Thank you very much for feedback.

I am satisfied with not changing the 64 client limit. I will look at re-writing my frontend to spawn threads rather than 
processses. The load of my frontend is low, so I do not anticipate issues with a threaded implementation. 

In this threaded scenario, it will be a reasonable amount of time until ALPHA bumps into the 64 client limit.

If it avoids confusion, I am happy for my experimental branch 'experimental-beyond_64_clients' to be deleted.

Perhaps a item for future discussion would be for the odbinit program to be able to 'upgrade' the ODB and enable some backwards 
compatibility.

Thanks again
Joseph

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?

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.

I have created a simple program that parses the message buffer in MIDAS and 
sends notifications by webhook to Discord, Slack and or Mattermost.

Active pull request can be found here:

https://bitbucket.org/tmidas/midas/pull-requests/21


Its written in python and CMake will install it in bin (if the Python3 binary 
is found by cmake). The only dependency outside of the MIDAS python library is 
'requests', full documentation are in the mmessenger.md 

A simple program to forward MIDAS messages to Discord, Slack and or Mattermost

(Python 3 required)

Pull request accepted! Documentation can be found on the wiki

https://midas.triumf.ca/MidasWiki/index.php/Mmessenger

There have been times in ALPHA that an alarm is triggered and the shift crew 
are unclear who to contact if they aren't trained to fix the specific 
failure mode.

I wish to add the property 'Users responsible' to the ODB for Alarms and 
Programs.

I have drafted what this might look like in a new pull request:
https://bitbucket.org/tmidas/midas/pull-requests/22/add-users-responsible-
field-for-specific

It requires changing of several data structures, I think I have found all 
instances of the definitions so the ODB should 'repair' any of the old 
structures adding in users responsible.

If 'Users responsible' is set, MIDAS messages append them after the message 
in brackets '()'. If used in conjunction with the MIDAS messenger 
(mmessenger), the users responsible can be 'tagged' directly.

I.e, for slack, simply set the 'users responsible' to <@UserID|Nickname>, 
for mattermost '@username', for discord '<@userid>'. Note that discord 
doesn't allow you to tag by username, but numeric userid



I have expanded char array in 'al_trigger_class' to handle the potentially 
longer MIDAS messages. Perhaps since I'm touching these lines I should 
change these temporary containers to std::string (line 383 and 386 of 
alarm.cxx)?

I have tested this quite a bit for my system, I am not sure how I can test 
mjsonrpc.

> I think this is a good idea and I support it. We have a similar problem in MEG and 
> we solved that with external (bash) scripts called in case of alarms. One feature 
> there we have is that for some alarms, several people want to get notified. So 
> people can "subscribe" to certain alarms. The subscription are now handled inside 
> Slack which I like better, but maybe it would be good to have more than one "user 
> responsible". Like if one person is sleeping/traveling, it's good to have a 
> substitute. Can you make an array out of that? Or a comma-separated list?
> 
> Best,
> Stefan

Presently there are 256 characters in the 'users responsible' field, so you can just 
list many users (no space, space or comma whatever). Discord, slack and mattermost 
don't care, they just parse the user tags.

I can still make this an array and pass a std::vector<std::string> into 
al_trigger_class function?

> > I can still make this an array and pass a std::vector<std::string> into 
> > al_trigger_class function?
> 
> Maybe 256 chars are enough at the moment. If other people complain in the future, we can 
> re-visit.
> 
> Stefan

Thinking about it, an array of maybe 80 character would give enough space for a name, a tag 
and phone number. Do I need to budget memory very strictly? Would 32 entries of 80 
characters be too much? 

I've updated the branch / pull request to use an array of 10 entries (80 chars each). 32 felt a 
little overkill when I saw it on screen, but absolutely happy to set it to any number you 
recommend.

