[ML] Adding asynchronous start up logic for the inference API internals

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/external/http/sender/HttpRequestSender.java

@@ -7,6 +7,7 @@
 
 package org.elasticsearch.xpack.inference.external.http.sender;
 
+import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.support.ContextPreservingActionListener;
@@ -42,6 +43,7 @@ public class HttpRequestSender implements Sender {
      */
     public static class Factory {
         private final HttpRequestSender httpRequestSender;
+        private static final TimeValue START_COMPLETED_WAIT_TIME = TimeValue.timeValueSeconds(5);
 
         public Factory(ServiceComponents serviceComponents, HttpClientManager httpClientManager, ClusterService clusterService) {
             Objects.requireNonNull(serviceComponents);
@@ -68,7 +70,8 @@ public Factory(ServiceComponents serviceComponents, HttpClientManager httpClient
                 httpClientManager,
                 requestSender,
                 service,
-                startCompleted
+                startCompleted,
+                START_COMPLETED_WAIT_TIME
             );
         }
 
@@ -77,45 +80,95 @@ public Sender createSender() {
         }
     }
 
-    private static final TimeValue START_COMPLETED_WAIT_TIME = TimeValue.timeValueSeconds(5);
+    private static final Logger logger = LogManager.getLogger(HttpRequestSender.class);
 
     private final ThreadPool threadPool;
     private final HttpClientManager manager;
-    private final AtomicBoolean started = new AtomicBoolean(false);
+    private final AtomicBoolean startInitiated = new AtomicBoolean(false);
+    private final AtomicBoolean startCompleted = new AtomicBoolean(false);
     private final RequestSender requestSender;
     private final RequestExecutor service;
-    private final CountDownLatch startCompleted;
+    private final CountDownLatch startCompletedLatch;
+    private final TimeValue startCompletedWaitTime;
 
-    private HttpRequestSender(
+    // Visible for testing
+    protected HttpRequestSender(
         ThreadPool threadPool,
         HttpClientManager httpClientManager,
         RequestSender requestSender,
         RequestExecutor service,
-        CountDownLatch startCompleted
+        CountDownLatch startCompletedLatch,
+        TimeValue startCompletedWaitTime
     ) {
         this.threadPool = Objects.requireNonNull(threadPool);
         this.manager = Objects.requireNonNull(httpClientManager);
         this.requestSender = Objects.requireNonNull(requestSender);
         this.service = Objects.requireNonNull(service);
-        this.startCompleted = Objects.requireNonNull(startCompleted);
+        this.startCompletedLatch = Objects.requireNonNull(startCompletedLatch);
+        this.startCompletedWaitTime = Objects.requireNonNull(startCompletedWaitTime);
     }
 
     /**
-     * Start various internal services. This is required before sending requests.
+     * Start various internal services asynchronously. This is required before sending requests.
      */
-    public void start() {
-        if (started.compareAndSet(false, true)) {
+    @Override
+    public void startAsynchronously(ActionListener<Void> listener) {
+        if (startInitiated.compareAndSet(false, true)) {
+            var preservedListener = ContextPreservingActionListener.wrapPreservingContext(listener, threadPool.getThreadContext());
+            threadPool.executor(UTILITY_THREAD_POOL_NAME).execute(() -> startInternal(preservedListener));
+        } else if (startCompleted.get() == false) {
+            var preservedListener = ContextPreservingActionListener.wrapPreservingContext(listener, threadPool.getThreadContext());
+            // wait on another thread so we don't potential block a transport thread
+            threadPool.executor(UTILITY_THREAD_POOL_NAME).execute(() -> waitForStartToCompleteWithListener(preservedListener));
+        } else {
+            listener.onResponse(null);
+        }
+    }
+
+    private void startInternal(ActionListener<Void> listener) {
+        try {
             // The manager must be started before the executor service. That way we guarantee that the http client
             // is ready prior to the service attempting to use the http client to send a request
             manager.start();
             threadPool.executor(UTILITY_THREAD_POOL_NAME).execute(service::start);
             waitForStartToComplete();
+            startCompleted.set(true);
+            listener.onResponse(null);
+        } catch (Exception ex) {
+            listener.onFailure(ex);
+        }
+    }
+
+    private void waitForStartToCompleteWithListener(ActionListener<Void> listener) {
+        try {
+            waitForStartToComplete();
+            listener.onResponse(null);
+        } catch (Exception e) {
+            listener.onFailure(e);
         }
     }
 
