beremiz

Rework of runtime non-real-time threading, and shared object dynamic loading :

2018-04-19, Edouard Tisserant
1fdc32be71b8
Rework of runtime non-real-time threading, and shared object dynamic loading :
- All exposed operations on PLCObject are now serialized through main thread
(@RunInMain). Only one exception : python trace thread calling _GetDebugData
- Re-loading of same shared object is prevented. dlclose/delte/rewrite/dlopen
don't happen in that case. This is a workaround for some xenomai copperplate
bug triggering segfault, inbetween delete and rewrite.
- Trace thread now waits for data, dies if no data, and dies instead of
suspending as before when no data consumed after 3 seconds.
- Disabled threading in Pyro client
- Enforced auxiliary threads starting sequence : Pyro -> [UI] ->
PLCWorker.RunLoop
Beremiz and Beremiz_service connectors
======================================
To connect a PLC, Beremiz provides 2 types of connectors :
* a Pyro connector
* a WAMP connector
To configure the connection, you have to set the *URI_location* in your project Config tab according to this documentation.
The Pyro connector
----------------------------
Pyro is an advanced and powerful Distributed Object Technology system written entirely in Python.
Beremiz_service spawns a Pyro server, serving a PLCObject (see runtime/PLCObject.py). Therefore, Beremiz acts as a Pyro client.
TODO:: link to PLCObject API documentation
URI_location :
* LOCAL:// is a facility that starts the PLC service locally and connect Beremiz to it via Pyro.
This is intended for use in development stage.
* PYRO://<ip:port> normal connection to a remote PLC. PLC default port is 3000.
* PYROS://<ip:port> SSL connection to a remote PLC, see below.
more information about Pyro can be found on http://pythonhosted.org//Pyro/1-intro.html
===========================
Setup a Pyro SSL connection
===========================
Pyro v3 has a limited TLS/SSL support based on m2crypto. Pyro v4 had dropped it.
In order to have a full and reliable SSL, we recommand to use a TLS/SSL wrapper as nginx, stub or stunnel.
--------------------
TLS-PSK with stunnel
--------------------
In this example, we setup a simple TLS-PSK connection according to rfc4279.
This ciphersuite avoid the need for public key operations and certificate management.
It is perfect for a performance-constrained environments with limited CPU power as a PLC.
Needed :
* stunnel >= 5.09
verify openssl support for PSK cipher::
openssl ciphers -v 'PSK'
----------------------
Client setup (Beremiz)
----------------------
You need to choose an identity for your client, here *client1*.
generate a valid and strong key::
$ echo client1:$(openssl rand -base64 48) > pskclient1.txt
write a stunnel client configuration file *stunnel-client.conf*::
output = stunnel-client.log
client = yes
[beremiz]
accept = 3002
connect = [PLC]:3001
PSKidentity = client1
PSKsecrets = pskclient1.txt
start stunnel client side::
stunnel stunnel-client.conf
You could now connect beremiz with classic URI_location = PYRO://127.0.0.1:3002
--------------------
Server setup (PLC)
--------------------
import the client key in a keyfile psk.txt, concatening all client key.
write a stunnel server configuration file *stunnel-server.conf*::
output = stunnel-server.log
[beremiz]
accept = 3001
connect = 127.0.0.1:3000
PSKsecrets = psk.txt
start stunnel server side::
stunnel stunnel-server.conf
more documentation on stunnel http://www.stunnel.org/docs.html
The WAMP connector
------------------
WAMP is an open standard WebSocket subprotocol that provides two application messaging
patterns in one unified protocol: Remote Procedure Calls + Publish & Subscribe.
Beremiz WAMP connector implementation uses Autobahn and crossbar.
URI_location :
* WAMP://127.0.0.1:8888#Automation#2534667845
more information about WAMP can be found on http://wamp.ws/