[bookkeeper] branch master updated: Enable PCBC completionObjects autoShrink to reduce memory usage and gc (#3913)

[chenhang]

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chenhang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/bookkeeper.git


The following commit(s) were added to refs/heads/master by this push:
     new ca33b31d39 Enable PCBC completionObjects autoShrink to reduce memory 
usage and gc (#3913)
ca33b31d39 is described below

commit ca33b31d3918d04bee63fba54b81b531709a6536
Author: wenbingshen <oliver.shen...@gmail.com>
AuthorDate: Sat Apr 22 10:23:52 2023 +0800

    Enable PCBC completionObjects autoShrink to reduce memory usage and gc 
(#3913)
    
    ### Motivation
    
    PerChannelBookieClient completionObjects occupy a lot of heap space and 
cannot be recycled.
    The figure below shows that the internal table array of 
ConcurrentOpenHashMap has used space size=0, but the array length is still 
16384, and the memory overhead is 65552bytes.
    
![image](https://user-images.githubusercontent.com/35599757/231114802-db90c49b-d295-46d7-b7db-785035b341f0.png)
    
    
![image](https://user-images.githubusercontent.com/35599757/231113930-bd9f3f54-9052-4c0b-9a3f-2fc493632e35.png)
    
    ConcurrentOpenHashMap default DefaultConcurrencyLevel=16. We have hundreds 
of bookie nodes. Due to the feature of bookie polling and writing, the client 
and server have long connection characteristics, which will as a result, the 
memory usage of about 65552 * 16 * 1776 = 1.74GB cannot be recycled, and the 
space take up by these tables is all size=0 (The broker's owner topic has 
drifted to other brokers due to Full GC).
    
![image](https://user-images.githubusercontent.com/35599757/231117087-08c80320-fa71-49c2-a199-cfee3d83ddc5.png)
    
    When the throughput of the pulsar cluster increases and the bookie cluster 
expands, these memory usage will also increase. Coupled with the unreasonable 
memory usage in other aspects of pulsar that we know, this will cause the 
pulsar broker to continuously generate full gc.
    
    ### Changes
    I think adding autoShrink to completionObjects can reduce this part of 
memory usage and reduce the frequency of Full GC.
---
 .../main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java
index 41add30ca5..f84343a71b 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java
@@ -187,7 +187,7 @@ public class PerChannelBookieClient extends 
ChannelInboundHandlerAdapter {
     final int startTLSTimeout;
 
     private final ConcurrentOpenHashMap<CompletionKey, CompletionValue> 
completionObjects =
-            ConcurrentOpenHashMap.<CompletionKey, 
CompletionValue>newBuilder().build();
+            ConcurrentOpenHashMap.<CompletionKey, 
CompletionValue>newBuilder().autoShrink(true).build();
 
     // Map that hold duplicated read requests. The idea is to only use this 
map (synchronized) when there is a duplicate
     // read request for the same ledgerId/entryId