sijie commented on a change in pull request #4079: PIP-34 Key_Shared
subscription core implementation.
URL: https://github.com/apache/pulsar/pull/4079#discussion_r278543317
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File path:
pulsar-client-api/src/main/java/org/apache/pulsar/client/api/TypedMessageBuilder.java
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@@ -103,6 +103,15 @@
*/
TypedMessageBuilder<T> keyBytes(byte[] key);
+ /**
+ * Sets the ordering key of the message for message dispatch in {@link
SubscriptionType#Key_Shared} mode.
+ * Partition key Will be used if ordering key not specified
+ *
+ * @param orderingKey the ordering key for the message
+ * @return the message builder instance
+ */
+ TypedMessageBuilder<T> orderingKey(byte[] orderingKey);
Review comment:
frankly speaking, I am not sure it is a good idea to add "consume" or
"dispatch" to the "ordering-key".
in a data system, "partition-key" and "ordering-key" is actually a clean
concept. "partition-key" is used for partitioning and "ordering-key" is used
for ordering. ideally a partition-key doesn't have any ordering implication.
but because pulsar is implementing a partition based on an ordered log, the
"ordering" on a "partition-key" is implicitly indicated.
If an application needs end-to-end ordering, it can omit "ordering-key" or
choose a sub-key of "partition-key" or another related key. since end-to-end
ordering requires producers and consumers have agreements on keys.
If an application doesn't require end-to-end ordering or only needs partial
ordering (e.g. in a map-reduce-ish pipeline, a topic is used for computing
partially aggregated state), it can just use a key for partitioning key and the
other key for ordering key.
decoupling the partition-key and ordering-key allows adopting to more use
case in future.
However as I said in previous comment, I don't have any strong opinions
about the naming. I would let the original authors and you decide which name to
pick.
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