You should replace:
int command = intReader.ReadByte();
By:
int command = @in.ReadByte();
... because you are using the return code of ReadByte() (which is -1) to
indicate EOF. A BinaryWriter never returns -1, but an EOF exception if there is
insufficient data. Only a stream returns -1, which is why the return value of
ReadByte() for a stream is an int, whereas the one for a BinaryReader is a byte.
Vincent
From: Shad Storhaug [mailto:[email protected]]
Sent: Thursday, July 20, 2017 11:59 AM
To: Van Den Berghe, Vincent <[email protected]>
Cc: [email protected]
Subject: RE: Debugging Help Requested
Vincent,
You are my hero. You should wear a cape and learn to fly.
However, there must be something different about the code on your machine than
mine because although that gets the code running, I am now getting an exception:
F:\temp\cli>dotnet lucene-cli.dll lock verify-server 127.0.0.4 2
Listening on 53559...
All clients started, fire gun...
Unhandled Exception: Unhandled Exception: System.Exception:
System.IO.EndOfStreamException: Unable to read beyond the end of the stream.
at System.IO.BinaryReader.ReadByte()
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
in F:\Projects\lucenenet\src\Lucene.Net\Store\LockVerifyServer.cs:line 134 --->
System.IO.EndOfStreamException: Unable to read beyond the end of the stream.
at System.IO.BinaryReader.ReadByte()
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
--- End of inner exception stack trace ---
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state)
System.Exception: System.IO.EndOfStreamException: Unable to read beyond the end
of the stream.
at System.IO.BinaryReader.ReadByte()
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
in F:\Projects\lucenenet\src\Lucene.Net\Store\LockVerifyServer.cs:line 134 --->
System.IO.EndOfStreamException: Unable to read beyond the end of the stream.
at System.IO.BinaryReader.ReadByte()
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
--- End of inner exception stack trace ---
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state)
I have pushed what I have here:
https://github.com/NightOwl888/lucenenet/blob/master/src/Lucene.Net/Store/LockVerifyServer.cs.
Could you compare with what you have and let me know what else needs to change?
Thanks,
Shad Storhaug (NightOwl888)
From: Van Den Berghe, Vincent [mailto:[email protected]]
Sent: Thursday, July 20, 2017 3:19 PM
To: Shad Storhaug
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
Hello Shad,
Bow before me, for I am the master of protocol violations. I assure you it's
true: just ask local law enforcement!
This has been exceedingly frustrating to debug. The reason for the bug is very
simple: in VerifyLockFactory, a SINGLE BYTE is written and read for
verification:
[email protected](message)<mailto:[email protected](message)>;
[email protected]()<mailto:[email protected]()>;
int ret =
[email protected]()<mailto:[email protected]()>;
... but in LockVerifyServer, a CHARACTER is read and a 4 BYTE INTEGER is
written:
int command = intReader.Read();
...
intWriter.Write(command);
os.Flush();
(because the writer is created using default parameters, a character is always
1 byte because the value is 0 or 1 and not a lead-in value for a multibyte
character).
Since sockets write their bytes in network order, writing a 01 as an integer
writes 01 00 00 00.
So this happens:
1. Server acquires lock and writes 01
2. Client reads 01 and writes 01 00 00 00
3. Server reads the first byte, which is 01: protocol matches, and 3
bytes are left unread: 00 00 00
4. Server releases lock and writes 00
5. Client reads 00 and writes 00 00 00 00. There are now 7 bytes waiting
to be read: 00 00 00 00 00 00 00
6. Server reads 00 (the first unread byte in step 3): protocol matches. 6
bytes are left unread 00 00 00 00 00 00
7. Server acquires lock and write 01
8. Client reads 01 and writes 01 00 00 00. There are now 6 + 4 == 10
bytes waiting to be read 00 00 00 00 00 00 01 00 00 00
9. Server reads 00 (the second unread byte in step 3): PROTOCOL VIOLATION
This is a confusing sequence of events, because steps 1 through 8 give the
impression of being correct, whereas everything is wrong from step 2 onwards
and we only see it 7 steps later.
The fact that the steps were distributed over 2 processes didn't exactly help.
At least in the beginning.
The solution is to change the following in LockVerifyServer.cs:
Replace:
int command = intReader.Read();
By:
int command = stream.ReadByte();
Note that although intReader.Read() "works", it is not correct: we don't want
to read characters, but a single byte!
And replace:
intWriter.Write(command);
By:
os.WriteByte((byte)command);
This doesn't mean there isn't something weird about FSNativeLockFactory. I'd
make the changes outlined in my previous e-mail, i.e. change the concurrent
dictionary definition with a static variant of lazily created values:
internal static readonly ConcurrentDictionary<string,
Lazy<NativeFSLock>> _locks = new ConcurrentDictionary<string,
Lazy<NativeFSLock>>();
... changing the Add code to:
var path = new DirectoryInfo(System.IO.Path.Combine(m_lockDir.FullName,
lockName));
return _locks.GetOrAdd(path.FullName, s => new Lazy<NativeFSLock>(() =>
new NativeFSLock(this, m_lockDir, s))).Value;
And the remove code to:
Lazy<NativeFSLock> _;
outerInstance._locks.TryRemove(path.FullName, out _);
Vincent
From: Shad Storhaug [mailto:[email protected]]
Sent: Saturday, July 15, 2017 3:28 PM
To: Van Den Berghe, Vincent
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
> I'm still at loss to explain the behavior of LockVerifyServer and
> LockStressTest, but here is what I found so far.
