> 
> The header file used to defined the CAEN types (CAENVMEtypes.h) defines 'CAEN_BOOL' like this:
> 
> 
> #ifdef LINUX
> #define CAEN_BYTE   	unsigned char
> #define CAEN_BOOL   	int
> #else
> #define CAEN_BYTE   	byte
> #define CAEN_BOOL   	VARIANT_BOOL
> #endif
> 

Complain to CAEN.

The year is 2020 and they should use standard C/C++ data types from stdint.h (uint32_t, etc).

K.O.

> Today I addressed a topic which bugged me since long time.

Right. No easy subject. For me, too, this has been a problem in MIDAS for a long time.

> Now, on each start of the frontend program, the values from equipment[] are written to 
> the ODB. They are still "live". If one changes them when the frontend is 
> running, that change takes effect immediately. But on the next restart of the 
> frontend, the old values from equipment[] is put back there.

There is a downside from this behaviour.

If some values in equipment/common are "live" and the user is expected to change them,
the user will be unpleasantly surprised when their changes magically disappear (after reboot,
after frontend crash, after run restart if experiment requires restarting some frontends
before starting a new run).

This change will also break some experiments that rely in things like specifying
event buffer names through ODB. But experiments can adapt and specify buffer names
through command line switch instead of ODB.

This new way also it makes the "live" Common/Period unusable. Sure I can speed up or slow
down a frontend even during the run, but if my change does not "stick", what good is it?

Personally, I think there is no easy solution for all these troubles.

I would advocate the following approach:

- think of MIDAS as a "mature" system,
- treasure backward compatibility
- (if we must break backward compatibility to introduce a new "must have" improvement, so be it)
- document how things work. if it is clearly written down what different fields in "common" do, fewer people 
"get burned" by unexpected or illogical things. (and any non-trivial system has plenty of those).

Going back to ODB equipment/common, my experience with midas and odb tells me
that one should avoid mixing together ODB entries set by user and ODB entries set by code.

For example, separating them as equipment/settings and equipment/variables works well. Mixing
them as in equipment/common and sequencer/state causes trouble.

So perhaps we should split Equipment/common into two pieces, user settable fields like
"Period" and "event buffer name" would move to equipment/settings or whatever.

This will open the discussion of which items in equipment/common should be user settable,
and some people would want event buffer specified in the code to prevail, while other
people would want the name from odb to prevail, and both are valid but conflicting preferences.

Or we could bite the bullet and say, equipment/common is controlled by the frontend code,
the user should not change it. (and mark it read-only in ODB).

For all the pain this may cause, at least this will make it self-consistent.

Per this proposal, in addition to Stefan's change, the hotlink on equipment/common goes away,
"period" is no longer "live" and the whole subdirectory is made "read-only".

K.O.

>
> Taking this down a tangent, I have a mild concern that a user could temporarily 
> flood our gigabit network if we do have faster disks to read the history data.
>

By my measurements, right now our javascript code can reach 30-50-70% of Gige ethernet
bandwidth, so, no, we cannot flood the network just by making history plots.

(we cannot reach 100% because javascript code is not multithreaded,
it cycles through "request new data" and "decode javascript, make plot" states,
and the network is idle in this second state).

>
> Have there been any plans or thoughts on limiting the bandwidth users can pull from 
> mhttpd?
>

10gige networking is here (and 5 and 2.5 Gige, too). I would not worry too much
about saturating 1gige network interfaces.

>
> I do not see this as a critical item as I can plan the future network 
> infrastructure at the same time as the next system upgrade (putting critical data 
> taking traffic on a separate physical network).
>

10gige network between all computers, everything on SSD ZFS arrays, except
bulk data on ZFS HDD arrays (only for cost reasons $$$/TB).

K.O.

> 
> Are you sure that the delay comes from the browser or actually from mhttpd
> digging through GBytes of history data?
>

I think we will need to address this question "head-on". The history plot
will need to display the following information:

"time to load data from disk: N seconds, time to transfer data to javascript: M 
seconds, time to make the plot: Q seconds".

The second and third items are already available, the first one will need
to be computed in mhttpd and passed to javascript.

K.O.

>
> With the current code, we are limited to loading history data up to 50% of
> the javascript memory limit.
>

The javascript memory limit itself seems to be a moving target. (google javascript 
memory limit, and good luck!).

