public TelemetryController(
ISatnogsDbApi satnogsDbApi,
ISatnogsNetworkApi satnogsNetworkApi,
IMemoryCache memoryCache,
ApplicationSettings settings)
{
this.satnogsDbApi = satnogsDbApi;
this.satnogsNetworkApi = satnogsNetworkApi;
this.memoryCache = memoryCache;
this.settings = settings;
}
public static async Task <List <ObservationEntry> > GetAllObservations(this ISatnogsNetworkApi api, int satelliteId, string vettedStatus = null, IEnumerable <ObservationEntry> previousObservations = null, int maxPages = 1024, int concurrentPages = 32)
{
// There are two ways to retrieve all observations:
//
// * One at a time.
// After each observation is fetched, the "link" header can be checked for a rel= "next" link which will give the next page.
//
// This will give all pages until the last page is reached, and no rel= "next" link is provided.
// This is the "cleanest" method supported by the API.
//
//
// * Multithreaded
// Attempt to get an entire batch of observations, all simultaneously at once.
// Continue grabbing entire batches until we hit a 404 Not Found (or we could technically check for missing rel= "next" link but doesn't make much difference).
// We can also save a cache of previous Observation Ids, and then stop as soon as we hit one (since we've "caught up" to the latest data").
//
// This is fast and it works, but it's technically not a supported way to use the API.
//
//
// We use Multithreaded because it's so, so much faster.
//
SortedDictionary <long, ObservationEntry> observations = new SortedDictionary <long, ObservationEntry>();
HashSet <long> previousObservationIds = previousObservations == null ? null : new HashSet <long>(previousObservations.Select(oe => oe.Id));
if (previousObservations != null)
{
foreach (var thisPreviousObservation in previousObservations)
{
observations[thisPreviousObservation.Id] = thisPreviousObservation;
}
}
for (int i = 1; i < maxPages; i += concurrentPages)
{
var tasks = new List <Task <List <ObservationEntry> > >();
for (int j = 0; j < concurrentPages; j++)
{
var task = api.GetObservations(null, satelliteId, vettedStatus, i + j);
tasks.Add(task);
}
bool end = false;
foreach (var task in tasks)
{
try
{
List <ObservationEntry> observationsPage = await task;
foreach (var thisObservation in observationsPage)
{
observations[thisObservation.Id] = thisObservation;
}
if (previousObservationIds != null)
{
// Check cache for observation.
// If we hit one, it indicates that we have "caught up" to the previous cache.
foreach (var observation in observationsPage)
{
if (previousObservationIds.Contains(observation.Id))
{
end = true;
break;
}
}
}
}
catch (ApiException ex) when(ex.StatusCode == HttpStatusCode.NotFound)
{
end = true;
}
}
if (end)
{
break;
}
}
return(observations.Values.ToList());
}
