Cat API: Add wildcard support for header names

This adds wildcard support (simple regexes) for specifying header names.
Aliases are supported as well.

Closes #10811

docs/reference/cat.asciidoc

@@ -66,6 +66,10 @@ only those columns to appear.
 192.168.56.30 9300 43.9 Ramsey, Doug
 --------------------------------------------------
 
+You can also request multiple columns using simple wildcards like
+`/_cat/thread_pool?h=ip,bulk.*` to get all headers (or aliases) starting
+with `bulk.`.
+
 [float]
 [[numeric-formats]]
 === Numeric formats

rest-api-spec/test/cat.thread_pool/10_basic.yaml

@@ -29,6 +29,18 @@
                /  #pid       id          host       ip                          port
                ^  (\d+  \s+  \S{4}  \s+  \S+   \s+  (\d{1,3}\.){3}\d{1,3}  \s+  (\d+|-) \s+ \n)+  $/
 
+
+  - do:
+      cat.thread_pool:
+          h: bulk.m*
+
+  - match:
+      $body: |
+               /^ bulk.max  \s+  bulk.min \s+ \n
+                 (\s+  \d+  \s+  \d+  \s+ \n)+  $/
+
+#(\s+  \d+  \s+  \d+ \n)+  $/
+
   - do:
       cat.thread_pool:
           h: id,ba,fa,gea,ga,ia,maa,ma,oa,pa

src/main/java/org/elasticsearch/rest/action/support/RestTable.java

@@ -24,6 +24,7 @@ import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.Table;
 import org.elasticsearch.common.io.UTF8StreamWriter;
 import org.elasticsearch.common.io.stream.BytesStreamOutput;
+import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.unit.SizeValue;
 import org.elasticsearch.common.unit.TimeValue;
@@ -32,8 +33,7 @@ import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.rest.*;
 
 import java.io.IOException;
-import java.util.ArrayList;
+import java.util.*;
-import java.util.List;
 
 /**
  */
@@ -96,11 +96,12 @@ public class RestTable {
         return new BytesRestResponse(RestStatus.OK, BytesRestResponse.TEXT_CONTENT_TYPE, bytesOut.bytes());
     }
 
-    private static List<DisplayHeader> buildDisplayHeaders(Table table, RestRequest request) {
+    static List<DisplayHeader> buildDisplayHeaders(Table table, RestRequest request) {
-        String pHeaders = request.param("h");
         List<DisplayHeader> display = new ArrayList<>();
-        if (pHeaders != null) {
+        if (request.hasParam("h")) {
-            for (String possibility : Strings.splitStringByCommaToArray(pHeaders)) {
+            Set<String> headers = expandHeadersFromRequest(table, request);
+
+            for (String possibility : headers) {
                 DisplayHeader dispHeader = null;
 
                 if (table.getAsMap().containsKey(possibility)) {
@@ -147,6 +148,41 @@ public class RestTable {
         return display;
     }
 
+    /**
+     * Extracts all the required fields from the RestRequest 'h' parameter. In order to support wildcards like
+     * 'bulk.*' this needs potentially parse all the configured headers and its aliases and needs to ensure
+     * that everything is only added once to the returned headers, even if 'h=bulk.*.bulk.*' is specified
+     * or some headers are contained twice due to matching aliases
+     */
+    private static Set<String> expandHeadersFromRequest(Table table, RestRequest request) {
+        Set<String> headers = new LinkedHashSet<>(table.getHeaders().size());
+
+        Map<String, Table.Cell> headerMap = table.getHeaderMap();
+        // check headers and aliases
+        for (String header : Strings.splitStringByCommaToArray(request.param("h"))) {
+            if (Regex.isSimpleMatchPattern(header)) {
+                for (Map.Entry<String, Table.Cell> configuredHeaderEntry : headerMap.entrySet()) {
+                    String configuredHeader = configuredHeaderEntry.getKey();
+                    if (Regex.simpleMatch(header, configuredHeader)) {
+                        headers.add(configuredHeader);
+                    } else if (configuredHeaderEntry.getValue().attr.containsKey("alias")) {
+                        String[] aliases = Strings.splitStringByCommaToArray(configuredHeaderEntry.getValue().attr.get("alias"));
+                        for (String alias : aliases) {
+                            if (Regex.simpleMatch(header, alias)) {
+                                headers.add(configuredHeader);
+                                break;
+                            }
+                        }
+                    }
+                }
+            } else {
+                headers.add(header);
+            }
+        }
+
+        return headers;
+    }
+
     public static int[] buildHelpWidths(Table table, RestRequest request) {
         int[] width = new int[3];
         for (Table.Cell cell : table.getHeaders()) {

src/test/java/org/elasticsearch/rest/action/support/RestTableTest.java

@@ -0,0 +1,82 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.rest.action.support;
+
+import org.elasticsearch.common.Table;
+import org.elasticsearch.test.ElasticsearchTestCase;
+import org.elasticsearch.test.rest.FakeRestRequest;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.elasticsearch.rest.action.support.RestTable.buildDisplayHeaders;
+import static org.hamcrest.Matchers.*;
+
+public class RestTableTest extends ElasticsearchTestCase {
+
+    private Table table = new Table();
+    private FakeRestRequest restRequest = new FakeRestRequest();
+
+    @Before
+    public void setup() {
+        table.startHeaders();
+        table.addCell("bulk.foo", "alias:f;desc:foo");
+        table.addCell("bulk.bar", "alias:b;desc:bar");
+        // should be matched as well due to the aliases
+        table.addCell("aliasedBulk", "alias:bulkWhatever;desc:bar");
+        table.addCell("aliasedSecondBulk", "alias:foobar,bulkolicious,bulkotastic;desc:bar");
+        // no match
+        table.addCell("unmatched", "alias:un.matched;desc:bar");
+        // invalid alias
+        table.addCell("invalidAliasesBulk", "alias:,,,;desc:bar");
+        table.endHeaders();
+    }
+
+    @Test
+    public void testThatDisplayHeadersSupportWildcards() throws Exception {
+        restRequest.params().put("h", "bulk*");
+        List<RestTable.DisplayHeader> headers = buildDisplayHeaders(table, restRequest);
+
+        List<String> headerNames = getHeaderNames(headers);
+        assertThat(headerNames, containsInAnyOrder("bulk.foo", "bulk.bar", "aliasedBulk", "aliasedSecondBulk"));
+        assertThat(headerNames, not(hasItem("unmatched")));
+    }
+
+    @Test
+    public void testThatDisplayHeadersAreNotAddedTwice() throws Exception {
+        restRequest.params().put("h", "nonexistent,bulk*,bul*");
+        List<RestTable.DisplayHeader> headers = buildDisplayHeaders(table, restRequest);
+
+        List<String> headerNames = getHeaderNames(headers);
+        assertThat(headerNames, containsInAnyOrder("bulk.foo", "bulk.bar", "aliasedBulk", "aliasedSecondBulk"));
+        assertThat(headerNames, not(hasItem("unmatched")));
+    }
+
+    private List<String> getHeaderNames(List<RestTable.DisplayHeader> headers) {
+        List<String> headerNames = new ArrayList<>();
+        for (RestTable.DisplayHeader header : headers) {
+            headerNames.add(header.name);
+        }
+
+        return headerNames;
+    }
+}