> > > odbedit can now save ODB in JSON-formatted files.
> encode NaN, Inf and -Inf as JSON string values "NaN", "Infinity" and "-Infinity". (Corresponding to the respective Javascript values).

A new standard just came out - Oasis OData JSON format 4.0 - 
http://docs.oasis-open.org/odata/odata-json-format/v4.0/os/odata-json-format-v4.0-os.html

Section 7.1 reads:

> Values of types [...] Edm.Single, Edm.Double, and Edm.Decimal are represented as JSON numbers, except for NaN, INF, and –INF which are represented as strings.

This is consistent with what we do in MIDAS - encode special numbers as strings. For now I think we stay with Javascript-standard "Infinity", "-Infinity",
but if more standards start using "INF", "-INF", maybe we will switch. It is easy enough to support both encodings in the JSON parser and in the ODB decoder.

https://xkcd.com/927/
K.O.

> > > > odbedit can now save ODB in JSON-formatted files.
> > encode NaN, Inf and -Inf as JSON string values "NaN", "Infinity" and "-Infinity". (Corresponding to the respective Javascript values).
> http://docs.oasis-open.org/odata/odata-json-format/v4.0/os/odata-json-format-v4.0-os.html
> > Values of types [...] Edm.Single, Edm.Double, and Edm.Decimal are represented as JSON numbers,
> except for NaN, INF, and –INF which are represented as strings "NaN", "INF" and "-INF".
> https://xkcd.com/927/

Per xkcd, there is a new json standard "json5". In addition to other things, numeric
values NaN, +Infinity and -Infinity are encoded as literals NaN, Infinity and -Infinity (without quotes):
https://spec.json5.org/#numbers

Good discussion of this mess here:
https://stackoverflow.com/questions/1423081/json-left-out-infinity-and-nan-json-status-in-ecmascript

K.O.

> Per xkcd, there is a new json standard "json5". In addition to other things, numeric
> values NaN, +Infinity and -Infinity are encoded as literals NaN, Infinity and -Infinity (without quotes):
> https://spec.json5.org/#numbers

Just for curiosity: Is this implemented by the midas json library now?

> > Per xkcd, there is a new json standard "json5". In addition to other things, numeric
> > values NaN, +Infinity and -Infinity are encoded as literals NaN, Infinity and -Infinity (without quotes):
> > https://spec.json5.org/#numbers
> 
> Just for curiosity: Is this implemented by the midas json library now?

MIDAS encodes NaN, Infinity and -Infinity as javascript compatible "NaN", "Infinity" and "-Infinity",
this encoding is popular with other projects and allows correct transmission of these values
from ODB to javascript. The test code for this is on the MIDAS "Example" page, scroll down
to "Test nan and inf encoding".

I think this type of encoding, using strings to encode special values, is more in the spirit of json,
compared to other approaches such as adding special literals just for a few special cases
leaving other special cases in the cold (ieee-754 specifies several different types of NaN,
you can encode them into different nan-strings, but not into the one nan-literal (need more nan-literals,
requires change to the standard and change to every json parser).

As editorial comment, it boggles my mind, what university or kindergarden these people went to
who made the biggest number, the smallest number and the imaginary number (sqrt(-1))
all equal to zero (all encoded as literal null).

K.O.

Somebody pointed out an error in the MIDAS documentation regarding maximum event size 
supported by MIDAS and the MAX_EVENT_SIZE #define in midas.h.

Since MIDAS svn rev 4801 (August 2010), one can create events with size bigger than 
MAX_EVENT_SIZE in midas.h (without having to recompile MIDAS):

To do so, one must increase:
- the value of ODB /Experiment/MAX_EVENT_SIZE
- the size of the SYSTEM shared memory event buffer (and any buffers used by the event builder, 
etc)
- max_event_size & co in your frontend.

