public async Task AddForecastSubscription(ForecastSubscription subscription)
{
await _retryPolicy.ExecuteAsync(async() =>
{
await _context.ForecastSubscriptions.AddAsync(subscription);
await _context.SaveChangesAsync();
});
}
public void StartTimer(ForecastSubscription subscription)
{
object timerState = new object();
// Start an accurate timer based on subscriptions.intervalseconds
Timer timer = new Timer(async(timerState) =>
{
await FetchData(subscription);
}, timerState, 0, (int)TimeSpan.FromSeconds(subscription.IntervalSeconds).TotalMilliseconds);
}
public async Task FetchData(ForecastSubscription subscription)
{
try
{
using var scope = _services.CreateScope();
var wundergroundService = scope.ServiceProvider.GetRequiredService <IWundergroundService>();
var data = await wundergroundService.Get5DayForecast(subscription.GeoCode);
await KafkaHelpers.SendMessageAsync(KafkaHelpers.WeatherDataTopic, data, _producer);
}
catch (HttpRequestException e)
{
_logger.LogError($"Fetch for GeoCode={subscription.GeoCode} threw an error: {e.Message}");
}
}
public async void ListenForSubscriptionsActions(CancellationToken stoppingToken, List <CurrentConditionSubscription> currentConditionSubscriptions, List <ForecastSubscription> forecastSubscriptions)
{
// Listening and waiting for new subscription requests from kafka
var consumerConfig = new ConsumerConfig
{
GroupId = "weather-station-new-subscription-group",
AutoOffsetReset = AutoOffsetReset.Earliest,
};
KafkaHelpers.SetKafkaConfigKerberos(consumerConfig);
using (var consumer = new ConsumerBuilder <Ignore, string>(consumerConfig).Build())
{
using (var scope = _services.CreateScope())
{
var repo = scope.ServiceProvider.GetRequiredService <ISubscriptionRepo>();
consumer.Subscribe(KafkaHelpers.SubscriptionActionsTopic);
_logger.LogInformation("Listening for subscription action requests");
while (!stoppingToken.IsCancellationRequested)
{
try
{
// consumer does not have an async method. So it is wrapped in a task, so that the rest of the application doesn't hang here
var consumeResult = await Task.Factory.StartNew(() => consumer.Consume(stoppingToken));
var messageJsonString = consumeResult.Message.Value;
// Checking format required.
SubscriptionRequestDTO request = JsonConvert.DeserializeObject <SubscriptionRequestDTO>(messageJsonString);
_logger.LogInformation("A subscription action request has arrived");
switch (request.Action)
{
case SubscriptionAction.CREATECURRENTCONDITION:
var currentConditionRequest = JsonConvert.DeserializeObject <NewCurrentConditionSubscriptionRequestDTO>(messageJsonString);
var currentConditionSubscription = new CurrentConditionSubscription
{
StationId = currentConditionRequest.StationId,
IntervalSeconds = currentConditionRequest.IntervalSeconds
};
// persisting the newly added subscription
await repo.AddCurrentConditionSubscription(currentConditionSubscription);
// adding it to the list of subscriptions
currentConditionSubscriptions.Add(currentConditionSubscription);
// starting the subscription. I want this to run in the background. So I discard the result with '_'
_ = Task.Run(() => StartTimer(currentConditionSubscription));
break;
case SubscriptionAction.CREATEFORECAST:
var forecastSubscriptionRequest = JsonConvert.DeserializeObject <ForecastSubscription>(messageJsonString);
var forecastSubscription = new ForecastSubscription
{
GeoCode = forecastSubscriptionRequest.GeoCode,
IntervalSeconds = forecastSubscriptionRequest.IntervalSeconds
};
// persisting the newly added subscription
await repo.AddForecastSubscription(forecastSubscription);
// adding it to the list of subscriptions
forecastSubscriptions.Add(forecastSubscription);
// starting the subscription. I want this to run in the background. So I discard the result with '_'
_ = Task.Run(() => StartTimer(forecastSubscription));
break;
case SubscriptionAction.DELETE:
// TODO: Delete
break;
default:
throw new Newtonsoft.Json.JsonException("Invalid Subscription action");
}
}
catch (ConsumeException ex)
{
_logger.LogError(ex.Error.ToString());
}
// If the request from kafka is not correctly formatted an error will be thrown and catched here
catch (Newtonsoft.Json.JsonException ex)
{
_logger.LogError(ex.Message);
}
// Cancelled background worker
catch (OperationCanceledException)
{
consumer.Close();
}
}
}
}
// If we reach this point it means the application is shutting down. Therefore we clean up
_logger.LogInformation("Cleaning up");
_producer.Flush(TimeSpan.FromSeconds(5));
_producer.Dispose();
}
