import ballerina/http;
import ballerina/lang.runtime;
// 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 `resetTime`.
http:Client backendClientEP = check new ("http://localhost:8080", {
// Configuration options that control the behavior of the circuit
// breaker.
circuitBreaker: {
// Failure calculation window. This is how long the circuit
// breaker keeps the statistics for the operations.
rollingWindow: {
// Time period in seconds for which the failure
// threshold is calculated.
timeWindow: 10,
// The granularity (in seconds) at which the time
// window slides. The `RollingWindow` is divided into
// buckets and slides by these increments.
bucketSize: 2,
// Minimum number of requests in the `RollingWindow` that
// will trip the circuit.
requestVolumeThreshold: 0
},
// The threshold for request failures.
// When this threshold exceeds, the circuit trips. This is the
// ratio between failures and total requests. The ratio is
// calculated using the requests received within the given
// rolling window.
failureThreshold: 0.2,
// The time period (in seconds) to wait before attempting to
// make another request to the upstream service.
resetTime: 10,
// HTTP response status codes that are considered as failures
statusCodes: [400, 404, 500]
},
timeout: 2
}
);
// Create an HTTP service bound to the endpoint (circuitBreakerEP).
service /cb on new http:Listener(9090) {
resource function get .(http:Request request)
returns http:Response|http:InternalServerError {
var backendResponse = backendClientEP->forward("/hello", request);
// If the `backendResponse` is an `http:Response`, it is sent back to
// the client. If `backendResponse` is an `http:ClientError`, an
// internal server error is returned to the client.
if (backendResponse is http:Response) {
return backendResponse;
} else {
return {body:backendResponse.message()};
}
}
}
int counter = 1;
// This sample service is used to mock connection timeouts and service outages.
// This should run separately from the `circuitBreakerDemo` service.
service /hello on new http:Listener(8080) {
resource function get .() returns string|http:InternalServerError {
if (counter % 5 == 0) {
counter += 1;
// Delay the response by 5 seconds to
// mimic the network level delays.
runtime:sleep(5);
return "Hello World!!!";
} else if (counter % 5 == 3) {
counter += 1;
return {body:"Error occurred while processing the request."};
} else {
counter += 1;
return "Hello World!!!";
}
}
}
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 seconds for which the failure threshold is calculated. |
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The granularity (in seconds) at which the time
window slides. The |
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Minimum number of requests in the |
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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. The ratio is calculated using the requests received within the given rolling window. |
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The time period (in seconds) to wait before attempting to make another request to the upstream service. |
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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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If the |
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This sample service is used to mock connection timeouts and service outages.
This should run separately from the |
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Delay the response by 5 seconds to mimic the network level delays. |
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