// Tests "stacking" multiple migration cleanup threads and their behavior when the collection
// changes
// @tags: [assumes_balancer_off]
(function() {
'use strict';

// start up a new sharded cluster
var st = new ShardingTest({shards: 2, mongos: 1});

var mongos = st.s;
var admin = mongos.getDB("admin");
var coll = mongos.getCollection("foo.bar");

// Enable sharding of the collection
assert.commandWorked(mongos.adminCommand({enablesharding: coll.getDB() + ""}));
st.ensurePrimaryShard(coll.getDB() + "", st.shard0.shardName);
assert.commandWorked(mongos.adminCommand({shardcollection: coll + "", key: {_id: 1}}));

var numChunks = 30;

// Create a bunch of chunks
for (var i = 0; i < numChunks; i++) {
    assert.commandWorked(mongos.adminCommand({split: coll + "", middle: {_id: i}}));
}

jsTest.log("Inserting a lot of small documents...");

// Insert a lot of small documents to make multiple cursor batches
var bulk = coll.initializeUnorderedBulkOp();
for (var i = 0; i < 10 * 1000; i++) {
    bulk.insert({_id: i});
}
assert.writeOK(bulk.execute());

jsTest.log("Opening a mongod cursor...");

// Open a new cursor on the mongod
var cursor = coll.find();
var next = cursor.next();

jsTest.log("Moving a bunch of chunks to stack cleanup...");

// Move a bunch of chunks, but don't close the cursor so they stack.
for (var i = 0; i < numChunks; i++) {
    assert.commandWorked(
        mongos.adminCommand({moveChunk: coll + "", find: {_id: i}, to: st.shard1.shardName}));
}

jsTest.log("Dropping and re-creating collection...");

coll.drop();

bulk = coll.initializeUnorderedBulkOp();
for (var i = 0; i < numChunks; i++) {
    bulk.insert({_id: i});
}
assert.writeOK(bulk.execute());

sleep(10 * 1000);

jsTest.log("Checking that documents were not cleaned up...");

for (var i = 0; i < numChunks; i++) {
    assert.neq(null, coll.findOne({_id: i}));
}

st.stop();
})();