mongodb/jstests/sharding/create_database.js

/**
 * Tests that creating a database causes it to be written to the sharding catalog with a
 * databaseVersion if FCV > 3.6, but not if FCV <= 3.6.
 */
import {ShardingTest} from "jstests/libs/shardingtest.js";

function createDatabase(mongos, dbName) {
    // A database is implicitly created when a collection inside it is created.
    assert.commandWorked(mongos.getDB(dbName).runCommand({create: collName}));
}

function cleanUp(mongos, dbName) {
    assert.commandWorked(mongos.getDB(dbName).runCommand({dropDatabase: 1}));
}

function assertDbVersionAssigned(mongos, dbName) {
    createDatabase(mongos, dbName);

    // Check that the entry in the sharding catalog contains a dbVersion.
    const dbEntry = mongos.getDB("config").getCollection("databases").findOne({_id: dbName});
    assert.neq(null, dbEntry);
    assert.neq(null, dbEntry.version);
    assert.neq(null, dbEntry.version.uuid);
    assert.eq(1, dbEntry.version.lastMod);

    // Check that the catalog cache on the mongos contains the same dbVersion.
    const cachedDbEntry = mongos.adminCommand({getShardVersion: dbName});
    assert.commandWorked(cachedDbEntry);
    assert.eq(dbEntry.version.uuid, cachedDbEntry.version.uuid);
    assert.eq(dbEntry.version.lastMod, cachedDbEntry.version.lastMod);

    cleanUp(mongos, dbName);

    return dbEntry;
}

function assertDbVersionNotAssigned(mongos, dbName) {
    createDatabase(mongos, dbName);

    // Check that the entry in the sharding catalog *does not* contain a dbVersion.
    const dbEntry = mongos.getDB("config").getCollection("databases").findOne({_id: dbName});
    assert.neq(null, dbEntry);
    assert.eq(null, dbEntry.version);

    // Check that the catalog cache on the mongos *does not* contain a dbVersion.
    const cachedDbEntry = mongos.adminCommand({getShardVersion: dbName});
    assert.commandWorked(cachedDbEntry);
    assert.eq(null, cachedDbEntry.version);

    cleanUp(mongos, dbName);

    return dbEntry;
}

const dbName = "db1";
const collName = "foo";
const ns = dbName + "." + collName;

var st = new ShardingTest({shards: 1});

// A new database is given a databaseVersion.
let dbEntry1 = assertDbVersionAssigned(st.s, dbName);

// A new incarnation of a database that was previously dropped is given a fresh databaseVersion.
let dbEntry2 = assertDbVersionAssigned(st.s, dbName);
assert.neq(dbEntry1.version.uuid, dbEntry2.version.uuid);

st.stop();