WIP: Handle retry-after header

src/main/java/io/qdrant/client/QdrantGrpcClient.java

@@ -269,6 +269,7 @@ private static ManagedChannel createChannel(
       }
 
       channelBuilder.userAgent(userAgent);
+      channelBuilder.intercept(new ResourceExhaustedInterceptor());
 
       return channelBuilder.build();
     }

src/main/java/io/qdrant/client/ResourceExhaustedInterceptor.java

@@ -0,0 +1,49 @@
+package io.qdrant.client;
+
+import io.grpc.*;
+
+/** An Interceptor that handles Resource Exhausted errors */
+public class ResourceExhaustedInterceptor implements ClientInterceptor {
+  /** Default constructor for {@link ResourceExhaustedInterceptor} */
+  public ResourceExhaustedInterceptor() {}
+
+  @Override
+  public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
+      MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
+    return new ForwardingClientCall.SimpleForwardingClientCall<ReqT, RespT>(
+        next.newCall(method, callOptions)) {
+
+      @Override
+      public void start(Listener<RespT> responseListener, Metadata headers) {
+        super.start(
+            new ForwardingClientCallListener.SimpleForwardingClientCallListener<RespT>(
+                responseListener) {
+              @Override
+              public void onClose(Status status, Metadata trailers) {
+                if (status.getCode() == Status.Code.RESOURCE_EXHAUSTED) {
+                  String retryAfter =
+                      trailers.get(
+                          Metadata.Key.of("Retry-After", Metadata.ASCII_STRING_MARSHALLER));
+                  if (retryAfter != null) {
+                    try {
+                      int retryAfterSeconds = Integer.parseInt(retryAfter);
+                      status =
+                          status.withCause(
+                              new ResourceExhaustedResponse(
+                                  "Too many requests", retryAfterSeconds));
+                    } catch (NumberFormatException e) {
+                      throw new QdrantException(
+                          "Retry-After header value is not a valid integer: " + retryAfter);
+                    }
+                  } else {
+                    super.onClose(status, trailers);
+                  }
+                }
+                super.onClose(status, trailers);
+              }
+            },
+            headers);
+      }
+    };
+  }
+}

src/main/java/io/qdrant/client/ResourceExhaustedResponse.java

@@ -0,0 +1,27 @@
+package io.qdrant.client;
+
+/** An exception indicating that rate limit is reached */
+public class ResourceExhaustedResponse extends RuntimeException {
+  /** The number of seconds to wait before retrying */
+  private final int retryAfterSeconds;
+
+  /**
+   * Instantiates a new instance of {@link ResourceExhaustedResponse}
+   *
+   * @param message The message to display
+   * @param retryAfterSeconds The number of seconds to wait before retrying
+   */
+  public ResourceExhaustedResponse(String message, int retryAfterSeconds) {
+    super(message);
+    this.retryAfterSeconds = retryAfterSeconds;
+  }
+
+  /**
+   * Gets the number of seconds to wait before retrying
+   *
+   * @return the number of seconds to wait before retrying
+   */
+  public int getRetryAfterSeconds() {
+    return retryAfterSeconds;
+  }
+}