Re: 回复: Re: Archiver Appliance cannot archive structured PV data

[Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov>]

On 7/3/26 3:17 AM, lvhh--- via Tech-talk wrote:

Hi all,

...
info(0:group,
"DEVITEST:waveStruct":{
     "shot id":{+channel:"VAL"}
}

}）
}

I use pva://DEVITEST:waveStruct to add to AA.
But this PV remains stuck in the initial sampling state, and no error logs are generated during the process.

Have you also run:

pvinfo DEVITEST:waveStruct

This is what AA sees.

The core point is this.  PVAccess protocol allows you to define arbitrary structures, such as the one you show with a single sub-structure named "shot it".  However, general purpose client applications like AA do not know how to interpret an arbitrary structure.  AA needs to be able to extra one time from each update.  The type definition you have does not provide this.  So AA can do nothing other than get "stuck".

The NT (Normative Type) definitions are meant to define some common structure understood by general purpose applications.  In the case of AA the primary one are NTScalar and NTScalarArray.  These are the type definitions which QSRV exports by default.  Try running:

pvinfo DEVITEST:shotID

You will see a field "value", also sub-structures "alarm" and "timeStamp".

Sky's previous reply mentions "timestamp".  He is referring to the "timeStamp" sub-structure, which is the absolute minimum which must be provided for AA (a time series archiver) to extract meaning from the value of a PV.

Another version of the link which Sky provided is:

https://docs.epics-controls.org/en/latest/pv-access/Normative-Types-Specification.html#ntscalar

Another link which may be informative:

https://epics-base.github.io/pvxs/nt.html

Thanks a lot for any suggestions.
Best regards,

Huihui

---

lvhh at sari.ac.cn

 

发件人： Sky Brewer

发送时间： 2026-07-01 14:38

收件人： 吕慧慧; tech-talk at aps.anl.gov

主题： Re: Archiver Appliance cannot archive structured PV data

Hi Huihui,

The archiver does support custom structures but they must follow the format https://github.com/epics-docs/epics-docs/pull/182/changes 

You’ll note here the timestamp, the timestamp is what looks to be the problem in the error log. 

Hope that helps.

Sky

Sent from Outlook for Mac

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of 吕慧慧 via Tech-talk <tech-talk at aps.anl.gov>
Date: Wednesday, 1 July 2026 at 04:39
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Archiver Appliance cannot archive structured PV data

Hi all,

I have implemented a structured PVA data in an EPICS V7 IOC. The db is as follows:

record(longin, "DEV1:RED:SHOT_ID_TEST") {
    field(DTYP, "PSC Reg")
    field(INP , "@$(NAME) 526 2")
    field(SCAN, "I/O Intr")
    field(TSE , "-2")
    info(Q:group, {
        "DEV1:RED:WAVE_TEST_PVA": {
            "COUNT": {
                +channel:"VAL"
            }
        }
    })
}

record(waveform, "DEV1:RED:WAVE_TEST_C1") {
    field(DTYP, "PSC Block I16 In")
    field(INP , "@$(NAME) 8193")
    field(SCAN, "I/O Intr")
    field(FTVL, "DOUBLE")
    field(NELM, "20000000")
    info(Q:group,{
        "DEV1:RED:WAVE_TEST_PVA": {
            "VALUE": {
                +channel:"VAL"
            }
        }
    })
}

When I try to archive this PV using the pva://pvname prefix in Archiver Appliance, the archiver throws error messages  and cannot establish persistent archiving. 

2026-06-30 15:48:19,766 ERROR [JCA Command Thread 9] pv.EPICS_V4_PV (EPICS_V4_PV.java:241) - Cannot determine the timestamp bitset for PV DEVI:RED:WAVE_TEST_PVA. This means we may not save any data at all for this PV
2026-06-30 15:48:19,767 ERROR [JCA Command Thread 9] pv.EPICS_V4_PV (EPICS_V4_PV.java:442) - exception when reading pv
java.lang.reflect.InvocationTargetException: null
at jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:72) ~[?:?]
at java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502) ~[?:?]
at java.lang.reflect.Constructor.newInstance(Constructor.java:486) ~[?:?]
at org.epics.archiverappliance.engine.pv.EPICS_V4_PV.fromStructure(EPICS_V4_PV.java:278) ~[classes/:?]
at org.epics.archiverappliance.engine.pv.EPICS_V4_PV.subscribe(EPICS_V4_PV.java:438) ~[classes/:?]
at org.epics.archiverappliance.engine.pv.EPICS_V4_PV.handleConnected(EPICS_V4_PV.java:388) ~[classes/:?]
at org.epics.archiverappliance.engine.pv.JCACommandThread.run(JCACommandThread.java:194) [classes/:?]
Caused by: java.lang.NullPointerException: Cannot invoke "org.epics.vtype.PVStructure.getString()" because "timestampPVStructure" is null
at org.epics.archiverappliance.common.TimeUtils.convertFromPVTimestamp(TimeUtils.java:531) ~[classes/:?]
at edu.stanford.slac.archiverappliance.PB.data.PBV4GenericBytes.<init>(PBV4GenericBytes.java:78) ~[classes/:?]
at jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62) ~[?:?]
... 6 more

I would like to ask two questions: 

1. What is the cause of this failure? I have attached the full error logs from AA engine. 

2. Does the current stable version of Archiver Appliance fully support archiving user-defined custom PVA structure PVs?

Thanks a lot for any suggestions.

 Best regards,

Huihui