Markus Zolliker
138b84e84c
inital reads from HW should be done in the thread started by startModule, not in startModule itself. - add a hook method 'initialReads' for this + add doc for init methods + fix some errors in doc Change-Id: I914e3b7ee05050eea1ee8aff3461030adf08a461 Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/31374 Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de> Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de> Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
2.9 KiB
Frappy Internals
Frappy is a powerful framework, which does everything behind the scenes you need for getting a SEC node to work. This section describes what the framwork does for you.
Startup
On startup several methods are called. First earlyInit is called on all
modules. Use this to initialize attributes independent of other modules,
if you can not initialize as a class attribute, for example for mutable
attributes.
Then initModule is
called for all modules. Use it to initialize things related to other
modules, for example registering callbacks.
After this, startModule is called with a callback function
argument. frappy.modules.Module.startModule starts the poller
thread, calling writeInitParams for writing initial parameters to
hardware, followed by initialReads. The latter is meant for reading values
from hardware, which are not polled continuously. Then all parameters
configured for poll are polled by calling the corresponding read*() method. The end of this last initialisation step is
indicated to the server by the callback function. After this, the poller
thread starts regular polling, see next section.
When overriding one of above methods, do not forget to super call.
Polling
By default, a module inheriting from Readable <frappy.modules.Readable> is polled
every pollinterval
seconds. More exactly, the doPoll method is called, which by default calls read_value and read_status.
The programmer might override the behaviour of doPoll, often it is wise to
super call the inherited method.
- Note
Even for modules not inheriting from
Readable <frappy.modules.Readable>,doPollis called regularly. Its default implementation is doing nothing, but may be overridden to do customized polling.
In addition, the read_<param> method is called every slowinterval seconds for all
parameters, in case the value was not updated since pollinterval seconds.
The decorator nopoll <frappy.rwhandler.nopoll> might be used
on a read_<param> method in order to indicate, that
the value is not polled by the slow poll mechanism.
Client Notification
Whenever a parameter is changed by assigning a value to the attribute
or by means of the access method, an update message is sent
to all activated clients. Frappy implements the extended version of the
activate message, where single modules and parameters might
be activated.
Type check and type conversion
Assigning a parameter to a value by setting the attribute via
self.<param> = <value> or
<module>.<param> = <value> involves a
type check and possible a type conversion, but not a range check for
numeric types. The range check is only done on a change
message.
TODO: error handling, logging