The array gets flattened out when an alarm is triggered, currently the formatting produces

AlarmClass : AlarmMessage (Flattened List Of Users Responsible Array With Space Separators)

If experiments want to use Discord / Slack / Mattermost tags and or add phone numbers, that 
should fit in 80 characters

This list of responsible being attached to alarm message strings will be great for the 
mmessenger, however, perhaps its going to generate very long messages for the speaker programs 
(web interface and mlxspeaker ):

AlarmClass : AlarmMessage (ResponsibleUser1 ResponsibleUser2 ResponsibleUser3 ResponsibleUser4 
... ResponsibleUser4)

especially if people put in user tags or emergency contact details...

Should we add a key word or character for the programs that create audio to parse that silence 
the list of responsible users? I'd be tempted to use a single character but there is a risk 
users might have that in a custom alarm message. Maybe something usual like the 'bel' 
character? '|'? 

Perhaps use the string 'Responsible:' or 'Users:' to trim out the Users Responsible list from 
the message string?

AlarmClass : AlarmMessage Responsible:(ResponsibleUser1 ResponsibleUser2 ResponsibleUser3 
ResponsibleUser4 ... ResponsibleUser4)

AlarmClass : AlarmMessage Users:(ResponsibleUser1 ResponsibleUser2 ResponsibleUser3 
ResponsibleUser4 ... ResponsibleUser4)

> > This list of responsible being attached to alarm message strings ...
> 
> This is a great idea. But I think we do not need to artificially limit ourselves
> to string and array lengths.
> 
> The code in alarm.c should be changes to use std::string and std::vector<std::string> (STRING_LIST 
> #define), db_get_record() should be replaced with individual ODB reads (that's what it does behind 
> the scenes, but in a non-type and -size safe way).
> 
> I think the web page code will work correctly, it does not care about string lengths.
> 
> K.O.

Ok, I'm working on this... I see a design choice to make, 1. Keep 'ALARM' as a struct, or 2. Replace ALARM struct with a class (keeping memory layout the same). Since we are adding STRING_LIST, I'd lean towards a C++ style with a class

1. Keep 'ALARM' as a struct:
Get rid of ALARM_ODB_STR for the default values
Add static functions (that take a hkey) to interact with the ODB (to save duplicating logic in al_reset_alarm, al_check, al_define_odb_alarm and al_trigger_alarm)

2. Replace ALARM struct with a class:
default ctor: Do nothing special (so it behaves like the old struct)
default dtor: std::vector<std::string> dtor will

It seems an opportunity to convert the alarm struct to a class with member functions that take hkey pointers?

default ctor: Do nothing special (so it behaves like the old struct)
default dtor: std::vector<std::string> dtor will
SetToDefault: This is where default values are hard coded (functionally replace ALARM_ODB_STR )

> > This list of responsible being attached to alarm message strings ...
> 
> This is a great idea. But I think we do not need to artificially limit ourselves
> to string and array lengths.
> 
> The code in alarm.c should be changes to use std::string and std::vector<std::string> (STRING_LIST 
> #define), db_get_record() should be replaced with individual ODB reads (that's what it does behind 
> the scenes, but in a non-type and -size safe way).
> 
> I think the web page code will work correctly, it does not care about string lengths.
> 
> K.O.

Auto growing lists is an excellent plan. I am making decent progress and should have something to 
report soon

> > > This list of responsible being attached to alarm message strings ...
> > 
> > This is a great idea. But I think we do not need to artificially limit ourselves
> > to string and array lengths.
> > 
> > The code in alarm.c should be changes to use std::string and std::vector<std::string> (STRING_LIST 
> > #define), db_get_record() should be replaced with individual ODB reads (that's what it does behind 
> > the scenes, but in a non-type and -size safe way).
> > 
> > I think the web page code will work correctly, it does not care about string lengths.
> > 
> > K.O.
> 
> Auto growing lists is an excellent plan. I am making decent progress and should have something to 
> report soon

This has sent me down a little rabbit hole, and I'd like to check in with efforts to improve the efficiency and simplicity of the alarm code.

I can keep with the current 'C' style of the alarm.cxx code, replace struct read and writes to the odb with individual odb entries... put functions in alarm.cxx to create, read and write to the odb... 

