Elasticsearch API Specification

The Elasticsearch API Specification provides the contract for communication between client and server components within the Elasticsearch stack. With almost 500 API endpoints and around 3000 data types across the entire API surface, this project is a vitally important part of sustaining our engineering efforts at scale.

The repository has the following structure:

Path	Description
api-design-guidelines/	Knowledge base of best practices for API design.
compiler/	TypeScript compiler for specification definition to JSON.
compiler-rs/
docs/
output/
specification/	Elasticsearch request/response definitions in TypeScript.
typescript-generator/

This JSON representation is formally defined by a set of TypeScript definitions (a meta-model) that also explains the various properties and their values.

Prepare the environment

For generating the JSON representation and running the validation code you need to install and configure Node.js in your development environment.

You can install Node.js with nvm:

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash

Once the installation is completed, install Node.js with nvm:

# this command will install the version configured in .nvmrc
nvm install

How to generate the JSON representation

# clone the project
$ git clone https://github.com/elastic/elasticsearch-specification.git

# install the dependencies
$ make setup

# generate the JSON representation
$ make generate

# the generated output can be found in ./output/schema/schema.json
$ cat output/schema/schema.json

Make Targets

Usage:
  make <target>
  validate         Validate a given endpoint request or response
  validate-no-cache  Validate a given endpoint request or response without local cache
  generate         Generate the output spec
  compile          Compile the specification
  license-check    Add the license headers to the files
  license-add      Add the license headers to the files
  spec-format-check  Check specification formatting rules
  spec-format-fix  Format/fix the specification according to the formatting rules
  spec-dangling-types  Generate the dangling types rreport
  setup            Install dependencies for contrib target
  clean-dep        Clean npm dependencies
  contrib          Pre contribution target
  help             Display help

Structure of the JSON representation

The JSON representation is formally defined as TypeScript definitions. Refer to them for the full details. It is an object with two top level keys:

{
  "types": [...],
  "endpoints": [...]
}

The first one, types, contains all the type definitions from the specification, such as IndexRequest or MainError, while the second one, endpoints, contains every endpoint of Elasticsearch and the respective type mapping. For example:

{
  "types": [    {
    "attachedBehaviors": [
      "CommonQueryParameters"
    ],
    "body": {
      "kind": "value",
      "value": {
        "kind": "instance_of",
        "type": {
          "name": "TDocument",
          "namespace": "_global.index"
        }
      }
    },
    "generics": [
      {
        "name": "TDocument",
        "namespace": "_global.index"
      }
    ],
    "inherits": {
      "type": {
        "name": "RequestBase",
        "namespace": "_types"
      }
    },
    "kind": "request",
    "name": {
      "name": "Request",
      "namespace": "_global.index"
    },
    "path": [...],
    "query": [...]
  }, {
    "inherits": {
      "type": {
        "name": "WriteResponseBase",
        "namespace": "_types"
      }
    },
    "kind": "response",
    "name": {
      "name": "Response",
      "namespace": "_global.index"
    }
  }],
  "endpoints": [{
      "accept": [
        "application/json"
      ],
      "contentType": [
        "application/json"
      ],
      "description": "Creates or updates a document in an index.",
      "docUrl": "https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-index_.html",
      "name": "index",
      "request": {
        "name": "Request",
        "namespace": "_global.index"
      },
      "requestBodyRequired": true,
      "response": {
        "name": "Response",
        "namespace": "_global.index"
      },
      "since": "0.0.0",
      "stability": "stable",
      "urls": [...],
      "visibility": "public"
    }]
}

The example above represents the index request, inside the endpoints array you can find the API name and the type mappings under request.name and response.name. The respective type definitons can be found inside the types array.

In some cases an endpoint might be defined, but there is no a type definition yet, in such case the request and response value will be null.

How to validate the specification

The specification is validated daily by the client-flight-recorder project. The validation result can be found here.

Validate the specification in your machine

The following step only apply if you don't have ~/.elastic/github.token in place.

Create GitHub token to allow authentication with Vault.

• Go to https://github.com/settings/tokens.
• Click Generate new token.
• Give your token a name and make sure to click the repo and read:org scopes.
• Create a file at ~/.elastic/github.token and paste the GitHub token into it.
• Change permissions on the file allow access only from the user. chmod 600 ~/.elastic/github.token

You can see here how to generate a token.

Once you have configured the environment, run the following commands:

git clone https://github.com/elastic/elasticsearch-specification.git
git clone https://github.com/elastic/clients-flight-recorder.git

cd elasticsearch-specification
# this will validate the xpack.info request type against the 8.1.0 stack version
make validate api=xpack.info type=request stack-version=8.1.0-SNAPSHOT

# this will validate the xpack.info request and response types against the 8.1.0 stack version
make validate api=xpack.info stack-version=8.1.0-SNAPSHOT

The last command above will install all the dependencies and run, download the test recordings and finally validate the specification. If you need to download the recordings again, run make validate-no-cache api=xpack.info type=request stack-version=8.1.0-SNAPSHOT.

Once you see the errors, you can fix the original definition in /specification and then run the command again until the types validator does not trigger any new error. Finally open a pull request with your changes.

Documentation

• How to add a new API
• Behaviors
• Compiler
• Documenting the API specification
• Known issues
• Modeling Guide
• Schema structure
• Specification structure
• Style Guide
• Fixing a defintion, a complete story

FAQ

I want to see a report of how types and namespaces are being used.

You can find a report of the main branch here.

A specific property is not always present, how do I define it?

When you define a property the syntax is propertyName: propertyType. By default a property is required to exist. If you know that a property will not always be there, you can add a question mark just before the column:

propertyRequired: string
propertyOptional?: string

A definition is missing, how do I add it?

See here.

A definition is not correct, how do I fix it?

All the definitons are inside /specification folder, search the bad defintion and update it, you can find above how to run the validation of the spec.

An endpoint is missing, how do I add it?

See here.

An endpoint definition is not correct, how do I fix it?

All the endpoint definitons are inside /specification/_json_spec folder, which contains a series of JSON files taken directly from the Elasticsearch rest-api-spec. You should copy from there the updated endpoint defintion and change it here.

The validation in broken on GitHub but works on my machine!

Very likely the recordings on your machine are stale, rerun the validation with the validate-no-cache make target.

You should pull the latest change from the client-flight-recorder as well.

cd client-flight-recorder
git pull

Where do I find the generated test?

Everytime you run make validate script, a series of test will be generated and dumped on disk. You can find the failed tests in clients-flight-recorder/scripts/types-validator/workbench. The content of this folder is a series of recorded responses from Elasticsearch wrapped inside an helper that verifies if the type definiton is correct.

Which editor should I use?

Any editor is fine, but to have a better development experience it should be configured to work with TypeScript. Visual Studio Code and IntelliJ IDEA come with TypeScript support out of the box.

Is there a complete example of the process?

Yes, take a look here.

realpath: command not found

The validation script uses realpath which may be not present in your system. If you are using MacOS, run the following command to fix the issue:

brew install coreutils

I need to modify che compiler, help!

Take a look at the compiler documentation.

BirdsEye overview

The work of several repositories come together in this repository. This diagram aims to sketch an overview of how different pieces connect