Welcome to my world. You are looking at code that was contributed a few years
ago. And since it has no test coverage, this is probably the first time anyone
has ever attempted to run it. I made a few changes to the original translation
of the socket code and I think it is now working but even that is uncertain. If
you drop back to the beta-00004 tag you can see what it looked like when I
started:
https://github.com/apache/lucenenet/blob/Lucene.Net_4_8_0_beta00004/src/Lucene.Net/Store/LockVerifyServer.cs
https://github.com/apache/lucenenet/blob/Lucene.Net_4_8_0_beta00004/src/Lucene.Net/Store/LockStressTest.cs
I have no objections if you want to port these from scratch or rework to be
more .NET friendly.
> When I tried to reproduce your problem, I got stuck in s.Accept() of
> LockVerifyServer.cs. The fact that you don't see this is baffling: s.Accept
> is designed to hang waiting for a connection, which is a weird way to create
> listening threads on sockets.
> Perhaps the behavior is different in .NET Core, but in .NET 4.5.2 s.Accept()
> wil hang waiting for a connection and since it's in a loop the program will
> hang until there are maxClients clients connected.
As I mentioned, I wasn't getting anywhere until I commented out the
startingGun.Wait() line (the one someone labeled "not sure about this"). That
was probably the wrong thing to do, but it did end up getting me further in the
process instead of stranded at no response.
Apparently, I misinterpreted the fact that maxClients is actually minClients (I
wonder why). I set the number to 10, but only connected 1 client so it didn't
kick off the process.
> When one examines NativeFSLockFactory, several things pop up that make you
> say "hmmm". Sadly, none of them correct the behavior.
> First, you have this:
return _locks.GetOrAdd(lockName, (s) => new NativeFSLock(this,
m_lockDir, s));
> This isn't exactly wrong, but it does create unnecessary garbage: there is no
> guarantee that the valueFactory (the delegate creating your new NativeFSLock)
> is called only once. It can be called an arbitrary number of times. The only
> thing that GetOrAdd guarantees is that the value will be inserted in the
> dictionary once with no errors.
> If you must use a ConcurrentDictionary, the standard solution is to change
> the definition of the value type to use Lazy<TValue>, like this:
// LUCENENET: NativeFSLocks in Java are infact singletons; this is how
we mimick that to track instances and make sure
// IW.Unlock and IW.IsLocked works correctly
internal readonly ConcurrentDictionary<string, Lazy<NativeFSLock>>
_locks = new ConcurrentDictionary<string, Lazy<NativeFSLock>>();
In Lucene, this _locks variable didn't exist. I tried going through the
javadocs to see if I could find any validity to the claim that NativeFSLocks
are singletons in Java, but I found no such evidence. I haven't gone through
the source code to find out, though - maybe if one digs deep enough the comment
can be confirmed. If you look at the way it was in Lucene, they simply returned
a new NativeFSLock every time. Perhaps it would make more sense to make that
class into a singleton?
https://github.com/apache/lucene-solr/blob/releases/lucene-solr/4.8.0/lucene/core/src/java/org/apache/lucene/store/NativeFSLockFactory.java#L105
> Something totally unrelated: not wanting to be pushy or anything, but what
> I'd really like to do is to start experimenting with Lucene.Net.Replication.
> Any chance of that appearing in the main soon?
That is a question for sir Jens Melgaard, the awesome contributor who is making
that happen. I took a look at his branch and it doesn't seem he has pushed his
latest work to GitHub yet, so the last 5 tests passing is not yet available.
https://issues.apache.org/jira/projects/LUCENENET/issues/LUCENENET-565.
Hopefully he submits a pull request soon, but you are welcome to ask about his
progress.
But now that you mention it I am a bit stuck because I haven't worked out how
to make the new lucene-cli tool compile on the command line. Actually, it is
the restore command that is the problem. Microsoft is absolutely of no help,
and is unwilling to help anyone who is on the project.json format (which
implicitly means that we are stuck on preview 2 of the CLI tool instead of the
production one). I reported an issue a few days ago
(https://github.com/NuGet/Home/issues/5593) that is blocking us from moving to
the new .csproj format (thus the latest CLI tool) and they have so far not
provided any answers.
I suppose that could be worked around by unzipping the .nupkg file, correcting
the version information in the .nuspec file, and then re-zipping them in the
build script. Or, we could check in the .nuspec files that would normally
auto-generate with the same dependencies as .csproj into the repo and use the
old NuGet pack tool (which may not even work because of some new elements they
added). But these are both hacky workarounds that should be unnecessary. I
don't understand why Microsoft has not fixed this obvious problem in what is
supposed to be production tooling (and seriously, I found a LOT of problems
trying to work with the versioning, but this is the only one I haven't found a
workaround for).
