From 4e9556f41551a5f46b4cca21952b2e092c9a3404 Mon Sep 17 00:00:00 2001
From: Allison Easton <allison.easton@mongodb.com>
Date: Fri, 25 Feb 2022 08:53:17 +0000
Subject: SERVER-63726 Defragmentation should be tested on a single collection
 as well as on multiple collections

---
 jstests/sharding/defragment_large_collection.js | 88 +++++++++++++------------
 1 file changed, 45 insertions(+), 43 deletions(-)

diff --git a/jstests/sharding/defragment_large_collection.js b/jstests/sharding/defragment_large_collection.js
index 12ce30040c4..b14539a70b7 100644
--- a/jstests/sharding/defragment_large_collection.js
+++ b/jstests/sharding/defragment_large_collection.js
@@ -16,73 +16,75 @@ Random.setRandomSeed();
 
 // Test parameters
 const numShards = Random.randInt(7) + 1;
-const numCollections = 3;
 const maxChunkFillMB = 20;
 const maxChunkSizeMB = 30;
 const chunkSpacing = 1000;
 
-jsTest.log("Creating new test with " + numCollections + " collections over " + numShards +
-           " shards.");
+jsTest.log("Creating new sharding test with " + numShards + " shards.");
 
 const st = new ShardingTest({
     mongos: 1,
     shards: numShards,
     other: {
-        enableBalancer: false,
+        enableBalancer: true,
         configOptions: {setParameter: {logComponentVerbosity: tojson({sharding: {verbosity: 3}})}},
     }
 });
 
-// setup the database for the test
-assert.commandWorked(st.s.adminCommand({enableSharding: 'db'}));
-const db = st.getDB('db');
-const coll_prefix = "testColl_";
+let runTest = function(numCollections, dbName) {
+    jsTest.log("Running test with " + numCollections + " collections.");
+    // setup the database for the test
+    assert.commandWorked(st.s.adminCommand({enableSharding: dbName}));
+    const db = st.getDB(dbName);
+    const coll_prefix = "testColl_";
 
-let collections = [];
+    let collections = [];
 
-for (let i = 0; i < numCollections; ++i) {
-    const numChunks = Random.randInt(28) + 2;
-    const numZones = Random.randInt(numChunks / 2);
-    const docSizeBytes = Random.randInt(1024 * 1024) + 50;
+    for (let i = 0; i < numCollections; ++i) {
+        const numChunks = Random.randInt(28) + 2;
+        const numZones = Random.randInt(numChunks / 2);
+        const docSizeBytes = Random.randInt(1024 * 1024) + 50;
 
-    const coll = db[coll_prefix + i];
+        const coll = db[coll_prefix + i];
 
-    defragmentationUtil.createFragmentedCollection(st.s,
-                                                   coll.getFullName(),
-                                                   numChunks,
-                                                   maxChunkFillMB,
-                                                   numZones,
-                                                   docSizeBytes,
-                                                   chunkSpacing,
-                                                   true);
+        defragmentationUtil.createFragmentedCollection(st.s,
+                                                       coll.getFullName(),
+                                                       numChunks,
+                                                       maxChunkFillMB,
+                                                       numZones,
+                                                       docSizeBytes,
+                                                       chunkSpacing,
+                                                       true);
 
-    collections.push(coll);
-}
+        collections.push(coll);
+    }
 
-st.printShardingStatus();
+    st.printShardingStatus();
 
-collections.forEach((coll) => {
-    assert.commandWorked(st.s.adminCommand({
-        configureCollectionBalancing: coll.getFullName(),
-        defragmentCollection: true,
-        chunkSize: maxChunkSizeMB,
-    }));
-});
+    collections.forEach((coll) => {
+        assert.commandWorked(st.s.adminCommand({
+            configureCollectionBalancing: coll.getFullName(),
+            defragmentCollection: true,
+            chunkSize: maxChunkSizeMB,
+        }));
+    });
 
-st.startBalancer();
+    collections.forEach((coll) => {
+        const ns = coll.getFullName();
 
-collections.forEach((coll) => {
-    const ns = coll.getFullName();
+        // Wait for defragmentation to end and check collection final state
+        defragmentationUtil.waitForEndOfDefragmentation(st.s, ns);
+        const finalNumberChunks = findChunksUtil.countChunksForNs(st.s.getDB('config'), ns);
+        jsTest.log("Finished defragmentation of collection " + coll + " with " + finalNumberChunks +
+                   " chunks.");
+        defragmentationUtil.checkPostDefragmentationState(st.s, ns, maxChunkSizeMB, "key");
+    });
 
-    // Wait for defragmentation to end and check collection final state
-    defragmentationUtil.waitForEndOfDefragmentation(st.s, ns);
-    const finalNumberChunks = findChunksUtil.countChunksForNs(st.s.getDB('config'), ns);
-    jsTest.log("Finished defragmentation of collection " + coll + " with " + finalNumberChunks +
-               " chunks.");
-    defragmentationUtil.checkPostDefragmentationState(st.s, ns, maxChunkSizeMB, "key");
-});
+    st.printShardingStatus();
+};
 
-st.printShardingStatus();
+runTest(1, "singleCollection");
+runTest(3, "threeCollections");
 
 st.stop();
 })();
-- 
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