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NuCache: troubleshooting

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This commit is contained in:
Stephan
2019-02-22 15:43:37 +01:00
parent c56b8863ee
commit 7e413ed406
3 changed files with 233 additions and 53 deletions
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174
src/Umbraco.Tests/Cache/SnapDictionaryTests.cs
View File

@@ -712,16 +712,102 @@ namespace Umbraco.Tests.Cache
}
[Test]
public void NestedWriteLocking()
public void NestedWriteLocking1()
{
var d = new SnapDictionary<int, string>();
var t = d.Test;
t.CollectAuto = false;
Assert.AreEqual(0, d.CreateSnapshot().Gen);
// no scope context: writers nest, last one to be disposed commits
var scopeProvider = GetScopeProvider();
using (var w1 = d.GetWriter(scopeProvider))
{
Assert.AreEqual(1, t.LiveGen);
Assert.AreEqual(1, t.WLocked);
Assert.IsTrue(t.NextGen);
using (var w2 = d.GetWriter(scopeProvider))
{
Assert.AreEqual(1, t.LiveGen);
Assert.AreEqual(2, t.WLocked);
Assert.IsTrue(t.NextGen);
Assert.AreNotSame(w1, w2); // get a new writer each time
d.Set(1, "one");
Assert.AreEqual(0, d.CreateSnapshot().Gen);
}
Assert.AreEqual(1, t.LiveGen);
Assert.AreEqual(1, t.WLocked);
Assert.IsTrue(t.NextGen);
Assert.AreEqual(0, d.CreateSnapshot().Gen);
}
Assert.AreEqual(1, t.LiveGen);
Assert.AreEqual(0, t.WLocked);
Assert.IsTrue(t.NextGen);
Assert.AreEqual(1, d.CreateSnapshot().Gen);
}
[Test]
public void NestedWriteLocking2()
{
var d = new SnapDictionary<int, string>();
d.Test.CollectAuto = false;
var scopeProvider = GetScopeProvider();
using (d.GetWriter(scopeProvider))
Assert.AreEqual(0, d.CreateSnapshot().Gen);
// scope context: writers enlist
var scopeContext = new ScopeContext();
var scopeProvider = GetScopeProvider(scopeContext);
using (var w1 = d.GetWriter(scopeProvider))
{
using (d.GetWriter(scopeProvider))
using (var w2 = d.GetWriter(scopeProvider))
{
Assert.AreSame(w1, w2);
d.Set(1, "one");
}
}
}
[Test]
public void NestedWriteLocking3()
{
var d = new SnapDictionary<int, string>();
var t = d.Test;
t.CollectAuto = false;
Assert.AreEqual(0, d.CreateSnapshot().Gen);
var scopeContext = new ScopeContext();
var scopeProvider1 = GetScopeProvider();
var scopeProvider2 = GetScopeProvider(scopeContext);
using (var w1 = d.GetWriter(scopeProvider1))
{
Assert.AreEqual(1, t.LiveGen);
Assert.AreEqual(1, t.WLocked);
Assert.IsTrue(t.NextGen);
using (var w2 = d.GetWriter(scopeProvider2))
{
Assert.AreEqual(1, t.LiveGen);
Assert.AreEqual(2, t.WLocked);
Assert.IsTrue(t.NextGen);
Assert.AreNotSame(w1, w2);
d.Set(1, "one");
}
}
@@ -846,7 +932,8 @@ namespace Umbraco.Tests.Cache
Assert.AreEqual(2, s2.Gen);
Assert.AreEqual("uno", s2.Get(1));
var scopeProvider = GetScopeProvider(true);
var scopeContext = new ScopeContext();
var scopeProvider = GetScopeProvider(scopeContext);
using (d.GetWriter(scopeProvider))
{
@@ -867,7 +954,7 @@ namespace Umbraco.Tests.Cache
Assert.AreEqual(2, s4.Gen);
Assert.AreEqual("uno", s4.Get(1));
((ScopeContext) scopeProvider.Context).ScopeExit(true);
scopeContext.ScopeExit(true);
var s5 = d.CreateSnapshot();
Assert.AreEqual(3, s5.Gen);
@@ -878,7 +965,8 @@ namespace Umbraco.Tests.Cache
public void ScopeLocking2()
{
var d = new SnapDictionary<int, string>();
d.Test.CollectAuto = false;
var t = d.Test;
t.CollectAuto = false;
// gen 1
d.Set(1, "one");
@@ -891,10 +979,11 @@ namespace Umbraco.Tests.Cache
Assert.AreEqual(2, s2.Gen);
Assert.AreEqual("uno", s2.Get(1));
var scopeProviderMock = new Mock<IScopeProvider>();
Assert.AreEqual(2, t.LiveGen);
Assert.IsFalse(t.NextGen);
var scopeContext = new ScopeContext();
scopeProviderMock.Setup(x => x.Context).Returns(scopeContext);
var scopeProvider = scopeProviderMock.Object;
var scopeProvider = GetScopeProvider(scopeContext);
using (d.GetWriter(scopeProvider))
