///<inheritdoc />
public async Task <NodeAndLoadBalancer> GetNode()
{
_lastUsageTime = DateTime.UtcNow;
NodeAndLoadBalancer nodeAndLoadBalancer = null;
string preferredEnvironment = TracingContext.GetPreferredEnvironment();
// 1. Use explicit host override if provided in request
// TBD: Theoretically if we only ever call a service through host overrides we might not have a health check for the service at all (though it is in use)
var hostOverride = TracingContext.GetHostOverride(ServiceName);
if (hostOverride != null)
{
return new NodeAndLoadBalancer {
Node = new Node(hostOverride.Host, hostOverride.Port),
LoadBalancer = null,
PreferredEnvironment = preferredEnvironment ?? Environment.DeploymentEnvironment,
}
}
;
// 2. Otherwise, use preferred environment if provided in request
if (preferredEnvironment != null && (nodeAndLoadBalancer = await GetNodeAndLoadBalancer(preferredEnvironment, preferredEnvironment)) != null)
{
return(nodeAndLoadBalancer);
}
// 3. Otherwise, try use current environment
if ((nodeAndLoadBalancer = await GetNodeAndLoadBalancer(Environment.DeploymentEnvironment, preferredEnvironment)) != null)
{
_healthStatus = new HealthMessage(Health.Healthy, message: null, suppressMessage: true); // No need for a health message since the load balancer we're returning already provides one
return(nodeAndLoadBalancer);
}
// 4. We're in prod env and service is not deployed, no fallback possible
if (Environment.DeploymentEnvironment == MASTER_ENVIRONMENT)
{
_healthStatus = new HealthMessage(Health.Unhealthy, "Service not deployed");
throw ServiceNotDeployedException();
}
// 5. We're not in prod, but fallback to prod is disabled
if (GetDiscoveryConfig().EnvironmentFallbackEnabled == false)
{
_healthStatus = new HealthMessage(Health.Unhealthy, "Service not deployed (and fallback to prod disabled)");
throw ServiceNotDeployedException();
}
// 6. Otherwise, try fallback to prod
if ((nodeAndLoadBalancer = await GetNodeAndLoadBalancer(MASTER_ENVIRONMENT, preferredEnvironment ?? Environment.DeploymentEnvironment)) != null)
{
_healthStatus = new HealthMessage(Health.Healthy, "Service not deployed, falling back to prod");
return(nodeAndLoadBalancer);
}
_healthStatus = new HealthMessage(Health.Unhealthy, "Service not deployed, fallback to prod enabled but service not deployed in prod either");
throw ServiceNotDeployedException();
}