Actual limits on the bank size and event size are written up here:
https://ladd00.triumf.ca/elog/Midas/757

The bottom line is that the maximum event size is limited by the size of the SYSTEM buffer which is 
limited by the physical memory of your computer. No recompilation of MIDAS necessary.

K.O.

Notes on installing midas from scratch. The instruction on midaswiki will be synced with this later.

cd ~/packages
git clone ...
cd midas
make
cd ~
mkdir ~/online
cd ~/online
~/git/midas/darwin/bin/odbinit --env
source env.sh
~/git/midas/darwin/bin/odbinit --exptab
~/git/midas/darwin/bin/odbinit
ls -la
send:online olchansk$ ls -la
total 2376
drwxr-xr-x   15 olchansk  staff      510 Aug  4 15:34 .
drwxr-xr-x+ 244 olchansk  staff     8296 Aug  4 15:33 ..
-rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .ALARM.SHM
-rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .ELOG.SHM
-rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .HISTORY.SHM
-rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .MSG.SHM
-rw-r--r--    1 olchansk  staff  1183808 Aug  4 15:34 .ODB.SHM
-rw-r--r--    1 olchansk  staff        8 Aug  4 15:34 .ODB_SIZE.TXT
-rw-r--r--    1 olchansk  staff       15 Aug  4 15:34 .SHM_HOST.TXT
-rw-r--r--    1 olchansk  staff       12 Aug  4 15:34 .SHM_TYPE.TXT
-rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .SYSMSG.SHM
-rw-r--r--    1 olchansk  staff      341 Aug  4 15:33 env.csh
-rw-r--r--    1 olchansk  staff      322 Aug  4 15:33 env.sh
-rw-r--r--    1 olchansk  staff       40 Aug  4 15:34 exptab
-rw-r--r--    1 olchansk  staff      287 Aug  4 15:34 midas.log
send:online olchansk$

odbedit ### works
mhttpd ### bombs, requires SSL certificate https://bitbucket.org/tmidas/midas/issues/57/initial-mhttpd-should-bind-to-localhost
odbedit ### cd /experiment, set "http redirect to https" to no, set "midas https port" to 0
mhttpd ### runs now
connect to http://localhost:8080 ### status page works
restart mhttpd as mhttpd -D
mlogger -D
fetest ### runs, prints time and data
start a run from web page ### works
### fetest generates crazy data rate https://bitbucket.org/tmidas/midas/issues/58/fetest-crazy-data-rate
### go to history, define plot for SLOW/SLOW, see sine wave ### works
### history is written to expt dir, no good, go to "history"
### data files written to expt dir, no good, go to "data"
### midas.log written to data dir, no good (want expt dir)
### elog written to expt dir, go to "elog"
### logger channel config is wrong - gzip compression and crc32c should be enabled by default
### history config is wrong - FILE per-variable history should be enabled by default

K.O.
 

Thanks for documenting this in detail. A few suggestions:

- is it really necessary to call odbedit three times? Maybe two or even three functions can be merged. Like you call odbinit, it checks if the environment is 
there, and creates it automatically if not. Same with the exptab.

- can we make "http redirecto to https = n" and "midas https port = 0" as the default? Of course this has to go with binding to localhost only.

- does it make sense to define default directories for history, data files and midas.log? Maybe we could come with a "default scheme" which can then later 
adjusted if needed.

- will you take care of the wrong logger channel config and history config?

