import ballerina/http;
import ballerina/log;
import ballerina/runtime;
http:Client backendClientEP = new("http://localhost:8080", {
circuitBreaker: {
rollingWindow: {
timeWindowInMillis: 10000,
bucketSizeInMillis: 2000,
requestVolumeThreshold: 0 },
failureThreshold: 0.2,
resetTimeInMillis: 10000,
statusCodes: [400, 404, 500] },
timeoutInMillis: 2000
});
@http:ServiceConfig {
basePath: "/cb"
}
service circuitbreaker on new http:Listener(9090) {
@http:ResourceConfig {
methods: ["GET"],
path: "/"
}
resource function invokeEndpoint(http:Caller caller, http:Request request) {
var backendResponse = backendClientEP->forward("/hello", request);
if (backendResponse is http:Response) {
var responseToCaller = caller->respond(backendResponse);
if (responseToCaller is http:ListenerError) {
log:printError("Error sending response", responseToCaller);
}
} else {
http:Response response = new;
response.statusCode = http:STATUS_INTERNAL_SERVER_ERROR;
response.setPayload(<string> backendResponse.detail()?.message);
var responseToCaller = caller->respond(response);
if (responseToCaller is http:ListenerError) {
log:printError("Error sending response", responseToCaller);
}
}
}
}int counter = 1;@http:ServiceConfig {
basePath: "/hello"
}
service helloWorld on new http:Listener(8080) {
@http:ResourceConfig {
methods: ["GET"],
path: "/"
}
resource function sayHello(http:Caller caller, http:Request req) {
if (counter % 5 == 0) {
runtime:sleep(5000); var result = caller->respond("Hello World!!!");
handleRespondResult(result);
} else if (counter % 5 == 3) {
http:Response res = new;
res.statusCode = 500;
res.setPayload(
"Internal error occurred while processing the request.");
var result = caller->respond(res);
handleRespondResult(result);
} else {
var result = caller->respond("Hello World!!!");
handleRespondResult(result);
}
counter = counter + 1;
}
}function handleRespondResult(error? result) {
if (result is http:ListenerError) {
log:printError("Error sending response from mock service", result);
}
}
Circuit BreakerThe Circuit Breaker is used to gracefully handle network related errors, which occur when using the HTTP Client. |
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The circuit breaker looks for errors across a rolling time window.
After the circuit is broken, it does not send requests to
the backend until the |
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Configuration options that control the behavior of the circuit breaker. |
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Failure calculation window. This is how long the circuit breaker keeps the statistics for the operations. |
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Time period in milliseconds for which the failure threshold is calculated. |
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The granularity (in milliseconds) at which the time window
slides.
The |
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Minimum number of requests in a |
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The threshold for request failures.
When this threshold exceeds, the circuit trips.
This is the ratio between failures and total requests and the
ratio is considered only within the configured |
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The time period (in milliseconds) to wait before attempting to
make another request to the upstream service.
When the failure threshold exceeds, the circuit trips to |
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HTTP response status codes that are considered as failures |
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Create an HTTP service bound to the endpoint (circuitBreakerEP). |
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Create a REST resource within the API. |
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The parameters include a reference to the caller and an object of the request data. |
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If the |
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This sample service is used to mock connection timeouts and service outages.
Mock a service outage by stopping/starting this service.
This should run separately from the |
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Delay the response by 5000 milliseconds to mimic the network level delays. |
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