From 7ddbda4c20a8dceb882f5470303fa2999ee05508 Mon Sep 17 00:00:00 2001
From: Marios Trivyzas <matriv@gmail.com>
Date: Fri, 6 Mar 2020 11:04:01 +0100
Subject: [PATCH] Check for query cancellation during rewrite (#53166) (#53203)

With ExitableDirectoryReader in place, check for query cancellation
during QueryPhase#preProcess where the query rewriting takes place.

Follows: #52822

(cherry picked from commit 0d38626d8e6e9e2620a7a446b617a2ac42852461)
---
 .../search/query/QueryPhase.java              | 19 ++++++-
 .../search/query/QueryPhaseTests.java         | 56 +++++++++++++++++++
 2 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/server/src/main/java/org/elasticsearch/search/query/QueryPhase.java b/server/src/main/java/org/elasticsearch/search/query/QueryPhase.java
index 7f91d778105..c85499411be 100644
--- a/server/src/main/java/org/elasticsearch/search/query/QueryPhase.java
+++ b/server/src/main/java/org/elasticsearch/search/query/QueryPhase.java
@@ -110,7 +110,24 @@ public class QueryPhase implements SearchPhase {
 
     @Override
     public void preProcess(SearchContext context) {
-        context.preProcess(true);
+        final Runnable cancellation;
+        if (context.lowLevelCancellation()) {
+            SearchShardTask task = context.getTask();
+            cancellation = context.searcher().addQueryCancellation(() -> {
+                if (task.isCancelled()) {
+                    throw new TaskCancelledException("cancelled");
+                }
+            });
+        } else {
+            cancellation = null;
+        }
+        try {
+            context.preProcess(true);
+        } finally {
+            if (cancellation != null) {
+                context.searcher().removeQueryCancellation(cancellation);
+            }
+        }
     }
 
     @Override
diff --git a/server/src/test/java/org/elasticsearch/search/query/QueryPhaseTests.java b/server/src/test/java/org/elasticsearch/search/query/QueryPhaseTests.java
index 4b70153261d..95330ea8fd0 100644
--- a/server/src/test/java/org/elasticsearch/search/query/QueryPhaseTests.java
+++ b/server/src/test/java/org/elasticsearch/search/query/QueryPhaseTests.java
@@ -53,6 +53,8 @@ import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.LeafCollector;
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.MatchNoDocsQuery;
+import org.apache.lucene.search.MultiTermQuery;
+import org.apache.lucene.search.PrefixQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.ScoreDoc;
 import org.apache.lucene.search.Sort;
@@ -76,6 +78,7 @@ import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.NumberFieldMapper;
 import org.elasticsearch.index.query.ParsedQuery;
+import org.elasticsearch.index.query.QueryShardContext;
 import org.elasticsearch.index.search.ESToParentBlockJoinQuery;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.index.shard.IndexShardTestCase;
@@ -84,6 +87,7 @@ import org.elasticsearch.search.internal.ContextIndexSearcher;
 import org.elasticsearch.search.internal.ScrollContext;
 import org.elasticsearch.search.internal.SearchContext;
 import org.elasticsearch.search.sort.SortAndFormats;
+import org.elasticsearch.tasks.TaskCancelledException;
 import org.elasticsearch.test.TestSearchContext;
 
 import java.io.IOException;
@@ -834,7 +838,59 @@ public class QueryPhaseTests extends IndexShardTestCase {
 
         reader.close();
         dir.close();
+    }
 
+    public void testCancellationDuringPreprocess() throws IOException {
+        try (Directory dir = newDirectory();
+             RandomIndexWriter w = new RandomIndexWriter(random(), dir, newIndexWriterConfig())) {
+
+            for (int i = 0; i < 10; i++) {
+                Document doc = new Document();
+                StringBuilder sb = new StringBuilder();
+                for (int j = 0; j < i; j++) {
+                    sb.append('a');
+                }
+                doc.add(new StringField("foo", sb.toString(), Store.NO));
+                w.addDocument(doc);
+            }
+            w.flush();
+            w.close();
+
+            try (IndexReader reader = DirectoryReader.open(dir)) {
+                TestSearchContext context = new TestSearchContextWithRewriteAndCancellation(
+                        null, indexShard, newContextSearcher(reader));
+                PrefixQuery prefixQuery = new PrefixQuery(new Term("foo", "a"));
+                prefixQuery.setRewriteMethod(MultiTermQuery.SCORING_BOOLEAN_REWRITE);
+                context.parsedQuery(new ParsedQuery(prefixQuery));
+                SearchShardTask task = mock(SearchShardTask.class);
+                when(task.isCancelled()).thenReturn(true);
+                context.setTask(task);
+                expectThrows(TaskCancelledException.class, () -> new QueryPhase().preProcess(context));
+            }
+        }
+    }
+
+    private static class TestSearchContextWithRewriteAndCancellation extends TestSearchContext {
+
+        private TestSearchContextWithRewriteAndCancellation(QueryShardContext queryShardContext,
+                                                            IndexShard indexShard,
+                                                            ContextIndexSearcher searcher) {
+            super(queryShardContext, indexShard, searcher);
+        }
+
+        @Override
+        public void preProcess(boolean rewrite) {
+            try {
+                searcher().rewrite(query());
+            } catch (IOException e) {
+                fail("IOException shouldn't be thrown");
+            }
+        }
+
+        @Override
+        public boolean lowLevelCancellation() {
+            return true;
+        }
     }
 
     private static ContextIndexSearcher newContextSearcher(IndexReader reader) throws IOException {