When using remote midas clients with mserver, you may have noticed the zero-size .RPC.SHM files 
these clients create in the directory where you run them. These files are associated with the semaphore 
created by the midas rpc layer (rpc_call) to synchronize rpc calls between multiple threads. This 
semaphore is always created, even for single-threaded midas applications. Also normally midas 
semaphore files are created in the midas experiment directory specified in exptab (same place as 
.ODB.SHM), but for remote clients, we do not know that location until we start making rpc calls, so the 
semaphore file is created in the current directory (and it is on a remote machine anyway, so this 
location may not be visible locally).

There are 2 problems with these semaphores:
1) in multiple experiments, we have observed the RPC.SHM semaphore stuck in a locked state, 
requiring manual cleanup (ipcrm -s xxx). So far, I have failed to duplicate this lockup using test 
programs and test experiments. The code appears to be coded correctly to automatically unlock the 
semaphore when the program exits or is killed.
2) RPC.SHM is created as a global shared semaphore so it synchronizes rpc calls not just for all threads 
inside one application, but across all threads in all applications (excessive locking - separate 
applications are connected to separate mservers and do not need this locking); but only for applications 
that run from the same current directory - RPC.SHM files in different directories are "connected" to 
different semaphores.

To try to fix this, I implemented "private semaphores" in system.c and made rpc_call() use them.

This introduced a major bug - a semaphore leak - quickly using up all sysv semaphores (see sysctl 
kernel.sem).

The code was now reverted back to using RPC.SHM as described above.

The "bad" svn revisions start with rev 4472, the problem is fixed in rev 4480.

If you use remote midas clients and have one of these bad revisions, either update midas.c to rev 4480 
or apply this patch to midas.c::rpc_call():
ss_mutex_create("", &_mutex_rpc);
should read
ss_mutex_create("RPC", &_mutex_rpc);

Apologies for any inconvenience caused by this problem
K.O.

(catching up on recent changes from t2k and pienu)

Various timeout problems fixed:
- cm_transition() timeouts now settable from ODB (/experiment/transition timeout, transition connect 
timeout). Rev 4479
- rpc_client_call() timeout did not work because of bad select() and alarm() interaction. Rev 4479
- implement rpc connect timeout (was hardwired 10 sec) via rpc_{set,get}_option(-2, RPC_OTIMEOUT). Rev 
4478
- ss_mutex_wait_for() timeout only worked if 1Hz alarm() interrupts are present. Now I use semtimedop() 
and timeout should always work. Rev 4472

K.O.

> I have one more question. I use <odb src="odb field" edit=1> to display an 
> editable ODB value, but how can I show this value in hexadecimal?

Again with JavaScript:

  var v = ODBGet('/some/path&format=%X');

this will retrieve /some/path and format it in hexadecimal. Then you can set a table 
cell with "v" as I wrote in the last reply. If you want to change this value 
however, you need to encode this yourself in JavaScript.

- Stefan

> 1) I display the status of the run with <odb src="/Runinfo/State">, but it 
> returns numbers which is not user friendly. How can I make something 
> like "Running" with green background and "Stopped" with red background in the 
> default status page?

Sorry my late reply, I was really busy. You need JavaScript to perform such a 
task. See the attached example.

> 2) When I click either Start/Stop/Pause/Resume, it can performs the right 
> things, but afterward it jumps to the page "http://domain.name:8081/CS/" 
> which shows "Invalid custom page: NULL path". How can I make it returns 
> to the correct page "http://domain.name:8081/CS/Control%20panel"?

You add a hidden redirect statement:

  <input type=hidden name=redir value="CS/Control panel">

Best regards,

  Stefan

Dear All,

I have one more question. I use <odb src="odb field" edit=1> to display an 
editable ODB value, but how can I show this value in hexadecimal?

Thanks.

