A developer writes code to implement a circuit breaker pattern using the Opossum library within a NestJS application. The process includes configuring parameters, defining an Axios-based action, and setting up event listeners for different breaker states like open, half-open, closed, rejected, and timed-out.
Length 11:43
Captions English (Generated), Spanish (Auto-translated), French (Auto-translated), Korean (Auto-translated), Portuguese (Auto-translated), Vietnamese (Auto-translated) #circuit breaker #typescript #nestjs #axios #opossum #error handling #programming #software engineering #backend development #resilience
0:00 All right, so now the first thing that I'll do inside of our circuit breaker 0:03 function is let's generate the name for it so that we can identify it 0:07 later on. So here we'll use our options object where 0:10 we pass through the 0:11 optional name parameter. Otherwise, let's just use a default and call it our 0:15 HTTP circuit breaker. Now, the name here controls what the circuit 0:19 breaker actually reports when it actually outputs its 0:22 stats. So if you have multiple circuit breakers, 0:25 this can be helpful in 0:26 actually determining which one is which. 0:29 Next up, we'll also declare the logger 0:31 that we're going to use. 0:32 So here, let's create a new NestJS logger 0:35 and pass in circuit 0:36 breaker 0:38 with the name of the circuit breaker that we have just assigned. 0:42 And so we'll use this logger inside of the event handler callbacks that 0:46 the circuit breaker provides, and this allows us to actually listen to 0:50 the underlying states of the circuit breaker. 0:53 Next up, we have the most important part of the 0:55 circuit breaker, which is the 0:56 underlying action. Now, the action is what the 1:00 breaker will actually wrap. It's the underlying function that gets 1:03 executed inside of the circuit breaker, and this is what 1:07 determines, based on its result, whether or not it succeeds, 1:11 fails, or times out, that determines how the circuit breaker 1:14 reacts. 1:15 If there's enough failures in a rolling window that we've set up, then it will 1:19 trigger into a closed state and fast fail 1:22 until we open it up in a half-open state to allow for a single 1:26 request to check for a success state and then ultimately open it back up. 1:30 And so this is the true meat of the circuit breaker, where we actually 1:34 execute the underlying function. 1:36 Now, in our case, we know that the underlying function we're
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