/*
 * Test that the balancer is redistributing data based on the actual amount of data
 * for a collection on each node, converging when the size difference becomes small.
 */

(function() {
'use strict';

load("jstests/sharding/libs/find_chunks_util.js");
load("jstests/libs/fail_point_util.js");

const maxChunkSizeMB = 1;
const st = new ShardingTest({
    shards: 2,
    mongos: 1,
    other: {
        chunkSize: maxChunkSizeMB,
        enableBalancer: false,
        configOptions: {setParameter: {logComponentVerbosity: tojson({sharding: {verbosity: 2}})}}
    }
});

const dbName = 'test';
const coll = st.getDB(dbName).getCollection('foo');
const ns = coll.getFullName();
const mongos = st.s;
const shard0 = st.shard0.shardName;
const shard1 = st.shard1.shardName;

// Shard collection with one chunk on shard0 [MinKey, 0) and one chunk on shard1 [0, MinKey)
assert.commandWorked(mongos.adminCommand({enablesharding: dbName, primaryShard: shard0}));
assert.commandWorked(mongos.adminCommand({shardcollection: ns, key: {_id: 1}}));
assert.commandWorked(mongos.adminCommand({split: ns, middle: {_id: 0}}));
assert.commandWorked(mongos.adminCommand({moveChunk: ns, find: {_id: 0}, to: shard1}));

const bigString = 'X'.repeat(1024 * 1024);  // 1MB

// Insert 10MB of documents in range [MinKey, 0) on shard0
var bulk = coll.initializeUnorderedBulkOp();
for (var i = -1; i > -11; i--) {
    bulk.insert({_id: i, s: bigString});
}
assert.commandWorked(bulk.execute());

// Insert 3MB of documents in range [0, MaxKey) on shard1
bulk = coll.initializeUnorderedBulkOp();
for (var i = 0; i < 3; i++) {
    bulk.insert({_id: i, s: bigString});
}
assert.commandWorked(bulk.execute());

// Create 3 more chunks on shard0
assert.commandWorked(mongos.adminCommand({split: ns, middle: {_id: 1}}));
assert.commandWorked(mongos.adminCommand({split: ns, middle: {_id: 2}}));
assert.commandWorked(mongos.adminCommand({split: ns, middle: {_id: 3}}));

// At this point, the distribution of chunks for the testing collection is the following:
//  - On shard0 (10MB):
//     { "_id" : { "$minKey" : 1 } } -->> { "_id" : 0 }
//  - On shard1 (3MB):
//     { "_id" : 0 } -->> { "_id" : 1 }
//     { "_id" : 1 } -->> { "_id" : 2 }
//     { "_id" : 2 } -->> { "_id" : 3 }
//     { "_id" : 3 } -->> { "_id" : { "$maxKey" : 1 } }
jsTestLog("Printing sharding status before starting balancer");
st.printShardingStatus();
st.startBalancer();

st.awaitCollectionBalance(coll, 60000 /* timeout */, 1000 /* interval */);
const chunksBeforeNoopRound = findChunksUtil.findChunksByNs(st.config, ns).toArray();

// Check that the collection is balanced
st.verifyCollectionIsBalanced(coll);

jsTestLog("Printing sharding status after waiting for collection balance");
st.printShardingStatus();

// Wait for some more rounds and then check the balancer is not wrongly moving around data
configureFailPointForRS(
    st.configRS.nodes, 'overrideBalanceRoundInterval', {intervalMs: 100}, 'alwaysOn');

st.awaitBalancerRound();
st.awaitBalancerRound();
st.awaitBalancerRound();

st.stopBalancer();
jsTestLog("Printing sharding status after stopping balancer");
st.printShardingStatus();

// Check that no move has been performed during the noop rounds (if the routing table did not
// change, it means data are still balanced)
const chunksAfterNoopRound = findChunksUtil.findChunksByNs(st.config, ns).toArray();
assert.eq(chunksBeforeNoopRound, chunksAfterNoopRound);

st.stop();
})();