A Cloud at the lowest level!

CloudI 1.6.0

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BSD License


What is CloudI?

(short answer) “An application server that efficiently integrates with many languages, many databases, and many messaging buses in a way that is both scalable and fault-tolerant.”

(shorter answer) “A rock-solid transaction processing system for flexible software development.”

(shortest answer) “A Cloud at the lowest level.”

Who would use CloudI?

Software developers that do not want to get locked into corporate vendors or frameworks that push for perpetual commercial support or licenses.

Why should CloudI be used?

CloudI makes software fault-tolerant and scalable, utilizing Erlang, even if the software is legacy source code. CloudI mitigates software development risk (delays or failures) when making software scale in non-Erlang programming languages, or during a conversion of a software system (fully or partially) to the Erlang programming language.

How should CloudI be used?

The CloudI API provides a simple set of functions for Service-Oriented Architecture (SOA) development in any supported language (currently C/C++, Go, Java, JavaScript, OCaml, Perl, PHP, Python, Ruby, and Erlang/Elixir):

  • subscribe, unsubscribe, subscribe_count
  • send_async, send_sync, mcast_async (mcast_async == publish)
  • recv_async
  • return, forward

External communication that needs to scale (beyond 10,000 connections) can use an existing internal CloudI service (implemented in Erlang or Elixir) which may do processing for one or more external CloudI services (implemented in C/C++, Go, Java, JavaScript, OCaml, Perl, PHP, Python, and/or Ruby)

Even if external communication doesn’t need to scale, private cloud computing tasks (number crunching) can gain fault-tolerance and internal system scalability within CloudI.

Where should I find more information?

Please see the FAQ for more details.



  • Erlang >= 19.0 (erlang/Ubuntu, erlang/macports)
  • C++ (g++/Ubuntu, libstdcxx/macports)
  • boost >= 1.36.0 (libboost-system-dev+libboost-thread-dev+libboost-dev/Ubuntu, boost/macports)

Optional (default=“yes”):

  • Java >= 1.5 JDK
    • (default-jdk/Ubuntu, (built-in)/OSX)
    • Use the “–enable-java-support=no” configure flag to disable
  • Javascript >= 0.8.0
    • (nodejs/Ubuntu)
    • Use the “–enable-javascript-support=no” configure flag to disable
  • Perl >= 5.10
    • (perl/Ubuntu)
    • Compress::Zlib (cpan)
    • Use the “–enable-perl-support=no” configure flag to disable
  • PHP >= 5.3.6
    • (php5/Ubuntu)
    • Use the “–enable-php-support=no” configure flag to disable
  • Python >= 2.7.0
    • (python+python-dev/Ubuntu, python27/macports)
    • Use the “–enable-python-support=no” and “–enable-python-c-support=no” configure flag to disable
  • Ruby >= 1.9.0
    • (ruby1.9.1/Ubuntu, ruby19/macports)
    • Use the “–enable-ruby-support=no” configure flag to disable
  • GNU MP library
    • (libgmp3-dev/Ubuntu, gmp/macports)
    • Used in the hexpi (C++) integration test only (“–with-integration-tests=no” configure flag to disable)

Optional (default=“no”):

  • Go >= 1.6
    • (golang/Ubuntu, go/macports)
    • Use the “–enable-go-support” configure flag to enable
  • OCaml >= 4.03.0
    • Use the “–enable-ocaml-support” configure flag to enable
  • ZeroMQ >= 3.x.x or 2.x.x
    • uuid-dev (uuid-dev/Ubuntu, ossp-uuid/macports)
    • Use the “–with-zeromq” configure flag to enable


For configuration options, see FAQ: 3.2 - Installation Options.

sudo make install


Within the installation directory the cloudi script controls CloudI.

To start CloudI:

sudo cloudi start

To stop CloudI:

sudo cloudi stop


See the Quick Start Guide or the API documentation

Integration points:

Dynamic Configuration and Monitoring:


The default CloudI configuration can run the included integration tests if all the supported programming languages are enabled at configure time (they are by default) and the --with-integration-tests-ran configuration argument is used (to choose the src/ file).

If the --with-integration-tests-ran configuration argument is not used, the more minimal CloudI configuration will be used instead (in the src/ file) to support basic things like the Quick Start Guide, the Dashboard and any tutorials or examples.


Michael Truog (mjtruog [at] gmail (dot) com)

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