pvmanager gabriele carcassi feb 18 2010. pvmanager goals simplify data collection and aggregation ...
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PVManagerGabriele Carcassi
Feb 18 2010
PVManager goals
Simplify data collection and aggregation Simplify (UI) development Re-use code as much as possible
So you want to write a UI…
channel.addListener(new Listener() { public void doSomething(Event evt) { myWidget.setFoo(evt.getWhatever()); }}
TOOLKIT IS SINGLE THREADED!
So you want to write a UI…
channel.addListener(new Listener() { public void doSomething(Event evt) { Toolkit.execute(new Runnable() { myWidget.setFoo(evt.getWhatever()); } }}
LACK OF SYNCHRONIZATION!
So you want to write a UI…
channel.addListener(new Listener() { public void doSomething(Event evt) { Toolkit.execute(new Runnable() { synchronized(evt) { myWidget.setFoo(evt.getWhatever()); } } }}
NO CHANGE BY ANOTHER THREADDURING/BETWEEN NOTIFICATIONS!
So you want to write a UI…
channel.addListener(new Listener() { public void doSomething(Event evt) { Toolkit.execute(new Runnable() { synchronized(evt) { myCopy = copy(evt.getWhatever()); myWidget.setFoo(myCopy); } } }}
SHOULD NOT UPDATE UI AT THE SAME RATEAS DATA ON THE NETWORK!
LACKING DISCONNECTION ANDRECONNECTION NOTIFICATIONS!
NEED TO QUERY METADATAON CONNECTION!
AGGREAGATE EVENTS!
CACHE!
Wish one could write
PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
pv.addPVValueChangeListener(new PVValueChangeListener() { public void pvValueChanged() { myWidget.setFoo( pv.getValue().getMoo()); } });
UI subsystem requirements
Single threaded Notification must be done on event thread Data objects must be changed on the event
thread only (avoid inconsistencies and simplify responding to events)
Work must be offloaded to other threads as much as possible (to prevent unresponsiveness)
Refresh rate up to 50Hz (faster is useless and counter productive)
Channel Access
Multi threaded Notification done on connection
threads Data objects changed on connection
threads Rate is not limited: aggregated can
be KHz
Collect, aggregate and notify
Need to collect the data at the source rate Collector could be a queue, a cache, a timed cache Aggregate the data at the UI rate, and notify on UI thread
Notifier Collector Monitor
Transform and calculate
While we are on other thread, we compose and calculate what we need (single array for a table, FFT of a waveform, statistics, prepare synch’ed arrays, …)
Notifier Collector Monitor
CachePV FunctionPV Function
UI or not UI
Everything you can do in the UI you should be able to do at the command line
PVManager can work without a UI (notification is simply done on the timer thread)• Command line clients• Logging/archiving• Republish the data through PVData/PVAccess
PVManager is a standalone library• pvmanager.sourceforge.net
3 APIs for the price of one
Data interfaces: where to put the data• Decoupled from the other two. Needed so that the client
can focus more on what he needs and can work with both EPICS V3 and EPICS V.
• Other talk
Building blocks API: perform computation• API based on interfaces, you can add your pieces though
the goal is to have most of them already there
Expression API: define what you want to read• Internal DSL (Doman Specific Language), type safe
BUILDING BLOCKS API
User objects
Notifier Collector Monitor
CachePV FunctionPV Function
PV<T>
Defines:• void add/removePVValueChangeListener
(PVValueChangeListener listener);• String getName() ;• T getValue();• void close();• boolean isClosed();
PVValueChangeListener defines:• void pvValueChanged();
Under the hood
Notifier Collector Monitor
CachePV FunctionPV Function
Function<T>
Defines:• T getValue();• Class<T> getType()
A function object returns a value of a particular type.• Argument number and types are determined by the
constructor of an actual function.