The bottom line is we probably need to move on to the new .csproj format sooner
rather than later, and that might throw a wrench into what Jens is working on
if his work is not merged first. On the other hand, it might help him work past
impossible issues he is now experiencing because of the pre-release tooling as
well.
UP FOR GRABS
But there are lots of other ways to help if you are looking for ideas:
https://github.com/apache/lucenenet/blob/master/CONTRIBUTING.md#porting-work---up-for-grabs.
Two things that stand out (other than what I have already mentioned) that I
don't have much hope for solving myself are:
1. The "native" C++ Directory implementations in Lucene.Net.Misc for
Windows and Posix/Unix.
2. An issue with interaction between Lucene.Net.ICU and icu-dotnet that
is causing the TestThaiAnalyzer.TestRandomStrings() and
TestThaiAnalyzer.TestRandomHugeStrings() (and some of the Highlighter tests)
to fail with an AccessViolationException (a fatal error in .NET Core) because
of "protected memory".
I took a short C++ course back in 1998, and have not touched it since. I am not
sure exactly how these Directories should be compiled. I might be able to work
out how to port the Java wrapper classes for these in order to call the C++
library(s) once it is compiled and call them. However, it sounds like "native"
Directories might be better than the other ones we have...?
The second issue I have looked into and I suspect it is concurrency related.
The icu-dotnet library throws an AccessViolationException frequently during
these tests. This causes total meltdown of the test runner in .NET Core because
this exception can no longer be caught. So these tests are currently manually
hard-coded to fail in that environment, otherwise the test runner would fatally
crash and never finish all of the tests. I tried to create a valid test case to
send to the icu-dotnet team by collecting all of the data that was passed to
icu-dotnet up to the point of failure, then replaying that data in a separate
unit test. The problem is, the unit test didn't fail even when it was run 2500
times in a row with the same set of random data that made it fail in
Lucene.Net. So, since the same data in the same order isn't causing it to fail,
I suspect it has something to do with 2 threads providing conflicting data in
the test that tries to use the same memory location in icu-dotnet. If we can
prove the problem is on their side (or ours) with a test, then we are on the
way to a solution.
FYI - Note that we are not using the production icu-dotnet library because they
do not yet have .NET Core support. It should work with that library in .NET
Framework (with the dependencies), but unfortunately the temporary icu-dotnet
package uses the same package ID with a higher version number than the
production one, so there is no way for the build to support both the production
and temporary ones simultaneously (or at least I haven't figured it out yet).
From: Van Den Berghe, Vincent [mailto:[email protected]]
Sent: Saturday, July 15, 2017 4:33 PM
To: Shad Storhaug
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
Hello Shad,
I'm still at loss to explain the behavior of LockVerifyServer and
LockStressTest, but here is what I found so far.
I made a lucene-cli.csproj file and a lucene-cli.project.js to make it compile
correctly. I had to make the latter file, since project.js confused the build
process. I don't know if both *project.js files can exist next to each other.
When I tried to reproduce your problem, I got stuck in s.Accept() of
LockVerifyServer.cs. The fact that you don't see this is baffling: s.Accept is
designed to hang waiting for a connection, which is a weird way to create
listening threads on sockets.
Perhaps the behavior is different in .NET Core, but in .NET 4.5.2 s.Accept()
wil hang waiting for a connection and since it's in a loop the program will
hang until there are maxClients clients connected.
So I changed the creation loop as follows:
for (int count = 0; count < maxClients; count++)
{
threads[count] = new
ThreadAnonymousInnerClassHelper(localLock, lockedID, startingGun, s);
threads[count].Start();
}
On the Thread.Run method, I needed to call cs.Accept(), and it doesn't hang
anymore.
A minor observation: it is completely unnecessary to create separate streams on
the same sockets for reading and writing: that's a Java-ism. You can just
create one stream and a binary reader and writer on the same stream. Also, the
socket can be closed outside it all (even though .NET guidelines tell us that
Dispose should never throw exceptions, and we could replace the IOUtils.Dispose
by a using() statement on the socket):
Hence the code becomes:
public override void Run()
{
var s = cs.Accept();
try
{
using (Stream stream = new NetworkStream(s))
{
BinaryReader intReader = new
BinaryReader(stream);
BinaryWriter intWriter = new
BinaryWriter(stream);
try
{
... same as original
code ...
}
catch (IOException ioe)
{
throw new
Exception(ioe.ToString(), ioe);
}
catch (Exception e)
{
// LUCENENET NOTE: We need to
throw a new exception
// to ensure this is Exception
and not some other type.
throw new
Exception(e.ToString(), e);
}
}
}
finally
{
IOUtils.DisposeWhileHandlingException(s);
}
}
But of course, the change of stream code is optional: it doesn't make any
difference in behavior.
Now, when I run this according to your guidelines, I'm seeing a crash on the
client first:
Connecting to server 127.0.0.1 and registering as client 3...
0% done.
