My bad, I pasted the interface code from a branch with experiment to cancel events. This is no longer needed. EventProcessingResult result is irrelevant, I updated the PIP.
It is not in the PR. On Fri, Jan 13, 2023 at 4:08 AM Yunze Xu <y...@streamnative.io.invalid> wrote: > I have some questions about the EventProcessingResult: > 1. What's the difference between FAILURE and NOT_ALLOWED? > 2. If we need to return the `message`, which indicates the error IIUC, > would it be better to replace the returned value with a checked > exception? > > Thanks, > Yunze > > On Fri, Jan 13, 2023 at 12:36 PM Andrey Yegorov <ayego...@apache.org> > wrote: > > > > Hi, > > > > I am starting discussion for PIP-241: TopicEventListener / topic events > for > > the BrokerService. > > > > PIP issue: https://github.com/apache/pulsar/issues/19224 > > > > ### Motivation > > > > Some Protocol Handlers may need to know about the topic-specific events > to > > update internal caches and/or state. > > > > These mechanisms will be useful also for core Pulsar components (like the > > Transactions subsystem) and probably we would be able to simplify the > > interaction between the internal components in the broker by using an > > unified mechanism to handle the lifecycle of topics. > > > > Specific use cases: > > > > KOP keeps some state for the topic and needs to handle such cases as: > > > > - Topic Unloaded: release resources dedicated to the topic > > - Topic Loaded: trigger loading of components tied to the partition > > (GroupCoordinator, TransactionManager) > > - Topic Deleted: remove any persistent state associated to the topic that > > is stored in additional side system topics > > - Topic Created: the same as “deleted” (ensure that there is no state on > > system topics related to the new topic) > > > > > > ### Goal > > > > This PIP defines a set of events needed for the protocol handlers (and > for > > internal broker components) to get notifications about topic-specific > > events as seen by BrokerService. PIP outlines changes needed for protocol > > handlers to keep/cache state consistent with BrokerService’s. > > > > The changes should not affect Pulsar running without protocol handlers or > > with protocol handlers that do not rely on the new events. > > > > > > ### API Changes > > > > ```java > > /** > > * Listener for the Topic events. > > */ > > @InterfaceAudience.LimitedPrivate > > @InterfaceStability.Evolving > > public interface TopicEventsListener { > > > > /** > > * Types of events currently supported. > > * create/load/unload/delete > > */ > > enum TopicEvent { > > // create events included into load events > > CREATE, > > LOAD, > > UNLOAD, > > DELETE, > > } > > > > /** > > * Stages of events currently supported. > > * before starting the event/successful completion/failed completion > > */ > > enum EventStage { > > BEFORE, > > SUCCESS, > > FAILURE > > } > > > > /** > > * Outcome of the listener. > > * Ignored for events at final stages (SUCCESS/FAILURE), > > * > > */ > > enum EventProcessingOutcome { > > OK, > > FAILURE, > > NOT_ALLOWED > > } > > > > /** > > * POJO for event processing result (outcome, message) > > */ > > @ToString(includeFieldNames=true) > > @Data(staticConstructor="of") > > class EventProcessingResult { > > private final EventProcessingOutcome outcome; > > private final String message; > > } > > > > /** > > * Handle topic event. > > * Choice of the thread / maintenance of the thread pool is up to the > > event handlers. > > * @param topicName - name of the topic > > * @param event - TopicEvent > > * @param stage - EventStage > > * @param t - exception in case of FAILURE, if present/known > > * @return - EventProcessingResult. > > * EventProcessingResult.EventProcessingOutcome != OK indicates > > request to cancel > > * event at BEFORE stage. > > */ > > EventProcessingResult handleEvent(String topicName, TopicEvent event, > > EventStage stage, Throwable t); > > } > > ``` > > > > BrokerService: > > ```java > > public void addTopicEventListener(TopicEventsListener... listeners) > > > > public void removeTopicEventListener(TopicEventsListener... > listeners) > > ``` > > > > ### Implementation > > > > See PR for the proposed implementation. > > https://github.com/apache/pulsar/pull/19153 > > > > > > ### Alternatives > > > > Add new methods to the BrokerInterceptor API > > > > -- > > Andrey > -- Andrey Yegorov