Best Regards,
Jimmy


> Dear All,
> 
> I have created a custom page (please see the attachment) and imported into 
> MIDAS with key name "Control panel&" (without the ""). I have the following 
> two questions:
> 
> 1) I display the status of the run with <odb src="/Runinfo/State">, but it 
> returns numbers which is not user friendly. How can I make something 
> like "Running" with green background and "Stopped" with red background in the 
> default status page?
> 
> 2) When I click either Start/Stop/Pause/Resume, it can performs the right 
> things, but afterward it jumps to the page "http://domain.name:8081/CS/" which 
> shows "Invalid custom page: NULL path". How can I make it returns to the 
> correct page "http://domain.name:8081/CS/Control%20panel"?
> 
> Thank you for your attention.
> 
> Best Regards,
> Jimmy

Dear All,

I have created a custom page (please see the attachment) and imported into 
MIDAS with key name "Control panel&" (without the ""). I have the following 
two questions:

1) I display the status of the run with <odb src="/Runinfo/State">, but it 
returns numbers which is not user friendly. How can I make something 
like "Running" with green background and "Stopped" with red background in the 
default status page?

2) When I click either Start/Stop/Pause/Resume, it can performs the right 
things, but afterward it jumps to the page "http://domain.name:8081/CS/" which 
shows "Invalid custom page: NULL path". How can I make it returns to the 
correct page "http://domain.name:8081/CS/Control%20panel"?

Thank you for your attention.

Best Regards,
Jimmy

Hi,

your log script sound to me like the analyzer either got into an infinite loop or 
did a segment violation and just died. I would recommend to run the analyzer from 
inside the debugger. When you then get the segment violation, you can inspect the 
stack trace and see where the bad things happen. Since the analyzer works nicely in 
other experiment, I expect that your problem is related to the user code. Maybe it 
happens at the end of the run, but there is a timeout before the crashed process 
gets cleaned from the ODB, that's why you might think that it happens "between" 
runs.

Best regards,

  Stefan

> 
> Hello Midas experts:
> 
> We have setup a DAQ using MIDAS to readout two ADCs in the crate.
> We are running into problem of analyzer getting killed between 
> runs.  Sometimes it would crash after a few runs and sometimes it 
> would go on for many many runs before analyzer gets killed.  It always 
> occurred between runs not when we are taking data.  Any suggestions 
> on what we could try?  The error message from the midas.log file is 
> appended below.
> 
> Thanks,
> 
> Dawei
> 
> Wed Mar  4 11:53:11 2009 [Analyzer,ERROR] [midas.c:1739:,ERROR]
> cm_disconnect_experiment not called at end of program
> Wed Mar  4 11:53:22 2009 [mhttpd,INFO] Client 'Analyzer' on buffer 'SYSMSG'
> removed by cm_watchdog (idle 10.7s,TO 10s)
> Wed Mar  4 11:53:22 2009 [mhttpd,INFO] Client 'Analyzer' (PID 1) on buffer 'ODB'
> removed by cm_watchdog (idle 10.7s,TO 10s)
> Wed Mar  4 11:53:22 2009 [AL Experiment Frontend,INFO] Client 'Analyzer' on
> buffer 'SYSTEM' removed by cm_watchdog (idle 10.9s,TO 10s)
> Wed Mar  4 11:53:29 2009 [AL Experiment Frontend,TALK] starting new run
> Wed Mar  4 11:53:29 2009 [AL Experiment Frontend,ERROR]
> [midas.c:8264:rpc_client_check,ERROR] Connection broken to "Analyzer" on host
> tsunami

Hello Midas experts:

We have setup a DAQ using MIDAS to readout two ADCs in the crate.
We are running into problem of analyzer getting killed between 
runs.  Sometimes it would crash after a few runs and sometimes it 
would go on for many many runs before analyzer gets killed.  It always 
occurred between runs not when we are taking data.  Any suggestions 
on what we could try?  The error message from the midas.log file is 
appended below.