If we go this 'C' style route, then I'll have duplication of the 'users responsible' setters and getter functions for structs ALARM and PROGRAM_INFO

What would the MIDAS developers thing of creating classes for ALARM and PROGRAM_INFO (I am thinking for binary compatibilities of not touching ALARM and PROGRAM_INFO structs, and inheriting from them:

class UsersResponsible
{
   public:
      STRING_LIST fUsersResponsible;
}

class Alarm: public ALARM, public UsersResponsible
{
}

class ProgramInfo: public PROGRAM_INFO, public UsersResponsible
{
}

Each of these three classes would have member to functions to Create, Read and Write to the ODB. We could get rid of the PROGRAM_INFO_STR precompiler macro and instead have a SetToDefault member function. 

It seems clear we should set the ODB path in the constructor of Alarm and ProgramInfo

mlogger (history_image) now supports rtsp cameras, in ALPHA we have 
acquisitioned several new network connected cameras. Unfortunately they dont 
have a way of just capturing a single frame using libcurl


========================================
Motivation to link to OpenCV libraries
========================================

After looking at the ffmpeg libraries, it seemed non trivial to use them to 
listen to a rtsp stream and write a series of jpgs.

OpenCV became an obvious choice (it is itself linked to ffmpeg and 
gstreamer), its a popular, multiplatform, open source library that's easy to 
use. It is available in the default package managers in centos 7 and ubuntu 
(an is installed by default on lxplus).

========================================
How it works:
========================================

The framework laid out in history_image.cxx is great. A separate thread is 
dedicated for each camera. This is continued with the rtsp support, using 
the same periodicity:

if (ss_time() >= o["Last fetch"] + o["Period"]) {
An rtsp camera is detected by its URL, if the URL starts with ‘rtsp://’ its 
obvious its using the rtsp protocol and the cv::VideoCapture object is 
created (line 147).

If the connection fails, it will continue to retry, but only send an error 
message on the first 10 attempts (line 150). This counter is reset on 
successful connection
If MIDAS has been built without OpenCV, mlogger will send an error message 
that OpenCV is required if a rtsp URL is given (line 166)
The VideoCapture ‘stays live' and will grab frames from the camera based on 
the sleep, saving to file based on the Period set in the ODB.

If the VideoCapture object is unable to grab a frame, it will release() the 
camera, send an error message to MIDAS, then destroy itself, and create a 
new version (this destroy and create fully resets the connection to a 
camera, required if its on flaky wifi)
If the VideoCapture gets an empty frame, it also follows the same reset 
steps.
If the VideoCaption fills a cv::Frame object successfully, the image is 
saved to disk in the same way as the curl tools.

========================================
Concerns for the future:
========================================

VideoCapture is decoding the video stream in the background, allowing us to 
grab frames at will. This is nice as we can be pretty agnostic to the video 
format in the stream (I tested with h264 from a TP-LINK TAPO C100, but the 
CPU usage is not negligible.

I noticed that this used ~2% of the CPU time on an intel i7-4770 CPU, given 
enough cameras this is considerable. In ALPHA, I have been testing with 10 
cameras:
elog:2220/1 

My suggestion / request would be to move the camera management out of 
mlogger and into a new program (mcamera?), so that users can choose to off 
load the CPU load to another system (I understand the OpenCV will use GPU 
decoders if available also, which can also lighten the CPU load).

In ALPHA, I get RPC timeouts running a (reasonably heavy) analyzer on a remote machine (connected directly via a ~30 meter 10Gbe Ethernet cable) after ~5 minutes of running. If I run the analyser locally, I dont not see a timeout...

gdb trace:

