> The function mhttpd_init() scans the custom page and installs handlers etc. for each modbxxx 
> element. If you create an modbvalue dynamically in your code, this is probably done after you 
> called mhttpd_init(), so the function has no chance to modify the dynamically created element.
> 
> To fix that, I separated mhttpd_init() into the old init function which installs the header and sidebar, 
> and a function mhttpd_scan() which scans the custom page and processes all modbxxx elements. 
> Next, I tapped the error you reported, and added an automatic call to mhttp_scan() in case that 
> happens. I tried it on a test page and it worked for me. Please give it a try (commit 090394e8).
> 
> Stefan

Also works for me

 thanks

> > The function mhttpd_init() scans the custom page and installs handlers etc. for each modbxxx 
> > element. If you create an modbvalue dynamically in your code, this is probably done after you 
> > called mhttpd_init(), so the function has no chance to modify the dynamically created element.
> > 
> > To fix that, I separated mhttpd_init() into the old init function which installs the header and sidebar, 
> > and a function mhttpd_scan() which scans the custom page and processes all modbxxx elements. 
> > Next, I tapped the error you reported, and added an automatic call to mhttp_scan() in case that 
> > happens. I tried it on a test page and it worked for me. Please give it a try (commit 090394e8).
> > 
> > Stefan
> 
> Also works for me
> 
>  thanks


This is more about aesthetic, but when I use the modbvalue div, it first only shows the odb value. However, 
after editing, the odb index gets added to the field, which is kinda ugly -> see attachments

I received my new 2020 mac book air, so between Stefan and myself, MacOS support for 
MIDAS is assured for 5 more years at the least. K.O.

I committed an updated lazylogger with updated documentation. The new version supports subruns and 
can save to external storage arbitrary files (i.e. odb dump files). It also moves most book keeping out of 
odb to permit handling more files on bigger storage disks.

Example lazylogger scripts for castor (CERN) and dcache (TRIUMF) are in the directory "utils".

The lazylogger documentation was updated to remove obsolete information and to describe the new 
functions. As usual "make dox; cd doxfiles/html; firefox index.html" or see my copy at:

http://ladd00.triumf.ca/~olchansk/midas/Utilities.html#lazylogger_task

svn rev 4615, 4616.
K.O.

the new history panel editor has been activated. it is meant to work the same as 
the old editor, with some improvements to the history variables selection page. 
this new version is written in html+javascript and it will be easier to improve, 
update and maintain compared to the old version written in c++. the old history 
panel editor is still usable and accessible by pressing the "edit in old editor" 
button. please report any problem, quirks and improvements in this thread or in 
the bitbucket bug reports. K.O.

the code for writing midas history to mysql has been updated to work against 
MYSQL 8.0.23 (CERN ALPHA-2):

- as ever mysql reports inconsistent data types (I create column with type 
"integer", mysql reports it has type "int" and so forth), the special kludge to 
take care of this had to be tweaked.

- this caused some columns to be marked "inactive" and the code to "reactivate" 
them was missing (fixed)

- binary history event data size was computed incorrectly for events with 
"inactive" columns (fixed) and caused assert() failure and mlogger crash.

- mysql read of column definitions for history event "system" (as in 
/history/links/system) bombed because of incorrect quoting (worked before, why? 
why bombed now?). this caused duplicate columns to be created in mysql table 
"system" and mlogger bomb-out with complaint about "duplicated columns" 
(actually the error message was missing, so it was a silent bomb-out). quoting 
fixed, missing error message fixed, but cleanup of duplicate columns has to be 
done by hand. in case of alpha-2 the fix was to remove the unused 
/history/links/system).

if you are using mysql history please update or patch src/history_schema.cxx.

commit 9d17d2fef233cf457121ca7c2a283c4c76ed33bc

K.O.

Hey,

while trying to compile Midas under openSUSE 15.0 with mysql support, I was
running into the problem that somehow the mysql header file my_global.h is not
included in the packages. This might be a bug that concerns the suse developers
more, but is it actually needed? Compilation worked fine with the include line
commented out.

