SERVER-39099 Make dropConnections test robust

1 files changed, 34 insertions, 5 deletions

diff --git a/jstests/noPassthrough/drop_connections_replSet.js b/jstests/noPassthrough/drop_connections_replSet.js
index 0d96a9a65b9..c449d2d7b13 100644
--- a/jstests/noPassthrough/drop_connections_replSet.js
+++ b/jstests/noPassthrough/drop_connections_replSet.js
@@ -12,19 +12,48 @@
 
     const primary = rst.getPrimary();
     rst.awaitSecondaryNodes();
-
     const cfg = primary.getDB('local').system.replset.findOne();
     const memberHost = cfg.members[2].host;
+
+    function assertConnPoolStats(expectedAvailable, numTries) {
+        var available, res;
+        for (var i = 0; i < numTries; i++) {
+            res = assert.commandWorked(primary.adminCommand({connPoolStats: 1}));
+            available = res.hosts[memberHost].available;
+            if (available == expectedAvailable) {
+                return;
+            }
+
+            sleep(100);
+        }
+
+        // Fail informatively
+        jsTestLog("pool stats: " + tojson(res));
+        assert.eq(
+            expectedAvailable,
+            available,
+            `wrong number of available connections to ${memberHost} after checking ${numTries} times`);
+    }
+
+    // In initial steady state, the primary should have 1 connection to the secondary
+    assertConnPoolStats(1, 10);
+
+    // To test the dropConnections command, first remove the secondary. This should have no effect
+    // on the existing connection pool, but it'll prevent the primary from reconnecting to it after
+    // dropConnections. Then, execute dropConnections and check that the primary has 0 connections
+    // to the secondary.
     const removedMember = cfg.members.splice(2, 1);
     cfg.version++;
-
     assert.commandWorked(primary.adminCommand({replSetReconfig: cfg}));
 
-    assert.eq(1, primary.adminCommand({connPoolStats: 1}).hosts[memberHost].available);
+    // Reconfig did not affect the connection pool
+    assertConnPoolStats(1, 10);
+
+    // Test dropConnections
     assert.commandWorked(primary.adminCommand({dropConnections: 1, hostAndPort: [memberHost]}));
-    assert.eq(0, primary.adminCommand({connPoolStats: 1}).hosts[memberHost].available);
+    assertConnPoolStats(0, 1);
 
-    // need to re-add removed node or test complain about the replset config
+    // Need to re-add removed node, or the test complains about the replset config
     cfg.members.push(removedMember[0]);
     cfg.version++;
     assert.commandWorked(primary.adminCommand({replSetReconfig: cfg}));