Thanks,

Dawei

Wed Mar  4 11:53:11 2009 [Analyzer,ERROR] [midas.c:1739:,ERROR]
cm_disconnect_experiment not called at end of program
Wed Mar  4 11:53:22 2009 [mhttpd,INFO] Client 'Analyzer' on buffer 'SYSMSG'
removed by cm_watchdog (idle 10.7s,TO 10s)
Wed Mar  4 11:53:22 2009 [mhttpd,INFO] Client 'Analyzer' (PID 1) on buffer 'ODB'
removed by cm_watchdog (idle 10.7s,TO 10s)
Wed Mar  4 11:53:22 2009 [AL Experiment Frontend,INFO] Client 'Analyzer' on
buffer 'SYSTEM' removed by cm_watchdog (idle 10.9s,TO 10s)
Wed Mar  4 11:53:29 2009 [AL Experiment Frontend,TALK] starting new run
Wed Mar  4 11:53:29 2009 [AL Experiment Frontend,ERROR]
[midas.c:8264:rpc_client_check,ERROR] Connection broken to "Analyzer" on host
tsunami

> mhttpd and mlogger have been updated with potentially troublesome changes.
> These new features are now available:
> - a "feature complete" implementation of "history in an SQL database".

The mlogger SQL history driver has been updated with improvements that make this new system usable in 
production environment: the silly "create all tables on startup, every time, even if they already exist" is fixed,
mlogger survives restarts of mysqld and checks that existing sql columns have data types compatible with the 
data we are trying to write.

There are still a few trouble spots remaining. For example, in mapping midas names into sql names (sql names 
have more restrictions on permitted characters) and in reverse mapping of sql data types to midas data types. 
To properly solve this, I may have to save the midas names and data types into an additional index table.

Included is the mh2sql utility for importing existing history files into an SQL database (in the same way as if 
they were written into the database by mlogger).

The mhttpd side of this system still needs polishing, but should be already fully functional.

A preliminary version of documentation for this new SQL history system is here. After additional review and 
editing it will be committed to the midas midox documentation. Included are full instructions on enabling 
writing of midas history into a MySQL database.
http://ladd00.triumf.ca/~olchansk/midas/Internal.html#History_sql_internal

svn revision 4452
K.O.

At present the only documentation on the Javascript library is in this elog
e.g. Message 496 31 Jul 08

The Javascript library which you can view
http://<your mhttpd host>/mhttpd.js
now supports ODBEdit as well as ODBGet and ODBSet
 
I advise you get the latest version of mhttpd.c so you can use ODBEdit which changes
the ODB value directly via ODBSet.

You use it like this:
document.write('<a href="#" onclick="ODBEdit(/Equipment/test/Variables/Demand[0])">');
document.write('<odb src="/Equipment/test/Variables/Demand[0]">');
document.write('</a>');

You can also use HTML to edit the variables, but the advantage of Javascript is that
you can use variable ODB paths, so it is more powerful.

Here is an example of using a form on a custom page to edit a variable (in the
example, the run number) using Javascript (ODBEdit) and HTML. 

To try this example, in ODB, create key (STRING)
/custom/try& 
 and set it to "/home/user/try.html"

where the path of the example code on the disk is  /home/user/try.html

This will put an alias link on the Main Status page called "try" which you click on
to see the custom page.

Code of try.html:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 TRANSITIONAL//EN">
<html><head>
<title> ODBEdit test</title>
<script src="/js/mhttpd.js" type="text/javascript"></script>

<script type="text/javascript">
var my_action = '"/CS/try&"'
var rn
var path

document.write('</head><body>')
document.write('<form method="get" name="form2" action='+my_action+'> ') 
document.write('<input name="exp" value="'+my_expt+'" type="hidden">');

document.write('Using Javascript and ODBEdit:
')
path='/runinfo/run number' 
rn = ODBGet(path)
document.write('Run Number: '+rn+'
')
document.write('Edit Run Number:')
document.write('<a href="#" onclick="ODBEdit(path)" >')
document.write(rn)
document.write('</a>');
document.write('
') ;
</script>


Using HTML :


Using edit=2 ...  Run Number:
<odb src="/runinfo/run number" edit=2>


Using edit=1 ...  Run Number:
<odb src="/runinfo/run number" edit=1>


</form>
</html>


Note the "edit=2" feature is handy so that you can use Javascript or HTML on your
page and the user sees no difference.


