mongodb/jstests/replsets/initial_sync_move_forward.js

// Test initial sync with documents moving forward.
//
// This tests that initial sync succeeds when the clone phase encounters the same _id twice. We test
// that the destination node has the correct document with that _id at the end of initial sync.
//
// We also test that the initial sync succeeds when the clone phase encounters the same 'x' value
// twice, for a collection with a unique index {x: 1}.
//
// It works by deleting a document at the end of the range we are cloning, then growing a document
// from the beginning of the range so that it moves to the hole in the end of the range.
//
// This also works for wiredTiger, because we grow the document by deleting and reinserting it, so
// the newly inserted document is included in the cursor on the source.
(function() {
"use strict";

load("jstests/libs/fail_point_util.js");
load("jstests/libs/get_index_helpers.js");

var rst = new ReplSetTest({name: "initial_sync_move_forward", nodes: 1});
rst.startSet();
rst.initiate();

var masterColl = rst.getPrimary().getDB("test").coll;

// Insert 500000 documents. Make the last two documents larger, so that {_id: 0, x: 0} and {_id:
// 1, x: 1} will fit into their positions when we grow them.
var count = 500000;
var bulk = masterColl.initializeUnorderedBulkOp();
for (var i = 0; i < count - 2; ++i) {
    bulk.insert({_id: i, x: i});
}
var longString = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
bulk.insert({_id: count - 2, x: count - 2, longString: longString});
bulk.insert({_id: count - 1, x: count - 1, longString: longString});
assert.commandWorked(bulk.execute());

// Create a unique index on {x: 1}.
assert.commandWorked(masterColl.ensureIndex({x: 1}, {unique: true}));

// Add a secondary.
var secondary =
    rst.add({setParameter: "numInitialSyncAttempts=1", rsConfig: {votes: 0, priority: 0}});
secondary.setSlaveOk();
var secondaryColl = secondary.getDB("test").coll;

// Pause initial sync when the secondary has copied {_id: 0, x: 0} and {_id: 1, x: 1}.
var failPoint = configureFailPoint(secondary,
                                   "initialSyncHangDuringCollectionClone",
                                   {namespace: secondaryColl.getFullName(), numDocsToClone: 2});
rst.reInitiate();
failPoint.wait();

// Delete {_id: count - 2} to make a hole. Grow {_id: 0} so that it moves into that hole. This
// will cause the secondary to clone {_id: 0} again.
// Change the value for 'x' so that we are not testing the uniqueness of 'x' in this case.
assert.commandWorked(masterColl.remove({_id: 0, x: 0}));
assert.commandWorked(masterColl.remove({_id: count - 2, x: count - 2}));
assert.commandWorked(masterColl.insert({_id: 0, x: count, longString: longString}));

// Delete {_id: count - 1} to make a hole. Grow {x: 1} so that it moves into that hole. This
// will cause the secondary to clone {x: 1} again.
// Change the value for _id so that we are not testing the uniqueness of _id in this case.
assert.commandWorked(masterColl.remove({_id: 1, x: 1}));
assert.commandWorked(masterColl.remove({_id: count - 1, x: count - 1}));
assert.commandWorked(masterColl.insert({_id: count, x: 1, longString: longString}));

// Resume initial sync.
failPoint.off();

// Wait for initial sync to finish.
rst.awaitSecondaryNodes();

// Check document count on secondary.
assert.eq(count - 2, secondaryColl.find().itcount());

// Check for {_id: 0} on secondary.
assert.eq(1, secondaryColl.find({_id: 0, x: count}).itcount());

// Check for {x: 1} on secondary.
assert.eq(1, secondaryColl.find({_id: count, x: 1}).itcount());

// Check for unique index on secondary.
var indexSpec = GetIndexHelpers.findByKeyPattern(secondaryColl.getIndexes(), {x: 1});
assert.neq(null, indexSpec);
assert.eq(true, indexSpec.unique);
rst.stopSet();
})();