java 31 lines · 7 steps

Bulkhead-protected HTTP calls in Spring

A Spring service caps concurrent warehouse calls with a semaphore bulkhead and degrades gracefully when it saturates or fails.

Explained by highlit

Spring Intermediate bulkhead resilience fallback http-client fault-tolerance

1@Service
2public class InventoryService {
3 
  private final RestClient warehouseClient;
5 
  public InventoryService(RestClient.Builder builder) {
      this.warehouseClient = builder
              .baseUrl("https://warehouse.internal/api")
              .build();
  }
11 
  @Bulkhead(name = "warehouse", type = Bulkhead.Type.SEMAPHORE, fallbackMethod = "cachedStock")
  public StockLevel currentStock(String sku) {
      return warehouseClient.get()
              .uri("/stock/{sku}", sku)
              .retrieve()
              .body(StockLevel.class);
  }
19 
  private StockLevel cachedStock(String sku, BulkheadFullException ex) {
      log.warn("Warehouse bulkhead saturated for sku={}, serving degraded stock", sku);
      return StockLevel.unknown(sku);
  }
24 
  private StockLevel cachedStock(String sku, Throwable ex) {
      log.error("Warehouse lookup failed for sku={}", sku, ex);
      return StockLevel.unknown(sku);
  }
29 
  private static final Logger log = LoggerFactory.getLogger(InventoryService.class);
31}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1A semaphore bulkhead bounds concurrent calls to a dependency so one slow service can't exhaust your threads.
2Fallback methods let you return a degraded-but-valid response instead of propagating failures to callers.
3Matching fallbacks by exception type lets you distinguish saturation from genuine downstream errors.

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