Circuit Breaker with gRPC - grpc

Question

In a REST service adding a circuit breaker with hystrix, I could do the following:
#HystrixCommand(fallbackMethod = "getBackupResult")
#GetMapping(value = "/result")
public ResponseEntity<ResultDto> getResult(#RequestParam("request") String someRequest) {
ResultDto resultDto = service.parserRequest(someRequest);
return new ResponseEntity<>(resultDto, HttpStatus.OK);
}
public ResponseEntity<ResultDto> getBackupResult(#RequestParam("request") String someRequest) {
ResultDto resultDto = new ResultDto();
return new ResponseEntity<>(resultDto, HttpStatus.OK);
}
Is there something similar I can do for the gRPC call?
public void parseRequest(ParseRequest request, StreamObserver<ParseResponse> responseObserver) {
try {
ParseResponse parseResponse = service.parseRequest(request.getSomeRequest());
responseObserver.onNext(parseResponse);
responseObserver.onCompleted();
} catch (Exception e) {
logger.error("Failed to execute parse request.", e);
responseObserver.onError(new StatusException(Status.INTERNAL));
}
}

Answer 1

I solved my problem by implementing the circuit-breaker on my client. I used the sentinel library
To react on exceptions ratio for example I added this rule:
private static final String KEY = "callGRPC";
private void callGRPC(List<String> userAgents) {
initDegradeRule();
ManagedChannel channel = ManagedChannelBuilder.forAddress(grpcHost, grpcPort).usePlaintext()
.build();
for (String userAgent : userAgents) {
Entry entry = null;
try {
entry = SphU.entry(KEY);
UserAgentServiceGrpc.UserAgentServiceBlockingStub stub
= UserAgentServiceGrpc.newBlockingStub(channel);
UserAgentParseRequest request = UserAgentRequest.newBuilder().setUserAgent(userAgent).build();
UserAgentResponse userAgentResponse = stub.getUserAgentDetails(request);
} catch (BlockException e) {
logger.error("Circuit-breaker is on and the call has been blocked");
} catch (Throwable t) {
logger.error("Exception was thrown", t);
} finally {
if (entry != null) {
entry.exit();
}
}
}
channel.shutdown();
}
private void initDegradeRule() {
List<DegradeRule> rules = new ArrayList<DegradeRule>();
DegradeRule rule = new DegradeRule();
rule.setResource(KEY);
rule.setCount(0.5);
rule.setGrade(RuleConstant.DEGRADE_GRADE_EXCEPTION_RATIO);
rule.setTimeWindow(60);
rules.add(rule);
DegradeRuleManager.loadRules(rules);
}