[pulsar.wiki] branch master updated: Created PIP 36: Max Message Size (markdown)

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     new de64205  Created PIP 36: Max Message Size (markdown)
de64205 is described below

commit de642057212cdb7fe9a004ffa5a070831fc997fc
Author: Sijie Guo <gu...@gmail.com>
AuthorDate: Thu May 9 10:48:07 2019 +0800

    Created PIP 36: Max Message Size (markdown)
---
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 1 file changed, 42 insertions(+)

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+# PIP 36: Max Message Size
+
+- Status: Proposed
+- Author: Yong Zhang
+- Discusstion Thread:
+- Issue: 
+
+## Motivation
+
+Currently `MaxMessageSize` is hardcoded in Pulsar and it can’t be modified in server configuration. So there is no way when user want to modify the limit to transfer larger size message. 
+Hence we add a `MaxMessageSize` config in `broker.conf` to solve this problem. Because broker server will decide how much message size will be received so client need know how much message client can be sent. 
+
+Hence we propose adding a new flag `max_message_size` in protocol to tell a client what is the max message size that it can use once it connected.
+
+## Changes
+### Wire Protocol
+We propose to introduce an optional field called `max_message_size` in `CommandConnected` .
+```
+message CommandConnected {
+	required string server_version = 1;
+	optional int32 protocol_version = 2 [default = 0];
+
+	// used for telling clients what is the max message size it can use
+	optional int64 max_message_size = 3 [default = 5 * 1024 * 1024];
+}
+
+```
+
+On server side, we need send `max_message_size` to clients when broker complete connect:
+```
+// complete the connect and sent newConnected command
+private void completeConnect(int clientProtoVersion, String clientVersion, long maxMessageSize) {
+    ctx.writeAndFlush(Commands.newConnected(clientProtoVersion, maxMessageSize));
+    state = State.Connected;
+    remoteEndpointProtocolVersion = clientProtoVersion;
+    if (isNotBlank(clientVersion) && !clientVersion.contains(" ") /* ignore default version: pulsar client */) {
+        this.clientVersion = clientVersion.intern();
+    }
+}
+```
+
+On client side, client should set max message size in configuration and it should be smaller than server support.