SERVER-43322 Add tunable oplog stone sizes and track truncation speeds

(cherry picked from commit 294a8f68615710b47936d5ee42439d01538ac746)

SERVER-43322 Disallow oplog_sampling.js on inMemory storage enigne

(cherry picked from commit b35dd89515473c97a87b3c06897e8a7ab51c93cc)

This backport was not a straightforward cherry-pick due to SERVER-40168
existing in master and not v4.2.

2 files changed, 49 insertions, 0 deletions

diff --git a/jstests/replsets/oplog_rollover.js b/jstests/replsets/oplog_rollover.js
index b9a08bbb80e..5199a1802fc 100644
--- a/jstests/replsets/oplog_rollover.js
+++ b/jstests/replsets/oplog_rollover.js
@@ -104,6 +104,14 @@ function doTest(storageEngine) {
         assert.soon(() => {
             return numInsertOplogEntry(secondaryOplog) === 2;
         }, "Timeout waiting for oplog to roll over on secondary");
+
+        if (jsTest.options().storageEngine == "wiredTiger") {
+            const res = primary.getDB("test").runCommand({serverStatus: 1});
+            assert.commandWorked(res);
+            assert.eq(res.oplogTruncation.truncateCount, 1, tojson(res.oplogTruncation));
+            assert.gt(
+                res.oplogTruncation.totalTimeTruncatingMicros, 0, tojson(res.oplogTruncation));
+        }
     } else {
         // Only test that oplog truncation will eventually happen.
         let numInserted = 2;
diff --git a/jstests/replsets/oplog_sampling.js b/jstests/replsets/oplog_sampling.js
new file mode 100644
index 00000000000..3407b1826c9
--- /dev/null
+++ b/jstests/replsets/oplog_sampling.js
@@ -0,0 +1,41 @@
+/**
+ * Ensure serverStatus reports the total time spent sampling the oplog for all storage engines that
+ * support OplogStones.
+ * @tags: [ requires_wiredtiger, requires_persistence ]
+ */
+(function() {
+"use strict";
+
+// Force oplog sampling to occur on start up for small numbers of oplog inserts.
+const replSet = new ReplSetTest(
+    {nodes: 1, nodeOptions: {setParameter: {"maxOplogTruncationPointsDuringStartup": 10}}});
+replSet.startSet();
+replSet.initiate();
+
+let coll = replSet.getPrimary().getDB("test").getCollection("testcoll");
+
+let res = replSet.getPrimary().getDB("test").serverStatus();
+assert.commandWorked(res);
+
+// Small (or empty) oplogs should be processed by scanning.
+assert.gt(res.oplogTruncation.totalTimeProcessingMicros, 0);
+assert.eq(res.oplogTruncation.processingMethod, "scanning");
+
+// Insert enough documents to force oplog sampling to occur on the following start up.
+const maxOplogDocsForScanning = 2000;
+for (let i = 0; i < maxOplogDocsForScanning + 1; i++) {
+    assert.commandWorked(coll.insert({m: 1 + i}));
+}
+
+// Restart replica set to load entries from the oplog for sampling.
+replSet.stopSet(null /* signal */, true /* forRestart */);
+replSet.startSet({restart: true});
+
+res = replSet.getPrimary().getDB("test").serverStatus();
+assert.commandWorked(res);
+
+assert.gt(res.oplogTruncation.totalTimeProcessingMicros, 0);
+assert.eq(res.oplogTruncation.processingMethod, "sampling");
+
+replSet.stopSet();
+})();