public async Task <RemoteUpdateResult> UpdateAsync(RemoteUpdateResult lastResult, CancellationToken cancellationToken)
{
if (!enabled)
{
return(CreateEmptyResult(lastResult));
}
var request = CreateRequest(lastResult?.Version);
var requestPriority = lastResult == null ? RequestPriority.Critical : RequestPriority.Ordinary;
var requestResult = await client.SendAsync(request, priority : requestPriority, cancellationToken : cancellationToken).ConfigureAwait(false);
if (cancellationToken.IsCancellationRequested)
{
throw new OperationCanceledException();
}
var updateResult = TryHandleFailure(requestResult, lastResult);
if (updateResult != null)
{
return(updateResult);
}
switch (requestResult.Response.Code)
{
case ResponseCode.NotModified:
return(HandleNotModifiedResponse(lastResult));
case ResponseCode.Ok:
return(HandleSuccessResponse(lastResult, requestResult.Response, requestResult.Replica));
}
throw NoAcceptableResponseException(requestResult);
}
private RemoteUpdateResult HandleSuccessResponse(RemoteUpdateResult lastUpdateResult, Response response, Uri replica)
{
if (!response.HasContent)
{
throw Empty200ResponseException();
}
if (response.Headers.LastModified == null)
{
throw MissingLastModifiedHeaderException();
}
var version = DateTime.Parse(response.Headers.LastModified, null, DateTimeStyles.AssumeUniversal).ToUniversalTime();
if (lastUpdateResult != null && version <= lastUpdateResult.Version)
{
if (version < lastUpdateResult.Version)
{
LogStaleVersion(version, lastUpdateResult.Version);
}
return(new RemoteUpdateResult(false, lastUpdateResult.Tree, lastUpdateResult.Version));
}
var tree = new RemoteTree(response.Content.ToArray(), TreeSerializers.V1);
LogReceivedNewZone(tree, version, replica);
return(new RemoteUpdateResult(true, tree, version));
}
private RemoteUpdateResult HandleNotModifiedResponse(RemoteUpdateResult lastUpdateResult)
{
if (lastUpdateResult == null)
{
throw UnexpectedNotModifiedResponseException();
}
return(new RemoteUpdateResult(false, lastUpdateResult.Tree, lastUpdateResult.Version));
}
private RemoteUpdateResult TryHandleFailure(ClusterResult requestResult, RemoteUpdateResult lastUpdateResult)
{
switch (requestResult.Status)
{
case ClusterResultStatus.ReplicasNotFound:
// (iloktionov): If no replicas were resolved during update and we haven't seen any non-trivial settings earlier,
// (iloktionov): we just silently assume CC is not deployed in current environment and return empty settings.
// (tsup): We make assumptions above in case we are not forced to assume that cluster config is deployed.
if (lastUpdateResult?.Tree == null && !assumeClusterConfigDeployed)
{
if (lastUpdateResult == null)
{
LogAssumingNoServer();
}
return(CreateEmptyResult(lastUpdateResult));
}
break;
case ClusterResultStatus.ReplicasExhausted:
// (iloktionov): Getting here means that no replica returned a 200 or 304 response.
// (iloktionov): If at least some of them responded with 404, it's reasonably safe to assume that zone does not exist.
if (requestResult.ReplicaResults.Any(r => r.Response.Code == ResponseCode.NotFound))
{
var updateResult = CreateEmptyResult(lastUpdateResult);
if (updateResult.Changed)
{
LogZoneDoesNotExist();
}
return(updateResult);
}
break;
}
return(null);
}
private static RemoteUpdateResult CreateEmptyResult([CanBeNull] RemoteUpdateResult lastResult) => new RemoteUpdateResult(lastResult?.Version != EmptyResultVersion, null, EmptyResultVersion);