Sudden close of Telegraf caused by OPC UA input plugin

[hybuild-project]

Relevent telegraf.conf

[[inputs.opcua]]
  name = "xyz"
  endpoint = "opc.tcp://xxx.yyy.wwww.zzz:4840"
  security_policy = "None"
  security_mode = "None"
  nodes = [
    { name="abc",  namespace="6",  identifier_type="s",  identifier="abc"},
    { name="def",  namespace="6",  identifier_type="s",  identifier="def"},
...
]

System info

Telegraf 1.20.3, Windows 10

Docker

No response

Steps to reproduce

1. Simly running Telegraf with that plugin

...

Expected behavior

No errors

Actual behavior

After some random time (hours, one day at most) it crashes:

goroutine 68418 [running]:
github.com/gopcua/opcua/uasc.(*SecureChannel).dispatcher(0xc0007b8000)
/go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2.0.20210409063412-baabb9b14fd2/uasc/secure_channel.go:208 +0x185
created by github.com/gopcua/opcua/uasc.(*SecureChannel).open.func1
/go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2.0.20210409063412-baabb9b14fd2/uasc/secure_channel.go:496 +0x5f

Additional info

No response

[R290]

I'm facing a similar issue after upgrading Telegraf to version 1.20.4:

2021-11-23T13:05:10Z E! [inputs.opcua] Error in plugin: RegisterNodes Read failed: The operation could not complete because the client is not connected to the server. StatusBadServerNotConnected (0x800D0000)
panic: send on closed channel

goroutine 8337 [running]:
github.com/gopcua/opcua/uasc.(*SecureChannel).dispatcher(0xc000cbec40)
        /go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2.0.20210409063412-baabb9b14fd2/uasc/secure_channel.go:208 +0x185
created by github.com/gopcua/opcua/uasc.(*SecureChannel).open.func1
        /go/pkg/mod/github.com/gopcua/opcua@v0.2.0-rc2.0.20210409063412-baabb9b14fd2/uasc/secure_channel.go:496 +0x5f

There is an extra line at the beginning about sending on a closed channel. In my case this is caused by the PLC closing the TCP connection. Let me see if I can find out what changed between versions. Could be Telegraf itself or the gopcua library.

EDIT: downgrading to 1.19.3 avoids the panic for now. For later versions the gopcua library might need an update. There is a specific commit about this: gopcua/opcua@809fb04 included in v0.2.1 (Telegraf uses v0.2.0).

[hybuild-project]

Very nice investigation R290! Let-s hope it will be included in v1.21...! Cheers and thank you so much.