An error occurred:
System.IO.IOException: Protocol violation.
at Lucene.Net.Store.VerifyingLockFactory.CheckedLock.Verify(Byte message) in
D:\SOURCE\GitHub\lucenenet\src\Lucene.Net\Store\VerifyingLockFactory.cs:line 64
at Lucene.Net.Store.VerifyingLockFactory.CheckedLock.Obtain() in
D:\SOURCE\GitHub\lucenenet\src\Lucene.Net\Store\VerifyingLockFactory.cs:line 75
at Lucene.Net.Store.Lock.Obtain(Int64 lockWaitTimeout) in
D:\SOURCE\GitHub\lucenenet\src\Lucene.Net\Store\Lock.cs:line 115
at Lucene.Net.Store.LockStressTest.Main(String[] args) in
D:\SOURCE\GitHub\lucenenet\src\Lucene.Net\Store\LockStressTest.cs:line 152
at
Lucene.Net.Cli.LockStressTestCommand.Configuration.<>c.<.ctor>b__0_0(String[]
args) in
D:\SOURCE\GitHub\lucenenet\src\tools\lucene-cli\commands\lock\lock-stress-test\LockStressTestCommand.cs:line
28
at Lucene.Net.Cli.LockStressTestCommand.Run(ConfigurationBase cmd) in
D:\SOURCE\GitHub\lucenenet\src\tools\lucene-cli\commands\lock\lock-stress-test\LockStressTestCommand.cs:line
53
at Lucene.Net.Cli.LockStressTestCommand.Configuration.<.ctor>b__0_1() in
D:\SOURCE\GitHub\lucenenet\src\tools\lucene-cli\commands\lock\lock-stress-test\LockStressTestCommand.cs:line
42
at Lucene.Net.Cli.ConfigurationBase.<>c__DisplayClass3_0.<OnExecute>b__0()
in D:\SOURCE\GitHub\lucenenet\src\tools\lucene-cli\ConfigurationBase.cs:line 62
at Lucene.Net.Cli.CommandLine.CommandLineApplication.Execute(String[] args)
in
D:\SOURCE\GitHub\lucenenet\src\tools\lucene-cli\CommandLine\CommandLineApplication.cs:line
304
at Lucene.Net.Cli.CommandLineOptions.Parse(String[] args) in
D:\SOURCE\GitHub\lucenenet\src\tools\lucene-cli\CommandLineOptions.cs:line 32
Specify --help for a list of available options and commands.
... this in turn triggers the crash on the server (which you are seeing)
because an error in the client simply makes it stop.
When one examines NativeFSLockFactory, several things pop up that make you say
"hmmm". Sadly, none of them correct the behavior.
First, you have this:
return _locks.GetOrAdd(lockName, (s) => new NativeFSLock(this,
m_lockDir, s));
This isn't exactly wrong, but it does create unnecessary garbage: there is no
guarantee that the valueFactory (the delegate creating your new NativeFSLock)
is called only once. It can be called an arbitrary number of times. The only
thing that GetOrAdd guarantees is that the value will be inserted in the
dictionary once with no errors.
If you must use a ConcurrentDictionary, the standard solution is to change the
definition of the value type to use Lazy<TValue>, like this:
// LUCENENET: NativeFSLocks in Java are infact singletons; this is how
we mimick that to track instances and make sure
// IW.Unlock and IW.IsLocked works correctly
internal readonly ConcurrentDictionary<string, Lazy<NativeFSLock>>
_locks = new ConcurrentDictionary<string, Lazy<NativeFSLock>>();
But (as they say in the commercials) wait, there's more. The remove operation
looks like this:
NativeFSLock _;
outerInstance._locks.TryRemove(path.FullName, out
_);
This will never work, because the key used for adding is just lockName, whereas
the key used for removal is path.FullName. The dictionary will only grow, never
shrink!
Given this, I changed the add code to:
var path = new DirectoryInfo(System.IO.Path.Combine(m_lockDir.FullName,
lockName));
return _locks.GetOrAdd(path.FullName, s => new Lazy<NativeFSLock>(() =>
new NativeFSLock(this, m_lockDir, s))).Value;
And the remove code to:
Lazy<NativeFSLock> _;
outerInstance._locks.TryRemove(path.FullName, out _);
Since the keys of the dictionary are the actual lock files, we could consider
making _locks a static: a single instance among all NativeFSLocks.
This would also get rid of the outerInstance member in the lock, replacing it
with the outer class name.
internal static readonly ConcurrentDictionary<string,
Lazy<NativeFSLock>> _locks = new ConcurrentDictionary<string,
Lazy<NativeFSLock>>();
Another thing I notice is the code used to delete the lock: I think the
directory deletion code is unnecessary: we're creating and deleting file locks,
not directory locks.
But the protocols violations I'm seeing are really strange. I'll try to debug
this another way: to be continued!
Something totally unrelated: not wanting to be pushy or anything, but what I'd
really like to do is to start experimenting with Lucene.Net.Replication. Any
chance of that appearing in the main soon?
Vincent
From: Shad Storhaug
Sent: Friday, July 14, 2017 2:33 AM
To: 'Van Den Berghe, Vincent'
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
Vincent,
Thanks. This was definitely the most important issue to fix. I have no fear of
replacing a buggy implementation with a functional one - there was no direct
way to port the Java implementation into .NET, so this wasn't another case of
it not working because it didn't match Lucene.
