[GitHub] [pulsar-site] tisonkun commented on a diff in pull request #386: [feat][doc] Add docs for message dispatch throttling

["tisonkun (via GitHub)" <gi...@apache.org>]

tisonkun commented on code in PR #386:
URL: https://github.com/apache/pulsar-site/pull/386#discussion_r1099994248


##########
docs/concepts-throttling.md:
##########
@@ -0,0 +1,167 @@
+---
+id: concepts-throttling
+title: Message dispatch throttling
+sidebar_label: "Message throttling"
+---
+
+## Overview
+
+### What is message dispatch throttling?
+
+Large message payloads can cause memory usage spikes that lead to performance decreases. Pulsar adopts a rate-limit throttling mechanism for message dispatch, avoiding a traffic surge and improving message deliverability. You can set a threshold to limit the number of messages and the byte size of entries that can be delivered to clients, blocking subsequent deliveries when the traffic per unit of time exceeds the threshold.
+
+For example, when you configure the dispatch rate limit to 10 messages per second, then the number of messages that can be delivered to the client per second is up to 10.
+
+![Rate-limit dispatch throttling](/assets/throttling-dispatch.svg)
+
+### Why use it?
+
+Message dispatch throttling brings the following benefits in detail:
+
+- **Limit broker’s read request loads to BookKeeper**

Review Comment:
   We may decide and consistently use either `‘` or `'`.



##########
docs/concepts-throttling.md:
##########
@@ -0,0 +1,167 @@
+---
+id: concepts-throttling
+title: Message dispatch throttling
+sidebar_label: "Message throttling"
+---
+
+## Overview
+
+### What is message dispatch throttling?
+
+Large message payloads can cause memory usage spikes that lead to performance decreases. Pulsar adopts a rate-limit throttling mechanism for message dispatch, avoiding a traffic surge and improving message deliverability. You can set a threshold to limit the number of messages and the byte size of entries that can be delivered to clients, blocking subsequent deliveries when the traffic per unit of time exceeds the threshold.
+
+For example, when you configure the dispatch rate limit to 10 messages per second, then the number of messages that can be delivered to the client per second is up to 10.
+
+![Rate-limit dispatch throttling](/assets/throttling-dispatch.svg)
+
+### Why use it?
+
+Message dispatch throttling brings the following benefits in detail:
+
+- **Limit broker’s read request loads to BookKeeper**
+
+  Messages are persistently stored in the BookKeeper cluster. If a large number of read requests cannot be fulfilled using the cached data, the BookKeeper cluster may become too busy to respond, and the broker's I/O or CPU resources can be fully occupied. Using the message dispatch throttling feature can regulate the data flow by limiting the broker’s I/O and CPU load, as well as BookKeeper’s read request load.
+
+- **Balance the allocation of broker’s hardware resources at topic/subscription levels**
+
+  A broker instance serves multiple topics at one time. If a topic is frequently looked up, it will occupy almost all of the I/O, CPU, and memory resources, causing other topics cannot be looked up. Using the message dispatch throttling feature can limit the allocation of broker’s hardware resources across topics.
+
+- **Limit the allocation of client’s hardware resources at topic/subscription levels**
+
+  When there is a large backlog of messages to consume, clients may receive a large amount of data in a short period of time, which monopolizes their computing resources. Since the client has no mechanisms to proactively limit the consumption rate, using the message dispatch throttling feature can also regulate the allocation of the client’s hardware resources.

Review Comment:
   >  Since the client has no mechanisms to proactively limit the consumption rate
   
   Why? `Consumer#receive` receives one message per call. Client app can define their consume logic.



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