add release notes (apache#6985)

Add release notes for 2.5.2

site2/website/release-notes.md

@@ -1,6 +1,70 @@
 
 ## Apache Pulsar Release Notes
 
+### 2.5.2 &mdash; 2020-05-19 <a id=“2.5.2”></a>
+
+#### Fixes and Enhancements
+
+##### Broker
+* [Broker] Implement AutoTopicCreation by namespace level override [#6471](https://github.com/apache/pulsar/pull/6471)
+* [Broker] Add custom deletionLag and threshold for offload policies per namespace  [#6422](https://github.com/apache/pulsar/pull/6422)
+* [Broker] Invalidate managed ledgers zookeeper cache instead of reloading on watcher triggered [#6659](https://github.com/apache/pulsar/pull/6659) 
+* [Broker] Retention policy should be respected when there is no traffic [#6676](https://github.com/apache/pulsar/pull/6676)
+* [Broker] Fixed double delete on a namespace [#6713](https://github.com/apache/pulsar/pull/6713)
+* [Broker] fix get batch message from http response, only get the first message[#6715](https://github.com/apache/pulsar/pull/6715)
+* [Broker] Fix Deadlock by Consumer and Reader[#6728](https://github.com/apache/pulsar/pull/6728)
+* [Broker] avoid backpressure by skipping dispatching if consumer channel is not writable [#6740](https://github.com/apache/pulsar/pull/6740)
+* [Broker] fix when producing encrypted messages, MessageMetadata objects are not released after they are created. [#6745](https://github.com/apache/pulsar/pull/6745)
+* [Broker] Bump netty version to 4.1.48.Final [#6746](https://github.com/apache/pulsar/pull/6746)
+* [Broker] Increase timeout for loading topics [#6750](https://github.com/apache/pulsar/pull/6750)
+* [Broker] Fix wrong cursor state for cursor without consumer  [#6766](https://github.com/apache/pulsar/pull/6766)
+* [Broker] change nondurable cursor to active to improve performance [#6769](https://github.com/apache/pulsar/pull/6769)
+* [Broker] register loadbalance znode should attempt to wait until session expired [#6788](https://github.com/apache/pulsar/pull/6788)
+* [Broker] Fix some empty message related problems in the compacted topic. [#6795](https://github.com/apache/pulsar/pull/6795)
+* [Broker] Avoid creating partitioned topic for partition name [#6846](https://github.com/apache/pulsar/pull/6846)
+* [Broker] Add Tls with keystore type config support [#6853](https://github.com/apache/pulsar/pull/6853)
+* [Broker] fix consumer stuck when batchReceivePolicy maxNumMessages > maxReceiverQueueSize [#6862](https://github.com/apache/pulsar/pull/6862)
+* [Broker] use originalAuthMethod on originalAuthChecker in Proxy Authentication [#6870](https://github.com/apache/pulsar/pull/6870)
+* [Broker] Close producer when the topic does not exists. [#6879](https://github.com/apache/pulsar/pull/6879)
+* [Broker] Handle all exceptions from `topic.addProducer` [#6881](https://github.com/apache/pulsar/pull/6881)
+* [Broker] fix topicPublishRateLimiter not effective after restart broker [#6893](https://github.com/apache/pulsar/pull/6893)
+* [Broker] Expose pulsar_out_bytes_total and pulsar_out_messages_total for namespace/subscription/consumer. [#6918](https://github.com/apache/pulsar/pull/6918)
+* [Broker] Policy ttlDurationDefaultInSeconds not applying  [#6920](https://github.com/apache/pulsar/pull/6920)
+* [Broker] Fix pulsar admin thread number explode bug. [#6940](https://github.com/apache/pulsar/pull/6940)
+
+##### Pulsar Schema
+
+* [Schema] Fix long field parse in GenricJsonRecord [#6622](https://github.com/apache/pulsar/pull/6622) 
+* [Schema] Fix the leak of cursor reset if message encode fails in Avro schema. [#6695](https://github.com/apache/pulsar/pull/6695) 
+* [Schema] fix Get schema by version can get the deleted schema info #6754 [#6754](https://github.com/apache/pulsar/pull/6754)
+* [Schema] Fix serialization of enums with json/avro schemas in python [#6808](https://github.com/apache/pulsar/pull/6808) 
+* [Schema] Pulsar SQL Support Avro Schema `ByteBuffer` Type [#6925](https://github.com/apache/pulsar/pull/6925) 
+
+##### CPP Client
+* [CPP Client] Auto update topic partitions [#6732](https://github.com/apache/pulsar/pull/6732)
+* [CPP Client] Subscription InitialPosition is not correctly set on regex consumers. [#6810](https://github.com/apache/pulsar/pull/6810)
+* [CPP Client] Fix message id is always the default value in send callback [#6812](https://github.com/apache/pulsar/pull/6812)
+* [CPP Client] Fix message id error if messages were sent to a partitioned topic [#6938](https://github.com/apache/pulsar/pull/6938)
+
+##### Python Client
+* [Python Client] Fix Python function protobuf missing field[#6641](https://github.com/apache/pulsar/pull/6641)
+
+##### Pulsar Functions
+* [Functions] Support function with format: Function<I, CompletableFuture<O>>[#6684](https://github.com/apache/pulsar/pull/6684)
+* [Functions] Function endpoint admin/v3/functions/{tenant}/{namespace} always returns 404 [#6767](https://github.com/apache/pulsar/pull/6767)
+* [Functions] Ensure that all dangling consumers are cleaned up during failures [#6778](https://github.com/apache/pulsar/pull/6778)
+* [Functions] Fix localrunner netty dependency issue [#6779](https://github.com/apache/pulsar/pull/6779)
+* [Functions] Fix SerDe validation of function's update [#6888](https://github.com/apache/pulsar/pull/6888)
+
+##### Tiered Storage
+* [Tiered Storage]  Extract common SerDe method in tiered storage to managed-ledger module [#6533](https://github.com/apache/pulsar/pull/6533)
+* [Tiered Storage]  Make SchemaStorage accessible in Offloader [#6567](https://github.com/apache/pulsar/pull/6567)
+* [Tiered Storage]  Avoid prefetch too much data causing OutOfMemory, when offloading data to HDFS [#6717](https://github.com/apache/pulsar/pull/6717)
+
+##### Pulsar IO
+* [IO] JDBC sink does not handle null in schema [#6848](https://github.com/apache/pulsar/pull/6848)
+
+
 ### 2.5.1 &mdash; 2020-04-20 <a id="2.5.1"></a>
 
 #### Features