Historically, javascript did not have any memory or cpu use limits, but with
the raise of abusive web sites, bitcoin miners, etc, I see browsers clamp down
on allowed/allocated CPU use (inactive tabs are throttled down). memory use
is already clamped down severely, on a 64 GB computer, a browser tab
can only allocate a handful of GBs.

This throttling of browser tabs is already intrusive enough that we need
to be careful in programming midas web pages. for examples throttled events
are not firing at the same rate or in the same order as in active tabs.

One logical conclusion of these restrictions could be that, eventually,
google-chrome permits only just enough cpu and memory to run gmail.

K.O.

> 
> Tested with midas-2020-08-a up until the HEAD of develop
> 

Just so you know, it took myself and Stefan quite a bit of effort
to improve memory and data handling in the new history plots
to be able to plot 1 year of data without bogging down too much. I got
to learn the google-chrome javascript cpu profiler, memory profiler
and the intricacies of javascript shift() and unshift() operators.

Before midas-2020-08-a, pressing the zoom-out button you would never
reach the javascript memory limit, the code would go into "100% cpu use"
and the browser tab will become progressively unresponsive well before
running out of memory. With the original code, our alpha-g history plots
could go back a few weeks at most, with the current code, we can go back
about 11 months. Compared to the old "C" history plots that can
do "last 10 years", no problem.

Loading all the history data into the browser is a design choice.

It has benefits and downsides.

The main benefit is that looking at immediate live data is much easier.

The main downside is that "plot last 10 years" becomes impossible.

As they say "appetite comes during eating", we have learned about these
downsides as we developed the new system. When we started, we did not
know much about javascript memory limits, cpu limits, etc. We did learn
a lot, though.

With the current code, we are limited to loading history data up to 50% of
the javascript memory limit. I know how to change the code to get up to 100%,
but I think it is not worth it, it still does not get as to plot "last 10 year".

We think the solution to recovering "last 10 years" capability is to use
binned data (which the history system can already deliver to javascript).
With binned data, the data volume in Mbytes remains constant, javascript
memory use has an upper-bound (we never use more memory than X Mbytes)
and data movement over the network is reduced.

Another way to look at this - typical display has only 1000-4000 vertical pixels,
it cannot physically display a bigger number of data points (no more
then 1 data point per pixel). So why load 1000000 data points when we only
can plot 1000-4000 of them?

So all the infrastructure for plotting binned data is already there,
but the javascript code still needs to be written. I think the biggest
challenge will be in blending or combining binned and unbinned data
on the same plot or in seamlessly switching the plot between binned and
unbinned data.

K.O.

> I've recently took the analyzer template from $MIDASSYS/examples/experiment and 
> modified it to be able to use Roody on a very simple frontend setup.

Hmm... the old midas analyzer framework is very old and I do not recommend
to use it for new experiments.

A newer analyzer system is ROOTANA and an even newer is the "m" analyzer (manalyzer). These
analyzers progressively introduce improved c++-style programming environments amongst other
improvements. If starting from scratch, I recommend that you use manalyzer (currently from the rootana
git repository).

> The analyzer works fine and I am able to view the online histograms but my console 
> prints out this error:
> 
> [Analyzer,ERROR] [odb.cxx:919:db_validate_name,ERROR] Invalid name 
> "/Analyzer/Tests/Always true/Rate [Hz]" passed to db_create_key_wlocked: should 
> not contain "["

The error says what it means. "[" is not a permitted character in odb names. It is used
by many odb functions to access array elements.

The midas analyzer example should be updated to change "[Hz]" to "(Hz)" or something similar.

K.O.

> The following all fail with "Cannot find ODB key "<key>""
> 
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[*]" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[0-9]" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[1]" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)*" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)" 0
> 

It would be cool if ODB pattern matching in the sequencer
were consistent with the ODB pattern matching in the json-rpc
interface for web pages:

https://midas.triumf.ca/MidasWiki/index.php/Mjsonrpc#Supported_array_index_syntax

K.O.

I think the issue may be the version of MIDAS I'm using.  Mine is current as of February 4, 2020.  

But since then there have been changes to the sequencer code, specifically parts that handle indexing.

