From 71864eaf8acab7b95d53d18578c2a38ab8ff83f0 Mon Sep 17 00:00:00 2001
From: Ali Mir <ali.mir@mongodb.com>
Date: Tue, 15 Jun 2021 21:02:54 +0000
Subject: SERVER-56605 Add testing for setting implicit default after a
 heartbeat reconfig

(cherry picked from commit 686dad084a738a44c2a298a98a21bdb81f0fe683)
---
 ...at_reconfig_propagates_default_write_concern.js | 58 ++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 jstests/replsets/heartbeat_reconfig_propagates_default_write_concern.js

diff --git a/jstests/replsets/heartbeat_reconfig_propagates_default_write_concern.js b/jstests/replsets/heartbeat_reconfig_propagates_default_write_concern.js
new file mode 100644
index 00000000000..4f713c100ca
--- /dev/null
+++ b/jstests/replsets/heartbeat_reconfig_propagates_default_write_concern.js
@@ -0,0 +1,58 @@
+/*
+ * Test that a heartbeat reconfig propagated from the primary to a new secondary
+ * successfully sets the default write concern on the secondary. To do this, we start either a PSS
+ * or PSA replica set. We then add a fourth secondary to the replica set, and verify that it sets
+ * its implicit default write concern correctly. We don't test cases with cluster-wide write concern
+ * set, because then the secondary won't set its implicit default write concern from a heartbeat
+ * reconfig.
+ * @tags: [requires_fcv_50]
+ */
+
+(function() {
+'use strict';
+
+load("jstests/replsets/rslib.js");
+
+function runTest(hasArbiter) {
+    jsTestLog("Running test with hasArbiter: " + tojson(hasArbiter));
+
+    let replSetNodes = 3;
+    if (hasArbiter) {
+        replSetNodes = [{}, {}, {arbiter: true}];
+    }
+    const rst = new ReplSetTest({
+        nodes: replSetNodes,
+    });
+
+    rst.startSet();
+    rst.initiate();
+    const primary = rst.getPrimary();
+
+    const newSecondary = rst.add();
+    assert.soon(() => isConfigCommitted(primary));
+    const config = rst.getReplSetConfigFromNode();
+
+    config.members.push({_id: 3, host: newSecondary.host});
+    config.version++;
+
+    assert.commandWorked(primary.adminCommand({replSetReconfig: config}));
+    assert.soon(() => isConfigCommitted(primary));
+
+    rst.waitForConfigReplication(primary);
+    rst.awaitReplication();
+
+    let res = assert.commandWorked(newSecondary.adminCommand({getDefaultRWConcern: 1}));
+    // A PSS set will have a default write concern of {w: "majority"}. A PSA set will have a default
+    // write concern of {w: 1}.
+    if (hasArbiter) {
+        assert(!res.defaultWriteConcern, tojson(res));
+    } else {
+        assert.eq(res.defaultWriteConcern, {w: "majority", wtimeout: 0}, tojson(res));
+    }
+    assert.eq(res.defaultWriteConcernSource, "implicit", tojson(res));
+    rst.stopSet();
+}
+
+runTest(false /* hasArbiter */);
+runTest(true /* hasArbiter */);
+})();
\ No newline at end of file
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