If it's not needed, I would like to suggest to remove line 735 of
src/history_schema.cxx (where it's included)

Cheers
Lukas

mysql  Ver 15.1 Distrib 10.2.22-MariaDB, for Linux (x86_64) using  EditLine wrapper
Also, all mariadb development packages are installed

Confirmed. my_global.h is removed in MySQL 8.0 (gives a compile error) and deprecated in 
MariaDB 10.2 (gives a #warning).

I removed include of my_global.h, it is not needed on el6, el7 and ubuntu.

Also added explicit support for mariadb via mariadb_config if it exists.

Note that the cmake build does not actually enable mysql, sqlite and odbc - it detects them, but 
does not do anything about it. We will fix this shortly.

K.O.




> Hey,
> 
> while trying to compile Midas under openSUSE 15.0 with mysql support, I was
> running into the problem that somehow the mysql header file my_global.h is not
> included in the packages. This might be a bug that concerns the suse developers
> more, but is it actually needed? Compilation worked fine with the include line
> commented out.
> 
> If it's not needed, I would like to suggest to remove line 735 of
> src/history_schema.cxx (where it's included)
> 
> Cheers
> Lukas
> 
> mysql  Ver 15.1 Distrib 10.2.22-MariaDB, for Linux (x86_64) using  EditLine wrapper
> Also, all mariadb development packages are installed

Thanks!

I have a web page and I try to use modbvalue, but nothing happens. The best I can tell, I follow the documentation 
(https://midas.triumf.ca/MidasWiki/index.php/Custom_Page#modbvalue).

<td id=setv0><div class="modbvalue" data-odb-path="/Equipment/CAEN_hvps01/Settings/VSET[0]" data-odb-editable="1">(ch0)</div></td>

I suppose I could add debug logging to the javascript framework for modbvalue to find out why it is not seeing
or how it is not liking my web page.

But how would a non-expert user (or an expert user in a hurry) would debug this?

Should the modbvalue framework log more error messages to the javascrpt console ("I am ignoring your modbvalue entry because...")?

Should it have a debug mode where it reports to the javascript console all the tags it scanned, all the tags it found, etc
to give me some clue why it does not find my modbvalue tag?

Right now I am not even sure if this framework is activated, perhaps I did something wrong in how I load the page
and the modbvalue framework is not loaded. The documentation gives some magic incantations but does not explain
where and how this framework is loaded and activated. (But I do not see any differences between my page and
the example in the documentation. Except that I do not load control.js, I do not need all the thermometer bars, etc.
If I do load it, still my modbvalue does not work).

K.O.

Can you post your complete page here so that I can have a look?

Stefan

> > > the midas release 2019-03 is ready for general use.
> A bug fix update for midas-2019-03:
> odbedit "ver" should report: Thu Jun 6 18:02:14 2019 -0700 - midas-2019-03-h on branch feature/midas-2019-03

For building this release of MIDAS, please use mxml branch feature/midas-2019-03, tag mxml-2019-03-a:

cd .../mxml
git fetch
git checkout feature/midas-2019-03

Going forward, I will try to remember to tag the mxml version that corresponds to specific midas versions.

K.O.

the mxml library was updated to make it thread-safe.
https://bitbucket.org/tmidas/mxml/src/master/

I also take an opportunity to remind all to update your copy to the latest version
as I just stumbled on old bug that I fixed 1 year ago (crash of mlogger)
but forgot to update all and every of my copies of mxml.

I also looked at the xml encoder and I see that it has several places where it may
truncate the data, but none of these places can cause truncation of ODB data
because the fixed-size internal buffers are big enough to hold the longest
values sent by the odb xml encoder.

K.O.

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

> 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

Thanks for raising that point. I realized that the odbxx API was also missing that functionality, so I added it: 
https://bitbucket.org/tmidas/midas/commits/6991a92c19292eaf67721cb80f182c61db077f45

Best,
Stefan

This is not a bug per se, but I find it a little odd that the MVOdb functions RS, 
RSA, RSAI, and WSA use std::string as their type, while WS ans WSAI use const 
char*

Seems to me like simple overloading a la
void WS(const char* varname, const std::string v, MVOdbError* error = NULL){
    WS(varname, v.c_str(), v.size(), error);
}

should be all that's needed, right?

> This is not a bug per se, but I find it a little odd that the MVOdb functions RS, 
> RSA, RSAI, and WSA use std::string as their type, while WS ans WSAI use const 
> char*
> 
> Seems to me like simple overloading a la
> void WS(const char* varname, const std::string v, MVOdbError* error = NULL){
>     WS(varname, v.c_str(), v.size(), error);
> }
> 
> should be all that's needed, right?

