In many cases, it may be more feasible to set up a MongoDB instance on a remote machine. This recipe will cover how to obtain data from a MongoDB hosted remotely.
We should create a remote database. MongoLab (https://mongolab.com) and MongoHQ (http://www.mongohq.com) offer MongoDB as a service and have free options to set up a small development database.
Tip
These services will require us to accept their terms and conditions. For some of us, it may be best to host the database in our own remote server.
Install the MongoDB package from Cabal as follows:
$ cabal install mongoDB
Also, install the helper following helper libraries as follows:
$ cabal install split $ cabal install uri
Use the
OverloadedStringandExtendedDefaultRuleslanguage extensions required by the library. Import helper functions as follows:{-# LANGUAGE OverloadedStrings, ExtendedDefaultRules #-} import Database.MongoDB import Text.URI import Data.Maybe import qualified Data.Text as T import Data.List.SplitSpecify the remote URI for the database connection as follows:
mongoURI = "mongodb://user:[email protected]:53788/mydb"
The username, password, hostname, port address number, and database name must be extracted from the URI, as presented in the following code snippet:
uri = fromJust $ parseURI mongoURI getUser = head $ splitOn ":" $ fromJust $ uriUserInfo uri getPass = last $ splitOn ":" $ fromJust $ uriUserInfo uri getHost = fromJust $ uriRegName uri getPort = case uriPort uri of Just port -> show port Nothing -> (last.words.show) defaultPort getDb = T.pack $ tail $ uriPath uriCreate a database connection by reading the host port of the remote URI as follows:
main :: IO () main = do let hostport = getHost ++ ":" ++ getPort pipe <- runIOE $ connect (readHostPort hostport) e <- access pipe master getDb run close pipe print eOptionally authenticate to the database and obtain data from the
"people"collection as follows:run = do auth (T.pack getUser) (T.pack getPass) getData getData = rest =<< find (select [] "people") {sort=[]}