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  1. Core Server
  2. SERVER-16429

Concurrent mapReduces with same replacement collection fail with WT

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      Run this script against mongod --storageEngine=wiredTiger:

      'use strict';

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

function client() {

    function mapper() {
        emit(this.key, 1);
    }

    function reducer() {
        return {};
    }

    while (true) {
        var options = {
            out: {replace: 'bar'}
        };

        db.foo.mapReduce(mapper, reducer, options);
    }
}

db.foo.drop();

var bulk = db.foo.initializeUnorderedBulkOp();
for (var i = 0; i < 3000; i++) {
    bulk.insert({i: i, key: Random.randInt()});
}
bulk.execute();

var threads = [];
for (var i = 0; i < 7; i++) {
    var t = new ScopedThread(client);
    threads.push(t);
    t.start();
}

threads.forEach(function(t) {
    t.join();
});
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      Run this script against mongod --storageEngine=wiredTiger : 'use strict' ; load( 'jstests/libs/parallelTester.js' ); function client() { function mapper() { emit( this .key, 1); } function reducer() { return {}; } while ( true ) { var options = { out: {replace: 'bar' } }; db.foo.mapReduce(mapper, reducer, options); } } db.foo.drop(); var bulk = db.foo.initializeUnorderedBulkOp(); for ( var i = 0; i < 3000; i++) { bulk.insert({i: i, key: Random.randInt()}); } bulk.execute(); var threads = []; for ( var i = 0; i < 7; i++) { var t = new ScopedThread(client); threads.push(t); t.start(); } threads.forEach(function(t) { t.join(); });

      Concurrent mapReduce operations that specify the same replacement collection can fail with "target namespace exists" errors when using WiredTiger. The same error is seemingly not reproducible with mmapv1.

      I wouldn't expect a mapReduce operation with a 'replace' action to fail due to an existing namespace.

      Error message:

      Error: map reduce failed:{
	"errmsg" : "exception: rename failed: { ok: 0.0, errmsg: \"target namespace exists\" }",
	"code" : 10076,
	"ok" : 0
}

      Version: b766e395167dc27

            Assignee:
            kaloian.manassiev@mongodb.com Kaloian Manassiev
            Reporter:
            kamran.khan Kamran K.
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              Created:
              Updated:
              Resolved: