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Show HN: Parapet – A purely functional library to build distributed systems

51 points by dmgcodevil 7y ago

linux2647 7y ago
Looks like a library for Scala and other JVM languages?
- theCodeStig 7y ago
  Yes
tunesmith 7y ago
Is this an alternative to something like Akka Cluster Sharding and Persistence/Distributed-Data?
- dmgcodevil 7y ago
  In theory, wherever Akka is used Parapet can be used instead. It's just not that big as Akka. Parapet provides a messaging module for interprocess communication based on ZMQ.
thekhatribharat 7y ago
How does this compare to Metaparticle (https://metaparticle.io/about/ https://metaparticle.io/about/)?
- dmgcodevil 7y ago
  as I can see Metaparticle is a tool specifically built for Kubernetes and uses its API underhood. Parapet can be extended to support Kubernetes ecosystem how it was done for ZMQ. Parapet can be integrated with Metaparticle, so that you can run the same distributed algorithms written in Patapet in a Kubernetes cluster.
vemv 7y ago
One specific thing I think FP distributed-system frameworks could bring is instantaneous, deterministic testing. e.g. I have N microservices, they communicate via IO (which means slow/brittle tests) but the framework abstracts over that, so I can run the whole system test suite under a second, because all IO (messaging, DB, concurrency) can be replaced with an in-memory implementation. Interestingly, one could also inject faults to those IO mocks, and test how the system respond to that. I believe FP is a prerequisite for meeting those goals, because otherwise having impure IO all over the place is hard (if not impossible) to mock out.
- polskibus 7y ago
  What you describe seems similar to Akka's multi node test kit.
- hderms 7y ago
  I agree, but what about when the persistent shared state ends up actually being most of what needs to be tested in a distributed system?
  - vemv 7y ago
    Can't see the problem in principle - all kinds of storage (DBs, S3, Redis) seem mockable.
- dmgcodevil 7y ago
  Yes, that's certainly possible. Also, you can choose between different effect systems, e.g.: Cats Effect, Monix and Scalaz ZIO

51 points by dmgcodevil 7y ago

linux2647 7y ago

Looks like a library for Scala and other JVM languages?

theCodeStig 7y ago
Yes

tunesmith 7y ago

Is this an alternative to something like Akka Cluster Sharding and Persistence/Distributed-Data?

dmgcodevil 7y ago
In theory, wherever Akka is used Parapet can be used instead. It's just not that big as Akka. Parapet provides a messaging module for interprocess communication based on ZMQ.

thekhatribharat 7y ago

How does this compare to Metaparticle (https://metaparticle.io/about/ https://metaparticle.io/about/)?

dmgcodevil 7y ago
as I can see Metaparticle is a tool specifically built for Kubernetes and uses its API underhood. Parapet can be extended to support Kubernetes ecosystem how it was done for ZMQ. Parapet can be integrated with Metaparticle, so that you can run the same distributed algorithms written in Patapet in a Kubernetes cluster.

vemv 7y ago

One specific thing I think FP distributed-system frameworks could bring is instantaneous, deterministic testing. e.g. I have N microservices, they communicate via IO (which means slow/brittle tests) but the framework abstracts over that, so I can run the whole system test suite under a second, because all IO (messaging, DB, concurrency) can be replaced with an in-memory implementation. Interestingly, one could also inject faults to those IO mocks, and test how the system respond to that. I believe FP is a prerequisite for meeting those goals, because otherwise having impure IO all over the place is hard (if not impossible) to mock out.

polskibus 7y ago
What you describe seems similar to Akka's multi node test kit.
hderms 7y ago
I agree, but what about when the persistent shared state ends up actually being most of what needs to be tested in a distributed system?
- vemv 7y ago
  Can't see the problem in principle - all kinds of storage (DBs, S3, Redis) seem mockable.
dmgcodevil 7y ago
Yes, that's certainly possible. Also, you can choose between different effect systems, e.g.: Cats Effect, Monix and Scalaz ZIO