public async Task Invoke(HttpContext context)
{
if (context.Request.Path != _options.Path)
{
await _next(context);
return;
}
if (_options.AuthorizationPolicy != null)
{
var principal = await SecurityHelper.GetUserPrincipal(context, _options.AuthorizationPolicy);
if (!await _authorizationService.AuthorizeAsync(principal, context, _options.AuthorizationPolicy))
{
_logger.AuthorizationFailed();
await _next(context);
return;
}
}
var response = context.Response;
// Canary response must not be cached
response.Headers[HeaderNames.CacheControl] = "no-cache";
response.Headers[HeaderNames.Pragma] = "no-cache";
response.Headers[HeaderNames.Expires] = "-1";
var serverSwitchContext = new ServerSwitchContext(context);
await _serverSwitch?.CheckServerStateAsync(serverSwitchContext);
if (serverSwitchContext.ServerDisabled)
{
_logger.ServerDisabled();
response.StatusCode = StatusCodes.Status503ServiceUnavailable;
response.WriteRetryAfterHeader(serverSwitchContext.RetryAfter);
}
else if (_options.EnableHealthCheck)
{
var healthCheckResponse = await _healthService.CheckHealthAsync(_defaultPolicy);
if (healthCheckResponse.HasCriticalErrors)
{
_logger.CanaryFailed(healthCheckResponse.Errors);
response.StatusCode = StatusCodes.Status503ServiceUnavailable;
response.WriteRetryAfterHeader(healthCheckResponse.RetryAfter);
}
else
{
_logger.CanarySucceeded();
response.StatusCode = StatusCodes.Status200OK;
}
}
}
public Task CheckServerStateAsync(ServerSwitchContext context)
{
if (_fileExists)
{
context.Disable(_options.RetryDelay);
}
else
{
context.Enable();
}
return(TaskCache.CompletedTask);
}
