Integrate PeerSim into the project

[mschuwalow]

In order to ensure that the implementations are reliable we should use something like PeerSim to run simulations. Scope of this ticket is to figure out a way to test Membership layer implementations using it

[chlin501]

I am interested in this ticket. However when checking PeerSim's source, I notice it depends on a third party library, which uses a license[1] I am not sure if it's compatible with zio-keeper's Apache License. Is it ok to integrate it or any alternative recommended?

If it's fine, then I suppose pulling PeerSim's code every time when it's needed to do simulation would be enough. Otherwise any suggestions?

Thanks
[1]. http://www.singularsys.com/order/license.html

[mschuwalow]

Thanks for picking this up. This will be a very valuable contribution 🙇‍♂️

I'm not an expert on this.
But it seems like they are using LGPLv2 https://sourceforge.net/projects/peersim/ as their license.
This should allow us to stay licensed as AL 2.0 if I'm not mistaken https://www.gnu.org/licenses/lgpl-java.html.

BTW, alternatively you could also look at Jepsen or other tools for this. We really haven't decided on using PeerSim yet.

[chlin501]

No problem. Will check Jepsen or others to see if there are more suitable ones for this purpose. Thanks for suggestions!

[chlin501]

When checking the source code, I found a few files such as [1], [2], and [3] where [2] and [3] looks like what this ticket want to test. However I don't find corresponded operations, except [4] and [5]. Is it correct that the behavior in [4] and [5] are what this ticket want to examine? Otherwise where should I look into for the protocols in this project? Many thanks.

[1]. https://github.com/zio/zio-keeper/blob/master/keeper/src/main/scala/zio/keeper/transport/Protocol.scala
[2]. https://github.com/zio/zio-keeper/blob/master/keeper/src/main/scala/zio/keeper/MembershipProtocol.scala
[3]. https://github.com/zio/zio-keeper/blob/master/keeper/src/main/scala/zio/keeper/ConsensusProtocol.scala
[4]. https://github.com/zio/zio-keeper/blob/master/keeper/src/test/scala/zio/keeper/hyparview/ActiveProtocolSpec.scala
[5]. https://github.com/zio/zio-keeper/blob/master/keeper/src/test/scala/zio/keeper/hyparview/InitialProtocolSpec.scala