Ballerina (programming language)

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Ballerina Language
Designed bySanjiva Weerawarana, James Clark, Sameera Jayasoma, Hasitha Aravinda, Srinath Perera, Frank Leymann and WSO2[1]
First appeared2017
Typing disciplineStructural, strong, static, inferred
Implementation languageJava, Ballerina, TypeScript [2]
LicenseApache License 2.0[3]
Influenced by
Java, Javascript, Go, Rust, C#[4]

Ballerina is an open source general-purpose programming language and platform designed by WSO2 for cloud-era application programmers. It is easy to write and modify and is suitable for application programmers.[5][6][7]

It is an open source project [2] started in 2015 by architects from WSO2 as a code-based alternative to the configuration-based integration tools such as EAI, ESB, and workflow products.[8][9]

It has various constructs geared toward cloud-native development including support for modern data formats and protocols, reliability, distributed transactions, APIs, and event streams.[10][11][12]


Ballerina was designed by WSO2 to improve productivity for application developers that have to work with distributed cloud-native systems. The designers, who provided enterprise products in the integration space for over 10 years, used their knowledge of the industry when designing the language.[13][14] Ballerina was first publicly announced in 2017 and version 1.0 was released on September 10, 2019.[15]


Some key concepts in Ballerina include:

  • The network in the language - Ballerina introduces fundamental, new abstractions of client objects, services, resource functions, and listeners to bring networking into the language. [16]
  • Sequence diagrams for programming - In Ballerina, every program has a corresponding sequence diagram that illustrates distributed and concurrent interactions automatically. [17]
  • Structural, open-by-default typing - Ballerina has a statically-typed, structural type system that is designed to be network data schema friendly. [18]
  • Moving from code to cloud - Ballerina brings the entire program execution process to the hands of the developer with extensible metadata that gets compiled to runnable programs for all major cloud platforms. [19]
  • Automated observability - Ballerina incorporates automatic observability features into the language itself that helps keep track of metrics, logs and tracing. [20]


Hello World Service

import ballerina/http;

service hello on new http:Listener(9090) {

    resource function sayHello(http:Caller caller,
        http:Request req) returns error? {

        check caller->respond("Hello, World!");

To start the service, navigate to the directory that contains the `.bal` file, and execute the `ballerina run` command below.

$ ballerina run hello_world.bal
[ballerina/http] started HTTP/WS listener

curl http://localhost:9090/hello/sayHello
Hello, World!



import ballerina/http;
import ballerina/lang.'int;
import ballerina/io;

// Workers interact with each other by sending and receiving messages.
// Ballerina validates every worker interaction (send and receive)
// to avoid deadlocks.
public function main() {
    worker w1 {
        int w1val = checkpanic calculate("2*3");
        // Sends a message asynchronously to the worker `w2`.
        w1val -> w2;
        // Receives a message from the worker `w2`.
        int w2val = <- w2;
        io:println("[w1] Message from w2: ", w2val);
        // Sends messages synchronously to the worker `w3`. The worker `w1` will wait
        // until the worker `w3` receives the message.
        w1val ->> w3;
        w2val -> w3;
        // Flushes all messages sent asynchronously to the worker `w3`. The worker
        // will halt at this point until all messages are sent or until the worker `w3`
        // fails.
        checkpanic flush w3;

    // A worker can have an explicit return type, or else, if a return type is not mentioned,
    // it is equivalent to returning ().
    worker w2 {
        int w2val = checkpanic calculate("17*5");
        // Receives a message from the worker `w1`.
        int w1val = <- w1;
        io:println("[w2] Message from w1: ", w1val);
        // Sends a message asynchronously to the worker `w1`.
        w1val + w2val -> w1;

    worker w3 {


gRPC Unary Blocking

import ballerina/grpc;
import ballerina/log;

service HelloWorld on new grpc:Listener(9090) {

    resource function hello(grpc:Caller caller, string name,
                             grpc:Headers headers) {
        log:printInfo("Server received hello from " + name);
        string message = "Hello " + name;

        // Reads custom headers in request message.
        string reqHeader = headers.get("client_header_key") ?: "none";
        log:printInfo("Server received header value: " + reqHeader);

        // Writes custom headers to response message.
        grpc:Headers resHeader = new;
        resHeader.setEntry("server_header_key", "Response Header value");

        // Sends response message with headers.
        grpc:Error? err = caller->send(message, resHeader);
        if (err is grpc:Error) {
            log:printError("Error from Connector: " + err.message());

        // Sends `completed` notification to caller.
        grpc:Error? result = caller->complete();
        if (result is grpc:Error) {
            log:printError("Error in sending completed notification to caller",
                err = result);



  1. ^ "Ballerina Language Specification". WSO2.
  2. ^ a b Open Source Contributors (18 June 2019). "Ballerina source code". GitHub.
  3. ^ "WSO2 / LICENSE". WSO2. 2017-03-08. Retrieved 2018-03-01.
  4. ^ "Ballerina, A modern programming language focused on integration" (PDF): 15. Cite journal requires |journal= (help)
  5. ^ Jackson, Joab. "Ballerina: An API-First Programming Language". The New Stack. Retrieved 2018-06-11.
  6. ^ Foremski, Tom (2019-03-01). "Technology and the Arts: Celebrating Ballerina, a computer language of integration". Retrieved 2019-07-14.
  7. ^ Lawton, George (2018-11-01). "Ballerina language promises to improve app integration". Retrieved 2019-07-23.
  8. ^ "Ballerina Microservices Programming Language: Introducing the Latest Release and "Ballerina Central"". InfoQ. Retrieved 2018-06-07.
  9. ^ Earls, Alan (2019-03-01). "How does Ballerina stack up as a cloud-native programming language?". Retrieved 2019-07-23.
  10. ^ Doyle, Kerry. "10 of the best programming languages to learn in 2020". Retrieved 2020-09-16.
  11. ^ Posta, Christian. "Evolution of Integration and Microservices with Service Mesh and Ballerina". Retrieved 2019-07-24.
  12. ^ staff, Techworld. "Top programming languages you should try". Techworld. Retrieved 2018-06-07.
  13. ^ Clark, James. "Ballerina Programming Language Part 0 - Context". Retrieved 2020-09-16.
  14. ^ Clark, James. "Ballerina Programming Language Part 1 - Concepts". Retrieved 2020-09-16.
  15. ^ "Ballerina Reinvents Cloud-Native Middleware as a Programming Language"". GlobeNewswire. Retrieved 2020-09-16.
  16. ^ Warusawithana, Lakmal. "Rethinking Programming: The Network in the Language". Retrieved 2020-09-16.
  17. ^ Fernando, Anjana. "Rethinking Programming: Making Sequence Diagrams Cool Again". Retrieved 2020-09-16.
  18. ^ Fernando, Anjana. "Rethinking Programming: Network Aware Type System". Retrieved 2020-09-16.
  19. ^ Warusawithana, Lakmal. "Rethinking Programming: From Code to Cloud". Retrieved 2020-09-16.
  20. ^ Fernando, Anjana. "Rethinking Programming: Automated Observability". Retrieved 2020-09-16.
  21. ^ Ballerina Team (16 September 2020). "Hello world service".
  22. ^ Ballerina Team (16 September 2020). "Worker interaction".
  23. ^ Ballerina Team (16 September 2020). "gRPC unary blocking".

Further reading

Edited: 2021-06-18 18:11:50