I'll try this out with an updated version of MIDAS and report back if there are still any issues after updating.

> I created some keys in my ODB to try to match yours.
> The ODBSET commands you wrote are all working fine (of course with different results), except only for the "/Detectors/Det*/Settings/Charge/Bias (V)*" which I will have to 
> look into.
> In any case the error message I'm getting is "could not match ay key" and not the one you are reporting.
> 
> Now I'm a bit puzzled:
> Are you sure your ODB contains those keys?
> Are you testing the ODBSET inside a more complex sequencer or on its own?
> 
> Maybe I can try to reproduce it using your ODB setup.
> Could you send an ODB dump of the "/Detectors" folder using the "save" command of odbedit ("cd /Detectors" and then "save detector.odb")?
> 
> Best,
> 
> Marco
> 
> 
> > The following all fail with "Cannot find ODB key "<key>""
> > 
> > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[*]" 0
> > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[0-9]" 0
> > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[1]" 0
> > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)*" 0
> > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)" 0
> > 
> > 
> > > Hi,
> > > I guess the issue is in the "[?]" part of the command, the indexing is handled differently from the odb path and does not 
> > > support "?".
> > > Are you trying to set only the first 9 channels?
> > > Could you try with "[*]" or "[0-9]" instead?
> > > 
> > > Marco
> > > 
> > > > I'm interested in using the matching feature for ODBSET explained on 
> > > > https://midas.triumf.ca/MidasWiki/index.php/Sequencer for settings that are in an 
> > > > array, like:
> > > > 
> > > > COMMENT "Ground the detectors"
> > > > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[?]" 0
> > > > 
> > > > Currently I get an error when I try to run this script.  Is this expected?  Would it 
> > > > be possible to implement matching for array values?
> > > > 
> > > > Thanks!

I created some keys in my ODB to try to match yours.
The ODBSET commands you wrote are all working fine (of course with different results), except only for the "/Detectors/Det*/Settings/Charge/Bias (V)*" which I will have to 
look into.
In any case the error message I'm getting is "could not match ay key" and not the one you are reporting.

Now I'm a bit puzzled:
Are you sure your ODB contains those keys?
Are you testing the ODBSET inside a more complex sequencer or on its own?

Maybe I can try to reproduce it using your ODB setup.
Could you send an ODB dump of the "/Detectors" folder using the "save" command of odbedit ("cd /Detectors" and then "save detector.odb")?

Best,

Marco


> The following all fail with "Cannot find ODB key "<key>""
> 
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[*]" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[0-9]" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[1]" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)*" 0
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)" 0
> 
> 
> > Hi,
> > I guess the issue is in the "[?]" part of the command, the indexing is handled differently from the odb path and does not 
> > support "?".
> > Are you trying to set only the first 9 channels?
> > Could you try with "[*]" or "[0-9]" instead?
> > 
> > Marco
> > 
> > > I'm interested in using the matching feature for ODBSET explained on 
> > > https://midas.triumf.ca/MidasWiki/index.php/Sequencer for settings that are in an 
> > > array, like:
> > > 
> > > COMMENT "Ground the detectors"
> > > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[?]" 0
> > > 
> > > Currently I get an error when I try to run this script.  Is this expected?  Would it 
> > > be possible to implement matching for array values?
> > > 
> > > Thanks!

The following all fail with "Cannot find ODB key "<key>""

ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[*]" 0
ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[0-9]" 0
ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[1]" 0
ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)*" 0
ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)" 0


> Hi,
> I guess the issue is in the "[?]" part of the command, the indexing is handled differently from the odb path and does not 
> support "?".
> Are you trying to set only the first 9 channels?
> Could you try with "[*]" or "[0-9]" instead?
> 
> Marco
> 
> > I'm interested in using the matching feature for ODBSET explained on 
> > https://midas.triumf.ca/MidasWiki/index.php/Sequencer for settings that are in an 
> > array, like:
> > 
> > COMMENT "Ground the detectors"
> > ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[?]" 0
> > 
> > Currently I get an error when I try to run this script.  Is this expected?  Would it 
> > be possible to implement matching for array values?
> > 
> > Thanks!

Hi,
I guess the issue is in the "[?]" part of the command, the indexing is handled differently from the odb path and does not 
support "?".
Are you trying to set only the first 9 channels?
Could you try with "[*]" or "[0-9]" instead?