No short answer to this one.

This situation is an excellent example of c++ bloat. Reduced to bare basics:

1) "naive" c++ code:

void foo(std::string xxx) { ... };
int main() { foo("bar"); }

nominally:
a new string object is created to hold "bar"
a new string object is copy-created to pass it as argument to foo()

result:
two object creations (two calls to malloc + constructors)
plus memcpy() of string data. (compiler may or may not optimize the 2nd string)

2) "advanced" c++ code:

void foo(const std::string& xxx) { ... };
int main() { foo("bar"); }

copy-created 2nd string is avoided, but string object to hold "bar" is still must be 
made, 1 malloc(), 1 memcpy().

3) "pure C" code:

void foo(const char xxx) { ... };
int main() { foo("bar"); }

address of "bar" (placed in read-only memory) is passed in a register, no malloc(), no 
memcpy(), nada, zilch.

One can argue that bloat does not matter, "just buy a bigger computer".

This ignores the fact that malloc() is quite expensive, nominally requires taking a 
mutex, and suddenly multiple threads calling foo() are unexpectedly serialized against 
the malloc() internal mutex.

I guess you can have an advanced malloc() that uses per-thread memory pools, but now 
instead of deterministic "always take a lock", we have non-deterministic "take a lock 
sometimes, when per-thread memory pools decide to jockey for more memory".

This type of non-deterministic behaviour is bad for real-time applications.

Ultimately it boils down to personal style, I prefer "C-like" efficiency and 
transparency, when I call foo() it is obvious there will be no hidden malloc(), no 
hidden mutex.

I guess mvodb could have "const std::string&" version of each "const char*" function, 
as if there is too few functions there already...

This problem is not isolated to mvodb, but pertains to any API, including midas.h.

I would say, if most function calls are foo("abc"); then "const char*" version is 
sufficient, if most calls are foo(string + "something"); then "const std::string&" is 
more appropriate.

K.O.

> 2) "advanced" c++ code:
> 
> void foo(const std::string& xxx) { ... };
> int main() { foo("bar"); }
> 
> copy-created 2nd string is avoided, but string object to hold "bar" is still must be 
> made, 1 malloc(), 1 memcpy().

Are you sure about this? I always thought that foo only receives a pointer to xxx which it puts on the stack, so
no additional malloc/free is involved.

Have a look here: https://en.cppreference.com/w/cpp/language/reference.html

It says "References are not objects; they do not necessarily occupy storage".

Stefan

> > 2) "advanced" c++ code:
> > 
> > void foo(const std::string& xxx) { ... };
> > int main() { foo("bar"); }
> > 
> > copy-created 2nd string is avoided, but string object to hold "bar" is still must be 
> > made, 1 malloc(), 1 memcpy().
> 
> Are you sure about this? I always thought that foo only receives a pointer to xxx which it puts on the stack, so
> no additional malloc/free is involved.

Yes, "bar" is not an std::string, cannot be used to call foo(), and the c++ compiler has to automagically rewrite 
the function call

from: int main() { foo("bar"); }
to:   int main() { foo(std::string("bar"); }

the temporary std::string object may be on the stack, but storage for text "bar" is on the heap (unless std::string 
is optimized to store short strings internally).

one can put a printf() inside foo() to print the address of xxx (should be on the stack) and xxx.c_str() (should be 
on the heap). one could also try to print the address of "bar" (should be in the read-only-constant-strings memory 
area). (I am not sure if compiler-linker combines all instances of "bar" into one, this is also easy to check).

K.O.

Just in time, enter std::string_view.
https://stackoverflow.com/questions/40127965/how-exactly-is-stdstring-view-faster-than-const-stdstring

I was looking at https://root.cern/doc/v638/classROOT_1_1Experimental_1_1RFile.html and they use it everywhere instead of 
std::string and const char*.

(so now we have 4 string types to deal with, counting ROOT's TString).

P.S. For extra safety, this code compiles, then explodes:

std::string_view get_temporary_string() {
  std::string s = "temporary";
  return s; // DANGER! 's' is destroyed, view dangles.
}

K.O.