I ended up making a few changes:
1. According to MSDN, FileStream.Flush() could throw an IOException,
which would skip the Dispose() call on the file if it happened in a finally
block. Looking at the call to base.Dispose() in the try block, it actually
calls the Flush() method on BufferedIndexOutput. So, it makes more sense to
override Flush() and call file.Flush(true), which ensures Flush() will work
consistently everywhere.
2. I removed the loop that calls FSync instead of taking the call out of
that method. FSync is not called anywhere else, but this way can still be
utilized by subclasses.
3. Changed from new ReadOnlyHeapByteBuffer(BytesRef.EMPTY_BYTES, 0, 0) to
ByteBuffer.Allocate(0).AsReadOnlyBuffer(). We shouldn't be using the internal
members that weren't meant for public use in Java.
You can review here:
https://github.com/apache/lucenenet/commit/c0e7a25c4a5901a4b6bea4f92088b5135c1f550a
The TestStressLocks test looks stable. However, on .NET Core when I put
[Repeat(20)] on the TestStressLocksNativeFSLockFactory test I got a concurrent
file access exception. I suspect this has to do with the same LockFactory issue
that is causing the CLI tool to fail, not the MMapDirectory.
I also fixed the IndexInputSlicer:
https://github.com/apache/lucenenet/commit/de62e95746f23d6026412e22c6f724fed03b5fa7
I'd appreciate if you could look into the LockFactory issue when you get a
chance.
Thanks,
Shad Storhaug (NightOwl888)
From: Van Den Berghe, Vincent [mailto:[email protected]]
Sent: Thursday, July 13, 2017 8:31 PM
To: Shad Storhaug
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
>> but I found a similar problem when trying to get all of the tests to pass on
>> the MMapDirectory. When MemoryMappedFile.CreateViewAccessor() is called with
>> more bytes on the size parameter than the actual file size, it throws
>> UnauthorizedAccessException.
You are correct, of course. That is indeed the culprit. It also invalidates my
"solution" to catch UnauthorizedAccessException: the real problem is the
implementation of MMapDirectory.
I had a look at
https://issues.apache.org/jira/projects/LUCENENET/issues/LUCENENET-530 but I
have doubts about the scalability of the approach. The call to
_memoryMappedFile.CreateViewStream(0, 0, MemoryMappedFileAccess.Read); needs a
single continuous chunk of virtual memory as large as the size of the mapped
file. For a lot of large files , this might be problematic. The "list of
buffers" approach is probably the better approach. I do have a working
implementation based on MemoryMappedFile.CreateViewStream, if you're
interested: it does work and corrects all the problems I'm seeing, but I'm
hesitant to just replace the existing implementation, even if all the tests run.
However, by making minimal modifications, I was able to make all MMapDirectory
tests run flawlessly, including my own.
Here's what I did:
In FSDirectory.cs:
- Implemented the file.Flush(true); call in the
FSDirectory.FSIndexOutput, and commented out the call to IOUtils.Fsync in
FSDirectory.Fsync. This remains vitally important.
In MMapDirectory.cs:
- In MMapDirectory.OpenInput, change the call from:
var c = new FileStream(file.FullName, FileMode.Open,
FileAccess.ReadWrite, FileShare.ReadWrite);
To:
var c = new FileStream(file.FullName, FileMode.Open,
FileAccess.Read, FileShare.ReadWrite);
- In MMapDirectory.Map, replace
long fileCapacity = length == 0 ? ushort.MaxValue : length;
if (input.memoryMappedFile == null)
{
#if NETSTANDARD
input.memoryMappedFile = MemoryMappedFile.CreateFromFile(fc,
null, fileCapacity, MemoryMappedFileAccess.ReadWrite,
HandleInheritability.Inheritable, false);
#else
input.memoryMappedFile = MemoryMappedFile.CreateFromFile(fc,
null, fileCapacity, MemoryMappedFileAccess.ReadWrite, null,
HandleInheritability.Inheritable, false);
#endif
}
By:
if (length == 0)
return new[] { new
ReadOnlyHeapByteBuffer(BytesRef.EMPTY_BYTES, 0, 0) };
if (input.memoryMappedFile == null)
{
#if NETSTANDARD
input.memoryMappedFile = MemoryMappedFile.CreateFromFile(fc, null,
length, MemoryMappedFileAccess.Read, HandleInheritability.Inheritable, false);
#else
input.memoryMappedFile =
MemoryMappedFile.CreateFromFile(fc, null, length, MemoryMappedFileAccess.Read,
null, HandleInheritability.Inheritable, false);
#endif
}
(you may need to add a using Util; inside the namespace Lucene.Net.Store to
access BytesRef).
I've been running hundreds of iterations of the StressTestLocks and
TestStressLocksNativeFSLockFactory and haven't seen any single failure yet.
Vincent
From: Shad Storhaug [mailto:[email protected]]
Sent: Wednesday, July 12, 2017 4:00 PM
To: Van Den Berghe, Vincent
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
Vincent,
Thanks for looking into these.
