Access Flow#

Once you have configured your Flow API you can access it over the network. There are multiple ways of doing this.

HTTP access#

Available Protocols

Jina Flows can use one of three protocols: gRPC, HTTP, or Websocket. Only Flows that use HTTP can be accessed via the methods described below.

Apart from using the Jina Client, the most common way of interacting with your deployed Flow is via HTTP.

You can always use post to interact with a Flow, using the /post HTTP endpoint.

Use HTTP client to send request#

With the help of OpenAPI schema, one can send data requests to a Flow via cURL, JavaScript, Postman, or any other HTTP client or programming library.

via cURL

Here’s an example that uses cURL.

curl --request POST 'http://localhost:12345/post' --header 'Content-Type: application/json' -d '{"data": [{"text": "hello world"}],"execEndpoint": "/search"}'

via JavaScript

Sending a request from the front-end JavaScript code is a common use case too. Here’s how this would look like:

fetch('http://localhost:12345/post', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json'
    },
    body: JSON.stringify({"data": [{"text": "hello world"}],"execEndpoint": "/search"})
}).then(response => response.json()).then(data => console.log(data));

Arguments#

Your HTTP request can include the following parameters:

Name	Required	Description	Example
`execEndpoint`	required	Executor endpoint to target	`"execEndpoint": "/index"`
`data`	optional	List specifying the input Documents	`"data": [{"text": "hello"}, {"text": "world"}]`.
`parameters`	optional	Dictionary of parameters to be sent to the Executors	`"parameters": {"param1": "hello world"}`
`targetExecutor`	optional	String indicating an Executor to target. Default targets all Executors	`"targetExecutor": "MyExec"`

Instead of using the generic /post endpoint, you can directly use endpoints like /index or /search to perform a specific operation. In this case your data request will be sent to the corresponding Executor endpoint, so the parameter execEndpoint does not need to be specified.

The response you receive includes data (an array of Documents), as well as the fields routes, parameters, and header.

Use Swagger UI to send HTTP request#

Flows provide a customized Swagger UI which can be used to interact with the Flow visually, through a web browser.

Available Protocols

Only Flows that have enabled CORS expose the Swagger UI interface.

For a Flow that is exposed on port PORT, you can navigate to the Swagger UI via http://localhost:PORT/docs:

Here you can see all the endpoints that are exposed by the Flow, such as /search and /index.

To send a request, click on the endpoint you want to target, then on Try it out.

Now you can enter your HTTP request, and send it by clicking on Execute. You can again use the REST HTTP request schema, but do not need to specify execEndpoint.

Below, in Responses, you can see the reply, together with a visual representation of the returned Documents.

Postman Collection#

Postman is an application that allows the testing of web APIs from a graphical interface. You can store all the templates for your REST APIs in it, using Collections.

We provide a suite of templates for the Jina Flow, in this collection. You can import it in Postman in Collections, with the Import button. It provides templates for the main operations. You need to create an Environment to define the {{url}} and {{port}} environment variables. These would be the hostname and the port where the Flow is listening.

This contribution was made by Jonathan Rowley, in our community Slack.

GraphQL Interface#

Mutations and arguments#

The Flow GraphQL API exposes the mutation docs, which sends its inputs to the Flow’s Executors, just like HTTP post as described above.

A GraphQL mutation takes same set of arguments used in HTTP.

The response from GraphQL can include all fields available on a DocumentArray.

Fields#

The available fields in the GraphQL API are defined by the Document Strawberry type.

Essentially, you can ask for any property of a Document, including embedding, text, tensor, id, matches, tags, and more.

gRPC#

If you want to create a gRPC client in another language, you will need to compile the Protobuf definitions. In Python, you can use our own client.

Websocket#

Websocket uses persistent connections between the client & Flow, hence allowing streaming use cases. While you can always use the Python client to stream requests like any other protocol, websocket allows streaming JSON from anywhere (CLI / Postman / any other programming language). The same set of arguments as HTTP can be used in the payload.

We use subprotocols to separate streaming JSON vs bytes. The Flow defaults to json when a subprotocol is not passed during connection establishment (Our Python client uses bytes streaming by using jina.proto definition).

Hint

Choose Websocket over HTTP if you want to stream requests.
Choose Websocket over gRPC if
- you want to stream using JSON, not bytes
- your client language doesn’t support gRPC
- you don’t want to compile the Protobuf definitions for your gRPC client