Best regards,
Stefan

> Notes on installing midas from scratch. The instruction on midaswiki will be synced with this later.
> 
> cd ~/packages
> git clone ...
> cd midas
> make
> cd ~
> mkdir ~/online
> cd ~/online
> ~/git/midas/darwin/bin/odbinit --env
> source env.sh
> ~/git/midas/darwin/bin/odbinit --exptab
> ~/git/midas/darwin/bin/odbinit
> ls -la
> send:online olchansk$ ls -la
> total 2376
> drwxr-xr-x   15 olchansk  staff      510 Aug  4 15:34 .
> drwxr-xr-x+ 244 olchansk  staff     8296 Aug  4 15:33 ..
> -rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .ALARM.SHM
> -rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .ELOG.SHM
> -rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .HISTORY.SHM
> -rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .MSG.SHM
> -rw-r--r--    1 olchansk  staff  1183808 Aug  4 15:34 .ODB.SHM
> -rw-r--r--    1 olchansk  staff        8 Aug  4 15:34 .ODB_SIZE.TXT
> -rw-r--r--    1 olchansk  staff       15 Aug  4 15:34 .SHM_HOST.TXT
> -rw-r--r--    1 olchansk  staff       12 Aug  4 15:34 .SHM_TYPE.TXT
> -rw-r--r--    1 olchansk  staff        0 Aug  4 15:34 .SYSMSG.SHM
> -rw-r--r--    1 olchansk  staff      341 Aug  4 15:33 env.csh
> -rw-r--r--    1 olchansk  staff      322 Aug  4 15:33 env.sh
> -rw-r--r--    1 olchansk  staff       40 Aug  4 15:34 exptab
> -rw-r--r--    1 olchansk  staff      287 Aug  4 15:34 midas.log
> send:online olchansk$
> 
> odbedit ### works
> mhttpd ### bombs, requires SSL certificate https://bitbucket.org/tmidas/midas/issues/57/initial-mhttpd-should-bind-to-localhost
> odbedit ### cd /experiment, set "http redirect to https" to no, set "midas https port" to 0
> mhttpd ### runs now
> connect to http://localhost:8080 ### status page works
> restart mhttpd as mhttpd -D
> mlogger -D
> fetest ### runs, prints time and data
> start a run from web page ### works
> ### fetest generates crazy data rate https://bitbucket.org/tmidas/midas/issues/58/fetest-crazy-data-rate
> ### go to history, define plot for SLOW/SLOW, see sine wave ### works
> ### history is written to expt dir, no good, go to "history"
> ### data files written to expt dir, no good, go to "data"
> ### midas.log written to data dir, no good (want expt dir)
> ### elog written to expt dir, go to "elog"
> ### logger channel config is wrong - gzip compression and crc32c should be enabled by default
> ### history config is wrong - FILE per-variable history should be enabled by default
> 
> K.O.
>  

Some notes on the MIDAS history.

MIDAS documentation at
http://midas.psi.ch/htmldoc/F_History_logging.html
describes:

- midas equipment concepts
- midas equipment event ids
- midas data banks
- midas history concepts
- history records (correspond to data banks)
- history record ids (correspond to equipment ids)
- history tags (describe the structure
- describes the code path from the user read function through odb to the mlogger to the history file
- midas history file internal data format
- documents the tool for looking inside history files - mhdump

But some things remain unclear after reading the documentation - where are the history definitions 
saved? what happens if an equipment is deleted or renamed? what's all the mumbling about 
/History/Events and /History/Tags? what's this /History/PerVariableHistory?

As I go through my review of the MIDAS history code, I will attempt to clarify some of this information.

1) PerVariableHistory.

The default value of 0 is intended to operate the midas history in "traditional" mode. In this mode:
- there is one history record for each equipment
- history record id is equal to the equipment id
- /History/Events and /History/Tags are not required and can be safely deleted

The downside of this history mode is that there is only one history record per equipment. If some 
equipment has many banks not all of which are updated all at the same time, every time one bank is 
updated, data for all banks is written to the history file, even if data in all those other banks had not 
changed. The result is undesired duplication of data in midas history files. In turn, this leads to slow 
down while making history plots (mhttpd has to read more data from bigger data files, which takes time) 
and for long running experiments may pose problems with disk space for storing history files.

In addition, when logging history data into an SQL database, each history record is mapped into an SQL 
table, so all variables from all banks of an equipment end up in the same SQL table - and in addition to 
data duplication described above, a data presentation problem is created - database users and 
administrators dislike having SQL tables with "too many" columns!

