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Implement connection draining feature

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This commit is contained in:
SteveSandersonMS
2016-07-07 13:18:48 +01:00
parent be13f0b7bf
commit ce127f0d70
1 changed files with 41 additions and 8 deletions
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49
src/Microsoft.AspNetCore.NodeServices/NodeServicesImpl.cs
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@@ -14,16 +14,16 @@ namespace Microsoft.AspNetCore.NodeServices
/// class will create a new instance and dispatch future calls to it, while keeping the old instance
/// alive for a defined period so that any in-flight RPC calls can complete. This latter feature is
/// analogous to the "connection draining" feature implemented by HTTP load balancers.
///
/// TODO: Implement everything in the preceding paragraph.
/// </summary>
/// <seealso cref="Microsoft.AspNetCore.NodeServices.INodeServices" />
internal class NodeServicesImpl : INodeServices
{
private static TimeSpan ConnectionDrainingTimespan = TimeSpan.FromSeconds(15);
private NodeServicesOptions _options;
private Func<INodeInstance> _nodeInstanceFactory;
private INodeInstance _currentNodeInstance;
private object _currentNodeInstanceAccessLock = new object();
private Exception _instanceDelayedDisposalException;
internal NodeServicesImpl(NodeServicesOptions options, Func<INodeInstance> nodeInstanceFactory)
{
@@ -43,6 +43,7 @@ namespace Microsoft.AspNetCore.NodeServices
public async Task<T> InvokeExportWithPossibleRetryAsync<T>(string moduleName, string exportedFunctionName, object[] args, bool allowRetry)
{
ThrowAnyOutstandingDelayedDisposalException();
var nodeInstance = GetOrCreateCurrentNodeInstance();
try
@@ -56,11 +57,13 @@ namespace Microsoft.AspNetCore.NodeServices
if (allowRetry && ex.NodeInstanceUnavailable)
{
// Perform the retry after clearing away the old instance
// Since we disposal is delayed even though the node instance is replaced immediately, this produces the
// "connection draining" feature whereby in-flight RPC calls are given a certain period to complete.
lock (_currentNodeInstanceAccessLock)
{
if (_currentNodeInstance == nodeInstance)
{
DisposeNodeInstance(_currentNodeInstance);
DisposeNodeInstance(_currentNodeInstance, delay: ConnectionDrainingTimespan);
_currentNodeInstance = null;
}
}
@@ -83,17 +86,47 @@ namespace Microsoft.AspNetCore.NodeServices
{
if (_currentNodeInstance != null)
{
DisposeNodeInstance(_currentNodeInstance);
DisposeNodeInstance(_currentNodeInstance, delay: TimeSpan.Zero);
_currentNodeInstance = null;
}
}
}
private static void DisposeNodeInstance(INodeInstance nodeInstance)
private void DisposeNodeInstance(INodeInstance nodeInstance, TimeSpan delay)
{
// TODO: Implement delayed disposal for connection draining
// Or consider having the delayedness of it being a responsibility of the INodeInstance
nodeInstance.Dispose();
if (delay == TimeSpan.Zero)
{
nodeInstance.Dispose();
}
else
{
Task.Run(async () => {
try
{
await Task.Delay(delay);
nodeInstance.Dispose();
}
catch(Exception ex)
{
// Nothing's waiting for the delayed disposal task, so any exceptions in it would
// by default just get ignored. To make these discoverable, capture them here so
// they can be rethrown to the next caller to InvokeExportAsync.
_instanceDelayedDisposalException = ex;
}
});
}
}
private void ThrowAnyOutstandingDelayedDisposalException()
{
if (_instanceDelayedDisposalException != null)
{
var ex = _instanceDelayedDisposalException;
_instanceDelayedDisposalException = null;
throw new AggregateException(
"A previous attempt to dispose a Node instance failed. See InnerException for details.",
ex);
}
}
private INodeInstance GetOrCreateCurrentNodeInstance()