[Finding 1]
> Why does it throw UnauthorizedAccessException? I have no idea
This may not be related, but I found a similar problem when trying to get all
of the tests to pass on the MMapDirectory. When
MemoryMappedFile.CreateViewAccessor() is called with more bytes on the size
parameter than the actual file size, it throws UnauthorizedAccessException.
See: https://stackoverflow.com/a/5501331/181087
Note that if you are on 64 bit Windows, the line
FSDirectory.Open(@"E:\Temp\LuceneStressTest"); will always return MMapDirectory.
When recently going through the old JIRA issues, I noticed that someone
contributed an MMapDirectory implementation that was never actually used.
Frankly, that "array of ByteBuffers" is probably not a sound approach in .NET,
so it is worth at least reviewing to see if this other implementation is a
better design approach. See:
https://issues.apache.org/jira/projects/LUCENENET/issues/LUCENENET-530. I was
able to determine that MMapDirectory (or something it is dependent on) is
definitely causing 2 of the intermittent test failures by checking each
Directory implementation individually in the test framework.
If this is the source of the UnauthorizedAccessException, it makes more sense
to fix the source than to patch it in a catch block (which likely would need to
be done in multiple places).
> I know this isn't a direct answer to your debugging request on your .NET
> Core thing, but I got zero experience on that .NET Core thing and thought
> that continuing an ongoing investigation would be a more efficient use of my
> time.
Actually, the issue is not .NET Core-specific. If you feel more comfortable
working on .NET Framework, you could add a `.csproj` file to the lucene-cli
tool (which is now on master) and run the same thing on .NET Framework. But we
have no plans to have a .NET Framework version of this tool, since it won't
really make any difference anyway on the command line (other than the fact that
.NET Framework only runs on Windows). You will need to adjust the first part of
the command-line commands to "lucene-cli.exe" (or whatever you put in the
assembly name box of project properties) rather than "dotnet lucene-cli.dll" in
that case.
Thanks,
Shad Storhaug (NightOwl888)
From: Van Den Berghe, Vincent [mailto:[email protected]]
Sent: Wednesday, July 12, 2017 8:36 PM
To: Shad Storhaug
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
Something I forgot to mention wrt to the previous e-mail: the test application
to reproduce should be running in 32-bit ("32-bit preferred").
For some strange reason, the problem is different in 64-bit and is not
corrected by it.
I'm starting to think the "access denied" is an antivirus problem... I'll keep
you informed.
Vincent
From: Van Den Berghe, Vincent [mailto:[email protected]]
Sent: Wednesday, July 12, 2017 7:32 PM
To: Shad Storhaug
Cc: [email protected]<mailto:[email protected]>
Subject: RE: Debugging Help Requested
Hello Shad,
Ever since you've mentioned in your e-mail of Tue 6/13/2017 2:54 PM that we
still have multithreading problems, I've been attempting to track them down
(and why I couldn't see them). Your previous e-mail caused me to redouble my
efforts.
I got 2 findings to report so far.
[Finding 1]
I've discovered at least one problem when one thread is appending documents,
and another one is reading from the same directory.
At some point when the IndexWriter is disposed, I've observed one of two
possible stack traces (note that the lines are those of my own build):
Lucene.Net.dll!Lucene.Net.Util.IOUtils.Fsync(string fileToSync,
bool isDir) Line 468 C#
Lucene.Net.dll!Lucene.Net.Store.FSDirectory.Fsync(string name)
Line 536 C#
Lucene.Net.dll!Lucene.Net.Store.FSDirectory.Sync(System.Collections.Generic.ICollection<string>
names) Line 365 C#
Lucene.Net.dll!Lucene.Net.Index.SegmentInfos.WriteSegmentsGen(Lucene.Net.Store.Directory
dir, long generation) Line 301 C#
Lucene.Net.dll!Lucene.Net.Index.SegmentInfos.FinishCommit(Lucene.Net.Store.Directory
dir) Line 1261 C#
Lucene.Net.dll!Lucene.Net.Index.IndexWriter.FinishCommit() Line
3792 C#
Lucene.Net.dll!Lucene.Net.Index.IndexWriter.CommitInternal()
Line 3775 C#
Lucene.Net.dll!Lucene.Net.Index.IndexWriter.CloseInternal(bool
waitForMerges, bool doFlush) Line 1253 C#
Lucene.Net.dll!Lucene.Net.Index.IndexWriter.Dispose(bool
waitForMerges) Line 1093 C#
Lucene.Net.dll!Lucene.Net.Index.IndexWriter.Dispose() Line 1051
C#
More specifically, in the above stack trace, this statement in IOUtils.Fsync
succeeded (fileToSync is the "segments.gen" file):
file = new FileStream(fileToSync,
FileMode.Open, // We shouldn't create a file when
syncing.
// Java version uses FileChannel which doesn't create
the file if it doesn't already exist,
// so there should be no reason for attempting to
create it in Lucene.Net.