+    /**
+     * Start various internal services. This is required before sending requests.
+     *
+     * NOTE: This method blocks until the startup is complete.
+     */
+    @Override
+    public void startSynchronously() {
+        if (startInitiated.compareAndSet(false, true)) {
+            ActionListener<Void> listener = ActionListener.wrap(
+                unused -> {},
+                exception -> logger.error("Http sender failed to start", exception)
+            );
+            startInternal(listener);
+        }
+        // Handle the case where start*() was already called and this would return immediately because the started flag is already true
+        waitForStartToComplete();
+    }
+
     private void waitForStartToComplete() {
         try {
-            if (startCompleted.await(START_COMPLETED_WAIT_TIME.getSeconds(), TimeUnit.SECONDS) == false) {
+            if (startCompletedLatch.await(startCompletedWaitTime.getMillis(), TimeUnit.MILLISECONDS) == false) {
                 throw new IllegalStateException("Http sender startup did not complete in time");
             }
         } catch (InterruptedException e) {
@@ -145,7 +198,7 @@ public void send(
         @Nullable TimeValue timeout,
         ActionListener<InferenceServiceResults> listener
     ) {
-        assert started.get() : "call start() before sending a request";
+        assert startInitiated.get() : "call start() before sending a request";
         waitForStartToComplete();
         service.execute(requestCreator, inferenceInputs, timeout, listener);
     }
@@ -167,7 +220,7 @@ public void sendWithoutQueuing(
         @Nullable TimeValue timeout,
         ActionListener<InferenceServiceResults> listener
     ) {
-        assert started.get() : "call start() before sending a request";
+        assert startInitiated.get() : "call start() before sending a request";
         waitForStartToComplete();
 
         var preservedListener = ContextPreservingActionListener.wrapPreservingContext(listener, threadPool.getThreadContext());

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/external/http/sender/Sender.java

@@ -18,7 +18,9 @@
 import java.io.Closeable;
 
 public interface Sender extends Closeable {
-    void start();
+    void startSynchronously();
+
+    void startAsynchronously(ActionListener<Void> listener);
 
     void send(
         RequestManager requestCreator,

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/SenderService.java

@@ -9,6 +9,7 @@
 
 import org.elasticsearch.ElasticsearchStatusException;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.SubscribableListener;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.core.IOUtils;
@@ -73,10 +74,11 @@ public void infer(
         @Nullable TimeValue timeout,
         ActionListener<InferenceServiceResults> listener
     ) {
-        timeout = ServiceUtils.resolveInferenceTimeout(timeout, inputType, clusterService);
-        init();
-        var inferenceInput = createInput(this, model, input, inputType, query, returnDocuments, topN, stream);
-        doInfer(model, inferenceInput, taskSettings, timeout, listener);
+        SubscribableListener.newForked(this::init).<InferenceServiceResults>andThen((inferListener) -> {
+            var resolvedInferenceTimeout = ServiceUtils.resolveInferenceTimeout(timeout, inputType, clusterService);
+            var inferenceInput = createInput(this, model, input, inputType, query, returnDocuments, topN, stream);
+            doInfer(model, inferenceInput, taskSettings, resolvedInferenceTimeout, inferListener);
+        }).addListener(listener);
     }
 
     private static InferenceInputs createInput(
@@ -121,8 +123,9 @@ public void unifiedCompletionInfer(
         TimeValue timeout,
         ActionListener<InferenceServiceResults> listener
     ) {
-        init();
-        doUnifiedCompletionInfer(model, new UnifiedChatInput(request, true), timeout, listener);
+        SubscribableListener.newForked(this::init).<InferenceServiceResults>andThen((completionInferListener) -> {
+            doUnifiedCompletionInfer(model, new UnifiedChatInput(request, true), timeout, completionInferListener);
+        }).addListener(listener);
     }
 
     @Override
@@ -135,16 +138,16 @@ public void chunkedInfer(
         TimeValue timeout,
         ActionListener<List<ChunkedInference>> listener
     ) {
-        init();
-
-        ValidationException validationException = new ValidationException();
-        validateInputType(inputType, model, validationException);
-        if (validationException.validationErrors().isEmpty() == false) {
-            throw validationException;
-        }
+        SubscribableListener.newForked(this::init).<List<ChunkedInference>>andThen((chunkedInferListener) -> {
+            ValidationException validationException = new ValidationException();
+            validateInputType(inputType, model, validationException);
+            if (validationException.validationErrors().isEmpty() == false) {
+                throw validationException;
+            }
 
-        // a non-null query is not supported and is dropped by all providers
-        doChunkedInfer(model, input, taskSettings, inputType, timeout, listener);
+            // a non-null query is not supported and is dropped by all providers
+            doChunkedInfer(model, input, taskSettings, inputType, timeout, chunkedInferListener);
+        }).addListener(listener);
     }
 
     protected abstract void doInfer(
@@ -176,8 +179,9 @@ protected abstract void doChunkedInfer(
     );
 
     public void start(Model model, ActionListener<Boolean> listener) {
-        init();
-        doStart(model, listener);
+        SubscribableListener.newForked(this::init)
+            .<Boolean>andThen((doStartListener) -> doStart(model, doStartListener))
+            .addListener(listener);
     }
 
     @Override
@@ -189,8 +193,8 @@ protected void doStart(Model model, ActionListener<Boolean> listener) {
         listener.onResponse(true);
     }
 
-    private void init() {
-        sender.start();
+    private void init(ActionListener<Void> listener) {
+        sender.startAsynchronously(listener);
     }
 
     @Override

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/amazonbedrock/AmazonBedrockService.java

