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.

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:

  • Data-source implementations import Haxl.Core,

  • Client code import your data sources and Haxl.Prelude, or some other client-level API that you provide.

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Change log changelog.md
Dependencies aeson (>=0.6 && <2.1), base (>=4.10 && <5), binary (>=0.7 && <0.10), bytestring (>=0.9 && <0.11), containers (>=0.5 && <0.7), deepseq, exceptions (>=0.8 && <0.11), filepath (>=1.3 && <1.5), ghc-prim, hashable (>=1.2 && <1.4), hashtables (>=, haxl, optparse-applicative, pretty (>=1.1 && <1.2), stm (>=2.4 && <2.6), text (>= && <1.3), time (>=1.4 && <1.10), transformers, unordered-containers (>=0.2 && <0.3), vector (>=0.10 && <0.13) [details]
License BSD-3-Clause
Copyright Copyright (c) 2014-present, 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 2022-04-19T08:57:56Z
Reverse Dependencies 10 direct, 0 indirect [details]
Executables cachebench, monadbench
Downloads 13004 total (65 in the last 30 days)
Rating 2.25 (votes: 2) [estimated by Bayesian average]
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Status Docs available [build log]
Last success reported on 2022-04-19 [all 1 reports]

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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,
  • memoize computations.

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:

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.

There is a generic datasource in "Haxl.DataSource.ConcurrentIO" that can be used for performing arbitrary IO operations concurrently, given a bit of boilerplate to define the IO operations you want to perform.

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?


We welcome contributions! See CONTRIBUTING for details on how to get started, and our Code of Conduct.


Haxl uses the BSD 3-clause License, as found in the LICENSE file.