{
@@ -905,18 +994,72 @@ namespace Umbraco.Tests.Cache
Assert.AreEqual(2, s3.Gen);
Assert.AreEqual("uno", s3.Get(1));
// we made some changes, so a next gen is required
Assert.AreEqual(3, t.LiveGen);
Assert.IsTrue(t.NextGen);
Assert.AreEqual(1, t.WLocked);
// but live snapshot contains changes
var ls = d.Test.LiveSnapshot;
var ls = t.LiveSnapshot;
Assert.AreEqual("ein", ls.Get(1));
Assert.AreEqual(3, ls.Gen);
}
// nothing is committed until scope exits
Assert.AreEqual(3, t.LiveGen);
Assert.IsTrue(t.NextGen);
Assert.AreEqual(1, t.WLocked);
// no changes until exit
var s4 = d.CreateSnapshot();
Assert.AreEqual(2, s4.Gen);
Assert.AreEqual("uno", s4.Get(1));
// fixme - remove debugging code
/*
Exception caught = null;
var genFlip = 0;
var lckFlip = 0;
var thread = new System.Threading.Thread(() =>
{
try
{
for (var i = 0; i < 20; i++)
{
if (t.LiveGen == 2 && genFlip == 0) genFlip = i; // flips at 1
if (t.WLocked == 0 && lckFlip == 0) lckFlip = i; // flips at 10 ie 5s, as expected
d.CreateSnapshot();
System.Threading.Thread.Sleep(500);
}
}
catch (Exception e)
{
caught = e;
}
});
thread.Start();
*/
scopeContext.ScopeExit(false);
// fixme - remove debugging code
/*
thread.Join();
Assert.IsNull(caught); // but then how can it be not null?
Console.WriteLine(genFlip);
Console.WriteLine(lckFlip);
Assert.AreEqual(1, genFlip);
Assert.AreEqual(10, lckFlip);
*/
// now things have changed
Assert.AreEqual(2, t.LiveGen);
Assert.IsFalse(t.NextGen);
Assert.AreEqual(0, t.WLocked);
// no changes since not completed
var s5 = d.CreateSnapshot();
Assert.AreEqual(2, s5.Gen);
Assert.AreEqual("uno", s5.Get(1));
@@ -955,12 +1098,11 @@ namespace Umbraco.Tests.Cache
Assert.AreEqual("four", all[3]);
}
private IScopeProvider GetScopeProvider(bool withContext = false)
private IScopeProvider GetScopeProvider(ScopeContext scopeContext = null)
{
var scopeProviderMock = new Mock<IScopeProvider>();
var scopeContext = withContext ? new ScopeContext() : null;
scopeProviderMock.Setup(x => x.Context).Returns(scopeContext);
var scopeProvider = scopeProviderMock.Object;
var scopeProvider = Mock.Of<IScopeProvider>();
Mock.Get(scopeProvider)
.Setup(x => x.Context).Returns(scopeContext);
return scopeProvider;
}
}

7
src/Umbraco.Web/PublishedCache/NuCache/ContentStore.cs
View File

@@ -95,7 +95,8 @@ namespace Umbraco.Web.PublishedCache.NuCache
private class ContentStoreWriter : ScopeContextualBase
{
private readonly WriteLockInfo _lockinfo = new WriteLockInfo();
private ContentStore _store;
private readonly ContentStore _store;
private int _released;
public ContentStoreWriter(ContentStore store, bool scoped)
{
@@ -105,9 +106,9 @@ namespace Umbraco.Web.PublishedCache.NuCache
public override void Release(bool completed)
{
if (_store== null) return;
if (Interlocked.CompareExchange(ref _released, 1, 0) != 0)
return;
_store.Release(_lockinfo, completed);
_store = null;
}
}

105
src/Umbraco.Web/PublishedCache/NuCache/SnapDictionary.cs
View File

@@ -90,7 +90,8 @@ namespace Umbraco.Web.PublishedCache.NuCache
private class SnapDictionaryWriter : ScopeContextualBase
{
private readonly WriteLockInfo _lockinfo = new WriteLockInfo();
private SnapDictionary<TKey, TValue> _dictionary;
private readonly SnapDictionary<TKey, TValue> _dictionary;
private int _released;
public SnapDictionaryWriter(SnapDictionary<TKey, TValue> dictionary, bool scoped)
{
@@ -100,14 +101,18 @@ namespace Umbraco.Web.PublishedCache.NuCache
public override void Release(bool completed)
{
if (_dictionary == null) return;
if (Interlocked.CompareExchange(ref _released, 1, 0) != 0)
return;
_dictionary.Release(_lockinfo, completed);
_dictionary = null;
}
}
// gets a scope contextual representing a locked writer to the dictionary
// GetScopedWriter? should the dict have a ref onto the scope provider?
