SERVER-46288 Reconfig in 4.2 style with the current config on FCV downgrade

- Refactoring doReplSetConfig to accept a callback.
- Use replset tag system to wait for config replication.
- Revert kConfigMajority write concern.
- Include all nodes including arbiters in config replication quorum.
- Reconfig with term -1 using the current config on downgrade.

1 files changed, 20 insertions, 9 deletions

diff --git a/jstests/replsets/awaitable_ismaster_fcv_change.js b/jstests/replsets/awaitable_ismaster_fcv_change.js
index 872e9ff33e8..5099acf462d 100644
--- a/jstests/replsets/awaitable_ismaster_fcv_change.js
+++ b/jstests/replsets/awaitable_ismaster_fcv_change.js
@@ -40,7 +40,7 @@ assert(secondaryTopologyVersion.hasOwnProperty("counter"), tojson(secondaryTopol
 function runAwaitableIsMasterBeforeFCVChange(
     topologyVersionField, isUpgrade, isPrimary, prevMinWireVersion, serverMaxWireVersion) {
     db.getMongo().setSlaveOk();
-    const firstResponse = assert.commandWorked(db.runCommand({
+    let response = assert.commandWorked(db.runCommand({
         isMaster: 1,
         topologyVersion: topologyVersionField,
         maxAwaitTimeMS: 99999999,
@@ -48,26 +48,37 @@ function runAwaitableIsMasterBeforeFCVChange(
             {minWireVersion: NumberInt(0), maxWireVersion: NumberInt(serverMaxWireVersion)},
     }));
 
+    // On downgrade from 4.4 to 4.2, the primary will reconfig the replset and signal isMaster.
+    if (prevMinWireVersion === response.minWireVersion) {
+        jsTestLog("Min wire version didn't change: " + prevMinWireVersion + ". Retry isMaster.");
+        topologyVersionField = response.topologyVersion;
+        response = assert.commandWorked(db.runCommand({
+            isMaster: 1,
+            topologyVersion: topologyVersionField,
+            maxAwaitTimeMS: 99999999,
+            internalClient:
+                {minWireVersion: NumberInt(0), maxWireVersion: NumberInt(serverMaxWireVersion)},
+        }));
+    }
     // We only expect to increment the server TopologyVersion when the minWireVersion has changed.
     // This can only happen in two scenarios:
     // 1. Setting featureCompatibilityVersion from downgrading to fullyDowngraded.
     // 2. Setting featureCompatibilityVersion from fullyDowngraded to upgrading.
-    assert.eq(
-        topologyVersionField.counter + 1, firstResponse.topologyVersion.counter, firstResponse);
+    assert.eq(topologyVersionField.counter + 1, response.topologyVersion.counter, response);
     const expectedIsMasterValue = isPrimary;
     const expectedSecondaryValue = !isPrimary;
 
-    assert.eq(expectedIsMasterValue, firstResponse.ismaster, firstResponse);
-    assert.eq(expectedSecondaryValue, firstResponse.secondary, firstResponse);
+    assert.eq(expectedIsMasterValue, response.ismaster, response);
+    assert.eq(expectedSecondaryValue, response.secondary, response);
 
-    const minWireVersion = firstResponse.minWireVersion;
-    const maxWireVersion = firstResponse.maxWireVersion;
+    const minWireVersion = response.minWireVersion;
+    const maxWireVersion = response.maxWireVersion;
     assert.neq(prevMinWireVersion, minWireVersion);
     if (isUpgrade) {
         // minWireVersion should always equal maxWireVersion if we have not fully downgraded FCV.
-        assert.eq(minWireVersion, maxWireVersion, firstResponse);
+        assert.eq(minWireVersion, maxWireVersion, response);
     } else {
-        assert.eq(minWireVersion + 1, maxWireVersion, firstResponse);
+        assert.eq(minWireVersion + 1, maxWireVersion, response);
     }
 }