validator plugin for MADS

This is a Sink plugin for MADS.

This plugins validates the JSON messages received from the subscribed topics against the JSON schemas defined in schemas.json. If a message does not conform to the schema, an error is logged.

Required MADS version: 2.1.0.

Supported platforms

Currently, the supported platforms are:

• Linux
• MacOS
• Windows

Package install

with MADS v2.1.1 or later, install with:

mads package --install validator.plugin

Install from binaries

Linux and MacOS:

cmake -Bbuild -DCMAKE_INSTALL_PREFIX="$(mads -p)"
cmake --build build -j4
sudo cmake --install build

Windows:

cmake -Bbuild -DCMAKE_INSTALL_PREFIX="$(mads -p)"
cmake --build build --config Release
cmake --install build --config Release

INI settings

The plugin supports the following settings in the INI file:

[validator]
schemas = "schemas.json" # path to the JSON schemas file (default="schemas.json")
sub_topic = [""] # subscribe to these topics for validation (default=[])

All settings are optional; if omitted, the default values are used.

NOTE: the plugin never deals with messages on the agent_event topic to avoid potential infinite loop, as the plugin itself may generate agent_event messages when validation fails.

JSON schemas

The plugin expects a JSON file containing the schemas for validating the messages. The file should be in the following format:

{
  "topic_name": {
    "$id": "https://example.com/schema_name.json",
    "$schema": "http://json-schema.org/draft/2020-12/schema",
    "properties": {
      // schema properties
    },
    "required": [
      // required properties
    ]
  },
  // more schemas for other topics...
}

There is a useful schema editor online: JSON Schema Editor. Simply select Infer from JSON, then possibly correct the resulting schema, and finally copy the schema into the schemas.json file, under a key that matches the topic name you want to validate.

Executable demo

Runs some simple tests to demonstrate the plugin functionality.

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