SERVER-26625 Make collStats command consistent on background index reporting

2 files changed, 63 insertions, 2 deletions

diff --git a/jstests/noPassthroughWithMongod/collstats_shows_ready_and_in_progress_indexes.js b/jstests/noPassthroughWithMongod/collstats_shows_ready_and_in_progress_indexes.js
new file mode 100644
index 00000000000..3c509bdc32f
--- /dev/null
+++ b/jstests/noPassthroughWithMongod/collstats_shows_ready_and_in_progress_indexes.js
@@ -0,0 +1,54 @@
+/**
+ * Ensures that the 'collStats' command lists indexes that are ready and in-progress.
+ */
+(function() {
+    'use strict';
+
+    load('jstests/noPassthrough/libs/index_build.js');
+
+    const failpoint = 'hangAfterStartingIndexBuildUnlocked';
+    assert.commandWorked(db.adminCommand({configureFailPoint: failpoint, mode: "alwaysOn"}));
+
+    const conn = db.getMongo();
+
+    const collName = 'collStats';
+    const coll = db.getCollection(collName);
+
+    const bulk = coll.initializeUnorderedBulkOp();
+    const numDocs = 5;
+    for (let i = 0; i < numDocs; i++) {
+        bulk.insert({a: i, b: i * i});
+    }
+    assert.commandWorked(bulk.execute());
+
+    // Start two index builds in the background.
+    const awaitParallelShell = startParallelShell(() => {
+        db.runCommand({
+            createIndexes: 'collStats',
+            indexes: [
+                {key: {a: 1}, name: 'a_1', background: true},
+                {key: {b: 1}, name: 'b_1', background: true}
+            ]
+        });
+    }, conn.port);
+
+    // Wait until both index builds begin.
+    IndexBuildTest.waitForIndexBuildToStart(db);
+
+    const collStats = assert.commandWorked(db.runCommand({collStats: collName}));
+
+    // Ensure the existence of the indexes in the following fields: 'indexSizes', 'nindexes' and
+    // 'indexDetails'.
+    assert.gte(collStats.indexSizes._id_, 0);
+    assert.gte(collStats.indexSizes.a_1, 0);
+    assert.gte(collStats.indexSizes.b_1, 0);
+
+    assert.eq(3, collStats.nindexes);
+
+    assert.eq(2, collStats.indexBuilds.length);
+    assert.eq('a_1', collStats.indexBuilds[0]);
+    assert.eq('b_1', collStats.indexBuilds[1]);
+
+    assert.commandWorked(db.adminCommand({configureFailPoint: failpoint, mode: "off"}));
+    awaitParallelShell();
+})();
diff --git a/src/mongo/db/stats/storage_stats.cpp b/src/mongo/db/stats/storage_stats.cpp
index fed4a513a90..88ab2323839 100644
--- a/src/mongo/db/stats/storage_stats.cpp
+++ b/src/mongo/db/stats/storage_stats.cpp
@@ -86,11 +86,13 @@ Status appendCollectionStorageStats(OperationContext* opCtx,
     recordStore->appendCustomStats(opCtx, result, scale);
 
     IndexCatalog* indexCatalog = collection->getIndexCatalog();
-    result->append("nindexes", indexCatalog->numIndexesReady(opCtx));
+    result->append("nindexes", indexCatalog->numIndexesTotal(opCtx));
 
     BSONObjBuilder indexDetails;
+    std::vector<std::string> indexBuilds;
 
-    std::unique_ptr<IndexCatalog::IndexIterator> it = indexCatalog->getIndexIterator(opCtx, false);
+    std::unique_ptr<IndexCatalog::IndexIterator> it =
+        indexCatalog->getIndexIterator(opCtx, /*includeUnfinishedIndexes=*/true);
     while (it->more()) {
         const IndexCatalogEntry* entry = it->next();
         const IndexDescriptor* descriptor = entry->descriptor();
@@ -101,9 +103,14 @@ Status appendCollectionStorageStats(OperationContext* opCtx,
         if (iam->appendCustomStats(opCtx, &bob, scale)) {
             indexDetails.append(descriptor->indexName(), bob.obj());
         }
+
+        if (!entry->isReady(opCtx)) {
+            indexBuilds.push_back(descriptor->indexName());
+        }
     }
 
     result->append("indexDetails", indexDetails.obj());
+    result->append("indexBuilds", indexBuilds);
 
     BSONObjBuilder indexSizes;
     long long indexSize = collection->getIndexSize(opCtx, &indexSizes, scale);