Marco

> I'm interested in using the matching feature for ODBSET explained on 
> https://midas.triumf.ca/MidasWiki/index.php/Sequencer for settings that are in an 
> array, like:
> 
> COMMENT "Ground the detectors"
> ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[?]" 0
> 
> Currently I get an error when I try to run this script.  Is this expected?  Would it 
> be possible to implement matching for array values?
> 
> Thanks!

I'm interested in using the matching feature for ODBSET explained on 
https://midas.triumf.ca/MidasWiki/index.php/Sequencer for settings that are in an 
array, like:

COMMENT "Ground the detectors"
ODBSET "/Detectors/Det*/Settings/Charge/Bias (V)[?]" 0

Currently I get an error when I try to run this script.  Is this expected?  Would it 
be possible to implement matching for array values?

Thanks!

Hi everyone,

I've recently took the analyzer template from $MIDASSYS/examples/experiment and 
modified it to be able to use Roody on a very simple frontend setup. The 
analyzer works fine and I am able to view the online histograms but my console 
prints out this error:

[Analyzer,ERROR] [odb.cxx:919:db_validate_name,ERROR] Invalid name 
"/Analyzer/Tests/Always true/Rate [Hz]" passed to db_create_key_wlocked: should 
not contain "["                      
[Analyzer,ERROR] [odb.cxx:919:db_validate_name,ERROR] Invalid name 
"/Analyzer/Tests/low_sum/Rate [Hz]" passed to db_create_key_wlocked: should not 
contain "["
[Analyzer,ERROR] [odb.cxx:919:db_validate_name,ERROR] Invalid name 
"/Analyzer/Tests/high_sum/Rate [Hz]" passed to db_create_key_wlocked: should not 
contain "["

The error keeps getting printed even after stopping the run.

I do have these 3 keys under Analyzer/Tests/ in my ODB but I do not know where 
they come from. Any suggestions on what the root of the issue is?

Thanks for the help!

Isaac

Indeed this "mirror" of the ODB in settings option can cause frustration in 
particular when we think the ODB is empty but is not.
In the other hand, over time the settings are adjusted to a particular 
configuration or touched or not by the individual run preset parameters. Later, if 
a bug or code correction requires multiple restart of the fe, for every start of 
the application, you loose the latest configuration. This can be frustrating as 
well until you force a post-setting or report the specifics parameters in the fe 
code.
BTW I believe, we originally went for the ODB priority for that specific reason.
 
I would be in favour for having a general flag (FALSE) in /experiment which would 
define this global behaviour.  
PAA

> Today I addressed a topic which bugged me since long time. The ODB contains 
> settings under /Equipment/<name>/Common which are a "mirror" of the equipment[] 
> setting in a frontend (using the mfe.cxx framework). If the "Common" entry in 
> the ODB is not present (fresh experiment), the equipment[] settings from the 
> frontend are copied to the ODB. But if it exists, it takes precedence over the 
> equipment[] entries, which is wrong in my opinion. Like if you change some 
> settings in equipment[] (like the logging period of the history), then recompile 
> and restart the frontend, the old values in the ODB are kept and your 
> modification in the frontend code has no effect.
> 
> Starting on commit c3017c6c on Nov. 17th 2020 I reversed the precedence: Now, on 
> each start of the frontend program, the values from equipment[] are written to 
> the ODB. They are still "live". If one changes them when the frontend is 
> running, that change takes effect immediately. But on the next restart of the 
> frontend, the old values from equipment[] is put back there.
> 
> I fell too many times into this trap, and I hope the modification helps 
> everybody. If there are however experiments which rely on the fact that the 
> common settings in the ODB are NOT overwritten by the frontend, please let me 
> know and I can put a flag "EQUIPMENT_FE_PRECEDENCE = FALSE" somewhere to restore 
> the old behaviour.
> 
> Stefan

 > Taking this down a tangent, I have a mild concern that a user could temporarily 
> flood our gigabit network if we do have faster disks to read the history data. Have 
> there been any plans or thoughts on limiting the bandwidth users can pull from 
> mhttpd?

