Integration with REST based Light Config Server

[santoshaherkar]

No description provided.

[codecov-io]

Codecov Report

Merging #612 into 1.6.x will decrease coverage by 0.42%.
The diff coverage is 4.26%.

@@             Coverage Diff              @@
##              1.6.x     #612      +/-   ##
============================================
- Coverage     51.15%   50.72%   -0.43%     
- Complexity     1905     1912       +7     
============================================
  Files           258      258              
  Lines         11386    11489     +103     
  Branches       1615     1621       +6     
============================================
+ Hits           5824     5828       +4     
- Misses         4880     4975      +95     
- Partials        682      686       +4

Impacted Files	Coverage Δ	Complexity Δ
...java/com/networknt/server/DefaultConfigLoader.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...c/main/java/com/networknt/server/ServerConfig.java	70.21% <14.28%> (-4.79%)	40 <0> (ø)
...rc/main/java/com/networknt/client/Http2Client.java	44.93% <31.57%> (-1.05%)	42 <12> (+7)

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[stevehu]

Is there any particular reason that the apache httpclient is introduced? Why cannot we use Http2Client from the client module?

[santoshaherkar]

@stevehu we used apache client to connect to config server initially with its own ssl context & we wanted to keep this ssl context separated from light4j context (for this initial config server connection). Once the connection is made with config server, it downloads the configs/certs and make them available for Light4j ssl context. If we use HTTP2Client upfront for this purpose, then it would setup ssl context during config server connection only and then it would be difficult to revert it (as those properties are static).
Your suggestions are welcome here.

[stevehu]

@santoshaherkar This is a very complicated bootstrap issue and I never thought about using another library to solve the problem before. Let's have an offline discussion on this issue. Thanks.

[miklish]

@stevehu Do you still have concerns with the Apache client? I know @santoshaherkar @jsu216 and @zabooma spent a long time working on this problem before arriving at this solution. It is well vetted.

[stevehu]

It seems very easy to use another XnioSsl object to make a connection with Http2Client. I have tested with a live server running locally from the DefaultConfigLoaderIT class and the Health endpoint returns OK. Please review and let us know if you have any questions or concerns. Thanks.

[jsu216]

@stevehu, I tried using new XionSsl object to create a connection with Http2Client, but surprisingly it had same chances of exceptions (if not more) thrown when close the connection. The test I did was for the issue #616. The cexceptions thrown seem to be more like a debug message than errors.

[stevehu]

@jsu216 I know there are a lot of debug exceptions thrown in Undertow and I think they should change the level to trace. These exceptions are caused by the HTTP/2 server not following the spec gracefully and we can simply ignore it. If the logging level is Error, then it is a different story.

[jsu216]

The ERROR level messages happened in #616 are either Undertow/Xnio bugs or should be changed to DEBUG level. Because there is nothing wrong in our code and there seems to be no impact to the functionality.

[stevehu]

@jsu216 I totally agree with you and it seems this error only happens with the Influxdb connection which is implemented in Golang. Consul is implemented in Golang but I have never seen this error with Consul connections. There might be something in the Influxdb that causes the error. Do you think we should open a ticket in the Undertow repo? If yes, we need to find a way to reliably reproduce it.

[jsu216]

@stevehu The errors happen not only to influxdb connections. My test was to connect to another light4j service. There are open tickets in undertow/redhat. I post the links in the my comments of the issue #616 .
Errors were populated into log after trying to close the connection. The pattern is that you create a connection, use it and close it, repeat this every a few seconds. Most of the time you will get errors (NPE) within 20 mins. No exception was thrown in that case, which makes me think it is either a bug or debug message only.

[stevehu]

@jsu216 Sorry. I missed the links to Undertow and RedHat issues. The issue was opened for 2.0.8 and I am wondering if we should upgrade to the latest version to see if it is already resolved. Although the chances are very slim :)

[stevehu]

Integration with REST based Light Config Server