Error when trying to set MaxThreadCount on the merge scheduler

[whittssg]

NEST/Elasticsearch.Net version: 5.2.0

Elasticsearch version: 5.2.0

Description of the problem including expected versus actual behavior:

I am trying to set the the max thread count on one of my indexes via c#. I use the following code:

 client.CreateIndex(indexInfo.Value, c => c
                        .Settings(st => st
                            .Merge(mr => mr
                                .Scheduler(sc => sc.MaxThreadCount(1)))));

But i get this error:
An unhandled exception of type 'Elasticsearch.Net.UnexpectedElasticsearchClientException' occurred in Elasticsearch.Net.dll
Additional information: Object reference not set to an instance of an object.

The index is created fine if i remove the merge setting. I am setting this since i found out that it is recommended when running elastic on spinning disks.

Thanks,

[whittssg]

Adding an empty policy setting fixes it. Is this normal?

.Merge(mr => mr
 .Scheduler(sc => sc
    .MaxThreadCount(1))
 .Policy(po => po))

[gmarz]

Is this normal?

Nope, definitely looks like a bug. We'll have this fixed for the next release. Thanks for reporting!