/// <summary>
/// Polls the next command to execute locally from the server. The result of the
/// last executed command must be given, if there is one. The returned Task may block
/// some time, because the server uses the long polling technique to reduce network traffic.
/// If the server can not be reached, an exception is thrown (because the last result
/// has to be transmitted again).
/// </summary>
private async Task <RpcCommand?> PullFromServer(RpcCommandResult?lastResult)
{
// Long polling. The server returns null after the long polling time.
var bodyJson = lastResult != null?JsonLib.ToJson(lastResult) : null;
var httpResponse = await httpPull.PostAsync(clientConfig.ServerUrl + "/pull",
bodyJson != null?new StringContent(bodyJson, Encoding.UTF8, "application/json") : null);
if (httpResponse.IsSuccessStatusCode)
{
// Last result was received. The server responded with the next command or null,
// if there is currently none.
if (httpResponse.Content.Headers.ContentLength > 0)
{
return(JsonLib.FromJson <RpcCommand>(await httpResponse.Content.ReadAsStringAsync()));
}
else
{
return(null);
}
}
else
{
// Remote exception.
throw new Exception("Server responded with status code " + httpResponse.StatusCode);
}
}
public void EnqueueCommand(string clientID, RpcCommand command)
{
lock (syncLock) {
var dir = GetDirectory(clientID);
// Apply strategy
var strategy = command.RetryStrategy;
if (strategy == null || strategy == RpcRetryStrategy.None)
{
// No retry strategy chosen. This method should not have been called at all. Do nothing.
return;
}
else if (strategy == RpcRetryStrategy.RetryWhenOnline)
{
// No preparation needed; just enqueue this command
}
else if (strategy == RpcRetryStrategy.RetryNewestWhenOnline)
{
// Remove all preceding commands of this type
foreach (var file in GetFilesByCommandName(clientID, command.MethodName))
{
file.Delete();
}
}
var filename = command.ID + "-" + command.MethodName;
File.WriteAllText(Path.Combine(dir.FullName, filename), JsonLib.ToJson(command));
}
}
public async Task SayHelloToClient(Greeting greeting)
{
Console.WriteLine("Hello " + greeting.Name + "!");
if (greeting.MoreData is SampleData moreData)
{
Console.WriteLine("More information for you: " + JsonLib.ToJson(moreData));
}
}
/// <summary>
/// Creates a new encoded RPC command, using the given method name and parameters.
/// The parameters must be JSON-encodable objects.
/// </summary>
private RpcCommand(string methodName, params object[] methodParameters)
{
lock (syncLock) {
loop++;
if (loop > 999)
{
loop = 0;
}
ID = ((ulong)CoreUtils.TimeNow()) * 1000 + loop;
}
MethodName = methodName;
MethodParameters = methodParameters.Select(it => JsonLib.ToJson(it)).ToList();
}
/// <summary>
/// Sends the given command to the server now, reads the result or catches the
/// exception, and sets the command's state accordingly.
/// </summary>
private async Task ExecuteOnServerNow(RpcCommand command)
{
RpcCommandResult result;
var bodyJson = JsonLib.ToJson(command);
try {
var httpResponse = await httpPush.PostAsync(clientConfig.ServerUrl + "/push",
new StringContent(bodyJson, Encoding.UTF8, "application/json"));
if (httpResponse.IsSuccessStatusCode)
{
// Response (either success or remote failure) received.
result = JsonLib.FromJson <RpcCommandResult>(await httpResponse.Content.ReadAsStringAsync());
}
else
{
// The server did not respond with 200 (which it should do even in case of
// a remote exception). So there is a communication error.
result = RpcCommandResult.FromFailure(command.ID,
new RpcFailure(RpcFailureType.RpcError, "Remote side problem with RPC call. HTTP status code " +
(int)httpResponse.StatusCode));
}
}
catch {
// Could not reach server.
result = RpcCommandResult.FromFailure(command.ID,
new RpcFailure(RpcFailureType.Timeout, "Could not reach the server"));
}
// When a result was received (i.e. when there was no network problem), the command is finished
if (false == (result.Failure?.IsNetworkProblem == true) && command.ID == serverCache.CurrentCommand?.ID)
{
serverCache.FinishCurrentCommand();
}
// Finish command
command.Finish(result);
}