private async Task Upgrade <K, V>(UUID seriesId, PersistentSeries <K, V> series)
{
if (!series.IsWriter)
{
try {
_writeSeriesLocks.Add(seriesId, Pid);
series.IsWriter = true;
LogAcquireLock(seriesId, series.Version);
return;
} catch (ArgumentException) { }
}
while (true)
{
// wait if a writer from the same repo releases lock
var released = await series.LockReleaseEvent.WaitAsync(1000);
if (released)
{
try {
// TODO TryAdd atomic method
_writeSeriesLocks.Add(seriesId, Pid);
series.IsWriter = true;
LogAcquireLock(seriesId, series.Version);
break;
} catch (ArgumentException) {
Trace.WriteLine("Could not upgrade after lock release, some one jumped ahead of us");
}
}
else
{
int pid;
if (_writeSeriesLocks.TryGetValue(seriesId, out pid))
{
try {
Process.GetProcessById(pid & ((1 << 16) - 1));
Trace.TraceWarning("Tried to steal a lock but the owner process was alive.");
} catch (ArgumentException) {
// pid is not running anymore, steal lock
Trace.TraceWarning($"Current process {Pid} has stolen a lock left by a dead process {pid}. If you see this often then dispose SeriesRepository properly before application exit.");
_writeSeriesLocks[seriesId] = Pid;
series.IsWriter = true;
LogAcquireLock(seriesId, series.Version);
break;
}
}
}
}
}
protected virtual async Task <PersistentSeries <K, V> > GetSeries <K, V>(string seriesId, bool isWriter, bool allowBatches = false)
{
seriesId = seriesId.ToLowerInvariant().Trim();
var exSeriesId = GetExtendedSeriesId <K, V>(seriesId);
var uuid = new UUID(exSeriesId.UUID);
IAcceptCommand series;
if (_openStreams.TryGetValue(uuid, out series))
{
var ps = (PersistentSeries <K, V>)series;
Interlocked.Increment(ref ps.RefCounter);
if (isWriter && !ps.IsWriter)
{
var hasLockAcquired = await RequestWriteLock(uuid);
if (!hasLockAcquired)
{
throw new SingleWriterException();
}
// Upgrade to writer
ps.IsWriter = true;
}
return(ps);
}
// NB We restrict only opening more than once, once opened a series object could be modified by many threads
if (isWriter)
{
var hasLockAcquired = await RequestWriteLock(uuid);
if (!hasLockAcquired)
{
throw new SingleWriterException();
}
}
// NB: Writers now have lock acquired. Other logic is the same for both writers and readers.
Action <bool, bool> disposeCallback = (remove, downgrade) => {
IAcceptCommand temp;
if (remove)
{
// NB this callback is called from temp.Dispose();
var removed = _openStreams.TryRemove(uuid, out temp);
Trace.Assert(removed);
}
if (downgrade)
{
Downgrade(uuid);
}
};
var ipom = base.GetSeries <K, V>(exSeriesId.Id, exSeriesId.Version, false);
var pSeries = new PersistentSeries <K, V>(_appendLog, _pid, uuid, ipom, allowBatches, isWriter, disposeCallback);
// NB this is done in consturctor: pSeries.RefCounter++;
_openStreams[uuid] = pSeries;
await RequestSubscribeSynced(uuid, pSeries.Version, exSeriesId.ToString());
return(pSeries);
}
protected virtual async Task <PersistentSeries <K, V> > GetSeries <K, V>(string seriesId, bool isWriter, bool allowBatches = false)
{
seriesId = seriesId.ToLowerInvariant().Trim();
var exSeriesId = GetExtendedSeriesId <K, V>(seriesId);
var uuid = new UUID(exSeriesId.UUID);
IAcceptCommand series;
if (_openSeries.TryGetValue(uuid, out series))
{
var ps = (PersistentSeries <K, V>)series;
Interlocked.Increment(ref ps.RefCounter);
if (isWriter && !ps.IsWriter)
{
await Upgrade(uuid, ps);
}
return(ps);
}
Action <bool, bool> disposeCallback = (remove, downgrade) => {
IAcceptCommand temp;
if (remove)
{
// NB this callback is called from temp.Dispose();
var removed = _openSeries.TryRemove(uuid, out temp);
Trace.Assert(removed);
}
if (downgrade)
{
Downgrade(uuid);
}
};
var ipom = base.GetSeries <K, V>(exSeriesId.Id, exSeriesId.Version, false);
var pSeries = new PersistentSeries <K, V>(_appendLog, _pid, uuid,
ipom, allowBatches, isWriter,
disposeCallback);
// NB this is done in consturctor: pSeries.RefCounter++;
_openSeries[uuid] = pSeries;
LogSubscribe(uuid, pSeries.Version, exSeriesId.ToString());
if (isWriter)
{
try {
_writeSeriesLocks.Add(uuid, Pid);
LogAcquireLock(uuid, pSeries.Version);
} catch (ArgumentException) {
// NB do not wait // await Upgrade(uuid, pSeries);
throw new InvalidOperationException("Series is already opened for write. Only single writer is allowed.");
}
}
else
{
// wait for flush if there is a live writer
int pid;
if (_writeSeriesLocks.TryGetValue(uuid, out pid))
{
try {
Process.GetProcessById(pid & ((1 << 16) - 1));
await pSeries.FlushEvent.WaitAsync(-1);
} catch (ArgumentException) {
// pid is not running anymore, steal lock
Trace.TraceWarning($"Current process {Pid} has removed a lock left by a dead process {pid}. If you see this often then dispose SeriesRepository properly before application exit.");
_writeSeriesLocks.Remove(uuid);
LogReleaseLock(uuid);
}
}
}
return(pSeries);
}
