# Presentation: 199637

## Interval of Validity ServiceIOVSvc

**ATLAS Software Week**
**March 3 2003**
**Architecture Session**

## Interval of Validity Service

- Purpose:
- associates valid time ranges with objects
- triggers updates of data, and validity ranges when object enters a new validity range
- allows use of call back functions
- Use cases:
- alignment data
- calibration objects
- detector description information
- anything which has a timed validity range associated with it

## Access Patterns

- Two types of access/usage patterns:
- pure data, held in dB, used as a data member inside a class. Only needs to have it’s contents refreshed when it enters a new validity range.
- Container class, eg GeoNode, which has no representation inside the dB, contains one or more IOV data objects from dB as data members. Needs to know when any of its constituent members enters a new validity range, at which point a callback method is triggered.
- No overlap between these patterns
- will never have an IOV data object which needs a callback
- will never have a container class which has data stored in database

## Class Example

**Class Example**

**class myIOVClass {**
** ****public:****virtual StatusCode CallBackFcn(int,list<string> &dbKeys);**
** ****private:**** ****const**** DataHandle<CalAlign> m_align1;**** ****const**** DataHandle<CalAlign> m_align2;**
**      ****myIOVAlg2* that;**
**};**
**myIOVClass::initialize() {****  ****p_IOVSvc->regHandle(m_align1, dBkey1);****p_IOVSvc->regFcn(&myIOVClass::CallBackFcn, this, ****	****	****      m_align1, dBkey1);****p_IOVSvc->regFcn(&myIOVClass::CallBackFcn, this, **
**	****	****	****      ****m_align2, dBkey2);**
**   ****p_IOVSvc->regFcn(&myIOVClass::CallBackFcn, this,**
**                    ****&myIOVClass2::OtherCallBackFcn, that);**
**}**

## Sequence Diagram

**Alg**

**Handle**

**Storegate**

**Proxy**

**IOVSvc**

**CondDB**

**NovaCnv**

**PPSvc**

- regHandle(**handle,key**)

- 

- accessData()

**T***

**DataObj*******

- reset()

- callback(**dbKey**)

**T***

- 

- regFcn(**this,&Fcn,handle,key**)

- reset()

- initialize

- execute

- async

- bindHandle(**handle**)

**IOVDbSvc**

**IOV,string**

- getData(**key**)

**DataObj*******

**PersSvc**

- updateAddress(**TA**)

- updateAddress(**TA**)

- buildIOA(**string**)

**IOA**

- setRange(**clID,key,IOV**)

- createObj(**IOA**)

- setAddress(**IOA**)

**IOA**

**IOA**

- buildIOA(**string**)

- partial **IOA**

- regProxy(**proxy**)

- bind(**handle,key**)

## Sequence

- In **Initialize()**, alg registers **DataHandle<alignData>** with the IOVSvc using **IOVSvc->regHandle(handle,key)**, using the same dBkey as is used in the dB.
- Alternatively, the algorithm registers container class (eg GeoNode) with **IOVSvc->regFcn(...)**, supplying callback fcn, DataHandle, pointer to the object, and the key as parameters.
- At first deref of the DataHandle, call is passed through to Proxy, which calls **updateAddress(TransientAddress)** on the IOVDbSvc. IOVDbSvc  talks to the CondDB to retrieve storage location of an element given a **(clID,dbKey)** pair. It gets back an IOV and a string which points to the actual location of the data from which an IOA can be built. It then calls **setRange()** on the IOVSvc, which adds the IOV to its list of registered intervals. The IOA is set in the TransientAddress, and then the DataProxy calls **createObj()** on the persistency converter for the actual data using this information, and gets back a **DataObj***. The **DataObj*** is passed back through the chain of sequences to the Algorithm, eventually being converted to a **T***.

## Sequence (cont)

- The next time the DataHandle is derefed, a **T*** is automatically returned from the Proxy.
- At the start of each event, the IOVSvc parses its list of registered entries to see if any are out of range. When it finds one, it first resets the corresponding proxy, then triggers the registered callback function. The callback function gets a list of the keys of the items which have gone out of range as a parameter.
- The next time one of the DataHandles is derefed, the initial sequence is replayed, getting back a new IOV and data.

## Things Needed

**IOVDbSvc**
- provided by Database people. See RD’s talk later today.
- Can use **AtlasTest/IOVASCIIDbSvc** instead, which keeps IOV Range info in a hierarchical ASCII file based format. See that package for details.
- A converter/conversion svc for your class.
- an example can be found in **AtlasTest/SiAlignTest**

## Changes to DataHandle et al

- DataHandle
- inherits from **IResetable**, declares **reset**() method
- DataProxy
- list of bound handles (**list<IResetable*>** )
**bindHandle(IResetable*)****unbindHandle(IResetable*)**
**resetBoundHandles()**
- StoreGate
- ProxyProvider
**bind()**
- like retrieve, but also associates Handles with Proxy

