set maxRequestsPerHost of okhttp to support slow response requests and high TPS

[skyao]

Description

In dapr java sdk, there are some default settings in okhttp which we don't set and use the default value:

• maxRequests: default to 64
• maxRequestsPerHost: default to 5!
• maxIdleConnections

The default value 5 of maxRequestsPerHost is totally unacceptable, it will lead to very serious problems of very low throughput as discribed in issue #709.

And the default value 64 of maxRequests is not enough for the user case of high TPS. For example, if the response time is 100 ms, 64 connections leads to at most 640 TPS.

Issue reference

This PR is to fix this issue.

#709

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[mukundansundar]

@skyao Keep in mind that in future we will be moving away from OkHttp and move to native Java Client. But I believe these parameters will still add value there.

[skyao]

@skyao Keep in mind that in future we will be moving away from OkHttp and move to native Java Client. But I believe these parameters will still add value there.

OK.

Before we changed to native java client, we still need OkHttp. The fix for default maxRequestPerHost is very important.

[artursouza]

@skyao Please, sign off the commits. This is a new requirement in our repos since the CNCF donation.

[codecov]

Codecov Report

Merging #708 (b13a2fc) into master (b7e41a0) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #708      +/-   ##
============================================
+ Coverage     80.66%   80.72%   +0.06%     
  Complexity      993      993              
============================================
  Files            81       81              
  Lines          3010     3020      +10     
  Branches        340      340              
============================================
+ Hits           2428     2438      +10     
  Misses          416      416              
  Partials        166      166              

Impacted Files	Coverage Δ
.../src/main/java/io/dapr/client/DaprHttpBuilder.java	94.44% <100.00%> (+2.77%)	⬆️
sdk/src/main/java/io/dapr/config/Properties.java	81.81% <100.00%> (+4.04%)	⬆️

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[mukundansundar]

lgtm