To solve both problems - reduce data duplication and avoid creating over-large SQL tables - per-
variable history has been implemented.

to be continued...

K.O.

> 
> 1) PerVariableHistory.
> 
> The default value of 0 is intended to operate the midas history in "traditional" mode. In this mode:
> - there is one history record for each equipment
> - history record id is equal to the equipment id
> - /History/Events and /History/Tags are not required and can be safely deleted
>

I now commited an example experiment for testing and using non-per-variable history:
.../midas/examples/history1

I confirm that this example does work as expected after src/history_midas.cxx is updated to latest rev 4979 (today). I guess it also worked just 
fine before breakage in svn rev 4827 last September.

svn rev 4980.



Here is the README file:

Example experiment "history1"

Purpose:
example and test of a simple periodic frontend writing slow controls data into midas history

To run:
use bash shell
assuming MIDAS is installed in $HOME/packages/midas on linux, otherwise edit setup.sh and Makefile
run make to build feslow.exe
run source ./setup.sh
when starting this experiment for the very first time, load experiment settings from odb.xml: odbedit -c "load odb.xml"
run ./start_daq.sh
mlogger and mhttpd should now be running
connect to the midas status page at http://localhost:8080 (port number is set in start_daq.sh
start the example frontend from the "programs" page
observe event number of equipment "slow" is incrementing
go to the "Slow" equipment page (click on "Slow" on the midas status page)
observe numbers are changing when you refresh the web page
from the midas status page, go to "history" -> "slow" - observe history plot for "SLOW[2]" shows a sine wave
from shell, examine contents of history file: "mhdump *.hst"
study feslow.cxx

Enjoy,
K.O.

Notes on the implementation of the MIDAS alarm system.

Alarms are checked inside alarm.c::al_check(). This function is called by
cm_yield() every 10 seconds and by rpc_server_thread(), also every 10 seconds.

For remote midas clients, their al_check() issues an RPC_AL_CHECK RPC call into
the mserver, where rpc_server_dispatch() calls the local al_check().

As result, all alarm checks run inside a process directly attached to the local
midas shared memory (inside a local client or inside an mserver process for a
remote client).

Each and every midas client runs the alarm checks. To prevent race conditions
between different midas clients, access to al_check() is serialized using the
ALARM semaphore.

Inside al_check(), alarms are triggered using al_trigger_alarm(), which in turn
calls al_trigger_class(). Inside al_trigger_class(), the alarm is recorded into
an elog or into midas.log using cm_msg(MTALK).

Special note should be made of the ODB setting "/Alarm/Classes/xxx/System
message interval", which has a surprising effect - after an alarm is recorded
into system messages (using cm_msg(MTALK)), no record is made of any subsequent
alarms until the time interval set by this variable elapses. With default value
of 60 seconds, after one alarm, no more alarms are recorded for 60 seconds.
Also, because all the alarms are checked at the same time, only the first
triggered alarm will be recorded.

As of alarm.c rev 4683, "System message interval" set to 0 ensures that every
alarm is recorded into the midas log file. (In previous revisions, this setting
may still miss some alarms).

There are 3 types of alarms:

1) "program not running" alarms.

These alarms are enabled in ODB by setting "/Programs/ppp/Alarm class". Each
time al_check() runs, every program listed in "/Programs" is tested using
"cm_exist()" and if the program is not running, the time of first failure is
remembered in "/Programs/ppp/First failed".

If the program has not been running for longer than the time set in ODB
"/Programs/ppp/Check interval", an alarm is triggered (if enabled by
"/Programs/ppp/Alarm class" and the program is restarted (if enabled by
"/Programs/ppp/Auto restart").

The "not running" condition is tested every 10 seconds (each time al_check() is
called), but the frequency of "program not running" alarms can be reduced by
increasing the value of "/Alarms/Alarms/ppp/Check interval" (default value 60
seconds). This can be useful if "System message interval" is set to zero.