> Hi, I am looking for a way to mutate ODB values from a custom page. I have been
> using the edit attribute for the 'odb' tag, but for some things it would be nice
> if a form can handle the change. I have seen references to ODBSet on the forums,
> but I haven't been able to find documentation on it. Is there an available
> Javascript library for Midas and/or are there more tags than I am aware of (I am
> only aware of the 'odb' tag)?

Hi, I am looking for a way to mutate ODB values from a custom page. I have been
using the edit attribute for the 'odb' tag, but for some things it would be nice
if a form can handle the change. I have seen references to ODBSet on the forums,
but I haven't been able to find documentation on it. Is there an available
Javascript library for Midas and/or are there more tags than I am aware of (I am
only aware of the 'odb' tag)?

There is an obvious "unwanted feature" in this version of the mhttpd. It writes the
"plot time" into the gif (mhttpd, if-statement starting in line 8853). 

Please check this obvious things more carefully in the future before submitting code. ;-)

> mhttpd and mlogger have been updated with potentially troublesome changes.
> Before using these latest versions, please make a backup of your ODB. This is
> svn revisions 4434 (mhttpd.c) and 4435 (mlogger.c).
> 
> These new features are now available:
> - a "feature complete" implementation of "history in an SQL database". We use
> this new code to write history data from the T2K test setup in the TRIUMF M11
> beam line to a MySQL database (mlogger) and to make history plots directly from
> this database (mhttpd). We still write normal midas history files and we have a
> utility to import midas .hst files into an SQL database (utils/mh2sql). The code
> is functional, but incomplete. For best SQL database data layout, you should
> enable the "per variable history" (but backup your ODB before you do this!). All
> are welcome to try it, kick the tires, report any problems. Documentation TBW.
> - experimental implementation of "ODBRpc" added to the midas javascript library
> (ODBSet, ODBGet & co). This permits buttons on midas "custom" web pages to
> invoke RPC calls directly into user frontend programs, for example to turn
> things on or off. Documentation TBW.
> - the mlogger/mhttpd implementation of /History/Tags has proved troublesome and
> we are moving away from it. The SQL database history implementation already does
> not use it. During the present transition period:
> - mlogger and mhttpd will now work without /History/Tags. This implementation
> reads history tags directly from the history files themselves. Two downsides to
> this: it is slower and tags become non-persistent: if some frontends have not
> been running for a while, their variables may vanish from the history panel
> editor. To run in this mode, set "/History/DisableTags" to "y". Existing
> /History/Tags will be automatically deleted.
> - for the above 2 reasons, I still recommend using /History/Tags, but the format
> of the tags is now changed to simplify management and reduce odb size. mlogger
> will automatically convert the tags to this new format (this is why you should
> make a backup of your ODB).
> - using old mlogger with new mhttpd is okey: new mhttpd understands both formats
> of /History/Tags.
> - using old mhttpd with new mlogger is okey: please set ODB
> "/History/CreateOldTags" to "y" (type TID_BOOL/"boolean") before starting mlogger.
> 
> K.O.

• Set /Channels/x/Settings/Subrun Byte limit to the number of bytes for a subrun
  
• Set /Channels/x/Settings/Filename to something like run%05d_%02d.mid. The first %05d gets replaced by the run number, while the second one gets replaced by the subrun number. This will result in files such as

  run00001_00.mid    run #1
  run00001_01.mid      "
  run00001_02.mid      "
  run00001_03.mid      "
  run00002_00.mid    run #2
  run00002_01.mid      "
  run00002_02.mid      "
  run00002_03.mid      "

mhttpd and mlogger have been updated with potentially troublesome changes.
Before using these latest versions, please make a backup of your ODB. This is
svn revisions 4434 (mhttpd.c) and 4435 (mlogger.c).

