/// <summary>
/// Transfers the data with the key and entry to the local store.
/// </summary>
/// <param name="entry"></param>
/// <param name="value"></param>
/// <param name="dht"></param>
/// <param name="cancellationToken"></param>
/// <returns></returns>
async Task TransferAsync(IKsStoreEntry <TKey> entry, KsHashTableValue value, KsHashTableEntry dht, CancellationToken cancellationToken)
{
foreach (var uri in dht.Endpoints)
{
// we can't pull the value from ourselves, move to secondaries
if (uri == options.Value.Uri)
{
continue;
}
var client = clients.Get(uri);
if (client == null)
{
throw new KsException($"Could not obtain client for remote host: '{uri}'");
}
// existing token if we're resuming an operation after failure
var t = await entry.GetOwnerTokenAsync(cancellationToken);
var v = await client.ShiftLockAsync(entry.Key, t, cancellationToken);
// current owner returns no value, must not really own it, nothing to transfer
if (v == null)
{
return;
}
// track down owner by following forwards
while (v.Value.ForwardUri != null)
{
client = clients.Get(v.Value.ForwardUri);
v = await client.ShiftLockAsync(entry.Key, t, cancellationToken);
}
if (v.Value.Data == null)
{
throw new KsException("Data not retrieved.");
}
if (v.Value.Data == null)
{
throw new KsException("Data retrieved, but not token.");
}
// update local entry with latest information
await entry.SetOwnerTokenAsync(t = v.Value.Token);
await entry.SetAsync(v.Value.Data);
// finalize shift on remote node and publish entry
await client.ShiftAsync(entry.Key, t, options.Value.Uri, cancellationToken);
await hashtable.AddAsync(entry.Key, new KsHashTableValue(Serialize(new KsHashTableEntry(new[] { options.Value.Uri })), value.Version + 1, TimeSpan.FromDays(1)));
// we succeeded, exit loop
break;
}
// zero out lock token if we successfully complete process
await entry.SetOwnerTokenAsync(null);
}
async Task <KsHostShiftLockResult> ShiftLockAsyncImpl(IKsStoreEntry <TKey> entry, string token, CancellationToken cancellationToken)
{
// freeze
var f = await entry.FreezeAsync(token, TimeSpan.FromSeconds(5), cancellationToken);
if (f.ForwardUri != null)
{
return(new KsHostShiftLockResult(null, null, f.ForwardUri));
}
// get existing value
var d = await entry.GetAsync(f.Token, cancellationToken);
if (d.ForwardUri != null)
{
return(new KsHostShiftLockResult(null, null, d.ForwardUri));
}
return(new KsHostShiftLockResult(f.Token, d.Data, null));
}
async Task <byte[]> GetAsyncImpl(IKsStoreEntry <TKey> entry, CancellationToken cancellationToken)
{
var r = await entry.GetAsync(null, cancellationToken);
return(r.Data);
}
async Task ShiftAsyncImpl(IKsStoreEntry <TKey> entry, string token, Uri forwardUri, CancellationToken cancellationToken)
{
await hashtable.RemoveAsync(entry.Key, CancellationToken.None);
await entry.ForwardAsync(token, forwardUri, CancellationToken.None);
}