Montage: a riak resolution proxy

Even Rocky had a montage...

Install

Built and tested with ghc 7.4.1

Install the non-hackage dependencies:

git clone git@github.com:wmoss/StatsWeb.git
cd StatsWeb && cabal install

git clone git@github.com:bumptech/riak-haskell-client.git
cd riak-haskell-client && cabal install

From montage/ execute:

cabal install

We recommend using a sandbox, hsenv is particularly good.

Configuration

The montage proxy is port configurable (here given the Config handle set to 7078), with riak running on 8087:

import Network.Riak (defaultClient, connect, disconnect, Client(port), Connection)
import Data.Conduit.Pool (Pool, createPool)

import Network.Riak.Montage

main :: IO ()
main = do
    mainPool <- createPool
        (connect $ defaultClient {port = "8087"})
        disconnect
        1 -- stripes
        10 -- timeout
        300 -- max connections

    let cfg' = cfg { proxyPort = 7078 }

    runDaemon (cfg' :: Config ResObject) mainPool

ResObject is a concrete datatype you define. For Montage to work with this datatype, you must define:

1. translations from bytestring -> datatype, datatype -> bytestring,
2. methods for resolving siblings,
3. and how to obtain a bytestring key from values in the datatype

See examples/ for a definition of ResObject and how to implement (1), (2), and (3).

You can also set the mainPool argument to be a datatype with more than one pool, in case particular buckets have such variable resolution times that you want to isolate your bucket fetches:

data Pools = Pools {
    poolA :: Pool Connection
  , poolB :: Pool Connection
}

instance Poolable Pools where
    chooser pools "bucketA" = poolA pools
    chooser pools "bucketB" = poolB pools
    chooser pools "bucketC" = poolC pools

For a single pool, like mainPool, you're also required to define its datatype as an instance of Poolable, such that the bucket doesn't matter:

instance Poolable (Pool Connection) where
    chooser pool _ = pool

You can also a set the cfg field 'logger' to a logging function that fits the type signature:

logger :: B.Bytestring -> Maybe Double -> Value -> IO ()
logger errorType duration val = -- your defintion

where errorType is filled in by the Montage exception handler with the type of exception (useful as a prefix), duration is a timestamp Montage may provide (depending on where the error occurs), and val is JSON that Montage constructs with details about the error.

Since Montage provides these values, your logger would simply format the arguments and broadcasts them to a location of your choice. The default logger simply concatenates the arguments and broadcasts to stderr.

Examples

To setup the examples, first download hprotoc:

cabal install hprotoc

Then execute:

cd examples && hprotoc user.proto

Then:

cd examples && runhaskell basic_proxy.hs

For client examples to run against the basic_proxy, see github.com/bumptech/montage-haskell-client/examples

More

See the haddock documentation for type-signatures, descriptions, and source of client functions.