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Type: Bug
Resolution: Works as Designed
Priority: Major - P3
Fix Version/s: None
Affects Version/s: 2.10.2
Component/s: None
Labels:
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Case:
Confidence Status:
None

Aha! Reference:
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Tracking Level:
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Risk Status:
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Exec Notes:
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Goal Name:
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When awaiting multiple BulkWriteAsync tasks using Task.WhenAll wrapped in a transaction, if no other operations have been performed on the MongoClient the transaction will fail with: Only servers in a sharded cluster can start a new transaction at the active transaction number

For example, the following would fail:

Unable to find source-code formatter for language: csharp. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml

// ...
// _db.RunCommand((Command<BsonDocument>)"{ping:1}");
using (var session = await _client.StartSessionAsync().ConfigureAwait(false))
{
    session.StartTransaction();
    var writeModel1 = new List<WriteModel<BsonDocument>>();
    writeModel1.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));
    writeModel1.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));
    var writeModel2 = new List<WriteModel<BsonDocument>>();
    writeModel2.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));
    writeModel2.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));

    var task1 = _collection1.BulkWriteAsync(session, writeModel1);
    var task2 = _collection2.BulkWriteAsync(session, writeModel2);
    await Task.WhenAll(task1, task2).ConfigureAwait(false);
    await session.CommitTransactionAsync().ConfigureAwait(false);
}
// ...

but un-commenting the db operation would cause the code to run successfully.

--------------------

Reproduction:

mlaunch init --replicaset --nodes 3
mongo --eval 'db.getSiblingDB("test").collection1.insert({})'
mongo --eval 'db.getSiblingDB("test").collection2.insert({})'

Unable to find source-code formatter for language: csharp. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml

using Microsoft.VisualStudio.TestTools.UnitTesting;
using MongoDB.Bson;
using MongoDB.Driver;
using Shouldly;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading.Tasks;

namespace MongoDBCSharpTests
{
    [TestClass]
    public class UnitTest2
    {
        private const string connString = "mongodb://localhost:27017/test?replicaSet=replset";
        private IMongoDatabase _db;
        private MongoClient _client;
        private IMongoCollection<BsonDocument> _collection1;
        private IMongoCollection<BsonDocument> _collection2;

        [TestInitialize]
        public void Setup()
        {
            _client = new MongoClient(connString);
            _db = _client.GetDatabase("test");
            _collection1 = _db.GetCollection<BsonDocument>("collection1");
            _collection2 = _db.GetCollection<BsonDocument>("collection2");
        }

        public async Task RunTest()
        {
            using (var session = await _client.StartSessionAsync().ConfigureAwait(false))
            {
                session.StartTransaction();

                try
                {
                    var writeModel1 = new List<WriteModel<BsonDocument>>();
                    writeModel1.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));
                    writeModel1.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));
                    var writeModel2 = new List<WriteModel<BsonDocument>>();
                    writeModel2.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));
                    writeModel2.Add(new InsertOneModel<BsonDocument>(new BsonDocument { { "d", DateTime.Now } }));

                    var task1 = _collection1.BulkWriteAsync(session, writeModel1);
                    var task2 = _collection2.BulkWriteAsync(session, writeModel2);
                    await Task.WhenAll(task1, task2).ConfigureAwait(false);
                    await session.CommitTransactionAsync().ConfigureAwait(false);
                    Debug.WriteLine("Committed");
                }
                catch (Exception ex)
                {
                    await session.AbortTransactionAsync().ConfigureAwait(false);
                    Debug.WriteLine("Error... Aborting");
                    Debug.WriteLine(ex.Message);
                    throw ex;
                }

                Debug.WriteLine("Completed");
            }
        }

        [TestMethod]
        public void ShouldFailWithMongoCommandException()
        {
            Should.Throw<MongoCommandException>(() => RunTest()).Message.ShouldContain("Only servers in a sharded cluster can start a new transaction at the active transaction number");
        }

        [TestMethod]
        public void ShouldSucceed()
        {
            _db.RunCommand((Command<BsonDocument>)"{ping:1}");
            Should.NotThrow(() => RunTest());
        }
    }
}

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