AssertError: eventcore/drivers/posix/driver.d(243): Overwriting notification callback

[Abscissa]

I received a bug report over at mysql-native that I've tracked down to an assert failure in eventcore. It wasn't clear at first because there's another mysql-native issue that was covering up this assert failure during stack unwinding.

To reproduce:

1. Use the test case provided in the original post here

2. Edit mysql-native's source/mysql/protocol/sockets.d and comment out line 121: assert(!!socket); (I think it was supposed to be assert(socket !is null); but I'm getting a weird compile error from that - still figuring that one out) This change will allow the original AssertError to propagate to the top without being hijacked by mysql-native freaking out.

3. Run dub and receive this:

core.exception.AssertError@../../../.dub/packages/eventcore-0.8.29/eventcore/source/eventcore/drivers/posix/driver.d(243): Overwriting notification callback.
----------------
??:? _d_assert_msg [0x4cbb24ba]
??:? nothrow @nogc @safe void eventcore.drivers.posix.driver.PosixEventLoop.setNotifyCallback!(0).setNotifyCallback(eventcore.driver.Handle!("fd", ulong, -1uL).Handle, void delegate(eventcore.driver.Handle!("fd", ulong, -1uL).Handle) nothrow @safe) [0x4cb85b15]
??:? _D9eventcore7drivers5posix7sockets__T23PosixEventDriverSocketsHTCQClQCeQBz5epoll14EpollEventLoopZQCi4readMFNbNfSQEg6driver__T6HandleVAyaa12_73747265616d536f636b6574TSQGiQCc__TQByVQBua6_736f636b6574TSQHpQDj__TQDfVQDba2_6664TmVmN1ZQEaVQBjS1N1ZQEmVQDcS1S1N1ZQFaAhEQJzQFt6IOModeDFNbNfQGnEQKwQGq8IOStatusmZvZv [0x4cb73e01]
??:? _D4vibe4core3net13TCPConnection11waitForDataMFNfSQBq4time8DurationZ__T9__lambda2TDFNbNfS9eventcore6driver__T6HandleVAyaa12_73747265616d536f636b6574TSQCjQCc__TQByVQBua6_736f636b6574TSQDqQDj__TQDfVQDba2_6664TmVmN1ZQEaVQBjS1N1ZQEmVQDcS1S1N1ZQFaEQFyQFr8IOStatusmZvZQHjMFNbNfQHhZv [0x4cb679ae]
??:? _D4vibe8internal5async__T13asyncAwaitAnyVbi1SQBrQBpQBj__T8WaitableTDFNbNfS9eventcore6driver__T6HandleVAyaa12_73747265616d536f636b6574TSQCjQCc__TQByVQBua6_736f636b6574TSQDqQDj__TQDfVQDba2_6664TmVmN1ZQEaVQBjS1N1ZQEmVQDcS1S1N1ZQFaEQFyQFr8IOStatusmZvSQJl4core3net13TCPConnection11waitForDataMFNfSQBq4time8DurationZ9__lambda2SQMhQCwQCuQCtQChMFNfQBxZ9__lambda3SQNpQEeQEcQEbQDpMFNfQDfZ9__lambda4ZZQObMFNfQLjZv [0x4cb3913d]
??:? _D4vibe8internal5async__T13asyncAwaitAnyVbi1SQBrQBpQBj__T8WaitableTDFNbNfS9eventcore6driver__T6HandleVAyaa12_73747265616d536f636b6574TSQCjQCc__TQByVQBua6_736f636b6574TSQDqQDj__TQDfVQDba2_6664TmVmN1ZQEaVQBjS1N1ZQEmVQDcS1S1N1ZQFaEQFyQFr8IOStatusmZvSQJl4core3net13TCPConnection11waitForDataMFNfSQBq4time8DurationZ9__lambda2SQMhQCwQCuQCtQChMFNfQBxZ9__lambda3SQNpQEeQEcQEbQDpMFNfQDfZ9__lambda4ZZQObMFNfQEcQLmZv [0x4cb38fbd]
??:? @safe bool vibe.core.net.TCPConnection.waitForData(core.time.Duration) [0x4cb3804d]
??:? @safe bool vibe.core.net.TCPConnection.read(scope ubyte[], eventcore.driver.IOMode).__lambda3!(core.time.Duration).__lambda3(core.time.Duration) [0x4cb397b9]
??:? @safe void vibe.core.net.loopWithTimeout!(vibe.core.net.TCPConnection.read(scope ubyte[], eventcore.driver.IOMode).__lambda3, Exception).loopWithTimeout(core.time.Duration) [0x4cb3965e]
??:? @safe ulong vibe.core.net.TCPConnection.read(scope ubyte[], eventcore.driver.IOMode) [0x4cb3825a]
??:? @safe void vibe.core.net.TCPConnection.read(scope ubyte[]) [0x4cb38298]
??:? void mysql.protocol.sockets.MySQLSocketVibeD.read(ubyte[]) [0x4c985228]
??:? ubyte[] mysql.protocol.comms.getPacket(mysql.connection.Connection) [0x4c98013e]
??:? bool mysql.protocol.comms.execQueryImpl(mysql.connection.Connection, mysql.protocol.comms.ExecQueryImplInfo, out ulong) [0x4c97fdaa]
