legion-discovery-client (empty) → 0.1.0.0

raw patch · 5 files changed

+484/−0 lines, 5 filesdep +Cabaldep +aesondep +basesetup-changed

Dependencies added: Cabal, aeson, base, bytestring, containers, data-default-class, http-client, http-types, legion-discovery-client, load-balancing, network, text

Files

• LICENSE +202/−0
• Setup.hs +2/−0
• legion-discovery-client.cabal +53/−0
• src/Network/Legion/Discovery/Client.hs +225/−0
• test/Spec.hs +2/−0

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@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,53 @@+name:                legion-discovery-client+version:             0.1.0.0+synopsis:            Client library for communicating with legion-discovery.+description:         Please see README.md+homepage:            https://github.com/owensmurray/legion-discovery-client#readme+license:             Apache-2.0+license-file:        LICENSE+author:              Rick Owens+maintainer:          rick@owensmurray.com+copyright:           2016 Rick Owens+category:            Web+build-type:          Simple+-- extra-source-files:+cabal-version:       >=1.10++library+  hs-source-dirs:+    src+  exposed-modules:+    Network.Legion.Discovery.Client+  build-depends:+    Cabal >= 1.22.5.0 && < 1.25,+    aeson >= 0.11.2.1 && < 0.12,+    base >= 4.7 && < 5,+    bytestring >= 0.10.6.0 && < 0.11,+    containers >= 0.5.6.2 && < 0.6,+    data-default-class >= 0.0.1 && < 0.2,+    http-client >= 0.4.31.1 && < 0.5,+    http-types >= 0.9.1 && < 0.10,+    load-balancing >= 1.0 && < 1.1,+    network >= 2.6.3.1 && < 2.7,+    text >= 1.2.2.1 && < 1.3+  default-language:+    Haskell2010++test-suite legion-discovery-client-test+  type:+    exitcode-stdio-1.0+  hs-source-dirs:+    test+  main-is:+    Spec.hs+  build-depends:+    base,+    legion-discovery-client+  ghc-options:+    -threaded -rtsopts -with-rtsopts=-N+  default-language:+    Haskell2010++source-repository head+  type:     git+  location: https://github.com/owensmurray/legion-discovery-client

