What is Ballerina?
Swan Lake

ballerina/http

 2.4.0

import ballerina/http;

Package overview

This package provides APIs for connecting and interacting with HTTP and HTTP2 endpoints. It facilitates two types of network entry points as the Client and Listener.

Client

The Client is used to connect to and interact with HTTP endpoints. They support connection pooling and can be configured to have a maximum number of active connections that can be made with the remote endpoint. The Client activates connection eviction after a given idle period and also supports follow-redirects so that you do not have to manually handle 3xx HTTP status codes.

Resiliency

The Client handles resilience in multiple ways such as load balancing, circuit breaking, endpoint timeouts, and via a retry mechanism.

Load balancing is used in the round-robin or failover manner.

When a failure occurs in the remote service, the client connections might wait for some time before a timeout occurs. Awaiting requests consume resources in the system. Circuit Breakers are used to trip after a certain number of failed requests to the remote service. Once a circuit breaker trips, it does not allow the client to send requests to the remote service for a period of time.

The Ballerina circuit breaker supports tripping on HTTP error status codes and I/O errors. Failure thresholds can be configured based on a sliding window (e.g., 5 failures within 10 seconds). The Client also supports a retry mechanism that allows it to resend failed requests periodically for a given number of times.

Security

The Client supports Server Name Indication (SNI), Certificate Revocation List (CRL), Online Certificate Status Protocol (OCSP), and OCSP Stapling for SSL/TLS connections. Also, the Client can be configured to send authentication information to the endpoint being invoked. Ballerina has built-in support for Basic authentication, JWT authentication, and OAuth2 authentication.

In addition to that, it supports both HTTP/1.1 and HTTP2 protocols and connection keep-alive, content chunking, HTTP caching, data compression/decompression, response payload binding, and authorization can be highlighted as the features of the Clients.

A Client can be defined using the URL of the remote service that it needs to connect with as shown below:

1http:Client clientEndpoint = check new("https://my-simple-backend.com");

The defined Client endpoint can be used to call a remote service as follows:

1// Send a GET request to the specified endpoint.
2http:Response response = check clientEndpoint->get("/get?id=123");

The payload can be retrieved as the return value from the remote function as follows:

1// Retrieve payload as json.
2json payload = check clientEndpoint->post("/backend/Json", "foo");

Listener

The Listener is the underneath server connector that binds the given IP/Port to the network and it's behavior can be changed using the http:ListenerConfiguration. In HTTP, the http:Service-typed services can be attached to the Listener. The service type precisely describes the syntax for both the service and resource.

A Service represents a collection of network-accessible entry points and can be exposed via a Listener endpoint. A resource represents one such entry point and can have its own path, HTTP methods, body format, consumes and produces content types, CORS headers, etc. In resources, the HTTP method and resource path are mandatory parameters and the String literal and path parameters can be stated as the path. The resource function accepts the http:Caller, http:Request, http:Headers, query parameters, header parameters, and payload parameters as arguments. However, they are optional.

When a Service receives a request, it is dispatched to the best-matched resource.

A Listener endpoint can be defined as follows:

1// Attributes associated with the `Listener` endpoint are defined here.
2listener http:Listener helloWorldEP = new(9090);

Then a Service can be defined and attached to the above Listener endpoint as shown below:

1// By default, Ballerina assumes that the service is to be exposed via HTTP/1.1.
2service /helloWorld on helloWorldEP {
3
4 resource function post [string name](@http:Payload string message) returns string {
5 // Sends the response back to the client along with a string payload.
6 return "Hello, World! I’m " + name + ". " + message;
7 }
8}

Security

Listener endpoints can be exposed via SSL. They support Mutual SSL, Hostname Verification, and Application Layer Protocol Negotiation (ALPN) for HTTP2. Listener endpoints also support Certificate Revocation List (CRL), Online Certificate Status Protocol (OCSP), and OCSP Stapling. Also, The listener can be configured to authenticate and authorize the inbound requests. Ballerina has built-in support for basic authentication, JWT authentication, and OAuth2 authentication.

In addition to that, supports both the HTTP/1.1 and HTTP2 protocols and connection keep-alive, content chunking, HTTP caching, data compression/decompression, payload binding, and authorization can be highlighted as the features of a Service.

Report issues

To report bugs, request new features, start new discussions, view project boards, etc., go to the Ballerina standard library parent repository.

Useful links

Exported modules

ballerina/http


Digest

sha-256:

e8adbb14cdfbdb6f6ae5cc9cbe47039fdf1655a5be674236a4d4b76625b6f78b


License: Apache-2.0

Created date: 08 September,2022


Ballerina compatibility

Platform: java11

Ballerina version: 2201.2.0


Keywords

http

network

service

listener

client


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