A large number of httpclients and tcp are created when the oap server is unavailable

[saber-wang]

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• Why do you submit this issue?
• Question or discussion
• Bug
• Requirement
• Feature or performance improvement

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Bug

Here's the problem:

SkyAPM-dotnet/src/SkyApm.Transport.Grpc/ConnectionManager.cs

Lines 58 to 61 in 7e7693d

	if (_channel != null)
	{
	await ShutdownAsync();
	}

It is executed every 15 seconds. At this time, it is offline and the GrpcChannel is recreated. Each time the GrpcChannel is created, a new httpclient instance will be created.

Optional fixes:

Provide your own httpclient for GrpcChannel and reuse httpclient instances.

In addition, ShutdownAsync does not seem to be implemented?

[saber-wang]

@liuhaoyang There is a repair plan?

[saber-wang]

@liuhaoyang
I tried to process and found that the httpclient created when based on netstandard 2.0 is not available. If I reuse it directly_ Channel doesn't seem to be rebuilding Tongtong.

我尝试处理发现在基于netstandard2.0时创建的httpclient不可用，如果直接复用_channel 似乎不会重建通通。

[liuhaoyang]

@liuhaoyang I tried to process and found that the httpclient created when based on netstandard 2.0 is not available. If I reuse it directly_ Channel doesn't seem to be rebuilding Tongtong.

我尝试处理发现在基于netstandard2.0时创建的httpclient不可用，如果直接复用_channel 似乎不会重建通通。

It may be better to release the old connection completely when retrying the gRPC connection