I guess this will not be network limiting but CPU limiting of the mhttpd process. But I'm 
not 100% sure, depends on the actual hardware. But even if we improve the history 
retrieval to "window only", the user could request all data form 2010 to 2020. So one 
would need some code which estimates the amount of data, then tell the user "do you really 
want that?". But still, a novice user can simply click "yes" without much of a thought. So 
in conclusion I believe proper user training is better than software limits. Like the 
other guy "I did 'rm -rf /', and now nothing works any more, can you help?".

Stefan

Poking at the behavior of this, its fairly clear the slow response is from the data 
being loaded off an HDD, when we upgrade this system we will allocate enough SSD 
storage for the histories.

Using Firefox has resolved this issue for the user's project here

Taking this down a tangent, I have a mild concern that a user could temporarily 
flood our gigabit network if we do have faster disks to read the history data. Have 
there been any plans or thoughts on limiting the bandwidth users can pull from 
mhttpd? I do not see this as a critical item as I can plan the future network 
infrastructure at the same time as the next system upgrade (putting critical data 
taking traffic on a separate physical network).

> Of course one can only
> load that specific window, but when the user then scrolls right, one has to
> append new data to the "right side" of the array stored in the browser. If the
> user jumps to another location, then the browser has to keep track of which 
> windows are loaded and which windows not, making the history code much more 
> complicated. Therefore I'm only willing to spend a few days of solid work
> if this really becomes a problem. 

For now the user here has retrieved all the data they need, and I can direct others 
towards mhist in the near future. Being able to load just a specific window would be 
very useful in the future, but I comprehend how it would be a spike in complexity.

The history code is right now programmes in such a way that when you request
an old time window, then all data from that window until the present date
gets loaded. When we implemented that, this worked fine for data ranges of 
several years with a delay of just a few seconds. Of course one can only
load that specific window, but when the user then scrolls right, one has to
append new data to the "right side" of the array stored in the browser. If the
user jumps to another location, then the browser has to keep track of which 
windows are loaded and which windows not, making the history code much more 
complicated. Therefore I'm only willing to spend a few days of solid work
if this really becomes a problem. 

Are you sure that the delay comes from the browser or actually from mhttpd
digging through GBytes of history data? I realized that you need solid state
disks to get a real quick response.

Stefan

A user reported an issue that if they were to plot some history data from 
2019 (a range of one day), the plot would spend ~4 minutes loading then 
crash the browser tab. This seems to effect chrome (under default settings) 
and not firefox

I can reproduce the issue, "Data Being Loaded" shows, then the page and 
canvas loads, then all variables get a correct "last data" timestamp, then 
the 'Updating data ...' status shows... then the tab crashes (chrome)


It seems that the browser is loading all data until the present day (maybe 4 
Gb of data in this case). In chrome the tab then crashes. In firefox, I do 
not suffer the same crash, but I can see the single tab is using ~3.5 Gb of 
RAM

Tested with midas-2020-08-a up until the HEAD of develop

I could propose the user use firefox, or increase the memory limit in 
chrome, however are there plans to limit the data loaded when specifically 
plotting between two dates?

Today I addressed a topic which bugged me since long time. The ODB contains 
settings under /Equipment/<name>/Common which are a "mirror" of the equipment[] 
setting in a frontend (using the mfe.cxx framework). If the "Common" entry in 
the ODB is not present (fresh experiment), the equipment[] settings from the 
frontend are copied to the ODB. But if it exists, it takes precedence over the 
equipment[] entries, which is wrong in my opinion. Like if you change some 
settings in equipment[] (like the logging period of the history), then recompile 
and restart the frontend, the old values in the ODB are kept and your 
modification in the frontend code has no effect.

Starting on commit c3017c6c on Nov. 17th 2020 I reversed the precedence: Now, on 
each start of the frontend program, the values from equipment[] are written to 
the ODB. They are still "live". If one changes them when the frontend is 
running, that change takes effect immediately. But on the next restart of the 
frontend, the old values from equipment[] is put back there.

I fell too many times into this trap, and I hope the modification helps 
everybody. If there are however experiments which rely on the fact that the 
common settings in the ODB are NOT overwritten by the frontend, please let me 
know and I can put a flag "EQUIPMENT_FE_PRECEDENCE = FALSE" somewhere to restore 
the old behaviour.

Stefan