jiazhai closed pull request #3263: Improve documentation for message routing
mode
URL: https://github.com/apache/pulsar/pull/3263
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diff --git
a/pulsar-client/src/main/java/org/apache/pulsar/client/api/MessageRoutingMode.java
b/pulsar-client/src/main/java/org/apache/pulsar/client/api/MessageRoutingMode.java
index b5cd8ba1d7..3fb27428d6 100644
---
a/pulsar-client/src/main/java/org/apache/pulsar/client/api/MessageRoutingMode.java
+++
b/pulsar-client/src/main/java/org/apache/pulsar/client/api/MessageRoutingMode.java
@@ -26,12 +26,16 @@
*/
public enum MessageRoutingMode {
/**
- * The producer will chose one single partition and publish all the
messages into that partition.
+ * If no key is provided, The partitioned producer will randomly pick one
single partition and publish all the messages into that partition.
+ * If a key is provided on the message, the partitioned producer will hash
the key and assign message to a particular partition.
*/
SinglePartition,
/**
- * Publish messages across all partitions in round-robin.
+ * 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.
*/
RoundRobinPartition,
diff --git a/site2/docs/concepts-messaging.md b/site2/docs/concepts-messaging.md
index c7a80a5094..fae604ec06 100644
--- a/site2/docs/concepts-messaging.md
+++ b/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.
+
+### Hashing scheme
+
+{@inject:
javadoc:HashingScheme:/client/org/apache/pulsar/client/api/HashingScheme} is an
enum that represent sets of standard hashing functions available when choosing
the partition to use for a particular message.
+
+There are 2 types of standard hashing functions available: `JavaStringHash`
and `Murmur3_32Hash`.
+The default hashing function for producer is `JavaStringHash`.
+Please pay attention that `JavaStringHash` is not useful when producers can be
from different multiple language clients, under this use case, it is
recommended to use `Murmur3_32Hash`.
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