haxl: A Haskell library for efficient, concurrent, and concise data access.

[ bsd3, concurrency, library ] [ Propose Tags ]

Haxl is a library and EDSL for efficient scheduling of concurrent data accesses with a concise applicative API.

[Skip to Readme]
Versions [faq],,,,,,,,,,,,
Dependencies aeson (>=0.6 && <0.8), base (==4.*), bytestring (>=0.9 && <0.11), containers (==0.5.*), directory (>=1.1 && <1.3), filepath (==1.3.*), hashable (==1.2.*), HUnit (==1.2.*), pretty (==1.1.*), text (==1.1.*), time (==1.4.*), unordered-containers (==0.2.*), vector (==0.10.*) [details]
License BSD-3-Clause
Copyright 2014 (C) 2014 Facebook, Inc.
Author Facebook, Inc.
Maintainer The Haxl Team <haxl-team@fb.com>
Category Concurrency
Home page https://github.com/facebook/Haxl
Bug tracker https://github.com/facebook/Haxl/issues
Uploaded by SimonMarlow at Tue Jun 10 17:10:41 UTC 2014
Distributions LTSHaskell:, NixOS:, Stackage:
Downloads 5608 total (111 in the last 30 days)
Rating 2.25 (votes: 2) [estimated by rule of succession]
Your Rating
  • λ
  • λ
  • λ
Status Hackage Matrix CI
Docs available [build log]
Successful builds reported [all 1 reports]




Maintainer's Corner

For package maintainers and hackage trustees

Readme for haxl-

[back to package description]

Haxl Logo


Haxl is a Haskell library that simplifies access to remote data, such as databases or web-based services. Haxl can automatically

  • batch multiple requests to the same data source,
  • request data from multiple data sources concurrently,
  • cache previous requests.

Having all this handled for you behind the scenes means that your data-fetching code can be much cleaner and clearer than it would otherwise be if it had to worry about optimizing data-fetching. We'll give some examples of how this works in the pages linked below.

There are two Haskell packages here:

  • haxl: The core Haxl framework
  • haxl-facebook (in example/facebook): An (incomplete) example data source for accessing the Facebook Graph API

To use Haxl in your own application, you will likely need to build one or more data sources: the thin layer between Haxl and the data that you want to fetch, be it a database, a web API, a cloud service, or whatever. The haxl-facebook package shows how we might build a Haxl data source based on the existing fb package for talking to the Facebook Graph API.

Where to go next?

  • The Story of Haxl (a blog post to be published very soon!) explains how Haxl came about at Facebook, and discusses our particular use case.

  • An example Facebook data source walks through building an example data source that queries the Facebook Graph API concurrently.

  • The N+1 Selects Problem explains how Haxl can address a common performance problem with SQL queries by automatically batching multiple queries into a single query, completely invisibly to the programmer.

  • Haxl Documentation on Hackage.

  • There is no Fork: An Abstraction for Efficient, Concurrent, and Concise Data Access, our paper on Haxl, accepted for publication at ICFP'14. Online version coming soon (June 12).