/**
 * This test confirms that after sharding a collection with some pre-existing data,
 * the resulting chunks aren't auto-split too aggressively.
 *
 * @tags: [
 *    requires_fcv_51,
 *    requires_persistence
 * ]
 */
(function() {
'use strict';
load('jstests/sharding/autosplit_include.js');
load("jstests/sharding/libs/find_chunks_util.js");

var s = new ShardingTest({
    name: "shard_existing_coll_chunk_count",
    shards: 1,
    mongos: 1,
    other: {enableAutoSplit: true},
});

assert.commandWorked(s.s.adminCommand({enablesharding: "test"}));

var collNum = 0;
var overhead = Object.bsonsize({_id: ObjectId(), i: 1, pad: ""});

var getNumberChunks = function(ns) {
    return findChunksUtil.countChunksForNs(s.getDB("config"), ns);
};

var runCase = function(opts) {
    // Expected options.
    assert.gte(opts.docSize, 0);
    assert.gte(opts.stages.length, 2);

    // Compute padding.
    if (opts.docSize < overhead) {
        var pad = "";
    } else {
        var pad = (new Array(opts.docSize - overhead + 1)).join(' ');
    }

    collNum++;
    var db = s.getDB("test");
    var collName = "coll" + collNum;
    var coll = db.getCollection(collName);
    var i = 0;
    var limit = 0;
    var stageNum = 0;
    var stage = opts.stages[stageNum];

    // Insert initial docs.
    var bulk = coll.initializeUnorderedBulkOp();
    limit += stage.numDocsToInsert;
    for (; i < limit; i++) {
        bulk.insert({i, pad});
    }
    assert.commandWorked(bulk.execute());

    // Create shard key index.
    assert.commandWorked(coll.createIndex({i: 1}));

    // Shard collection.
    assert.commandWorked(s.s.adminCommand({shardcollection: coll.getFullName(), key: {i: 1}}));

    // Confirm initial number of chunks.
    var numChunks = getNumberChunks(coll.getFullName());
    assert.eq(numChunks,
              stage.expectedNumChunks,
              'in ' + coll.getFullName() + ' expected ' + stage.expectedNumChunks +
                  ' initial chunks, but found ' + numChunks + '\nopts: ' + tojson(opts) +
                  '\nchunks:\n' + s.getChunksString(coll.getFullName()));

    // Do the rest of the stages.
    for (stageNum = 1; stageNum < opts.stages.length; stageNum++) {
        stage = opts.stages[stageNum];

        // Insert the later docs (one at a time, to maximise the autosplit effects).
        limit += stage.numDocsToInsert;
        for (; i < limit; i++) {
            coll.insert({i, pad});

            waitForOngoingChunkSplits(s);
        }

        // Confirm number of chunks for this stage.
        var numChunks = getNumberChunks(coll.getFullName());
        assert.lte(numChunks,
                   stage.expectedNumChunks,
                   'in ' + coll.getFullName() + ' expected ' + stage.expectedNumChunks +
                       ' chunks for stage ' + stageNum + ', but found ' + numChunks + '\nopts: ' +
                       tojson(opts) + '\nchunks:\n' + s.getChunksString(coll.getFullName()));
    }
};

// Original problematic case.
runCase({
    docSize: 0,
    stages: [
        {numDocsToInsert: 20000, expectedNumChunks: 1},
        {numDocsToInsert: 7, expectedNumChunks: 1},
        {numDocsToInsert: 1000, expectedNumChunks: 1},
    ],
});

// Original problematic case (worse).
runCase({
    docSize: 0,
    stages: [
        {numDocsToInsert: 90000, expectedNumChunks: 1},
        {numDocsToInsert: 7, expectedNumChunks: 1},
        {numDocsToInsert: 1000, expectedNumChunks: 1},
    ],
});

// Pathological case #1.
runCase({
    docSize: 522,
    stages: [
        {numDocsToInsert: 8191, expectedNumChunks: 1},
        {numDocsToInsert: 2, expectedNumChunks: 1},
        {numDocsToInsert: 1000, expectedNumChunks: 1},
    ],
});

// Pathological case #2.
runCase({
    docSize: 522,
    stages: [
        {numDocsToInsert: 8192, expectedNumChunks: 1},
        {numDocsToInsert: 8192, expectedNumChunks: 1},
    ],
});

// Lower chunksize to 1MB, and restart the mongod for it to take. We also
// need to restart mongos for the case of the last-lts suite where the
// shard is also last-lts.
assert.commandWorked(
    s.getDB("config").getCollection("settings").update({_id: "chunksize"}, {$set: {value: 1}}, {
        upsert: true
    }));

s.restartMongos(0);
s.restartShardRS(0);

// Original problematic case, scaled down to smaller chunksize.
runCase({
    docSize: 0,
    stages: [
        {numDocsToInsert: 10000, expectedNumChunks: 1},
        {numDocsToInsert: 10, expectedNumChunks: 1},
        {numDocsToInsert: 20, expectedNumChunks: 1},
        {numDocsToInsert: 40, expectedNumChunks: 1},
        {numDocsToInsert: 1000, expectedNumChunks: 1},
    ],
});

// Docs just smaller than half chunk size.
runCase({
    docSize: 510 * 1024,
    stages: [
        {numDocsToInsert: 10, expectedNumChunks: 6},
        {numDocsToInsert: 10, expectedNumChunks: 12},
    ],
});

// Docs just larger than half chunk size.
runCase({
    docSize: 514 * 1024,
    stages: [
        {numDocsToInsert: 10, expectedNumChunks: 10},
        {numDocsToInsert: 10, expectedNumChunks: 20},
    ],
});

s.stop();
})();
