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ControlSystemStudio / phoebus

A framework and set of tools to monitor and operate large scale control systems, such as the ones in the accelerator community.
http://phoebus.org/
Eclipse Public License 1.0
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Assigning different pva:// PVs to different parts of the display causes some race condition #623

Closed wcork closed 5 years ago

wcork commented 5 years ago

Getting more than one PV from the same server and assigning them to different visual elements results in one or both of them disconnecting.

Phoebus then cannot probe either of the values desired, but pvget works. Refreshing the page sometimes swaps which visual element gets updated/connected. Closing the page allows probing of individual PV elements again.

I have two records that look like the following:

test:Monit:localhost:Service:sshd structure 
    time_t timeStamp 2019-04-04 13:39:23.059  
        long secondsPastEpoch 1554410363
        int nanoseconds 59000000
        int userTag 0
    epics:nt/NTScalar:1.0 name
        string value sshd
    epics:nt/NTScalar:1.0 enabled
        int value 1
    epics:nt/NTScalar:1.0 state
        int value 0
    epics:nt/NTScalar:1.0 running
        int value 1
        alarm_t alarm 
            int severity 0
            int status 0
            string message 
    epics:nt/NTScalar:1.0 type
        string value PROCESS
test:Monit:localhost structure 
    time_t timeStamp 2019-04-04 13:41:23.306  
        long secondsPastEpoch 1554410483
        int nanoseconds 306000000
        int userTag 0
    alarm_t alarm 
        int severity 0
        int status 0
        string message 
    epics:nt/NTScalar:1.0 host
        string value localhost
    epics:nt/NTScalar:1.0 pollRate
        int value 120
        display_t display
            double limitLow 0
            double limitHigh 0
            string description 
            string format 
            string units S

Error occurs when more than one element is looking at different PVs. Example: 2 TextUpdate elements. One displaying pva://test:Monit:localhost:Service:sshd/name The other pva://test:Monit:localhost/host

System Info: Phoebus commit 59e1073b7b56f93546538c715a4d23f5109544b7 Phoebus Build with Oracle JDK 11 Server written in Java (built with Oracle JDK 11).

Server EPICS dependencies (from Maven repo):

compile group: 'org.epics', name: 'epics-core', version: '7.0.2'
compile group: 'org.epics', name: 'epics-pvdatabase', version: '4.3.1'
compile group: 'org.epics', name: 'epics-pvdata', version: '6.1.2'
kasemir commented 5 years ago

Yes, this is a known bug in the pva:// support. Thank you for creating a ticket. Unclear if the problem is in the way we use the pva library, or in the Java pva library itself, since I don't remember seeing this problem with the RCP-based Display Builder that used an earlier version of the Java pva library.

kasemir commented 5 years ago

Simple demo runs this in softIocPVA:

record(calc, "ramp")
{
  field(SCAN, "1 second")
  field(INPA, "ramp")
  field(CALC, "A+1")
}
record(calc, "rnd")
{
  field(SCAN, "1 second")
  field(CALC, "100*RNDM")
}

A display for both pva://ramp and pva:rnd might work when executed the first time, but on reload, or when accessing the PVs with probe, PV tree etc. results in not all PVs connecting.

This works fine with the RCP-based DisplayBuilder.

kasemir commented 5 years ago

Distilled it down to example Java code that's totally unrelated to Phoebus, Display Builder, ..

Runs OK with older PVA library, but has connection errors with the latest PVA library. Reported there: https://github.com/epics-base/epicsCoreJava/issues/53

wcork commented 5 years ago

Latest pva libs in phoebus build seems to resolve this issue.

For the record, this MR seemed to have fixed it.

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