andrasbeni opened a new pull request, #16062:
URL: https://github.com/apache/pulsar/pull/16062
Fixes #14505
### Motivation
When using a pattern-based subscription, clients poll for new topics that
match the pattern. It can happen frequently that the first messages produced
to the topic will be consumed with a significant delay because the client
has not got information about the topic for a while.
This commit introduces topic list watchers. By using these objects
clients act as observers of the creation or deletion of topics closer to
real-time. This reduces latency in consuming the first messages
published to a topic when using a pattern-based subscription.
### Modifications
- New commands were added to the binary protocol to enable registering
and deregistering watchers.
- Pattern-based consumers create TopicListWatcher objects if the broker
supports this feature. Otherwise, they fall back to polling only.
- The watchers use ConnectionHandler to obtain a connection to a broker.
- Once connected, watchers register and wait for updates.
- ServerCnx uses the newly created TopicListService to manage watchers.
- TopicListService listens to metadata notifications and sends updates.
### Verifying this change
- [ ] Make sure that the change passes the CI checks.
This change added tests
### Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): no
- The public API: no
- The schema: no
- The default values of configurations: no
- The wire protocol: yes
- Adds new commands and a new optional field to an existing command
- The rest endpoints: no
- The admin cli options: no
- Anything that affects deployment: no
### Documentation
Check the box below or label this PR directly.
Need to update docs?
- [x] `doc-required`
(Your PR needs to update docs and you will update later)
- [ ] `doc-not-needed`
(Please explain why)
- [ ] `doc`
(Your PR contains doc changes)
- [ ] `doc-complete`
(Docs have been already added)
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