??:? mysql.result.ResultRange mysql.commands.queryImpl(mysql.commands.ColumnSpecialization[], mysql.connection.Connection, mysql.protocol.comms.ExecQueryImplInfo) [0x4c97b46a]
??:? mysql.result.ResultRange mysql.commands.query(mysql.connection.Connection, const(char[]), mysql.commands.ColumnSpecialization[]) [0x4c97b3ed]
??:? void app.WebInterface.index(vibe.http.server.HTTPServerResponse) [0x4c960492]
??:? void vibe.web.web.handleRequest!("index", app.WebInterface.index(vibe.http.server.HTTPServerResponse), app.WebInterface).handleRequest(vibe.http.server.HTTPServerRequest, vibe.http.server.HTTPServerResponse, app.WebInterface, vibe.web.web.WebInterfaceSettings) [0x4c96b111]
??:? @trusted void vibe.web.web.registerWebInterface!(app.WebInterface, 5).registerWebInterface(vibe.http.router.URLRouter, app.WebInterface, vibe.web.web.WebInterfaceSettings).__lambda4(vibe.http.server.HTTPServerRequest, vibe.http.server.HTTPServerResponse) [0x4c96a608]
??:? @safe bool vibe.http.router.URLRouter.handleRequest(vibe.http.server.HTTPServerRequest, vibe.http.server.HTTPServerResponse).__lambda4!(ulong, immutable(char)[][]).__lambda4(ulong, scope immutable(char)[][]) [0x4ca4a4a7]
??:? const @safe bool vibe.http.router.MatchTree!(vibe.http.router.Route).MatchTree.doMatch(immutable(char)[], scope bool delegate(ulong, scope immutable(char)[][]) @safe) [0x4ca4cbd5]
??:? @safe bool vibe.http.router.MatchTree!(vibe.http.router.Route).MatchTree.match(immutable(char)[], scope bool delegate(ulong, scope immutable(char)[][]) @safe) [0x4ca4c4d7]
??:? @safe void vibe.http.router.URLRouter.handleRequest(vibe.http.server.HTTPServerRequest, vibe.http.server.HTTPServerResponse) [0x4ca4a168]
??:? @safe bool vibe.http.server.handleRequest(vibe.internal.interfaceproxy.InterfaceProxy!(vibe.core.stream.Stream).InterfaceProxy, vibe.core.net.TCPConnection, vibe.http.server.HTTPServerContext, ref vibe.http.server.HTTPServerSettings, ref bool, scope stdx.allocator.IAllocator) [0x4cad024d]
??:? @trusted void vibe.http.server.handleHTTPConnection(vibe.core.net.TCPConnection, vibe.http.server.HTTPServerContext).__lambda3() [0x4cace7d0]
??:? @safe void vibe.http.server.handleHTTPConnection(vibe.core.net.TCPConnection, vibe.http.server.HTTPServerContext) [0x4cace57b]
??:? nothrow @safe void vibe.http.server.listenHTTPPlain(vibe.http.server.HTTPServerSettings, void delegate(vibe.http.server.HTTPServerRequest, vibe.http.server.HTTPServerResponse) @safe).doListen(vibe.http.server.HTTPServerContext, bool, bool).__lambda4(vibe.core.net.TCPConnection) [0x4ca56771]
??:? void vibe.core.task.TaskFuncInfo.set!(void delegate(vibe.core.net.TCPConnection) @safe, vibe.core.net.TCPConnection).set(ref void delegate(vibe.core.net.TCPConnection) @safe, ref vibe.core.net.TCPConnection).callDelegate(ref vibe.core.task.TaskFuncInfo) [0x4cb69a64]
??:? void vibe.core.task.TaskFuncInfo.call() [0x4cb4b3d9]
??:? nothrow void vibe.core.task.TaskFiber.run() [0x4cb4a9e1]
??:? void core.thread.Fiber.run() [0x4cc041c3]
??:? fiber_entryPoint [0x4cc04092]
??:? [0xffffffff]
Program exited with code -6

[Abscissa]

By adding this to the test case's WebInterface.index function:

import std.stdio;
writeln("*cast(void**)&conn: ", *cast(void**)&conn);

I can see that ConnectionPool is handing out the same connection to two different tasks before the first task has completed.

[Abscissa]

Nevermind the above post, I think my diagnostic code there is in error.

In any case, the corresponding mysql-native issue has made it clear that this was indeed a mysql-native issue after all, so I'm closing this. Thanks for the help, Sonke!