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  1. Core Server
  2. SERVER-31865

setFCV on config server should only generate UUIDs for non-dropped sharded collections

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    • Type: Icon: Bug Bug
    • Resolution: Fixed
    • Priority: Icon: Major - P3 Major - P3
    • 3.6.1, 3.7.1
    • Affects Version/s: 3.6.0-rc2
    • Component/s: Sharding
    • None
    • Fully Compatible
    • ALL
    • v3.6
    • Hide 
      (function() {
    "use strict";

    load('jstests/libs/parallelTester.js');

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

    const st = new ShardingTest({mongos: 1, config: 1, shards: 2, rs: {nodes: 1}});

    assert.commandWorked(st.s.adminCommand({enableSharding: dbName}));
    assert.commandWorked(st.s.adminCommand({shardCollection: ns, key: {x: 1}}));

    let collEntryBefore = st.s.getDB("config").getCollection("collections").find({ _id: ns }).toArray()[0];
    print("collEntryBefore: " + tojson(collEntryBefore));
    assert.neq(null, collEntryBefore.uuid);

    jsTest.log("dropping collection " + ns);
    assert.commandWorked(st.s.getDB(dbName).runCommand({ drop: collName }));

    let collEntryAfter = st.s.getDB("config").getCollection("collections").find({ _id: ns }).toArray()[0];
    print("collEntryAfter: " + tojson(collEntryAfter));
    // Expect this assert to fail, which demonstrates the bug.
    assert.neq(null, collEntryAfter.uuid);

    st.stop();
})();
      Show
      (function() { "use strict" ; load( 'jstests/libs/parallelTester.js' ); const dbName = "test" ; const collName = "foo" ; const ns = dbName + "." + collName; const st = new ShardingTest({mongos: 1, config: 1, shards: 2, rs: {nodes: 1}}); assert .commandWorked(st.s.adminCommand({enableSharding: dbName})); assert .commandWorked(st.s.adminCommand({shardCollection: ns, key: {x: 1}})); let collEntryBefore = st.s.getDB( "config" ).getCollection( "collections" ).find({ _id: ns }).toArray()[0]; print( "collEntryBefore: " + tojson(collEntryBefore)); assert .neq( null , collEntryBefore.uuid); jsTest.log( "dropping collection " + ns); assert .commandWorked(st.s.getDB(dbName).runCommand({ drop: collName })); let collEntryAfter = st.s.getDB( "config" ).getCollection( "collections" ).find({ _id: ns }).toArray()[0]; print( "collEntryAfter: " + tojson(collEntryAfter)); // Expect this assert to fail, which demonstrates the bug. assert .neq( null , collEntryAfter.uuid); st.stop(); })();
    • Sharding 2017-12-04
    • 0

      It may not cause any incorrect behavior (that I know of), but it's weird... we should make the write to mark the collection entry as 'dropped' use $set rather than a replacement-style update.

      Example collection entry after shardCollection (produced using the attached repro):

      collEntryBefore: {
    "_id" : "test.foo",
    "lastmodEpoch" : ObjectId("5a023322d22a4537cf47b2a1"),
    "lastmod" : ISODate("1970-02-19T17:02:47.296Z"),
    "dropped" : false,
    "key" : {
        "x" : 1
    },
    "unique" : false,
    "uuid" : UUID("052e805a-f4e5-4e0e-93a2-0865fbd59e1c")
}

      How that collection entry looks after drop:

      collEntryAfter: {
    "_id" : "test.foo",
    "lastmodEpoch" : ObjectId("000000000000000000000000"),
    "lastmod" : ISODate("2017-11-07T22:26:43.080Z"),
    "dropped" : true
}

      It also looks like dropCollection clears the lastmodEpoch (i.e., epoch); I don't see why it should do this?

            Assignee:
            esha.maharishi@mongodb.com Esha Maharishi (Inactive)
            Reporter:
            esha.maharishi@mongodb.com Esha Maharishi (Inactive)
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              Created:
              Updated:
              Resolved: