LLREST: Introduce a strict mode (#33708)

Introduces `RestClientBuilder#setStrictDeprecationMode` which defaults
to false but when set to true, causes a rest request to fail if a
deprecation warning header comes back in the response from Elasticsearch.
This should be valueable to Elasticsearch's tests, especially those of the
High Level REST Client where they will help catch divergence between the
client and the server.

client/rest/src/main/java/org/elasticsearch/client/Response.java

@@ -26,7 +26,11 @@ import org.apache.http.HttpResponse;
 import org.apache.http.RequestLine;
 import org.apache.http.StatusLine;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Objects;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * Holds an elasticsearch response. It wraps the {@link HttpResponse} returned and associates it with
@@ -96,6 +100,46 @@ public class Response {
         return response.getEntity();
     }
 
+    private static final Pattern WARNING_HEADER_PATTERN = Pattern.compile(
+            "299 " + // warn code
+            "Elasticsearch-\\d+\\.\\d+\\.\\d+(?:-(?:alpha|beta|rc)\\d+)?(?:-SNAPSHOT)?-(?:[a-f0-9]{7}|Unknown) " + // warn agent
+            "\"((?:\t| |!|[\\x23-\\x5B]|[\\x5D-\\x7E]|[\\x80-\\xFF]|\\\\|\\\\\")*)\" " + // quoted warning value, captured
+            // quoted RFC 1123 date format
+            "\"" + // opening quote
+            "(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun), " + // weekday
+            "\\d{2} " + // 2-digit day
+            "(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) " + // month
+            "\\d{4} " + // 4-digit year
+            "\\d{2}:\\d{2}:\\d{2} " + // (two-digit hour):(two-digit minute):(two-digit second)
+            "GMT" + // GMT
+            "\""); // closing quote
+
+    /**
+     * Returns a list of all warning headers returned in the response.
+     */
+    public List<String> getWarnings() {
+        List<String> warnings = new ArrayList<>();
+        for (Header header : response.getHeaders("Warning")) {
+            String warning = header.getValue();
+            final Matcher matcher = WARNING_HEADER_PATTERN.matcher(warning);
+            if (matcher.matches()) {
+                warnings.add(matcher.group(1));
+                continue;
+            }
+            warnings.add(warning);
+        }
+        return warnings;
+    }
+
+    /**
+     * Returns true if there is at least one warning header returned in the
+     * response.
+     */
+    public boolean hasWarnings() {
+        Header[] warnings = response.getHeaders("Warning");
+        return warnings != null && warnings.length > 0;
+    }
+
     HttpResponse getHttpResponse() {
         return response;
     }

client/rest/src/main/java/org/elasticsearch/client/ResponseException.java

@@ -58,6 +58,10 @@ public final class ResponseException extends IOException {
             response.getStatusLine().toString()
         );
 
+        if (response.hasWarnings()) {
+            message += "\n" + "Warnings: " + response.getWarnings();
+        }
+
         HttpEntity entity = response.getEntity();
         if (entity != null) {
             if (entity.isRepeatable() == false) {

client/rest/src/main/java/org/elasticsearch/client/RestClient.java

@@ -110,15 +110,17 @@ public class RestClient implements Closeable {
     private final FailureListener failureListener;
     private final NodeSelector nodeSelector;
     private volatile NodeTuple<List<Node>> nodeTuple;
+    private final boolean strictDeprecationMode;
 
-    RestClient(CloseableHttpAsyncClient client, long maxRetryTimeoutMillis, Header[] defaultHeaders,
-               List<Node> nodes, String pathPrefix, FailureListener failureListener, NodeSelector nodeSelector) {
+    RestClient(CloseableHttpAsyncClient client, long maxRetryTimeoutMillis, Header[] defaultHeaders, List<Node> nodes, String pathPrefix,
+            FailureListener failureListener, NodeSelector nodeSelector, boolean strictDeprecationMode) {
         this.client = client;
         this.maxRetryTimeoutMillis = maxRetryTimeoutMillis;
         this.defaultHeaders = Collections.unmodifiableList(Arrays.asList(defaultHeaders));
         this.failureListener = failureListener;
         this.pathPrefix = pathPrefix;
         this.nodeSelector = nodeSelector;
+        this.strictDeprecationMode = strictDeprecationMode;
         setNodes(nodes);
     }
 