// fixme GetScopedWriter? should the dict have a ref onto the scope provider?
// fixme this is not a "writer" but a "write lock" => rename GetWriteLock
// the dict is write-locked until the write-lock is released
// which happens when it is disposed (non-scoped)
// or when the scope context exits (scoped)
public IDisposable GetWriter(IScopeProvider scopeProvider)
{
return ScopeContextualBase.Get(scopeProvider, _instanceId, scoped => new SnapDictionaryWriter(this, scoped));
@@ -130,13 +135,22 @@ namespace Umbraco.Web.PublishedCache.NuCache
//RuntimeHelpers.PrepareConstrainedRegions();
try { } finally
{
// increment the lock count, and register that this lock is counting
_wlocked++;
lockInfo.Count = true;
// fixme - this comment: "ok to have holes in generation objects" is annoying
// 'cos if you have a hole, then doing _liveGen-1 in some places would be wrong
// besides, forceGen is used only when getting a scoped write lock, which is not reentrant?
//
// but... if _wlocked ==1 and we just incremented it, it means it was 0, so it wasnt locked, so wtf?
// this is the only place where _nextGen would turn true so ... this makes no sense at all!
if (_nextGen == false || (forceGen && _wlocked == 1)) // if true already... ok to have "holes" in generation objects
{
// because we are changing things, a new generation
// is created, which will trigger a new snapshot
_nextGen = true;
_nextGen = true; // this is the ONLY place where _nextGen becomes true
_liveGen += 1;
}
}
@@ -154,6 +168,10 @@ namespace Umbraco.Web.PublishedCache.NuCache
private void Release(WriteLockInfo lockInfo, bool commit = true)
{
// if the lock wasn't taken in the first place, do nothing
if (!lockInfo.Taken)
return;
if (commit == false)
{
var rtaken = false;
@@ -162,6 +180,7 @@ namespace Umbraco.Web.PublishedCache.NuCache
Monitor.Enter(_rlocko, ref rtaken);
try { } finally
{
// forget about the temp. liveGen
_nextGen = false;
_liveGen -= 1;
}
@@ -184,8 +203,12 @@ namespace Umbraco.Web.PublishedCache.NuCache
}
}
// fixme - pretend we need to do something that takes time
//System.Threading.Thread.Sleep(TimeSpan.FromSeconds(5));
// decrement the lock count, if counting, then exit the lock
if (lockInfo.Count) _wlocked--;
if (lockInfo.Taken) Monitor.Exit(_wlocko);
Monitor.Exit(_wlocko);
}
private void Release(ReadLockInfo lockInfo)
@@ -338,12 +361,12 @@ namespace Umbraco.Web.PublishedCache.NuCache
{
Lock(lockInfo);
// if no next generation is required, and we already have one,
// use it and create a new snapshot
// if no next generation is required, and we already have a gen object,
// use it to create a new snapshot
if (_nextGen == false && _genObj != null)
return new Snapshot(this, _genObj.GetGenRef());
// else we need to try to create a new gen ref
// else we need to try to create a new gen object
// whether we are wlocked or not, noone can rlock while we do,
// so _liveGen and _nextGen are safe
if (_wlocked > 0) // volatile, cannot ++ but could --
@@ -351,26 +374,32 @@ namespace Umbraco.Web.PublishedCache.NuCache
// write-locked, cannot use latest gen (at least 1) so use previous
var snapGen = _nextGen ? _liveGen - 1 : _liveGen;
// create a new gen ref unless we already have it
// create a new gen object if we don't already have one
// (happens the first time a snapshot is created)
if (_genObj == null)
_genObjs.Enqueue(_genObj = new GenObj(snapGen));
// fixme - getting a panic exception here
// means _genObj != null, means _nextGen == true
// if we have one already, ensure it's consistent
else if (_genObj.Gen != snapGen)
throw new Exception("panic");
}
else
{
// not write-locked, can use latest gen, create a new gen ref
// not write-locked, can use latest gen (_liveGen), create a corresponding new gen object
_genObjs.Enqueue(_genObj = new GenObj(_liveGen));
_nextGen = false; // this is the ONLY thing that triggers a _liveGen++
}
// so...
