[improve][pip] PIP-307: Support subscribing multi topics for WebSocket (

#21390)

pip/pip_307.md

@@ -0,0 +1,30 @@
+# Background knowledge
+
+WebSocket currently only supports the consumption of a single topic, which cannot satisfy users' consumption scenarios of multiple topics.
+
+# Motivation
+
+Supports consumption of multiple topics or pattern topics.
+
+
+# Detailed Design
+
+Currently, the topic name is specified through path for consumption, like:
+```
+/ws/v2/consumer/persistent/my-property/my-ns/my-topic/my-subscription
+```
+If we want to support subscribing multi-topics, adding parameters will be confusing. Therefore, add a new v3 request path as follows:
+
+For consumption of pattern-topics:
+```
+/ws/v3/consumer/subscription?topicsPattern="a.*"
+```
+For consumption of multi-topics:
+```
+/ws/v3/consumer/subscription?topics="a,b,c"
+```
+
+# Links
+
+* Mailing List discussion thread: https://lists.apache.org/thread/co8396ywny161x91dffzvxlt993mo1ht
+* Mailing List voting thread: https://lists.apache.org/thread/lk28o483y351s7m44p018320gq3g4507