## IOVSvc

**IOVSvc {**
**public:**
-    StatusCode regHandle(DataHandle<H> handle, string key);
-    StatusCode regFcn(void (T::*fcn)(), T* obj, DataHandle<H> handle, string key);
-    StatusCode regFcn(void (T1::*fcn1)(), T1* obj, void (T2::*fcn2)(), T2* obj);
**private:**
-    StatusCode regProxy(DataProxy *);
-    set<DataProxy*> m_proxies;
-    map<DataProxy*, IOVEntries* > m_entries;
-    multimap<DataProxy*, boost::function<StatusCode>* > m_proxyMap;
-    multiset<IOVEntry, IOVEntryStartCriterion>  m_startSet;
-    multiset<IOVEntry, IOVEntryStopCriterion> m_stopSet;
- };

**Service**

**IIncidentListener**

## Associated Classes

**IOVRange**
**   **IOVTime m_start
-    IOVTime m_stop

**IOVTime**
**   **IOVTime(int)
-    IOVTime(EventID)
-    unsigned long long m_time

**IOVEntry**
**  **DataProxy* m_proxy
-   IOVRange*  m_range

## Internals of IOVSvc

- indexing is done via **DataProxy***
- IOVs are held in **map<DataProxy*, IOVEntry*>**
- Callback functions are **multimap<DataProxy*, boost::function<StatusCode>* >**
- IOVs are ordered in two sets:
**std::multiset<IOVEntry*,IOVEntryStartCritereon> m_startSet;**
**std::multiset<IOVEntry*,IOVEntryStopCritereon>  m_stopSet;**
**m_startSet** is ordered by  decreasing start time, **m_stopSet** is ordered by increasing end time. As a result of this ordering, when the sets are scanned at the beginning of each event for entries that need to be marked invalid, as soon as the first valid entry is found in each set, the scanning can be stopped as one is assured that all subsequent entries are valid.
- When invalid entries in these multisets are found, the associated DataProxy* is added to a list. At the end of the scan, the IOVs of these DataProxies are updated, the DataProxies are reset (and thus the associated DataHandles) and the associated callback functions are activated.

## A Real Example: Pixel Detector

- Used to handle automatic alignments with the GeoModel.

**RCBase**

**GeoGraphNode**

**GeoAlignableTransform**

**GeoTransform**

**GeoSiAlTransform**
**public:**
-  HepTransform3D  getTransform()
-  HepTransform3D* getDelta()
-  void            setDelta(HepTransform3D &)
-  void            clearDelta()
**private:**
-  const DataHandle<GeoSiDeltaTransform> m_DHdelta

**InnerDetector/InDetAlignment/SiAlignment**

## How It Works

- The GeoSiAlTransform is associated with a GeoFullPhysVolume, which has a cache for the alignment data.
- When this alignment data is needed, **getDelta()** in GeoSiAlTransform is called, which in turn derefs the DataHandle **m_DHdelta**. This DataHandle has been registered with the IOVSvc, so the IOVSvc is able to manage its contents, updating it as necessary.
- The method **clearDelta()** has also been registered as the accompanying callback function for this DataHandle, and is called when a new alignment is read in. It invalidates the position caches for all elements in the detector hierarchy below it, so that the next time the position of any of them is needed, it is recalculated with the updated information.

## Example Output

- Alignment first checked at event [1,5]
- db file opened, appropriate range found ([1,4] -> [1,8]),  tag “tag2” read in
- Position loaded from converter (ideal + delta), identified by “tag2”
- Event [1,6] - start and stop sets show valid ranges for this detector element
- Event [1,10] - detector element is out of range, has been removed from stop set
- db file found and opened, next valid range found ([1,9]->[2,2]), tag “tag3” read in.
- Position loaded from converter, is now different from before (the delta has changed)
- Event [2,2] - start and stop sets show valid ranges for this detector element

- example taken from running package **AtlasTest/SiAlignTest**

- Colors provided by the colorized  MsgService, coming soon to a terminal near you!

## Caveats

- The callback function must be virtual. This will no longer be necessary when we move to gcc 3.2
- All DataHandles to elements that the IOVSvc will manage must be const, or you’ll get a runtime error.
- Don’t try to deref the DataHandle before the first event is loaded, eg in the initialize phase. The proxy hasn’t been filled, and you’ll get a pointer to a null object.
- Whenever you call **regFcn(...)**, you will get a warning that looks like this: ...lots of crap ... instantiated by ... instantiated by ...../../../Control/IOVSvc/IOVSvc-00-00-07/IOVSvc/CallBackID.icc:24: warning: unsigned int format, different type arg (arg 3)This is OK, and can be safely ignored. Warning will be gone in 6.1.0.

## What’s Next

- This is still a prototype, but has been demonstrated to work with the Pixel alignments in the Geo model.
- Has been in the release since 5.1.0, but has been evolving, along with StoreGate.
- Currently in stable form, don’t foresee any radical changes in the near future. Ready to use!

## Other Stuff

- Full online documentation:
- _http://annwm.lbl.gov/~leggett/Atlas/__IOVSvc_