FileAccess.Write,
FileShare.ReadWrite);
The other possible stack trace replaces the lines above FinishCommit() Line
3792 with
Lucene.Net.dll!Lucene.Net.Store.FSDirectory.FSIndexOutput.FSIndexOutput(Lucene.Net.Store.FSDirectory
parent, string name) Line 467 C#
Lucene.Net.dll!Lucene.Net.Store.FSDirectory.CreateOutput(string
name, Lucene.Net.Store.IOContext context) Line 323 C#
Lucene.Net.dll!Lucene.Net.Index.SegmentInfos.WriteSegmentsGen(Lucene.Net.Store.Directory
dir, long generation) Line 289 C#
Lucene.Net.dll!Lucene.Net.Index.SegmentInfos.FinishCommit(Lucene.Net.Store.Directory
dir) Line 1270 C#
... with a very similar statement which succeeds:
file = new FileStream(Path.Combine(parent.m_directory.FullName, name),
FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite);
At the same time, I had a failing IndexReader with the following stack trace:
>
> Lucene.Net.dll!Lucene.Net.Store.SimpleFSDirectory.OpenInput(string name,
> Lucene.Net.Store.IOContext context) Line 89 C#
Lucene.Net.dll!Lucene.Net.Store.Directory.OpenChecksumInput(string name,
Lucene.Net.Store.IOContext context) Line 115 C#
Lucene.Net.dll!Lucene.Net.Index.SegmentInfos.FindSegmentsFile.Run(Lucene.Net.Index.IndexCommit
commit) Line 908 C#
Lucene.Net.dll!Lucene.Net.Index.StandardDirectoryReader.Open(Lucene.Net.Store.Directory
directory, Lucene.Net.Index.IndexCommit commit, int termInfosIndexDivisor)
Line 55 C#
Lucene.Net.dll!Lucene.Net.Index.DirectoryReader.Open(Lucene.Net.Store.Directory
directory) Line 69 C#
And this statement in SimpleFSDirectory.OpenInput fails (path.FullName is the
same as fileToSync):
var raf = new FileStream(path.FullName, FileMode.Open,
FileAccess.Read, FileShare.ReadWrite);
This fails with the UnauthorizedAccessException. This exception is uncaught,
and propagates out of the DirectoryReader, causing it to fail.
Why does it throw UnauthorizedAccessException? I have no idea: the 2 FileStream
constructors are compatible since their FileAccess/FileShare mode allows both
reading and writing. But it does fail with that exception.
To make sure it's not an artifact of the test framework, I've written the
following small program that reproduces the problem. It's very similar to the
existing test in _testStressLocks, but doesn't use mock-ups since the overhead
seems to be a factor in reproducing it (on my machine). You should be able to
just cut & paste and see for yourself. If course, if you don't I shall have
made a fool of myself again.
Ah well. Here it goes:
using Lucene.Net.Index;
using Lucene.Net.Store;
using Lucene.Net.Util;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Documents;
using Lucene.Net.Search;
using System.Threading;
namespace StressTest
{
class Program
{
public static volatile bool WriterThreadActive;
private static void WriterThread(Directory directory, int
iterations)
{
WriterThreadActive = true;
try
{
for (int i = 0; i < iterations; ++i)
using (var writer = new
IndexWriter(directory, new IndexWriterConfig(LuceneVersion.LUCENE_48, new
StandardAnalyzer(LuceneVersion.LUCENE_48)) { OpenMode = OpenMode.APPEND }))
{
Document doc = new Document();
doc.Add(new TextField("content",
"aaa", Field.Store.NO));
writer.AddDocument(doc);
}
}
finally
{
WriterThreadActive = false;
}
}
private static void ReaderThread(Directory directory, int
iterations)
{
var query = new TermQuery(new Term("content", "aaa"));
for (int i = 0; WriterThreadActive || i < iterations; ++i)
{
using (var reader = DirectoryReader.Open(directory))
{
var searcher = new IndexSearcher(reader);
searcher.Search(query, null, 1000);
}
}
}
static void Main(string[] args)
{
var directory =
FSDirectory.Open(@"E:\Temp\LuceneStressTest");
using (var writer = new IndexWriter(directory, new
IndexWriterConfig(LuceneVersion.LUCENE_48, new
StandardAnalyzer(LuceneVersion.LUCENE_48)) { OpenMode = OpenMode.CREATE }))
{
Document doc = new Document();
doc.Add(new TextField("content", "aaa",
Field.Store.NO));
writer.AddDocument(doc);
}
const int MinimumIterations = 10000; // you may need
to increase this
var writerThread = new Thread(() =>
WriterThread(directory, MinimumIterations)) { Name = "WriterThread" };
var readerThread = new Thread(() =>
ReaderThread(directory, MinimumIterations)) { Name = "ReaderThread" };
writerThread.Start();
readerThread.Start();
writerThread.Join();
readerThread.Join();
directory.Dispose();
}
}
}
You may tweak the E:\Temp\LuceneStressTest and the MinimumIterations
accordingly.