@@ -75,6 +75,12 @@
 import static org.elasticsearch.xpack.inference.services.amazonbedrock.AmazonBedrockProviderCapabilities.getProviderDefaultSimilarityMeasure;
 import static org.elasticsearch.xpack.inference.services.amazonbedrock.AmazonBedrockProviderCapabilities.providerAllowsTaskType;
 
+/**
+ * TODO we should remove AmazonBedrockService's dependency on SenderService. Bedrock leverages its own SDK with handles sending requests
+ * and already implements rate limiting.
+ *
+ * https://github.com/elastic/ml-team/issues/1706
+ */
 public class AmazonBedrockService extends SenderService {
     public static final String NAME = "amazonbedrock";
     private static final String SERVICE_NAME = "Amazon Bedrock";

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/amazonbedrock/client/AmazonBedrockRequestSender.java

@@ -75,7 +75,7 @@ public Factory(
 
         public Sender createSender() {
             // ensure this is started
-            bedrockRequestSender.start();
+            bedrockRequestSender.startSynchronously();
             return bedrockRequestSender;
         }
     }
@@ -98,7 +98,13 @@ protected AmazonBedrockRequestSender(
     }
 
     @Override
-    public void start() {
+    public void startAsynchronously(ActionListener<Void> listener) {
+
+        throw new UnsupportedOperationException("not implemented");
+    }
+
+    @Override
+    public void startSynchronously() {
         if (started.compareAndSet(false, true)) {
             // The manager must be started before the executor service. That way we guarantee that the http client
             // is ready prior to the service attempting to use the http client to send a request

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/elastic/authorization/ElasticInferenceServiceAuthorizationRequestHandler.java

@@ -12,6 +12,7 @@
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.SubscribableListener;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.TimeValue;
@@ -82,37 +83,33 @@ public void getAuthorization(ActionListener<ElasticInferenceServiceAuthorization
                 return;
             }
 
-            // ensure that the sender is initialized
-            sender.start();
-
-            ActionListener<InferenceServiceResults> newListener = ActionListener.wrap(results -> {
-                if (results instanceof ElasticInferenceServiceAuthorizationResponseEntity authResponseEntity) {
-                    logger.debug(() -> Strings.format("Received authorization information from gateway %s", authResponseEntity));
-                    listener.onResponse(ElasticInferenceServiceAuthorizationModel.of(authResponseEntity));
-                } else {
-                    var errorMessage = Strings.format(
-                        "%s Received an invalid response type from the Elastic Inference Service: %s",
-                        FAILED_TO_RETRIEVE_MESSAGE,
-                        results.getClass().getSimpleName()
-                    );
-
-                    logger.warn(errorMessage);
-                    listener.onFailure(new ElasticsearchException(errorMessage));
-                }
-                requestCompleteLatch.countDown();
-            }, e -> {
+            var handleFailuresListener = listener.delegateResponse((authModelListener, e) -> {
                 // unwrap because it's likely a retry exception
                 var exception = ExceptionsHelper.unwrapCause(e);
 
                 logger.warn(Strings.format(FAILED_TO_RETRIEVE_MESSAGE + " Encountered an exception: %s", exception), exception);
-                listener.onFailure(e);
-                requestCompleteLatch.countDown();
+                authModelListener.onFailure(e);
             });
 
-            var requestMetadata = extractRequestMetadataFromThreadContext(threadPool.getThreadContext());
-            var request = new ElasticInferenceServiceAuthorizationRequest(baseUrl, getCurrentTraceInfo(), requestMetadata);
+            SubscribableListener.newForked(sender::startAsynchronously).<InferenceServiceResults>andThen((authListener) -> {
+                var requestMetadata = extractRequestMetadataFromThreadContext(threadPool.getThreadContext());
+                var request = new ElasticInferenceServiceAuthorizationRequest(baseUrl, getCurrentTraceInfo(), requestMetadata);
+                sender.sendWithoutQueuing(logger, request, AUTH_RESPONSE_HANDLER, DEFAULT_AUTH_TIMEOUT, authListener);
+            }).andThenApply(authResult -> {
+                if (authResult instanceof ElasticInferenceServiceAuthorizationResponseEntity authResponseEntity) {
+                    logger.debug(() -> Strings.format("Received authorization information from gateway %s", authResponseEntity));
+                    return ElasticInferenceServiceAuthorizationModel.of(authResponseEntity);
+                }
+
+                var errorMessage = Strings.format(
+                    "%s Received an invalid response type from the Elastic Inference Service: %s",
+                    FAILED_TO_RETRIEVE_MESSAGE,
+                    authResult.getClass().getSimpleName()
+                );
 
-            sender.sendWithoutQueuing(logger, request, AUTH_RESPONSE_HANDLER, DEFAULT_AUTH_TIMEOUT, newListener);
+                logger.warn(errorMessage);
+                throw new ElasticsearchException(errorMessage);
+            }).addListener(ActionListener.runAfter(handleFailuresListener, requestCompleteLatch::countDown));
         } catch (Exception e) {
             logger.warn(Strings.format("Retrieving the authorization information encountered an exception: %s", e));
             requestCompleteLatch.countDown();