Adjust SearchableSnapshotsBlobStoreCacheIntegTests.testBlobStoreCache (#77758) (#77848)

This test sometimes fails (#77753) when it tries to refresh the
snapshot blob cache index while it wasn't created at all due to
the test index being completely empty with 0 documents indexed.

Having an empty index in this test does not make much sense
because the index will contain no segments and therefore no
segments file to cache in the system index.

This commit adjusts the test to always index at least
some docs.

Backport of #77758

Author: tlrx

x-pack/plugin/searchable-snapshots/src/internalClusterTest/java/org/elasticsearch/xpack/searchablesnapshots/cache/blob/SearchableSnapshotsBlobStoreCacheIntegTests.java

@@ -114,24 +114,24 @@ protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
         return Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings)).put(cacheSettings).build();
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/77753")
     public void testBlobStoreCache() throws Exception {
         final String indexName = randomAlphaOfLength(10).toLowerCase(Locale.ROOT);
         final boolean useSoftDeletes = randomBoolean();
         createIndex(indexName, Settings.builder().put(INDEX_SOFT_DELETES_SETTING.getKey(), useSoftDeletes).build());
 
         final NumShards numberOfShards = getNumShards(indexName);
 
-        final int numberOfDocs = scaledRandomIntBetween(0, 20_000);
-        if (numberOfDocs > 0) {
-            final List<IndexRequestBuilder> indexRequestBuilders = new ArrayList<>();
-            for (int i = numberOfDocs; i > 0; i--) {
-                XContentBuilder builder = XContentFactory.smileBuilder();
-                builder.startObject().field("text", randomRealisticUnicodeOfCodepointLengthBetween(5, 50)).field("num", i).endObject();
-                indexRequestBuilders.add(client().prepareIndex(indexName, SINGLE_MAPPING_NAME).setSource(builder));
-            }
-            indexRandom(true, true, true, indexRequestBuilders);
+        final int numberOfDocs = scaledRandomIntBetween(10, 20_000);
+        logger.info("--> indexing [{}] documents in [{}]", numberOfDocs, indexName);
+
+        final List<IndexRequestBuilder> indexRequestBuilders = new ArrayList<>();
+        for (int i = numberOfDocs; i > 0; i--) {
+            XContentBuilder builder = XContentFactory.smileBuilder();
+            builder.startObject().field("text", randomRealisticUnicodeOfCodepointLengthBetween(5, 50)).field("num", i).endObject();
+            indexRequestBuilders.add(client().prepareIndex(indexName, SINGLE_MAPPING_NAME).setSource(builder));
         }
+        indexRandom(true, true, true, indexRequestBuilders);
+
         if (randomBoolean()) {
             logger.info("--> force-merging index before snapshotting");
             final ForceMergeResponse forceMergeResponse = client().admin()
@@ -200,20 +200,18 @@ public void testBlobStoreCache() throws Exception {
         }
 
         logger.info("--> verifying cached documents in system index [{}]", SNAPSHOT_BLOB_CACHE_INDEX);
-        if (numberOfDocs > 0) {
-            ensureYellow(SNAPSHOT_BLOB_CACHE_INDEX);
-            refreshSystemIndex();
+        ensureYellow(SNAPSHOT_BLOB_CACHE_INDEX);
+        refreshSystemIndex();
 
-            logger.info("--> verifying system index [{}] data tiers preference", SNAPSHOT_BLOB_CACHE_INDEX);
-            assertThat(
-                systemClient().admin()
-                    .indices()
-                    .prepareGetSettings(SNAPSHOT_BLOB_CACHE_INDEX)
-                    .get()
-                    .getSetting(SNAPSHOT_BLOB_CACHE_INDEX, DataTierAllocationDecider.INDEX_ROUTING_PREFER),
-                equalTo("data_content,data_hot")
-            );
-        }
+        logger.info("--> verifying system index [{}] data tiers preference", SNAPSHOT_BLOB_CACHE_INDEX);
+        assertThat(
+            systemClient().admin()
+                .indices()
+                .prepareGetSettings(SNAPSHOT_BLOB_CACHE_INDEX)
+                .get()
+                .getSetting(SNAPSHOT_BLOB_CACHE_INDEX, DataTierAllocationDecider.INDEX_ROUTING_PREFER),
+            equalTo("data_content,data_hot")
+        );
 
         final long numberOfCachedBlobs = systemClient().prepareSearch(SNAPSHOT_BLOB_CACHE_INDEX)
             .setIndicesOptions(IndicesOptions.LENIENT_EXPAND_OPEN)
@@ -267,9 +265,7 @@ public void testBlobStoreCache() throws Exception {
         assertHitCount(client().prepareSearch(restoredAgainIndex).setSize(0).setTrackTotalHits(true).get(), numberOfDocs);
 
         logger.info("--> verifying that no extra cached blobs were indexed [{}]", SNAPSHOT_BLOB_CACHE_INDEX);
-        if (numberOfDocs > 0) {
-            refreshSystemIndex();
-        }
+        refreshSystemIndex();
         assertHitCount(
             systemClient().prepareSearch(SNAPSHOT_BLOB_CACHE_INDEX).setIndicesOptions(IndicesOptions.LENIENT_EXPAND_OPEN).setSize(0).get(),
             numberOfCachedBlobs