Graceful Shutdown — Deploy Sırasında Kaç İstek Düşer?

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server:
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  shutdown: graceful                 # default since Boot 3.4, written out for older readers
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spring:
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  lifecycle:
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    timeout-per-shutdown-phase: 30s  # how long in-flight requests may take to finish
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  task:
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    execution:
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      shutdown:
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        await-termination: true      # graceful shutdown alone does not wait for @Async work
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        await-termination-period: 20s
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management:
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  endpoint:
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    health:
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      probes:
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        enabled: true                # /actuator/health/liveness and /readiness
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  endpoints:
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    web:
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      exposure:
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        include: health

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FROM eclipse-temurin:21-jre
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WORKDIR /app
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COPY build/libs/ebank-api.jar app.jar
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# Exec form, no shell in between: SIGTERM reaches the JVM, which runs Spring's shutdown hook.
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# JAVA_TOOL_OPTIONS is read by the JVM itself, so no wrapper script is needed for flags.
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ENTRYPOINT ["java", "-jar", "/app/app.jar"]

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apiVersion: apps/v1
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kind: Deployment
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metadata:
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  name: ebank-api
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spec:
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  replicas: 4
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  strategy:
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    rollingUpdate: { maxUnavailable: 0, maxSurge: 1 }
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  template:
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    spec:
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      terminationGracePeriodSeconds: 45     # > preStop (10) + shutdown phase (30)
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      containers:
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        - name: ebank-api
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          image: registry.example/ebank-api:3.18.0
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          lifecycle:
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            preStop:
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              exec:
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                # Keep serving while the load balancer drops this pod from its list.
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                command: ["sh", "-c", "sleep 10"]
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          readinessProbe:
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            httpGet: { path: /actuator/health/readiness, port: 8080 }
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            periodSeconds: 5
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          livenessProbe:
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            httpGet: { path: /actuator/health/liveness, port: 8080 }
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            periodSeconds: 10

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@RestController
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@RequestMapping("/accounts/{iban}/statement-exports")
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class StatementExportController {
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    private final StatementExportJobs jobs;
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    StatementExportController(StatementExportJobs jobs) {
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        this.jobs = jobs;
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    }
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    // Before: a year of movements for a corporate account, built inside the request.
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    // It took longer than the shutdown window, so every deploy cut it off halfway.
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    // Now: the request only records the job and returns immediately.
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    @PostMapping
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    ResponseEntity<StatementExportView> start(@PathVariable String iban,
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                                              @RequestBody @Valid StatementRequest request) {
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        StatementExportView job = jobs.enqueue(iban, request);
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        return ResponseEntity.accepted()
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                .location(URI.create("/accounts/" + iban + "/statement-exports/" + job.id()))
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                .body(job);
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    }
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    @GetMapping("/{id}")
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    StatementExportView status(@PathVariable String iban, @PathVariable UUID id) {
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        return jobs.find(id);           // PENDING, RUNNING, DONE (with a download link) or FAILED
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    }
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}

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@Service
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class StatementExportJobs {
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    private final StatementExportRepository repository;
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    private final StatementFileWriter writer;
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    StatementExportJobs(StatementExportRepository repository, StatementFileWriter writer) {
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        this.repository = repository;
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        this.writer = writer;
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    }
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    @Transactional
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    public StatementExportView enqueue(String iban, StatementRequest request) {
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        return StatementExportView.of(repository.save(StatementExport.pending(iban, request)));
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    }
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    // Any pod may run the next pending job. A job whose pod died stays RUNNING
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    // with an old heartbeat and is picked up again after the timeout.
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    @Scheduled(fixedDelay = 2_000)
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    public void runNext() {
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        repository.claimNext(Instant.now(), Duration.ofMinutes(2))   // UPDATE … SKIP LOCKED
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                .ifPresent(job -> {
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                    try {
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                        URI file = writer.write(job.iban(), job.request(), job::heartbeat);
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                        repository.markDone(job.id(), file);
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                    } catch (RuntimeException ex) {
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                        repository.markFailed(job.id(), ex.getMessage());
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                    }
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                });
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    }
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}

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@Component
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class ShutdownLog {
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    private static final Logger log = LoggerFactory.getLogger(ShutdownLog.class);
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    // Fires when Spring starts closing the context, i.e. right after SIGTERM.
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    @EventListener
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    void onClose(ContextClosedEvent event) {
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        log.info("shutdown started: readiness is now REFUSING_TRAFFIC, waiting for in-flight work");
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    }
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    @EventListener
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    void onReadiness(AvailabilityChangeEvent<ReadinessState> event) {
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        log.info("readiness -> {}", event.getState());
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    }
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}