Panic in websocket handling

[na--]

We saw this panic in a very complicated websocket script:

*errors.errorString: panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: Panic at 28: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: Panic at 28: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: Panic at 106: Panic at 28: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: Panic at 35: Panic at 106: Panic at 28: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: Panic at 35: Panic at 106: Panic at 28: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0xc21917]

goroutine 472 [running]:
github.com/loadimpact/k6/vendor/github.com/dop251/goja.AssertFunction.func1.1(0xc08e027d68)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1407 +0x9b
panic(0xd3ab80, 0xc085e41490)
	/usr/lib/go/src/runtime/panic.go:522 +0x1b5
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).try.func1(0xc00f314750, 0x0, 0xc08e027c70, 0x0, 0x0, 0x0, 0xc08e027cc8)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:364 +0x48e
panic(0xd3ab80, 0xc085dd0d40)
	/usr/lib/go/src/runtime/panic.go:522 +0x1b5
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).try.func1(0xc00f314750, 0x1, 0xc08e027958, 0xa, 0x0, 0x0, 0xc08e0279b0)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:364 +0x48e
panic(0xd3ab80, 0xc085dd0d30)
	/usr/lib/go/src/runtime/panic.go:522 +0x1b5
github.com/loadimpact/k6/vendor/github.com/dop251/goja.AssertFunction.func1.1(0xc08e026cf8)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1407 +0x9b
panic(0xd3ab80, 0xc085dd0d30)
	/usr/lib/go/src/runtime/panic.go:522 +0x1b5
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).try.func1(0xc00f314750, 0x3, 0xc08e026c00, 0x11, 0x0, 0x0, 0xc08e026c58)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:364 +0x48e
panic(0xd4f720, 0x19d2580)
	/usr/lib/go/src/runtime/panic.go:522 +0x1b5
github.com/loadimpact/k6/vendor/github.com/gorilla/websocket.(*Conn).WriteMessage(0x0, 0x1, 0xc0428e4d80, 0xba, 0xc0, 0xc0, 0x18)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/gorilla/websocket/conn.go:732 +0x37
github.com/loadimpact/k6/js/modules/k6/ws.(*Socket).Send(0xc084e49b80, 0xc0428e4cc0, 0xba)
	/home/go/src/github.com/loadimpact/k6/js/modules/k6/ws/ws.go:349 +0xde
reflect.callMethod(0xc081abde40, 0xc08e026508, 0xc08e0264f0)
	/usr/lib/go/src/reflect/value.go:690 +0x182
reflect.methodValueCall(0xc0428e4cc0, 0xba, 0xc07759a750, 0xc085dd0d20, 0xc08e026748, 0x4bb8e1, 0xc0720b6a50, 0xc081abde40, 0xc07759a750, 0x1000000010, ...)
	/usr/lib/go/src/reflect/asm_amd64.s:35 +0x42
reflect.Value.call(0xcfd6c0, 0xc081abde40, 0x13, 0xe6d4ff, 0x4, 0xc0850b7380, 0x1, 0x1, 0xe65740, 0x1098601, ...)
	/usr/lib/go/src/reflect/value.go:447 +0x461
reflect.Value.Call(0xcfd6c0, 0xc081abde40, 0x13, 0xc0850b7380, 0x1, 0x1, 0xc085dd0d20, 0x98, 0x0)
	/usr/lib/go/src/reflect/value.go:308 +0xa4
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*Runtime).wrapReflectFunc.func1(0x1098680, 0xc0850b6c40, 0xc08c1e0750, 0x1, 0x19, 0x1098860, 0xc085dd0d10)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1153 +0x791
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm)._nativeCall(0xc00f314750, 0xc0800a8210, 0x1)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:1826 +0x29a
github.com/loadimpact/k6/vendor/github.com/dop251/goja.call.exec(0x1, 0xc00f314750)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:1810 +0x4a4
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).run(0xc00f314750)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:288 +0x51
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*funcObject).Call(0xc0887926c0, 0x1098cc0, 0x1a08120, 0xc085dd0a20, 0x1, 0x1, 0xc08e026b50, 0xc08befd980)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/func.go:130 +0x2c4
github.com/loadimpact/k6/vendor/github.com/dop251/goja.AssertFunction.func1.2()
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1412 +0x96
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).try(0xc00f314750, 0xc08e026c70, 0x0)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:370 +0x10d