2) "evaluated" alarms
3) "periodic" alarms

There is nothing surprising in these alarms. Each alarm is checked with a time
period set by "/Alarm/xxx/Check interval". The value of an evaluated alarm is
computed using al_evaluate_condition().

K.O.

We have al_trigger_alarm(), but no matching al_clear_alarm(), and I need it to
clear my alarm once the alarm condition no longer exists. Any objections if I
add this function? K.O.

> We have al_trigger_alarm(), but no matching al_clear_alarm(), and I need it to
> clear my alarm once the alarm condition no longer exists. Any objections if I
> add this function? K.O.

The idea is that once an alarm got triggered, it stays until the user
acknowledged, even if the alarm condition has been disappeared. Through mhttpd,
the user can press the "Reset" button, which then executes al_reset_alarm().
However, it is possible to call al_reset_alarm() directly from user code to
achieve the same thing.

> > We have al_trigger_alarm(), but no matching al_clear_alarm(), and I need it to
> > clear my alarm once the alarm condition no longer exists. Any objections if I
> > add this function? K.O.
> 
> call al_reset_alarm()

Thanks. I must be quite blind as I did not see al_reset_alarm() in midas.h. I se eit
now. Thanks.

K.O.

I had two free afternoon and took the opportunity to write a new API for the MSCB 
system. I'm not sure if anybody else actually uses MSCB (MIDAS slow control bus), 
but anyhow. 

The new API is contained in a single header file mscbxx.h, and it's extremely 
simple to use. Here is some example code:

#include "mscbxx.h"

...
   // connect to node 10 at submaster mscb123
   midas::mscb m("mscb123", 10);

   // print node info and all variables
   std::cout << m << std::endl;

   // refresh all variables (read from MSCB device)
   m.read_range();
   
   // access individual variables
   float f = m[5];   // index access
   f = m["In0"];     // name access

   // write value to MSCB device
   m["In0"] = 1.234;
...


Any feedback is welcome.

Stefan

> Here is some example code:
> 
> #include "mscbxx.h"
>    f = m["In0"];     // name access
>    m["In0"] = 1.234;
> Any feedback is welcome.

Where is the example of error handling?

K.O.

> Where is the example of error handling?

#include "mscbxx.h"
#include "mexcept.h"

...
   try {
   
      // connect to node 10 at submaster mscb123
      midas::mscb m("mscb123", 10);

      // print a variable
      std::cout << m["Input0"] << std::endl;
   
   } catch (mexception e) {
      std::cout << e << std::endl; // simply print exception
   }
...

Context: out of the box  MIDAS (using cmake) on OSX Mojave. 

Running with mongoose/opensslm installation following instruction here:
https://midas.triumf.ca/MidasWiki/index.php/Quickstart_Linux

mhttpd crashing when midas webpage opened with Safari (12.1.2). Usually when opening the "chat" tab but sometimes also with the "message" tab.
mhttpd(11109,0x70000827a000) malloc: *** error for object 0x7f8669501ef0: pointer being freed was not allocated
mhttpd(11109,0x70000827a000) malloc: *** set a breakpoint in malloc_error_break to debug

No crash if using firefox (70.0.1 (64-bit))

> Context: out of the box  MIDAS (using cmake) on OSX Mojave. 
> 
> Running with mongoose/opensslm installation following instruction here:
> https://midas.triumf.ca/MidasWiki/index.php/Quickstart_Linux
> 
> mhttpd crashing when midas webpage opened with Safari (12.1.2). Usually when opening the "chat" tab but sometimes also with the "message" tab.
> mhttpd(11109,0x70000827a000) malloc: *** error for object 0x7f8669501ef0: pointer being freed was not allocated
> mhttpd(11109,0x70000827a000) malloc: *** set a breakpoint in malloc_error_break to debug
> 
> No crash if using firefox (70.0.1 (64-bit))

I think we also have reports of mhttpd crash on macos with safari from the Dragon experiment,
but cannot reproduce the problem.

