/// <summary>
/// Retrieves the next reachable <see cref="RemoteHost"/>.
/// </summary>
/// <param name="affinityToken">
/// A string to generate a consistent affinity to a specific host within the set of available hosts.
/// Identical strings will return the same host for a given pool of reachable hosts. A request ID is usually provided.
/// </param>
/// <returns>A reachable <see cref="RemoteHost"/>.</returns>
/// <exception cref="EnvironmentException">Thrown when there is no reachable <see cref="RemoteHost"/> available.</exception>
public IEndPointHandle GetNextHost(string affinityToken = null)
{
LastEndpointRequest = DateTime.UtcNow;
var hostOverride = TracingContext.GetHostOverride(DeploymentIdentifier.ServiceName);
if (hostOverride != null)
{
return(new OverriddenRemoteHost(DeploymentIdentifier.ServiceName, hostOverride.Hostname, hostOverride.Port ?? GetConfig().DefaultPort));
}
lock (_lock)
{
Health.Activate();
if (ReachableHosts.Count == 0)
{
var lastExceptionEndPoint = UnreachableHosts.FirstOrDefault();
// TODO: Exception throwing code should be in this class, not in another.
throw DiscoverySource.AllEndpointsUnreachable(EndPointsResult, lastExceptionEndPoint?.LastException, lastExceptionEndPoint == null ? null : $"{lastExceptionEndPoint.HostName}:{lastExceptionEndPoint.Port}", string.Join(", ", UnreachableHosts));
}
Counter++;
ulong hostId = affinityToken == null ? Counter : (ulong)affinityToken.GetHashCode();
return(ReachableHosts[(int)(hostId % (ulong)ReachableHosts.Count)]);
}
}
private ValueTask <HealthCheckResult> CheckHealth()
{
var config = GetConfig();
if (IsHealthCheckSuppressed(config))
{
return(new ValueTask <HealthCheckResult>(HealthCheckResult.Healthy($"Health check suppressed because service was not in use for more than {config.SuppressHealthCheckAfterServiceUnused.TotalSeconds} seconds.")));
}
int reachableCount;
int unreachableCount;
Exception exception;
string[] unreachableHosts;
lock (_lock)
{
reachableCount = ReachableHosts.Count;
unreachableHosts = UnreachableHosts.Select(x => $"{x.HostName}:{x.Port}").ToArray();
unreachableCount = unreachableHosts.Length;
exception = UnreachableHosts.FirstOrDefault()?.LastException;
}
if (reachableCount == 0)
{
return(new ValueTask <HealthCheckResult>(HealthCheckResult.Unhealthy($"All of the {unreachableCount} hosts are unreachable: " +
$"{string.Join(",", unreachableHosts)}. Last exception: {HealthMonitor.GetMessages(exception)}")));
}
else
{
if (unreachableCount > 0)
{
return(new ValueTask <HealthCheckResult>(HealthCheckResult.Unhealthy($"The following {unreachableCount} hosts " +
$"(out of {unreachableCount + reachableCount}) are unreachable: {string.Join(",", unreachableHosts)}. " +
$"Last exception: {HealthMonitor.GetMessages(exception)}")));
}
else
{
return(new ValueTask <HealthCheckResult>(HealthCheckResult.Healthy($"All {reachableCount} hosts are reachable.")));
}
}
}