@@ -296,7 +298,11 @@ public class RestClient implements Closeable {
                     Response response = new Response(request.getRequestLine(), node.getHost(), httpResponse);
                     if (isSuccessfulResponse(statusCode) || ignoreErrorCodes.contains(response.getStatusLine().getStatusCode())) {
                         onResponse(node);
-                        listener.onSuccess(response);
+                        if (strictDeprecationMode && response.hasWarnings()) {
+                            listener.onDefinitiveFailure(new ResponseException(response));
+                        } else {
+                            listener.onSuccess(response);
+                        }
                     } else {
                         ResponseException responseException = new ResponseException(response);
                         if (isRetryStatus(statusCode)) {

client/rest/src/main/java/org/elasticsearch/client/RestClientBuilder.java

@@ -56,6 +56,7 @@ public final class RestClientBuilder {
     private RequestConfigCallback requestConfigCallback;
     private String pathPrefix;
     private NodeSelector nodeSelector = NodeSelector.ANY;
+    private boolean strictDeprecationMode = false;
 
     /**
      * Creates a new builder instance and sets the hosts that the client will send requests to.
@@ -185,6 +186,15 @@ public final class RestClientBuilder {
         return this;
     }
 
+    /**
+     * Whether the REST client should return any response containing at least
+     * one warning header as a failure.
+     */
+    public RestClientBuilder setStrictDeprecationMode(boolean strictDeprecationMode) {
+        this.strictDeprecationMode = strictDeprecationMode;
+        return this;
+    }
+
     /**
      * Creates a new {@link RestClient} based on the provided configuration.
      */
@@ -199,7 +209,7 @@ public final class RestClientBuilder {
             }
         });
         RestClient restClient = new RestClient(httpClient, maxRetryTimeout, defaultHeaders, nodes,
-                pathPrefix, failureListener, nodeSelector);
+                pathPrefix, failureListener, nodeSelector, strictDeprecationMode);
         httpClient.start();
         return restClient;
     }

client/rest/src/test/java/org/elasticsearch/client/RestClientMultipleHostsTests.java

@@ -115,7 +115,7 @@ public class RestClientMultipleHostsTests extends RestClientTestCase {
         }
         nodes = Collections.unmodifiableList(nodes);
         failureListener = new HostsTrackingFailureListener();
-        return new RestClient(httpClient, 10000, new Header[0], nodes, null, failureListener, nodeSelector);
+        return new RestClient(httpClient, 10000, new Header[0], nodes, null, failureListener, nodeSelector, false);
     }
 
     /**

client/rest/src/test/java/org/elasticsearch/client/RestClientSingleHostTests.java

@@ -148,7 +148,7 @@ public class RestClientSingleHostTests extends RestClientTestCase {
         node = new Node(new HttpHost("localhost", 9200));
         failureListener = new HostsTrackingFailureListener();
         restClient = new RestClient(httpClient, 10000, defaultHeaders,
-                singletonList(node), null, failureListener, NodeSelector.ANY);
+                singletonList(node), null, failureListener, NodeSelector.ANY, false);
     }
 
     /**

client/rest/src/test/java/org/elasticsearch/client/RestClientTests.java

@@ -57,7 +57,7 @@ public class RestClientTests extends RestClientTestCase {
     public void testCloseIsIdempotent() throws IOException {
         List<Node> nodes = singletonList(new Node(new HttpHost("localhost", 9200)));
         CloseableHttpAsyncClient closeableHttpAsyncClient = mock(CloseableHttpAsyncClient.class);
-        RestClient restClient = new RestClient(closeableHttpAsyncClient, 1_000, new Header[0], nodes, null, null, null);
+        RestClient restClient = new RestClient(closeableHttpAsyncClient, 1_000, new Header[0], nodes, null, null, null, false);
         restClient.close();
         verify(closeableHttpAsyncClient, times(1)).close();
         restClient.close();
@@ -345,7 +345,7 @@ public class RestClientTests extends RestClientTestCase {
     private static RestClient createRestClient() {
         List<Node> nodes = Collections.singletonList(new Node(new HttpHost("localhost", 9200)));
         return new RestClient(mock(CloseableHttpAsyncClient.class), randomLongBetween(1_000, 30_000),
-                new Header[] {}, nodes, null, null, null);
+                new Header[] {}, nodes, null, null, null, false);
     }
 
     public void testRoundRobin() throws IOException {