Under the hood
Notifier Collector Monitor
CachePV FunctionPV Function
Collector<T> extends Function<List<T>>
Defines:• void collect();• List<T> getValue();
Collects a bunch of values of the same type Typically takes a Function<T> as argument
• On a collect call, will take a new value• On getValue returns a number of values
Could be a queue (values returned only once) or a cache (returns the last n values, last 30 sec of values)
Under the hood
Notifier Collector Monitor
CachePV FunctionPV Function
ValueCache<T> extends Function<T>
Defines:• void setValue(T);
You can put a value in (and read a value out)
Under the hood
Notifier Collector Monitor
CachePV FunctionPV Function
DataSource
Defines:• void connect(DataRecipe recipe);• void disconnect(DataRecipe recipe);
DataRecipe defines:• Map<Collector, Map<String, ValueCache>>
getChannelsPerCollectors()
For each collector, list of channels with their caches To update a channel:
• Lock Collector, update cache, Collector.collect()
Under the hood
Notifier Collector Monitor
CachePV FunctionPV Function
Notification
ThreadSwitch defines:• void post(Runnable run);
It allows to execute a piece of code on a target thread
Notifier defines:• Notifier(PV<T> pv, Function<T> function, ThreadSwitch
onThread);• void notifyPv();
On notifyPV() calculates the new value, switches thread and sets the pv’s value.
EXPRESSION API
PVManager
Example:• PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
Defines:• static <T> PVManagerExpression<T>
read(SourceRateExpression<T> pvExpression);• static <T> PVManagerExpression<T>
read(DesiredRateExpression<T> pvExpression);
PVManagerExpression<T>
Defines:• PVManagerExpression<T> from(DataSource
connectionManager) • PVManagerExpression<T> andNotify(ThreadSwitch
onThread)• PV<T> atHz(double rate)
Default DataSource and ThreadSwitch can be specified
Source/DesiredRateExpression<T>
Two different types for the two different data rates The collectors change Source to Desired:
• static <T> DesiredRateExpression<List<T>>
queueOf(SourceRateExpression<T> expression)
External libraries for either types or operations defines static constructors for expressions:• static SourceRateExpression<VDouble> vDouble(String
name)• static <T> DesiredRateExpression<List<T>>
listOf(List<DesiredRateExpression<T>> expressions)
Example (again)
PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
pv.addPVValueChangeListener(new PVValueChangeListener() { public void pvValueChanged() { myWidget.setFoo( pv.getValue().getMoo()); } });
List<String>
Example (again)
PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
pv.addPVValueChangeListener(new PVValueChangeListener() { public void pvValueChanged() { myWidget.setFoo( pv.getValue().getMoo()); } });
List<SourceRateExpression<VDouble>>
Which implies creating the caches for all channels
Example (again)
PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
pv.addPVValueChangeListener(new PVValueChangeListener() { public void pvValueChanged() { myWidget.setFoo( pv.getValue().getMoo()); } });
List<DesiredRateExpression<VStatistics>>
Creates all the collectors, and the functions that calculate the statistics
Example (again)
PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
pv.addPVValueChangeListener(new PVValueChangeListener() { public void pvValueChanged() { myWidget.setFoo( pv.getValue().getMoo()); } });
DesiredRateExpression<List<VStatistics>>
Creates the function that assembles the list
Example (again)
PV<List<VStatistics>> pv = PVManager.read( listOf(statisticsOf(vDouble(pvNames)))) .atHz(10);
pv.addPVValueChangeListener(new PVValueChangeListener() { public void pvValueChanged() { myWidget.setFoo(pv.getValue().getMoo()); } });
PV<List<VStatistics>>
Creates the Notifier, the DataRecipe, passes it to the DataSource, …
Low complexity point
The API is very expressive• You can combine operators, the syntax is very compact,
you specify things once
But it does not hide choices• You need to specify all transformations, including how to go
from source rate to desired rate
It hides the complexity of the implementation of your choices• The API actually does something!
Eclipse/CSS integration
The library is packaged in org.csstudio.utility.pvmanager• Extension point based on DataSource• The activator configures the default ThreadSwitch to use
SWT and default DataSource to use a CompositeDataSource made up of all extensions point
All other plugins can simply use PVManager.read() Other plugins for extension points
• org.csstudio.utility.pvmanager.sim for simulated data• org.csstudio.utility.pvmanager.epics for epics v3
What’s done
SimulationDataSource• Same syntax for channels as utility.pv.som
JCADataSource• Supports VDouble, VInt, VString and VEnum
Probe was ported to use PVManager (in BNL branch)
OrbitViewer prototype built on PVManager
What’s need to be done
JCADataSource• Mass connection can be optimized to scale better
Operators• Will need to understand which operators are useful, how to
define them for “maximum combination power”• Allow to easily define “custom functions”• Add other common operators
- A CALC operator?- A histogram operator?- An FFT operator?- …