The solution is to add the UnauthorizedAccessException to the catch clause in
SegmentInfos.cs: (SegmentInfos.FindSegmentFile.Run):
try
{
genInput =
directory.OpenChecksumInput(IndexFileNames.SEGMENTS_GEN, IOContext.READ_ONCE);
}
catch (IOException e)
{
if (infoStream != null)
{
Message("segments.gen open: IOException " + e);
}
}
catch (UnauthorizedAccessException e)
{
if (infoStream != null)
{
Message("segments.gen open:
UnauthorizedAccessException " + e);
}
}
UnauthorizedAccessException doesn't inherit from IOException, you you need to
catch both of them.
After this modification, the problem (obviously) disappears. Maybe similar code
would need similar additions, but there is a lack of evidence to do so.
[Finding 2]
I am on the trail of the intermittent failure of StressTestLocks /
TestStressLocksNativeFSLockFactory but the margin of this e-mail is too small
to contain it. More later.
Hopefully, this helps a bit.
I know this isn't a direct answer to your debugging request on your .NET Core
thing, but I got zero experience on that .NET Core thing and thought that
continuing an ongoing investigation would be a more efficient use of my time.
Vincent
From: Shad Storhaug [mailto:[email protected]]
Sent: Thursday, July 06, 2017 11:32 PM
To: Van Den Berghe, Vincent
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>
Subject: Debugging Help Requested
Vincent,
If you have the time, I'd appreciate your assistance with a fix for a
long-standing concurrency bug. I have been putting together wrapper console
application for the various utilities that ship with Lucene and discovered that
2 of them are non-functional because of this bug, but on the upside is now
there is a reliable way to reproduce it. I suspect the bug is also causing some
of the random test failures that we are seeing on certain FSDirectory
implementations.
I have pushed the WIP application to my local repository
(https://github.com/NightOwl888/lucenenet/tree/cli/src/tools/lucene-cli). It
only runs on .NET Core and in Visual Studio 2015 Update 3. I don't think it
makes sense to support .NET framework for this utility since .NET Core will run
side-by-side with .NET Framework anyway.
You can run a specific commands directly on the command line or in Visual
Studio 2015. There is a server that needs to be started first, and then a
client that connects. The problem seems to be the server.
Command Line
dotnet lucene-cli.dll lock verify-server 127.0.0.4 10
dotnet lucene-cli.dll lock stress-test 3 127.0.0.4 <THE_PORT>
NativeFSLockFactory F:\temp2 50 10
Note the port is dynamically chosen by the server at runtime and displayed on
the console.
Visual Studio 2015
In Visual Studio 2015, you can just copy everything after "dotnet
lucene-cli.dll" and paste it into the project properties > Debug > Application
Arguments text box. Do note I am not sure if those options are optimal (or even
if they may be causing the issue).
What I Have Found
When the client calls the server, the server locks on LockVerifyServer.cs line
129
(https://github.com/NightOwl888/lucenenet/blob/cli/src/Lucene.Net/Store/LockVerifyServer.cs#L129).
I tried removing that line, and it gets a bit further and then crashes with
this error:
An unhandled exception of type 'System.Exception' occurred in
System.Private.CoreLib.ni.dll
Additional information: System.IO.IOException: Unable to read data from the
transport connection: An existing connection was forcibly closed by the remote
host. ---> System.Net.Sockets.SocketException: An existing connection was
forcibly closed by the remote host
at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32
size, SocketFlags socketFlags)
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32
size)
--- End of inner exception stack trace ---
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32
size)
at System.IO.Stream.ReadByte()
at System.IO.BinaryReader.InternalReadOneChar()
at Lucene.Net.Store.LockVerifyServer.ThreadAnonymousInnerClassHelper.Run()
in F:\Projects\lucenenet\src\Lucene.Net\Store\LockVerifyServer.cs:line 135
I suspect that has something to do with removing the wait so the timing is off,
but I compared the thread handling code to some similar tests and it looks the
same (including the call to Wait()), so I haven't worked out why that method
call isn't completing in this case.
I believe this bug is related to a couple of intermittently failing tests that
also seem to indicate the LockFactory is broken.
https://teamcity.jetbrains.com/viewLog.html?buildId=1101813&tab=buildResultsDiv&buildTypeId=LuceneNet_PortableBuilds_TestOnNet451
https://teamcity.jetbrains.com/viewLog.html?buildId=1084071&tab=buildResultsDiv&buildTypeId=LuceneNet_PortableBuilds_TestOnNet451
https://teamcity.jetbrains.com/viewLog.html?buildId=1071425&tab=buildResultsDiv&buildTypeId=LuceneNet_PortableBuilds_TestOnNet451
Namely, the TestLockFactory.StressTestLocks and
TestLockFactory.TestStressLocksNativeFSLockFactory tests.
FYI, the TestIndexWriter.TestTwoThreadsInterruptDeadlock test also fails
intermittently, and is apparently concurrency related. I don't recall which
tests they were, but I discovered a while back that if you put the [Repeat(20)]
attribute on them, they would fail more consistently. I also noticed that they
always fail if MMapDirectory is made as the only option provided by the test
framework.
Anyway, I would really appreciate if you could have a look to see if you can
work out what is going on.
Thanks,
Shad Storhaug (NightOwl888)
