SERVER-20720 mongos now returns dead tailable cursor over an empty capped collection

1 files changed, 80 insertions, 61 deletions

diff --git a/jstests/core/tailable_skip_limit.js b/jstests/core/tailable_skip_limit.js
index d0da0a15b28..1fae7263a8f 100644
--- a/jstests/core/tailable_skip_limit.js
+++ b/jstests/core/tailable_skip_limit.js
@@ -1,63 +1,82 @@
 // Test that tailable cursors work correctly with skip and limit.
+(function() {
+    "use strict";
 
-// Setup the capped collection.
-var collname = "jstests_tailable_skip_limit"
-var t = db[collname];
-t.drop();
-db.createCollection(collname, {capped: true, size: 1024});
-
-t.save({_id: 1});
-t.save({_id: 2});
-
-// Non-tailable with skip
-var cursor = t.find().skip(1);
-assert.eq(2, cursor.next()["_id"]);
-assert(!cursor.hasNext());
-t.save({_id: 3});
-assert(!cursor.hasNext());
-
-// Non-tailable with limit
-var cursor = t.find().limit(100);
-for (var i = 1; i <= 3; i++) {
-    assert.eq(i, cursor.next()["_id"]);
-}
-assert(!cursor.hasNext());
-t.save({_id: 4});
-assert(!cursor.hasNext());
-
-// Non-tailable with negative limit
-var cursor = t.find().limit(-100);
-for (var i = 1; i <= 4; i++) {
-    assert.eq(i, cursor.next()["_id"]);
-}
-assert(!cursor.hasNext());
-t.save({_id: 5});
-assert(!cursor.hasNext());
-
-// Tailable with skip
-cursor = t.find().addOption(2).skip(4);
-assert.eq(5, cursor.next()["_id"]);
-assert(!cursor.hasNext());
-t.save({_id: 6});
-assert(cursor.hasNext());
-assert.eq(6, cursor.next()["_id"]);
-
-// Tailable with limit
-var cursor = t.find().addOption(2).limit(100);
-for (var i = 1; i <= 6; i++) {
-    assert.eq(i, cursor.next()["_id"]);
-}
-assert(!cursor.hasNext());
-t.save({_id: 7});
-assert(cursor.hasNext());
-assert.eq(7, cursor.next()["_id"]);
-
-// Tailable with negative limit
-var cursor = t.find().addOption(2).limit(-100);
-for (var i = 1; i <= 7; i++) {
-    assert.eq(i, cursor.next()["_id"]);
-}
-assert(!cursor.hasNext());
-t.save({_id: 8});
-assert(cursor.hasNext());
-assert.eq(8, cursor.next()["_id"]);
+    // Setup the capped collection.
+    var collname = "jstests_tailable_skip_limit"
+    var t = db[collname];
+    t.drop();
+    db.createCollection(collname, {capped: true, size: 1024});
+
+    t.save({_id: 1});
+    t.save({_id: 2});
+
+    // Non-tailable with skip
+    var cursor = t.find().skip(1);
+    assert.eq(2, cursor.next()["_id"]);
+    assert(!cursor.hasNext());
+    t.save({_id: 3});
+    assert(!cursor.hasNext());
+
+    // Non-tailable with limit
+    var cursor = t.find().limit(100);
+    for (var i = 1; i <= 3; i++) {
+        assert.eq(i, cursor.next()["_id"]);
+    }
+    assert(!cursor.hasNext());
+    t.save({_id: 4});
+    assert(!cursor.hasNext());
+
+    // Non-tailable with negative limit
+    var cursor = t.find().limit(-100);
+    for (var i = 1; i <= 4; i++) {
+        assert.eq(i, cursor.next()["_id"]);
+    }
+    assert(!cursor.hasNext());
+    t.save({_id: 5});
+    assert(!cursor.hasNext());
+
+    // Tailable with skip
+    cursor = t.find().addOption(2).skip(4);
+    assert.eq(5, cursor.next()["_id"]);
+    assert(!cursor.hasNext());
+    t.save({_id: 6});
+    assert(cursor.hasNext());
+    assert.eq(6, cursor.next()["_id"]);
+
+    // Tailable with limit
+    var cursor = t.find().addOption(2).limit(100);
+    for (var i = 1; i <= 6; i++) {
+        assert.eq(i, cursor.next()["_id"]);
+    }
+    assert(!cursor.hasNext());
+    t.save({_id: 7});
+    assert(cursor.hasNext());
+    assert.eq(7, cursor.next()["_id"]);
+
+    // Tailable with negative limit
+    var cursor = t.find().addOption(2).limit(-100);
+    for (var i = 1; i <= 7; i++) {
+        assert.eq(i, cursor.next()["_id"]);
+    }
+    assert(!cursor.hasNext());
+    t.save({_id: 8});
+    assert(cursor.hasNext());
+    assert.eq(8, cursor.next()["_id"]);
+
+    // Tests that a tailable cursor over an empty capped collection produces a dead cursor, intended
+    // to be run on both mongod and mongos. For SERVER-20720.
+    t.drop();
+    db.createCollection(t.getName(), {capped: true, size: 1024});
+
+    var cmdRes = db.runCommand({find: t.getName(), tailable: true});
+    assert.commandWorked(cmdRes);
+    assert.eq(cmdRes.cursor.id, NumberLong(0));
+    assert.eq(cmdRes.cursor.ns, t.getFullName());
+    assert.eq(cmdRes.cursor.firstBatch.length, 0);
+
+    // Test that the cursor works in the shell.
+    assert.eq(t.find().addOption(2).itcount(), 0);
+    assert.writeOK(t.insert({a: 1}));
+    assert.eq(t.find().addOption(2).itcount(), 1);
+})();