If you can reproduce this, can you capture the crash stack trace?

One way to do this is to enable core dumps in odb "/expt/enable core dumps" set to "y", restart mhttpd,
wait for the crash. I think macos writes core dumps into /cores/... Or you can run mhttpd inside lldb
and wait for the crash. the lldb command to show the stack trace is "bt", but you may need
to switch to different threads to see which one actually crashed. I forget what the command
for that is.

BTW, the mhttpd networking code has not changed in a long time, but an update
of mongoose web server library is overdue (to fix a memory leak, at least).

K.O.

It is reproducible alright.
Here are the core dump and the backtrace (I think  the former is more informative).



> > Context: out of the box  MIDAS (using cmake) on OSX Mojave. 
> > 
> > Running with mongoose/opensslm installation following instruction here:
> > https://midas.triumf.ca/MidasWiki/index.php/Quickstart_Linux
> > 
> > mhttpd crashing when midas webpage opened with Safari (12.1.2). Usually when opening the "chat" tab but sometimes also with the "message" tab.
> > mhttpd(11109,0x70000827a000) malloc: *** error for object 0x7f8669501ef0: pointer being freed was not allocated
> > mhttpd(11109,0x70000827a000) malloc: *** set a breakpoint in malloc_error_break to debug
> > 
> > No crash if using firefox (70.0.1 (64-bit))
> 
> I think we also have reports of mhttpd crash on macos with safari from the Dragon experiment,
> but cannot reproduce the problem.
> 
> If you can reproduce this, can you capture the crash stack trace?
> 
> One way to do this is to enable core dumps in odb "/expt/enable core dumps" set to "y", restart mhttpd,
> wait for the crash. I think macos writes core dumps into /cores/... Or you can run mhttpd inside lldb
> and wait for the crash. the lldb command to show the stack trace is "bt", but you may need
> to switch to different threads to see which one actually crashed. I forget what the command
> for that is.
> 
> BTW, the mhttpd networking code has not changed in a long time, but an update
> of mongoose web server library is overdue (to fix a memory leak, at least).
> 
> K.O.

> It is reproducible alright.

Thanks. At first blush, a guess, read_passwords() is not thread-safe and is called from multiple threads, not protected by semaphore. Crash report shows 2 active threads 
(one made it is far as processing the mjson rpc, the other one crashed in read_passwords()).

K.O.


> Here are the core dump and the backtrace (I think  the former is more informative).
> 
> 
> 
> > > Context: out of the box  MIDAS (using cmake) on OSX Mojave. 
> > > 
> > > Running with mongoose/opensslm installation following instruction here:
> > > https://midas.triumf.ca/MidasWiki/index.php/Quickstart_Linux
> > > 
> > > mhttpd crashing when midas webpage opened with Safari (12.1.2). Usually when opening the "chat" tab but sometimes also with the "message" tab.
> > > mhttpd(11109,0x70000827a000) malloc: *** error for object 0x7f8669501ef0: pointer being freed was not allocated
> > > mhttpd(11109,0x70000827a000) malloc: *** set a breakpoint in malloc_error_break to debug
> > > 
> > > No crash if using firefox (70.0.1 (64-bit))
> > 
> > I think we also have reports of mhttpd crash on macos with safari from the Dragon experiment,
> > but cannot reproduce the problem.
> > 
> > If you can reproduce this, can you capture the crash stack trace?
> > 
> > One way to do this is to enable core dumps in odb "/expt/enable core dumps" set to "y", restart mhttpd,
> > wait for the crash. I think macos writes core dumps into /cores/... Or you can run mhttpd inside lldb
> > and wait for the crash. the lldb command to show the stack trace is "bt", but you may need
> > to switch to different threads to see which one actually crashed. I forget what the command
> > for that is.
> > 
> > BTW, the mhttpd networking code has not changed in a long time, but an update
> > of mongoose web server library is overdue (to fix a memory leak, at least).
> > 
> > K.O.