/// <inheritdoc />
public async Task <Response> DistributeQueryAsync(Request request)
{
if (!request.Validate(out var validationResult))
{
return(Response.Fail(validationResult.ErrorMessage));
}
var servers = _statisticsStorage.Get(request.Type);
var maxSessions = _configuration.GetMaxSessionsParameter(request.Type);
var availableServer = _serverDecider.FindAvailableServer(servers, maxSessions);
if (availableServer is null)
{
return(HandleNoAvailableServerScenario(request));
}
var serializedData = string.Empty;
try
{
if (request.IsSelect)
{
serializedData = await _queryExecutor.QueryAsync(availableServer, request.Query);
}
else
{
await _queryExecutor.ExecuteAsync(availableServer, request.Query);
}
if (request.IsRetried)
{
_responseStorage.Add(Response.Completed(serializedData, request.RequestId));
}
return(Response.Completed(serializedData, request.RequestId));
}
catch (PostgresException postgresException)
{
var message = $"Query is not correct: {postgresException.Message}";
// postgres errors are client-side problems
if (!request.AcceptRetries)
{
return(Response.Fail(message));
}
request.RequestId = Guid.NewGuid();
_responseStorage.Add(Response.Fail(message, request.RequestId));
return(Response.Queued(request.RequestId));
}
catch (Exception)
{
// if not postgres error, must be system error
// failing if request does not support queue
if (!request.AcceptRetries)
{
return(Response.Fail("No server available right now."));
}
var maxRetryCount = _configuration.MaxRetryCount;
if (request.IsRetried && request.CurrentRetryAttempt >= maxRetryCount)
{
_responseStorage.Add(Response.Fail("Number of allowed attempts exceeded", request.RequestId));
return(Response.Fail());
}
request.IsRetried = true;
request.RequestId = Guid.NewGuid();
_queue.Add(request);
return(Response.Completed(request.RequestId.ToString()));
}
}