REST client: introduce a strict deprecation mode

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

@@ -26,7 +26,11 @@
 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 HttpEntity getEntity() {
         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 @@ private static String buildMessage(Response response) throws 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 void completed(HttpResponse httpResponse) {
                     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 RestClientBuilder setNodeSelector(NodeSelector nodeSelector) {
         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 CloseableHttpAsyncClient run() {
             }
         });
         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 void run() {
         }
         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 void run() {
         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 @@ private static String assertSelectAllRejected( NodeTuple<List<Node>> nodeTuple,
     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 {