protected static Channel TryGetChannelFromLoadBalancer(Channel lbChannel,
ChannelCredentials credentials,
string serviceName,
int maxMesssageLength)
{
ServiceDiscoveryGrpc.ServiceDiscoveryGrpcClient lbClient =
new ServiceDiscoveryGrpc.ServiceDiscoveryGrpcClient(lbChannel);
DiscoverServicesResponse lbResponse = lbClient.DiscoverTopServices(
new DiscoverServicesRequest
{
ServiceName = serviceName,
MaxCount = 1
});
if (lbResponse.ServiceLocations.Count > 0)
{
ServiceLocationMsg serviceLocation = lbResponse.ServiceLocations[0];
Channel result = GrpcUtils.CreateChannel(serviceLocation.HostName,
serviceLocation.Port, credentials,
maxMesssageLength);
_msg.DebugFormat("The load balancer is suggesting {0}", result.ResolvedTarget);
return(result);
}
// Assumption: A load balancer is never also serving real requests -> lets not use it at all!
_msg.Debug("The load balancer has no service locations available.");
return(null);
}
protected void OpenChannel(bool useTls,
string clientCertificate = null,
bool assumeLoadBalancer = false)
{
if (string.IsNullOrEmpty(HostName))
{
_msg.Debug("Host name is null or empty. No channel opened.");
return;
}
ChannelCredentials credentials =
GrpcUtils.CreateChannelCredentials(useTls, clientCertificate);
var enoughForLargeGeometries = (int)Math.Pow(1024, 3);
Channel channel = GrpcUtils.CreateChannel(
HostName, Port, credentials, enoughForLargeGeometries);
if (assumeLoadBalancer)
{
ChannelIsLoadBalancer =
IsServingLoadBalancerEndpoint(channel, credentials, ServiceName,
enoughForLargeGeometries);
}
Channel = channel;
_msg.DebugFormat("Created grpc channel to {0} on port {1}", HostName, Port);
_healthClient = new Health.HealthClient(Channel);
ChannelOpenedCore(Channel);
}
public async Task <bool> CanAcceptCallsAsync()
{
if (!TryGetHealthClient(out Health.HealthClient healthClient))
{
return(false);
}
string serviceName = ChannelServiceName;
StatusCode statusCode = await GrpcUtils.IsServingAsync(healthClient, serviceName);
_msg.DebugFormat("Health status for service {0} at {1}: {2}.", serviceName,
Channel?.ResolvedTarget, statusCode);
return(statusCode == StatusCode.OK);
}
public bool CanAcceptCalls()
{
if (!TryGetHealthClient(out Health.HealthClient healthClient))
{
return(false);
}
string serviceName = ChannelServiceName;
bool result = GrpcUtils.IsServing(healthClient, serviceName, out StatusCode statusCode);
_msg.DebugFormat("Service {0} is serving at {1}: {2}. Status: {3}", serviceName,
Channel?.ResolvedTarget, result, statusCode);
return(result);
}
private static bool IsServingLoadBalancerEndpoint(
[NotNull] Channel channel,
[NotNull] ChannelCredentials credentials,
string serviceName,
int enoughForLargeGeometries)
{
var channelHealth = new Health.HealthClient(channel);
bool isServingEndpoint = GrpcUtils.IsServing(channelHealth, serviceName, out _);
if (isServingEndpoint)
{
return(false);
}
bool isLoadBalancer = GrpcUtils.IsServing(channelHealth, nameof(ServiceDiscoveryGrpc),
out StatusCode lbStatusCode);
if (isLoadBalancer)
{
_msg.DebugFormat("{0} is a load balancer address.", channel.ResolvedTarget);
Channel suggestedLocation =
TryGetChannelFromLoadBalancer(channel, credentials, serviceName,
enoughForLargeGeometries);
if (suggestedLocation != null)
{
_msg.DebugFormat("Using serving load balancer at {0}", channel.ResolvedTarget);
return(true);
}
// Assumption: A load balancer is never also serving real requests -> lets not use it at all!
_msg.Debug(
"The load balancer has no service locations available. It will not be used.");
return(false);
}
_msg.DebugFormat("No {0} service and no serving load balancer at {1}. Error code: {2}",
serviceName, channel.ResolvedTarget, lbStatusCode);
return(false);
}
protected void OpenChannel(bool useTls, string clientCertificate = null)
{
if (string.IsNullOrEmpty(HostName))
{
_msg.Debug("Host name is null or empty. No channel opened.");
return;
}
var enoughForLargeGeometries = (int)Math.Pow(1024, 3);
ChannelCredentials credentials =
GrpcUtils.CreateChannelCredentials(useTls, clientCertificate);
Channel = GrpcUtils.CreateChannel(
HostName, Port, credentials, enoughForLargeGeometries);
_msg.DebugFormat("Created grpc channel to {0} on port {1}", HostName, Port);
_healthClient = new Health.HealthClient(Channel);
ChannelOpenedCore(Channel);
}
