Lua Sandbox Extensions

1. Overview

Package management for Lua Sandbox modules and sandboxes. The goal is to simplify the lua_sandbox core by decoupling the module and business logic maintenance and deployment.

Full Documentation

2. Installation

2.1. Prerequisites

2.1.1. Optional (used for documentation)

2.2. CMake Build Instructions

git clone
cd lua_sandbox_extensions
mkdir release
cd release

# or cherry pick using -DEXT_xxx=on i.e. -DEXT_lpeg=on (specifying no
# extension will provide a list of all available extensions)
make packages

# Windows Visual Studio 2013
cmake -DCMAKE_BUILD_TYPE=release -G "NMake Makefiles" -DEXT_lpeg=on ..
nmake packages

2.3. Docker Images

Docker images are built from the dev and master branches. These images contain hindsight, lua_sandbox and have all of the extensions from this repository installed.

# Get master branch docker image
docker pull mozilla/lua_sandbox_extensions:master

# Get dev branch docker image
docker pull mozilla/lua_sandbox_extensions:dev

3. Releases

  • The master branch is the current release and is considered stable at all times.
  • New versions can be released as frequently as every two weeks (our sprint cycle). The only exception would be for a high priority patch.
  • All active work is flagged with the sprint milestone and tracked in the project dashboard.
  • New releases occur the day after the sprint finishes.
    • The version in the dev branch is updated
    • The changes are merged into master
    • A new tag is created

4. Contributions

  • All pull requests must be made against the dev branch, direct commits to master are not permitted.
  • All non trivial contributions should start with an issue being filed (if it is a new feature please propose your design/approach before doing any work as not all feature requests are accepted).

Heka Sandbox

5. Decoder API Convention

Each decoder module should implement a decode function according to the specification below. Also, if the decoder requires configuration options it should look for a table, in the cfg, with a variable name matching the module name (periods replaced by underscores "" -> "decoders_foo"). This naming convention only allows for a single instance of each decoder per sandbox i.e., if you need to parse more than one type of Nginx access log format you should use multiple input sandboxes (one for each).

5.1. decode

The decode function should parse, decode, and/or transform the original data and inject one or more Heka messages into the system.


  • data (string) - Raw data from the input sandbox that needs parsing/decoding/transforming
  • default_headers (table/nil/none) - Heka message table containing the default header values to use, if they are not populated by the decoder. If 'Fields' is specified it should be in the hashed based format see: In the case of multiple decoders this may be the message from the previous input/decoding step.
  • mutable (bool/nil/none) - Flag indicating if the decoder can modify the default_headers/msg structure in place or if it has to be copied first.


  • err (nil, string) or throws an error on invalid data or an inject message failure
    • nil - if the decode was successful
    • string - error message if the decode failed (e.g. no match)

6. Encoder API Convention

Each encoder module should implement an encode function according to the specification below. Also, if the encoder requires configuration options it should look for a table, in the cfg, with a variable name matching the module name (periods replaced by underscores "" -> "encoders_foo").

6.1. encode

The encode function should concatenate, encode, and/or transform the Heka message into a byte array.


  • none


  • data (string, userdata, nil)
    • string - raw data ready to be output
    • userdata - a userdata object that supports the lua_sandbox zero copy API
    • nil - the output sandbox should skip the message and return -2
    • error - throws an error on an invalid transformation or incompatible userdata

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