StackOverflowException when iterating through Redis keys

[rpmrmartin]

Describe the bug
When our ASP.NET application iterates through all the keys on a Redis server, it causes the Datadog .NET Tracer to throw a StackOverflowException.

To Reproduce
Run the following code inside an application that is being profiled by the Datadog .NET Tracer:

using StackExchange.Redis;
ConnectionMultiplexer redis = RedisCaching.GetRedisMultiplexer();
IServer server = redis.GetServer("MyServer");
IEnumerator ide = server.Keys().GetEnumerator();
while (ide.MoveNext())
{
	// Do something
}

The exception is thrown when calling ide.MoveNext() for the first time

Expected behavior
The application should iterate over the keys without issue

Runtime environment (please complete the following information):

• Instrumentation mode: Automatic with MSI installer
• Tracer version: 1.5.0
• OS: Found on Windows Server 2016, reproduced on Windows 10 Pro 1809
• CLR: .NET Framework 4.7.2

Additional context
Stack trace:

<Repeat the last four calls ad infinitum>  

StackExchange.Redis.dll!StackExchange.Redis.RedisServer.ExecuteAsync<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>(StackExchange.Redis.Message message, StackExchange.Redis.ResultProcessor<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult> processor, StackExchange.Redis.ServerEndPoint server) Line 577	C#  

Datadog.Trace.ClrProfiler.Managed.dll!Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.ExecuteAsyncInternal<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>(object redisBase, object message, object processor, object server)	Unknown  

mscorlib.dll!System.Runtime.CompilerServices.AsyncTaskMethodBuilder<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>.Start<Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.<ExecuteAsyncInternal>d__7<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>>(ref Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.<ExecuteAsyncInternal>d__7<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult> stateMachine)	Unknown  

Datadog.Trace.ClrProfiler.Managed.dll!Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.ExecuteAsyncInternal<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>(object redisBase, object message, object processor, object server)	Unknown  

StackExchange.Redis.dll!StackExchange.Redis.RedisServer.ExecuteAsync<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>(StackExchange.Redis.Message message, StackExchange.Redis.ResultProcessor<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult> processor, StackExchange.Redis.ServerEndPoint server) Line 577	C#  

Datadog.Trace.ClrProfiler.Managed.dll!Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.ExecuteAsyncInternal<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>(object redisBase, object message, object processor, object server)	Unknown  

mscorlib.dll!System.Runtime.CompilerServices.AsyncTaskMethodBuilder<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>.Start<Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.<ExecuteAsyncInternal>d__7<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>>(ref Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.<ExecuteAsyncInternal>d__7<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult> stateMachine)	Unknown  

Datadog.Trace.ClrProfiler.Managed.dll!Datadog.Trace.ClrProfiler.Integrations.StackExchange.Redis.RedisBatch.ExecuteAsyncInternal<StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.ScanResult>(object redisBase, object message, object processor, object server)	Unknown  

StackExchange.Redis.dll!StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.GetNextPageAsync(StackExchange.Redis.IScanningCursor obj, long cursor, out StackExchange.Redis.Message message) Line 179	C#  

StackExchange.Redis.dll!StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.CursorEnumerator.LoadNextPageAsync() Line 203	C#  

StackExchange.Redis.dll!StackExchange.Redis.RedisBase.CursorEnumerable<StackExchange.Redis.RedisKey>.CursorEnumerator.MoveNext() Line 258	C#  

<Our code>

The error happens every time on our test servers (Windows Server 2016 + IIS). On my development workstation (Windows 10 Pro 1809), the error usually happens when running the application from Visual Studio 2019 using IIS express, but not when using Local IIS.

(edit: formatting)

[lucaspimentel]

Thanks for reporting this issue, @rpmrmartin. What version of the StackExchange.Redis library is your app using?

[rpmrmartin]

We are using v2.0.601.

[lucaspimentel]

@rpmrmartin: We merged the fix for this issue in #448 (and further clean-up in #452) and will be included in release 1.6. Thanks!

[rpmrmartin]

Thanks! Looking forward to getting APM up and running for our app.