created from this > class, unpredictable problems can be prevented > > > > Let me know if you have different ideas or suggestions！！ > > Thanks! > Bo Cong