@@ -0,0 +1,225 @@+{-# LANGUAGE GeneralizedNewtypeDeriving #-}+{-# LANGUAGE LambdaCase #-}+{-# LANGUAGE OverloadedStrings #-}+{- |+  This module contains a client library for communicating with the+  'om-discovery' service discovery program.+-}+module Network.Legion.Discovery.Client (+  -- * Establishing a Connection.+  connect,+  -- * Performing Queries.+  query,+  -- * Registering a Service.+  withService,+  -- * HTTP Utilities.+  newLB,+  withResponse,+  -- * Other Types.+  LBHttp,+  Discovery,+  Name(..),+  ServiceAddr(..),+) where++import Control.Concurrent (newEmptyMVar, MVar, putMVar, tryTakeMVar,+  forkIO, threadDelay)+import Control.Concurrent.LoadDistribution (withResource,+  evenlyDistributed, LoadBalanced)+import Control.Exception (bracket)+import Control.Monad (void)+import Data.Aeson (eitherDecode, Value, encode, object, (.=))+import Data.ByteString.Lazy (fromChunks)+import Data.Default.Class (def)+import Data.Map (Map)+import Data.Monoid ((<>))+import Data.Set (Set)+import Data.String (IsString)+import Data.Text (Text, unpack, pack)+import Data.Text.Encoding (encodeUtf8)+import Distribution.Text (display)+import Distribution.Version (VersionRange, Version)+import Network.HTTP.Client (Request, Response, BodyReader,+  parseRequest, host, secure, port, Manager, requestHeaders,+  checkStatus, responseStatus, brConsume, responseBody, path, method,+  RequestBody(RequestBodyLBS), requestBody)+import Network.HTTP.Types (urlEncode, statusIsSuccessful)+import qualified Data.Map as Map+import qualified Data.Set as Set+import qualified Network.HTTP.Client as C++{- | This type represents a handle on the discovery service.  -}+data Discovery = D {+       dName :: Name,+    dVersion :: Version,+         dLb :: LBHttp+  }+++{- | Create a connection to the discovery service.  -}+connect+  :: Name+    {- ^+      The name of the local program. This is used to track and display+      a network graph of service dependencies.+    -}+  -> Version+    {- ^ The version of the local program. -}+  -> Set ServiceAddr+    {- ^ The well-known set of urls where the discovery service lives.  -}+  -> Manager+    {- ^+      The http manager used to manage communication to the discovery+      service, and also for communication with any services accessed+      via the 'withResponse' function.+    -}+  -> IO Discovery+connect name version urls manager =+  D name version . LB manager <$> evenlyDistributed (return urls)+++{- |+  Run a registered service, making sure to unregister upon ternination.+-}+withService :: ServiceAddr -> Discovery -> IO a -> IO a+withService addy d =+    bracket launchPing stopPing . const+  where+    launchPing :: IO (MVar ())+    launchPing = do+      stop <- newEmptyMVar+      void . forkIO $+        let+          loop =+            tryTakeMVar stop >>= \case+              Nothing -> ping >> threadDelay tenSeconds >> loop+              Just () -> return ()+        in loop+      return stop++    stopPing :: MVar () -> IO ()+    stopPing stop = putMVar stop ()++    ping :: IO ()+    ping = do+      let+        userAgent = encodeUtf8+          $ unName (dName d) <> "-" <> pack (display (dVersion d))+        req = def {+            path = +              "/v1/ping/"+              <> urlEncode False (encodeUtf8 (unName (dName d)))+              <> "/"+              <> urlEncode False (encodeUtf8 (pack (display (dVersion d)))),+            method = "POST",+            requestHeaders = [("user-agent", userAgent)],+            checkStatus = const . const . const $ Nothing,+            requestBody = RequestBodyLBS . encode . object $ [+                "serviceAddress" .= unServiceAddr addy+              ]+          }+      {- TODO figure out what we want to do when the ping failes.  -}+      withResponse req (dLb d) (const (return ()))++    tenSeconds :: Int+    tenSeconds = 10000000 {- in microseconds.  -}+++{- | Query the discovery service.  -}+query+  :: Name+    {- ^ The name of the service you are looking for.  -}+  -> VersionRange+    {- ^ The range of service versions with which you are compatible.  -}+  -> Discovery+    {- ^ A handle on the discovery service.  -}+  -> IO (Set ServiceAddr)+query name range d = do+  let+    userAgent = encodeUtf8+      $ unName (dName d) <> "-" <> pack (display (dVersion d))+    req = def {+        path = +          "/v1/services/"+          <> urlEncode False (encodeUtf8 (unName name))+          <> "/"+          <> urlEncode False (encodeUtf8 (pack (display range))),+        method = "GET",+        requestHeaders = [("user-agent", userAgent)],+        checkStatus = const . const . const $ Nothing+      }+  withResponse req (dLb d) (\case+      Nothing -> fail "No Discovery instances available."+      Just resp -> do+        body <- brConsume (responseBody resp)+        case responseStatus resp of+          status | statusIsSuccessful status ->+            case eitherDecode (fromChunks body) of+              Left err -> fail+                $ "Couldn't decode Discovery response: " ++ show err+              Right instances -> return (+                  Set.fromList+                    (ServiceAddr <$> Map.keys (instances :: Map Text Value))+                )+          status -> fail $ "Bad response from Discovery:" ++ show (status, body)+    )+++{- | The name of a service.  -}+newtype Name = Name {unName :: Text} deriving (IsString)+++{- |+  The type of a service address.+  +  A 'ServiceAddr' is a wrapper around an unstructured text value. The+  meaning of the text value is dependent on the registered service,+  as it is the one responsible for publishing the service address. We+  __highly__ recommend that registered services choose to publish a+  fully qualified URL as their service address.+-}+newtype ServiceAddr = ServiceAddr {unServiceAddr :: Text}+  deriving (IsString, Eq, Ord, Show)+++{- |+  Similar to 'C.withResponse', but automatically replaces the host,+  port, and scheme portions with one obtained from the load balancer.++  If a 'Nothing' value is passed to the response handler, that means+  that there are no available instances that match the query params that were+  passed to 'newLB'.+-}+withResponse+  :: Request+  -> LBHttp+  -> (Maybe (Response BodyReader) -> IO a)+  -> IO a+withResponse r lb f = withResource (lbLb lb) (\case+    Nothing -> f Nothing+    Just url -> do+      lbReq <- parseRequest (unpack (unServiceAddr url))+      let+        req = r {+            host = host lbReq,+            secure = secure lbReq,+            port = port lbReq+          }+      C.withResponse req (lbManager lb) (f . Just)+  )+++{- | A handle on the load balancing context.  -}+data LBHttp = LB {+    lbManager :: Manager,+         lbLb :: LoadBalanced ServiceAddr+  }+++{- |+  Create a new load balanced http client, for use with 'withResponse'.+-}+newLB :: Discovery -> Name -> VersionRange -> IO LBHttp+newLB d n r = LB (lbManager (dLb d)) <$> evenlyDistributed (query n r d)++

@@ -0,0 +1,2 @@+main :: IO ()+main = putStrLn "Test suite not yet implemented"