The haxl package

[Tags:library, program, test]

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

To use Haxl, you need to implement one or more data sources, which provide the means for accessing remote data or other I/O that you want to perform using Haxl.

Haxl provides two top-level modules:

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Change log
Dependencies aeson (>=0.6 && <1.3), base (==4.*), binary (>=0.7 && <0.10), bytestring (>=0.9 && <0.11), containers (==0.5.*), deepseq, exceptions (==0.8.*), filepath (>=1.3 && <1.5), ghc-prim, hashable (==1.2.*), haxl, HUnit (>=1.2 && <1.7), pretty (==1.1.*), text (>= && <1.3), time (>=1.4 && <1.9), transformers, unordered-containers (==0.2.*), vector (>=0.10 && <0.13) [details]
License OtherLicense[multiple license files]
Copyright Copyright (c) 2014-present, Facebook, Inc.
Author Facebook, Inc.
Maintainer The Haxl Team <>
Category Concurrency
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Uploaded Tue Jul 25 11:51:34 UTC 2017 by niteria
Distributions LTSHaskell:, NixOS:, Stackage:
Downloads 1807 total (73 in the last 30 days)
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Status Docs uploaded by user
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Maintainer's Corner

For package maintainers and hackage trustees

Readme for haxl

Readme for haxl-

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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?

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