These new features are now available:
- a "feature complete" implementation of "history in an SQL database". We use
this new code to write history data from the T2K test setup in the TRIUMF M11
beam line to a MySQL database (mlogger) and to make history plots directly from
this database (mhttpd). We still write normal midas history files and we have a
utility to import midas .hst files into an SQL database (utils/mh2sql). The code
is functional, but incomplete. For best SQL database data layout, you should
enable the "per variable history" (but backup your ODB before you do this!). All
are welcome to try it, kick the tires, report any problems. Documentation TBW.
- experimental implementation of "ODBRpc" added to the midas javascript library
(ODBSet, ODBGet & co). This permits buttons on midas "custom" web pages to
invoke RPC calls directly into user frontend programs, for example to turn
things on or off. Documentation TBW.
- the mlogger/mhttpd implementation of /History/Tags has proved troublesome and
we are moving away from it. The SQL database history implementation already does
not use it. During the present transition period:
- mlogger and mhttpd will now work without /History/Tags. This implementation
reads history tags directly from the history files themselves. Two downsides to
this: it is slower and tags become non-persistent: if some frontends have not
been running for a while, their variables may vanish from the history panel
editor. To run in this mode, set "/History/DisableTags" to "y". Existing
/History/Tags will be automatically deleted.
- for the above 2 reasons, I still recommend using /History/Tags, but the format
of the tags is now changed to simplify management and reduce odb size. mlogger
will automatically convert the tags to this new format (this is why you should
make a backup of your ODB).
- using old mlogger with new mhttpd is okey: new mhttpd understands both formats
of /History/Tags.
- using old mhttpd with new mlogger is okey: please set ODB
"/History/CreateOldTags" to "y" (type TID_BOOL/"boolean") before starting mlogger.

K.O.

> The problem was already fixed some time ago, so please update your version from the SVN 
> revision (see https://midas.psi.ch/download.html for details).

I wanted to check out the latest websvn midas repository viewer installed at PSI, so I used the web "annotate/blame" tools 
to trace the fix to this bug down to revision 3660 committed in April 2007. (It turns out that "svn blame" is not very useful 
for tracing *removed* lines, so I ended up doing a manual binary search across different revisions of mlogger.c)

K.O.

The UDP connection you mention is only used locally for inter-process communication. When I implemented that, I 
made extensive tests and found that there is never a packet being dropped. This happens for UDP only if the packet 
goes over a physical network. Maybe this is different in modern Linux versions, so one should double check this 
again.

For remote hot-link notification, the notification is sent over the TCP link, so it should not be lost either. But 
your second point is correct. The hot-link mechanism was developed to change parameters in front-end programs for 
example. So by design it is guaranteed that if you change a value in the ODB, any client hot-linked to that will 
see the change (sooner or later). If there are many changes in short intervals (or the callback function on the 
remote client takes long time), only the last change is guaranteed to arrive. Therefore, as you correctly state, 
the hot-link mechanism is not a save replacement for the RPC layer (That's why the RPC layer is there after all).

> Sorry for being vague. I cleaned up the ODB, but it doesn't seem to be the
> problem. Here is a sample run of mlogger and gdb:

Thanks for the info, that explained the problem. It is related to the lines

rargv[rargc] = (char *)malloc(3);
rargv[rargc++] = "-b";

where one first allocates some memory (3 bytes), but then overwrites the pointer with 
another pointer to some static memory ("-b"). The following

free(rargv[1]);

then tries to free the static memory which fails.

The problem was already fixed some time ago, so please update your version from the SVN 
revision (see https://midas.psi.ch/download.html for details).