/// <summary>
/// Pull-based iterator interface for scanning FASTER log
/// </summary>
/// <param name="beginAddress">Begin address for scan.</param>
/// <param name="endAddress">End address for scan (or long.MaxValue for tailing).</param>
/// <param name="name">Name of iterator, if we need to persist/recover it (default null - do not persist).</param>
/// <param name="recover">Whether to recover named iterator from latest commit (if exists). If false, iterator starts from beginAddress.</param>
/// <param name="scanBufferingMode">Use single or double buffering</param>
/// <param name="scanUncommitted">Whether we scan uncommitted data</param>
/// <returns></returns>
public FasterLogScanIterator Scan(long beginAddress, long endAddress, string name = null, bool recover = true, ScanBufferingMode scanBufferingMode = ScanBufferingMode.DoublePageBuffering, bool scanUncommitted = false)
{
FasterLogScanIterator iter;
if (recover && name != null && RecoveredIterators != null && RecoveredIterators.ContainsKey(name))
{
iter = new FasterLogScanIterator(this, allocator, RecoveredIterators[name], endAddress, getMemory, scanBufferingMode, epoch, headerSize, name, scanUncommitted);
}
else
{
iter = new FasterLogScanIterator(this, allocator, beginAddress, endAddress, getMemory, scanBufferingMode, epoch, headerSize, name, scanUncommitted);
}
if (name != null)
{
if (name.Length > 20)
{
throw new FasterException("Max length of iterator name is 20 characters");
}
if (PersistedIterators.ContainsKey(name))
{
Debug.WriteLine("Iterator name exists, overwriting");
}
PersistedIterators[name] = iter;
}
if (Interlocked.Increment(ref logRefCount) == 1)
{
throw new FasterException("Cannot scan disposed log instance");
}
return(iter);
}
/// <summary>
/// Pull-based iterator interface for scanning FASTER log
/// </summary>
/// <param name="beginAddress">Begin address for scan.</param>
/// <param name="endAddress">End address for scan (or long.MaxValue for tailing).</param>
/// <param name="name">Name of iterator, if we need to persist/recover it (default null - do not persist).</param>
/// <param name="recover">Whether to recover named iterator from latest commit (if exists). If false, iterator starts from beginAddress.</param>
/// <param name="scanBufferingMode">Use single or double buffering</param>
/// <returns></returns>
public FasterLogScanIterator Scan(long beginAddress, long endAddress, string name = null, bool recover = true, ScanBufferingMode scanBufferingMode = ScanBufferingMode.DoublePageBuffering)
{
FasterLogScanIterator iter;
if (recover && name != null && RecoveredIterators != null && RecoveredIterators.ContainsKey(name))
{
iter = new FasterLogScanIterator(this, allocator, RecoveredIterators[name], endAddress, getMemory, scanBufferingMode, epoch, headerSize, name);
}
else
{
iter = new FasterLogScanIterator(this, allocator, beginAddress, endAddress, getMemory, scanBufferingMode, epoch, headerSize, name);
}
if (name != null)
{
if (name.Length > 20)
{
throw new Exception("Max length of iterator name is 20 characters");
}
if (FasterLogScanIterator.PersistedIterators.ContainsKey(name))
{
Debug.WriteLine("Iterator name exists, overwriting");
}
FasterLogScanIterator.PersistedIterators[name] = iter;
}
return(iter);
}
private static async ValueTask <bool> SlowWaitUncommittedAsync(FasterLogScanIterator @this, CancellationToken token)
{
while (true)
{
if (@this.disposed)
{
return(false);
}
var refreshUncommittedTask = @this.fasterLog.RefreshUncommittedTask;
if (@this.NextAddress < @this.fasterLog.SafeTailAddress)
{
return(true);
}
// Ignore refresh-uncommitted exceptions, except when the token is signaled
try
{
await refreshUncommittedTask.WithCancellationAsync(token);
}
catch (ObjectDisposedException) { return(false); }
catch when(!token.IsCancellationRequested)
{
}
}
}
private static async ValueTask <bool> SlowWaitAsync(FasterLogScanIterator @this, CancellationToken token)
{
while (true)
{
if (@this.disposed)
{
return(false);
}
if (@this.Ended)
{
return(false);
}
var commitTask = @this.fasterLog.CommitTask;
if (@this.NextAddress < @this.fasterLog.CommittedUntilAddress)
{
return(true);
}
// Ignore commit exceptions, except when the token is signaled
try
{
await commitTask.WithCancellationAsync(token).ConfigureAwait(false);
}
catch (ObjectDisposedException) { return(false); }
catch when(!token.IsCancellationRequested)
{
}
}
}
// use static local function to guarantee there's no accidental closure getting allocated here
static async ValueTask SlowWaitAsync(FasterLogScanIterator @this, CancellationToken token)
{
while (true)
{
var commitTask = @this.fasterLog.CommitTask;
if (@this.nextAddress >= @this.fasterLog.CommittedUntilAddress)
{
// Ignore commit exceptions, except when the token is signaled
try
{
await commitTask.WithCancellationAsync(token);
}
catch when(!token.IsCancellationRequested)
{
}
}
else
{
break;
}
}
}
