fix(endpoints): resolve service-specific endpoint once per client (#1382

)

.changeset/hot-items-sing.md

@@ -0,0 +1,5 @@
+---
+"@smithy/middleware-endpoint": patch
+---
+
+resolve service-specific endpoint once per client

packages/middleware-endpoint/src/adaptors/getEndpointFromConfig.ts

@@ -2,4 +2,7 @@ import { loadConfig } from "@smithy/node-config-provider";
 
 import { getEndpointUrlConfig } from "./getEndpointUrlConfig";
 
-export const getEndpointFromConfig = async (serviceId: string) => loadConfig(getEndpointUrlConfig(serviceId))();
+/**
+ * @internal
+ */
+export const getEndpointFromConfig = async (serviceId?: string) => loadConfig(getEndpointUrlConfig(serviceId ?? ""))();

packages/middleware-endpoint/src/adaptors/getEndpointFromInstructions.ts

@@ -39,9 +39,19 @@ export const getEndpointFromInstructions = async <
   context?: HandlerExecutionContext
 ): Promise<EndpointV2> => {
   if (!clientConfig.endpoint) {
-    const endpointFromConfig = await getEndpointFromConfig(clientConfig.serviceId || "");
+    let endpointFromConfig: string | undefined;
+
+    // This field is guaranteed by the type indicated by the config resolver, but is new
+    // and some existing standalone calls to this function may not provide the function, so
+    // this check should remain here.
+    if (clientConfig.serviceConfiguredEndpoint) {
+      endpointFromConfig = await clientConfig.serviceConfiguredEndpoint();
+    } else {
+      endpointFromConfig = await getEndpointFromConfig(clientConfig.serviceId);
+    }
+
     if (endpointFromConfig) {
-      clientConfig.endpoint = () => Promise.resolve(toEndpointV1(endpointFromConfig));
+      clientConfig.endpoint = () => Promise.resolve(toEndpointV1(endpointFromConfig!));
     }
   }
 

packages/middleware-endpoint/src/resolveEndpointConfig.ts

@@ -1,6 +1,7 @@
 import { Endpoint, EndpointParameters, EndpointV2, Logger, Provider, UrlParser } from "@smithy/types";
 import { normalizeProvider } from "@smithy/util-middleware";
 
+import { getEndpointFromConfig } from "./adaptors/getEndpointFromConfig";
 import { toEndpointV1 } from "./adaptors/toEndpointV1";
 
 /**
@@ -42,13 +43,20 @@ export interface EndpointInputConfig<T extends EndpointParameters = EndpointPara
    * Enables FIPS compatible endpoints.
    */
   useFipsEndpoint?: boolean | Provider<boolean>;
+
+  /**
+   * @internal
+   * This field is used internally so you should not fill any value to this field.
+   */
+  serviceConfiguredEndpoint?: never;
 }
 
 interface PreviouslyResolved<T extends EndpointParameters = EndpointParameters> {
   urlParser: UrlParser;
   region: Provider<string>;
   endpointProvider: (params: T, context?: { logger?: Logger }) => EndpointV2;
   logger?: Logger;
+  serviceId?: string;
 }
 
 /**
@@ -95,6 +103,12 @@ export interface EndpointResolvedConfig<T extends EndpointParameters = EndpointP
    * @internal
    */
   serviceId?: string;
+
+  /**
+   * A configured endpoint global or specific to the service from ENV or AWS SDK configuration files.
+   * @internal
+   */
+  serviceConfiguredEndpoint?: Provider<string | undefined>;
 }
 
 /**
@@ -111,12 +125,22 @@ export const resolveEndpointConfig = <T, P extends EndpointParameters = Endpoint
 
   const isCustomEndpoint = !!endpoint;
 
-  return {
+  const resolvedConfig = {
     ...input,
     endpoint: customEndpointProvider,
     tls,
     isCustomEndpoint,
     useDualstackEndpoint: normalizeProvider(input.useDualstackEndpoint ?? false),
     useFipsEndpoint: normalizeProvider(input.useFipsEndpoint ?? false),
   } as T & EndpointResolvedConfig<P>;
+
+  let configuredEndpointPromise: undefined | Promise<string | undefined> = undefined;
+  resolvedConfig.serviceConfiguredEndpoint = async () => {
+    if (input.serviceId && !configuredEndpointPromise) {
+      configuredEndpointPromise = getEndpointFromConfig(input.serviceId);
+    }
+    return configuredEndpointPromise;
+  };
+
+  return resolvedConfig;
 };