// the genRefRef has a weak ref to the genRef, and is queued
// the snapshot has a ref to the genRef, which has a ref to the genRefRef
// when the snapshot is disposed, it decreases genRefRef counter
// the genObj has a weak ref to the genRef, and is queued
// the snapshot has a ref to the genRef, which has a ref to the genObj
// when the snapshot is disposed, it decreases genObj counter
// so after a while, one of these conditions is going to be true:
// - the genRefRef counter is zero because all snapshots have properly been disposed
// - the genRefRef weak ref is dead because all snapshots have been collected
// - genObj.Count is zero because all snapshots have properly been disposed
// - genObj.WeakGenRef is dead because all snapshots have been collected
// in both cases, we will dequeue and collect
var snapshot = new Snapshot(this, _genObj.GetGenRef());
@@ -486,7 +515,7 @@ namespace Umbraco.Web.PublishedCache.NuCache
{
task = _collectTask;
}
return task ?? Task.FromResult(0);
return task ?? Task.CompletedTask;
//if (task != null)
// await task;
}
@@ -514,6 +543,7 @@ namespace Umbraco.Web.PublishedCache.NuCache
public long LiveGen => _dict._liveGen;
public long FloorGen => _dict._floorGen;
public bool NextGen => _dict._nextGen;
public int WLocked => _dict._wlocked;
public bool CollectAuto
{
@@ -563,15 +593,20 @@ namespace Umbraco.Web.PublishedCache.NuCache
public class Snapshot : IDisposable
{
private readonly SnapDictionary<TKey, TValue> _store;
private readonly GenerationReference _generationReference;
private long _gen; // copied for perfs
private readonly GenRef _genRef;
private readonly long _gen; // copied for perfs
private int _disposed;
internal Snapshot(SnapDictionary<TKey, TValue> store, GenerationReference generationReference)
//private static int _count;
//private readonly int _thisCount;
internal Snapshot(SnapDictionary<TKey, TValue> store, GenRef genRef)
{
_store = store;
_generationReference = generationReference;
_gen = generationReference.GenObj.Gen;
_generationReference.GenObj.Reference();
_genRef = genRef;
_gen = genRef.GenObj.Gen;
_genRef.GenObj.Reference();
//_thisCount = _count++;
}
internal Snapshot(SnapDictionary<TKey, TValue> store, long gen)
@@ -580,17 +615,21 @@ namespace Umbraco.Web.PublishedCache.NuCache
_gen = gen;
}
private void EnsureNotDisposed()
{
if (_disposed > 0)
throw new ObjectDisposedException("snapshot" /*+ " (" + _thisCount + ")"*/);
}
public TValue Get(TKey key)
{
if (_gen < 0)
throw new ObjectDisposedException("snapshot" /*+ " (" + _thisCount + ")"*/);
EnsureNotDisposed();
return _store.Get(key, _gen);
}
public IEnumerable<TValue> GetAll()
{
if (_gen < 0)
throw new ObjectDisposedException("snapshot" /*+ " (" + _thisCount + ")"*/);
EnsureNotDisposed();
return _store.GetAll(_gen);
}
@@ -598,8 +637,7 @@ namespace Umbraco.Web.PublishedCache.NuCache
{
get
{
if (_gen < 0)
throw new ObjectDisposedException("snapshot" /*+ " (" + _thisCount + ")"*/);
EnsureNotDisposed();
return _store.IsEmpty(_gen);
}
}
@@ -608,17 +646,16 @@ namespace Umbraco.Web.PublishedCache.NuCache
{
get
{
if (_gen < 0)
throw new ObjectDisposedException("snapshot" /*+ " (" + _thisCount + ")"*/);
EnsureNotDisposed();
return _gen;
}
}
public void Dispose()
{
if (_gen < 0) return;
_gen = -1;
_generationReference?.GenObj.Release();
if (Interlocked.CompareExchange(ref _disposed, 1, 0) != 0)
return;
_genRef?.GenObj.Release();
GC.SuppressFinalize(this);
}
}