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Subject [GitHub] merlimat commented on a change in pull request #3263: Improve documentation for message routing mode
Date Mon, 31 Dec 2018 19:01:53 GMT
merlimat commented on a change in pull request #3263: Improve documentation for message routing
mode
URL: https://github.com/apache/pulsar/pull/3263#discussion_r244540163
 
 

 ##########
 File path: site2/docs/concepts-messaging.md
 ##########
 @@ -199,15 +199,32 @@ Partitioned topics need to be explicitly created via the [admin API](admin-api-o
 
 When publishing to partitioned topics, you must specify a *routing mode*. The routing mode
determines which partition---that is, which internal topic---each message should be published
to.
 
-There are three routing modes available by default:
+There are three {@inject: javadoc:MessageRoutingMode:/client/org/apache/pulsar/client/api/MessageRoutingMode}
available:
 
-Mode | Description | Ordering guarantee
-:----|:------------|:------------------
-Key hash | If a key property has been specified on the message, the partitioned producer
will hash the key and assign it to a particular partition. | Per-key-bucket ordering
-Single default partition | If no key is provided, each producer's message will be routed
to a dedicated partition, initially random selected | Per-producer ordering
-Round robin distribution | If no key is provided, all messages will be routed to different
partitions in round-robin fashion to achieve maximum throughput. | None
+Mode     | Description 
+:--------|:------------
+RoundRobinPartition | If no key is provided, the producer will publish messages across all
partitions in round-robin fashion to achieve maximum throughput. Please note that round-robin
is not done per individual message but rather it's set to the same boundary of batching delay,
to ensure batching is effective. While if a key is specified on the message, the partitioned
producer will hash the key and assign message to a particular partition. This is the default
mode. 
+SinglePartition     | If no key is provided, the producer will randomly pick one single partition
and publish all the messages into that partition. While if a key is specified on the message,
the partitioned producer will hash the key and assign message to a particular partition.
+CustomPartition     | Use custom message router implementation that will be called to determine
the partition for a particular message. User can create a custom routing mode by using the
[Java client](client-libraries-java.md) and implementing the {@inject: javadoc:MessageRouter:/client/org/apache/pulsar/client/api/MessageRouter}
interface.
 
-In addition to these default modes, you can also create a custom routing mode if you're using
the [Java client](client-libraries-java.md) by implementing the {@inject: javadoc:MessageRouter:/client/org/apache/pulsar/client/api/MessageRouter}
interface.
+### Ordering guarantee
+
+The ordering of messages is related to MessageRoutingMode and Message Key. Usually, user
would want an ordering of Per-key-partition guarantee.
+
+If there is a key attached to message, the messages will be routed to corresponding partitions
based on the hashing scheme specified by {@inject: javadoc:HashingScheme:/client/org/apache/pulsar/client/api/HashingScheme}
in {@inject: javadoc:ProducerBuilder:/client/org/apache/pulsar/client/api/ProducerBuilder},
when using either SinglePartition or RoundRobinPartition mode.
+
+Ordering guarantee | Description | Routing Mode and Key
+:------------------|:------------|:------------
+Per-key-partition  | All the messages with the same key will be in order and be placed in
same partition. | Use either SinglePartition or RoundRobinPartition mode, and Key is provided
by each message.
+Per-producer       | All the messages from the same producer will be in order. | Use SinglePartition
mode, and no Key is provided for each message.
 
 Review comment:
   ```suggestion
    Per-producer       | All the messages from the same producer will be in order. | Use `SinglePartition`
mode, and no Key is provided for each message.
   ```

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