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Server API

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Overview

CVAT server provides HTTP REST API for interaction. Each client application - be it a command line tool, browser or a script - all interact with CVAT via HTTP requests and responses:

API schema

You can obtain schema for your server at <yourserver>/api/docs. For example, the official CVAT.ai application has API documentation here.

Examples

Here you can see how a task is created in CVAT:

  1. At first, we have to login
  2. Then we create a task from its configuration
  3. Then we send task data (images, videos etc.)
  4. We wait for data processing and finish

Design principles

Common pattern for our REST API is <VERB> [namespace] <objects> <id> <action>.

  • VERB can be POST, GET, PATCH, PUT, DELETE.
  • namespace should scope some specific functionality like auth, lambda. It is optional in the scheme.
  • Typical objects are tasks, projects, jobs.
  • When you want to extract a specific object from a collection, just specify its id.
  • An action can be used to simplify REST API or provide an endpoint for entities without objects endpoint like annotations, data, data/meta. Note: action should not duplicate other endpoints without a reason.

When you're developing new endpoints, follow these guidelines:

  • Use nouns instead of verbs in endpoint paths. For example, POST /api/tasks instead of POST /api/tasks/create.
  • Accept and respond with JSON whenever it is possible
  • Name collections with plural nouns (e.g. /tasks, /projects)
  • Try to keep the API structure flat. Prefer two separate endpoints for /projects and /tasks instead of /projects/:id1/tasks/:id2. Use filters to extract necessary information like /tasks/:id2?project=:id1. In some cases it is useful to get all tasks. If the structure is hierarchical, it cannot be done easily. Also you have to know both :id1 and :id2 to get information about the task. Note: for now we accept GET /tasks/:id2/jobs but it should be replaced by /jobs?task=:id2 in the future.
  • Handle errors gracefully and return standard error codes (e.g. 201, 400)
  • Allow filtering, sorting, and pagination
  • Maintain good security practices
  • Cache data to improve performance
  • Versioning our APIs. It should be done when you delete an endpoint or modify its behaviors. Versioning uses a schema with Accept header with vendor media type.

Playground

Sometimes, it may be necessary to send customized requests or simply test some endpoints available on the server. It's possible to send custom requests to a CVAT server directly from your web browser without special extensions. This can be done at the Swagger page provided by the server. The page is available at <cvat_host>/api/swagger (e.g. https://app.cvat.ai/api/swagger). The Swagger page provides the autogenerated documentation, supports multiple authentication options and allows sending custom requests to various server endpoints.

Swagger documentation is visible on allowed hosts. If necessary, the list can be modified by updating the environment variable in docker-compose.ymlfile with cvat hosted machine IP or domain name. Example - ALLOWED_HOSTS: 'localhost, 127.0.0.1'.

Make a request to a resource stored on a server and the server will respond with the requested information.

The endpoints are grouped by APIs:

  • auth - user authentication queries
  • comments - requests to post/delete comments to issues
  • issues - update, delete and view problem comments
  • jobs -requests to manage the job
  • lambda - requests to work with lambda function
  • projects - project management queries
  • reviews -adding and removing the review of the job
  • server - server information requests
  • tasks - requests to manage tasks
  • users - user management queries etc.

In the Models section below you can also find various data structures used in the endpoints.

Each group contains queries related to a different types of HTTP methods such as: GET, POST, PATCH, DELETE, etc. Different methods are highlighted in different color. Each item has a name and description. Clicking on an element opens a form with a name, description and settings input field or an example of json values.

To find out more, read swagger specification.

To try to send a request, click Try it now and type Execute. You'll get a response in the form of Curl, Request URL and Server response.