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https://issues.apache.org/jira/browse/HADOOP-19120?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pranav Saxena updated HADOOP-19120:
-----------------------------------
    Fix Version/s: 3.5.0
                   3.4.1

> [ABFS]: ApacheHttpClient adaptation as network library
> ------------------------------------------------------
>
>                 Key: HADOOP-19120
>                 URL: https://issues.apache.org/jira/browse/HADOOP-19120
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/azure
>    Affects Versions: 3.5.0
>            Reporter: Pranav Saxena
>            Assignee: Pranav Saxena
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.5.0, 3.4.1
>
>
> Apache HttpClient is more feature-rich and flexible and gives application 
> more granular control over networking parameter.
> ABFS currently relies on the JDK-net library. This library is managed by 
> OpenJDK and has no performance problem. However, it limits the application's 
> control over networking, and there are very few APIs and hooks exposed that 
> the application can use to get metrics, choose which and when a connection 
> should be reused. ApacheHttpClient will give important hooks to fetch 
> important metrics and control networking parameters.
> A custom implementation of connection-pool is used. The implementation is 
> adapted from the JDK8 connection pooling. Reasons for doing it:
> 1. PoolingHttpClientConnectionManager heuristic caches all the reusable 
> connections it has created. JDK's implementation only caches limited number 
> of connections. The limit is given by JVM system property 
> "http.maxConnections". If there is no system-property, it defaults to 5. 
> Connection-establishment latency increased with all the connections were 
> cached. Hence, adapting the pooling heuristic of JDK netlib,
> 2. In PoolingHttpClientConnectionManager, it expects the application to 
> provide `setMaxPerRoute` and `setMaxTotal`, which the implementation uses as 
> the total number of connections it can create. For application using ABFS, it 
> is not feasible to provide a value in the initialisation of the 
> connectionManager. JDK's implementation has no cap on the number of 
> connections it can have opened on a moment. Hence, adapting the pooling 
> heuristic of JDK netlib,



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