github.com/loadimpact/k6/vendor/github.com/dop251/goja.AssertFunction.func1(0x1098cc0, 0x1a08120, 0xc085dd0a20, 0x1, 0x1, 0x0, 0x0, 0x0, 0x0)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1411 +0x10d
github.com/loadimpact/k6/js/modules/k6/ws.(*WS).Connect(0x1a08450, 0x108b5e0, 0xc088217e30, 0xc00049c300, 0x3c, 0xc085080f40, 0x2, 0x2, 0x0, 0x0, ...)
	/home/go/src/github.com/loadimpact/k6/js/modules/k6/ws/ws.go:196 +0x7af
reflect.Value.call(0xd3aee0, 0x1a08450, 0x213, 0xe7288b, 0x9, 0xc0878fcc80, 0x3, 0x3, 0xde3e80, 0xc085d92b60, ...)
	/usr/lib/go/src/reflect/value.go:447 +0x461
reflect.Value.CallSlice(0xd3aee0, 0x1a08450, 0x213, 0xc0878fcc80, 0x3, 0x3, 0x194, 0xc08e027628, 0x8b5d26)
	/usr/lib/go/src/reflect/value.go:321 +0xa4
github.com/loadimpact/k6/js/common.Bind.func1(0x1098680, 0xc0104e9200, 0xc08c1e06e0, 0x3, 0x20, 0xc0882498c0, 0xc08e027840)
	/home/go/src/github.com/loadimpact/k6/js/common/bridge.go:239 +0x78a
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm)._nativeCall(0xc00f314750, 0xc088ae2dc0, 0x3)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:1826 +0x29a
github.com/loadimpact/k6/vendor/github.com/dop251/goja.call.exec(0x3, 0xc00f314750)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:1810 +0x4a4
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).run(0xc00f314750)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:288 +0x51
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).try(0xc00f314750, 0xc08e0279b8, 0x0)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:370 +0x10d
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).runTry(0xc00f314750, 0xd35a40)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:375 +0x4e
github.com/loadimpact/k6/vendor/github.com/dop251/goja.try.exec(0x13, 0x0, 0xc00f314750)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:2245 +0x51
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).run(0xc00f314750)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:288 +0x51
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*funcObject).Call(0xc0105752c0, 0x1098cc0, 0x1a08120, 0xc085d929a0, 0x1, 0x1, 0xc00fcc5728, 0xc08befd980)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/func.go:130 +0x2c4
github.com/loadimpact/k6/vendor/github.com/dop251/goja.AssertFunction.func1.2()
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1412 +0x96
github.com/loadimpact/k6/vendor/github.com/dop251/goja.(*vm).try(0xc00f314750, 0xc08e027ce0, 0x0)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/vm.go:370 +0x10d
github.com/loadimpact/k6/vendor/github.com/dop251/goja.AssertFunction.func1(0x1098cc0, 0x1a08120, 0xc085d929a0, 0x1, 0x1, 0x0, 0x0, 0x0, 0x0)
	/home/go/src/github.com/loadimpact/k6/vendor/github.com/dop251/goja/runtime.go:1411 +0x10d
github.com/loadimpact/k6/js.(*VU).runFn(0xc01058c2d0, 0x108b520, 0xc0653b7bc0, 0xc0036ae300, 0xc010578a00, 0xc085d929a0, 0x1, 0x1, 0x1098cc0, 0xc08e027f30, ...)
	/home/go/src/github.com/loadimpact/k6/js/runner.go:443 +0x394
github.com/loadimpact/k6/js.(*VU).RunOnce(0xc01058c2d0, 0x108b520, 0xc0653b7bc0, 0x0, 0x0)
	/home/go/src/github.com/loadimpact/k6/js/runner.go:403 +0x1f0
github.com/loadimpact/k6/core/local.(*vuHandle).run(0xc00f530ec0, 0xc00007a240, 0xc0026dc8a0, 0xc00050cba0)
	/home/go/src/github.com/loadimpact/k6/core/local/local.go:70 +0x145

I can't reproduce it with a simple test script, and I can't paste the original script, since it's very complex and has private data in it... 😞 Potentially connected: #581 (comment)

[mstoykov]

This is the case the panic above originated from:

import ws from "k6/ws";

export default function() {

    var response = ws.connect("ws://nonexistant", null, function(socket) {
        socket.on("open", function() {
            socket.send('my-message');
        });
        socket.send('mesage to break ti')
    });
}

[na--]

Ah, and I tried so hard to trigger it with a working websocket connection... 😆 Then this should be easy to fix, and is likely unconnected to the other websocket panic we've seen...