README

This repository contains two implementations of an in-memory cache
written an exercise in learning Go (golang) and Haskell's STM
(software transactional memory).  This is also an exercise in learning
godoc and Haddock.

The cache is implemented as a trie.  A server implementing a subset of
the memcache protocol is implemented on top of the cache.  A client
implementing the memcache protocol subset allows the two
implementations to interoperate.

Other than using explicit locks in Go and STM in Haskell, the two
implementations are very similar.

In the Go implementation, the trie cache and the remote cache client
implement a Cache interface.  In the Haskell implementation, the trie
cache and the remote cache client are instances of a Cache typeclass.

In the Go implementation, the remote cache client is a goroutine that
receives requests from a channel, talks to the server, and returns 
the result via a channel included in the request.  In the Haskell
implementation, the remote cache client is a thread that receives
requests from a Control.Concurrent.Chan, talks to the server, and
returns the result via a Control.Concurrent.MVar included in the
request.

Building the servers:

  * Go: go build server.go
  * Haskell: ghc --make server

Building test clients:

  * Go: go build test.go
  * Haskell: ghc --make test

Running the server:

  * ./server [-d] [port-number]

The -d flag turns on debug tracing.  The port-number is the port to
listen on, and defaults to 22122.

Running the test client:

  * ./test [-t nthreads] [-c nconnections] [-d] [hostname port-number]

The -d flag turns on debug tracing.  The hostname and port-number
is the location of the remote cache.  If omitted, the in-memory trie
cache is used.  nthreads is the number of threads, defaulting to 4.
nconnections is the number of connections to the remote cache,
defaulting to 2.  Each thread will only use one connection.