#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007ffff5d35859 in __GI_abort () at abort.c:79
#2  0x00005555555a2a22 in rpc_call (routine_id=11111) at /home/alpha/packages/midas/src/midas.cxx:13866
#3  0x000055555562699d in bm_receive_event_rpc (buffer_handle=buffer_handle@entry=2, buf=buf@entry=0x0, buf_size=buf_size@entry=0x0, ppevent=ppevent@entry=0x0, pvec=pvec@entry=0x7fffffffd700,
    timeout_msec=timeout_msec@entry=100) at /home/alpha/packages/midas/src/midas.cxx:10510
#4  0x0000555555631082 in bm_receive_event_vec (buffer_handle=2, pvec=pvec@entry=0x7fffffffd700, timeout_msec=timeout_msec@entry=100) at /home/alpha/packages/midas/src/midas.cxx:10794
#5  0x0000555555673dbb in TMEventBuffer::ReceiveEvent (this=this@entry=0x555557388b30, e=e@entry=0x7fffffffd700, timeout_msec=timeout_msec@entry=100) at /home/alpha/packages/midas/src/tmfe.cxx:312
#6  0x0000555555607b56 in ReceiveEvent (b=0x555557388b30, e=0x7fffffffd6c0, timeout_msec=100) at /home/alpha/packages/midas/manalyzer/manalyzer.cxx:1411
#7  0x000055555560d8dc in ProcessMidasOnlineTmfe (args=..., progname=<optimized out>, hostname=<optimized out>, exptname=<optimized out>, bufname=<optimized out>, event_id=<optimized out>,
    trigger_mask=<optimized out>, sampling_type_string=<optimized out>, num_analyze=0, writer=<optimized out>, multithread=<optimized out>, profiler=<optimized out>,
    queue_interval_check=<optimized out>) at /home/alpha/packages/midas/manalyzer/manalyzer.cxx:1534
#8  0x000055555560f93b in manalyzer_main (argc=<optimized out>, argv=<optimized out>) at /usr/include/c++/9/bits/basic_string.h:2304
#9  0x00007ffff5d37083 in __libc_start_main (main=0x5555555b1130 <main(int, char**)>, argc=8, argv=0x7fffffffdda8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>,
    stack_end=0x7fffffffdd98) at ../csu/libc-start.c:308
#10 0x00005555555b184e in _start () at /usr/include/c++/9/bits/stl_vector.h:94

Any suggestions? Many thanks

I want to read data from the ODB with the mvodb interface in one of my frontends, it's useful to know how old that data is, so I prototyped functionality in a pull request to mvodb:

https://bitbucket.org/tmidas/mvodb/pull-requests/2/add-readkeylastwritten-function-to-extract

Hi all, I hope this is the right place to post two pull requests, if not, please let me know where I should be submitting them

Both are fairly small changes, please see them listed below (more details written on the PRs themselves)


- Enable ROOT's thread safety when running in multithreaded mode

This helps avoid users having to write their call to a global thread lock when calling ->Fill() on ROOT histograms and Trees
https://bitbucket.org/tmidas/manalyzer/pull-requests/5


- Add command argument to specify an IP of the root HTTP server to bind to

This was a problem I painted around when at ALPHA (quickly hardcoding the right external IP address into the local build. Obviously a bad habit)
https://bitbucket.org/tmidas/manalyzer/pull-requests/6

> Hi all, I hope this is the right place to post two pull requests, if not, please let me know where I should be submitting them
> 
> Both are fairly small changes, please see them listed below (more details written on the PRs themselves)
> 
> 
> - Enable ROOT's thread safety when running in multithreaded mode
> 
> This helps avoid users having to write their call to a global thread lock when calling ->Fill() on ROOT histograms and Trees
> https://bitbucket.org/tmidas/manalyzer/pull-requests/5
> 
> 
> - Add command argument to specify an IP of the root HTTP server to bind to
> 
> This was a problem I painted around when at ALPHA (quickly hardcoding the right external IP address into the local build. Obviously a bad habit)
> https://bitbucket.org/tmidas/manalyzer/pull-requests/6

Further to the pull manalyzer pull requests, I have another feature I would like to add. Took a little longer to test than planned... here I present an effort to use smart pointers to manage the lifetime of TMEvents and TAFlow.

I will be interested to discuss the implications of this pull request (its possible to return to previous 'raw' pointers via a cmake toggle)

https://bitbucket.org/tmidas/manalyzer/pull-requests/8

This is a super small pull request, simple replace deprecated sprintf with snprintf

https://bitbucket.org/tmidas/manalyzer/pull-requests/9