public FetchPayload OpenStream()
{
var retRec = new FetchPayload();
var filter = Builders <BakedVolumes> .Filter.Eq("_id", Volume);
VolumeRec = Bvs.FindSync(filter).FirstOrDefault();
if (VolumeRec == null)
{
retRec.Error = $"Volume: {Volume} does not exist";
return(retRec);
}
if (!VolumeRec.Parts.ContainsKey(Part))
{
retRec.Error = $"Volume: {Volume} Part {Part} does not exist";
return(retRec);
}
var p = VolumeRec.Parts[Part];
fName = Path.Combine(p.Path, p.Name);
try
{
binOpen = new BinaryReader(File.Open(fName, FileMode.Open, FileAccess.Read));
VolumeStream = binOpen.BaseStream;
}
catch (Exception ex)
{
retRec.Error = ex.Message;
if (logger != null)
{
logger.LogError(ex, $"Cannot open file {fName} for {Volume}/{Part}");
}
return(retRec);
}
//Console.WriteLine($"[Open Volume: {fName}]");
return(retRec);
}
public FetchPayload GetRecord(FetchRequest request)
{
var volume = request.BakedVolume;
var part = request.Part;
if (bvs == null)
{
bvs = NeoMongo.NeoDb.BakedVolumes();
}
var cacheKey = volume + "/" + part;
VolCacheRec cache;
if (!openFileCache.TryGetValue <VolCacheRec>(cacheKey, out cache))
{
cache = new VolCacheRec(bvs, volume, part, _logger);
}
openFileCache.Set <VolCacheRec>(cacheKey, cache);
// Our caches work, but we're not really managing any kind of residency.
// We'll play with this and see how they work, but it's trivial to
// simply DDOS the cache into insanity.
// We're also not handling error retry, though that may not be our job.
// We may have to make some specific errors flow back so the client can
// deal with a moved file or a service down. It theoretically can even
// use the X file if one of the main 4 is not available to regen the
// data flow with XOR (in degraded mode). This service will read any part.
var retRec = new FetchPayload();
retRec.Error = String.Empty;
if (cache.VolumeStream == null)
{
retRec = cache.OpenStream();
}
if (retRec.Error != String.Empty)
{
Console.WriteLine($"? Encountered error: {retRec.Error}");
return(retRec);
}
// Now if the file is gone/moved we might get an error seeking
var didSeek = cache.VolumeStream.Seek(request.Offset, SeekOrigin.Begin);
var length = Math.Min(BUFSIZ, request.RequestCount);
var count = cache.VolumeStream.Read(buffer, 0, length);
retRec.Length = count; // Not sure what's efficient here - nice if we didn't have to copy
retRec.Payload = ByteString.CopyFrom(buffer, 0, count);
Console.WriteLine($"[Read: {request.BakedVolume}/{request.Part} Count={count} Offset={request.Offset} (actual={didSeek}, newpos={cache.VolumeStream.Position})");
return(retRec);
}
