I now merged almost all the mhttpd changes from CERN AD-5/ALPHA. Only the code
for mhttpd HTTP:// access control list remains unmerged.

Changes to the history display code merged from ALPHA: 
- add option to show latest values of history variables: "show values of
variables" check box on the history config panel 
- add custom labels for each variables: instead of midas variable name, history
plots would show the text entered into the "label" text area 
- show history errors on the plot: before, if one out of 10 history variables
could not be plotted, nothing was shown at all, now all variables are \
show, those that could not be read with hs_read() show the error code 
- the selection of which variables to plot is alphanumerically sorted (adc11 >
adc9) [this code is not active for standard midas because mlogger sup\
port has not yet been committed] 
- the selection of which variables to plot shows the last variable selected, not
the first one - useful when entering variables from a long list [th\
is code is not active for standard midas because mlogger support has not yet
been committed] 
 
These changes have been extensively tested since last Summer at the AD-5 ALPHA
expt at CERN. 
I could only do minimal testing for this merged code, so if there are any errors, 
they would most likely be merge errors. This new code will be heavily used at
TRIUMF, 
so if any errors got any, we hope to flush them out quickly. 
 
As noted, mlogger support for some of the mhttpd functions is not in standard
midas yet. It will be committed shortly. 

K.O.

> But to make things more interesting we had another history outage this week - we
> happen to write history files to an NFS server (not recommened! do not do this!) and
> when the NFS server had a glitch, history files got corrupted - because during the
> glitch NFS was not available, I think this roll-back feature would not have helped.

Actually I put our history data on a separate file system, on a separate disk controlled
by a separate RAID controller! If you write bulk data with the logger, and want to read
history files at the same time with mhttpd, you get a bottleneck if both data are at the
same physical disk. Separating this (and even the controller) speeded things up
dramatically.

The rollback will not work for NFS, since it requires truncating the file if an event
gets only partially written. While on a full file system you always can *delete* data,
this does not work if NFS is down. This explains the behavior.

> Anyhow, I now have a patch to allow hs_read() to "skip the bad spots" in the history
> files. (hs_gen_index() also needs a patch).
> 
> In the nutshell, if invalid history data is detected, the code continues to read the
> data one byte at a time, looking for valid event_id markers (etc).
> 
> The code looks sane by inspection, and if nobody objects, I would like to commit it
> in the next few days.

Great. I was thinking of something like this myself. Having a quick look at your code
looks good. The best of course would be if we would have some "magic number" for
re-synchronizating the data stream, but that would blow up the file length. So searching
for the right event id is good, but will not work 100%. Also the check

  if (irec.time < last_irec_time)

to see if the history is broken is very weak. If you take random data, it will be true
50% and false 50%. If one makes however a check

  if ((irec.time - last_irec_time) > 3600*24)

this would work correctly with random data in >99% of all cases (3600*24/2^32). Maybe
you should change that.

You misspelled one ODB entry:

Line 9014:
            sprintf(str, "/History/Display/%s/Label", path);

Line 9028:

            sprintf(str, "/History/Display/%s/Labels", path);
                                                ---^

I wonder how you could have tested that code for 1/2 year without noticing this error.
I fixed and committed it.
 

Backend computer with SLC4.4 Linux did'not work as mserver because some security
protection under iptables service (could not connect with frontend computers).
The connection established if to make ( under root ) iptables disable
by command: service iptables stop, or much more gently
just to accept mserver port with command (under root):
iptables -I INPUT -p tcp --dport 1175 -j ACCEPT
( in /etc/service 
  midas    1175/tcp       #Midas server)
To check which ports is open
it is possible to use the command: "netstat -n" to see digital numbers of ports.

> You misspelled one ODB entry:
> Line 9014:
>             sprintf(str, "/History/Display/%s/Label", path);
> 
> Line 9028:
>             sprintf(str, "/History/Display/%s/Labels", path);
>                                                 ---^
> 
> I wonder how you could have tested that code for 1/2 year without noticing this error.
> I fixed and committed it.


It turns out that the program was tested as originally committed. With the above
modification, it corrupts ODB - originally, it used the wrong array element size to create
the wrong array. Corrected, it creates the right array with the wrong size, then
subsequent db_set_data_index() happily corrupts ODB.

Fix for mhttpd committed as svn revision 4128.
Fix for ODB corruption committed at svn revision 4129 (also fixes extract_key())


K.O.

> > Affected files:
> > Makefile (add cnaf_callback.o)
> That's a good idea.
> To make things a bit easier, I modified the midas\examples\experiment\fronted.c to
> contain this call, so people should be guided by that. I also added cnaf_callback.c
> to the Makefile of the example frontend.

A request was made to remove cnaf_callback.o from libmidas as it creates a unwanted dependency on the CAMAC 
hardware driver when libmidas.so is used in programs that do not use CAMAC.

After looking around, it appears that removing cnaf_callback.o from libmidas would not break anything critical, 
other than CAMAC frontends that would fail to link with an obvious and easy to fix error.

I am leaving cnaf_callback.o in the Makefile - so it will be built and placed in linux/lib/cnaf_callback.o for anybody 
who wants to use it.

svn revision 4130.

K.O.

The changes to mlogger implementing per-variable history have been committed to
svn. Revision 4145.

The rationale for these changes is roughly described in
https://ladd00.triumf.ca/elog/Midas/347

The main user-visible effect is reduction of data volume written to history
files and better integration with the history plot system in mhttpd.

The new functionality is disabled by default, pending review by Stefan (Except
for /history/tags stuff, which will be created by mlogger and used by mhttpd).
To enable it, set "/equipment/xxx/Common/PerVariableHistory" to 1 (type TID_INT).

In the "per-variable" mode, each entry in /equipment/xxx/variables is assigned
it's own event id and creates it's own events in the history file. In the
"classical" (or per-equipment) mode, all variables are assigned the same event
id (equal to the equipment id) and are written to disk at the same time.

In other words, in per-equipment mode, if there are 100 variables and 1 of them
is updated, all 100 numbers are written to disk. In per-variable mode, only the
one updated variable is written out.

The one point for review in this implementation is the assignment of event id's.
Committed code uses the formula "1000*eq_id + n" (i.e. variables in equipment id
2 get 2001, 2002, etc..., equipment id 3 get 3001, 3002, ...). This formula
works for most experiments, but as I understand is no good for some experiments
at PSI. Other than inventing a better formula that would work for everybody in
every case, one can also assign event id's manually by creating appropriate
entries in "/history/events".

This code has been used at CERN for running ALPHA since last Summer and it will
be used extensively at TRIUMF for T2K/ND280 slow controls. Per-variable history
is also required for the pending implementation of "history logged directly to
an SQL database", to be used at T2K/ND280.

If history (ahem) is any guide, we will now have a brief period of fixing merge
errors and "works for me" mistakes.

K.O.

> The changes to mlogger implementing per-variable history have been committed to
> svn. Revision 4145.

To make code changes more clear, the commit was done in 3 stages:

revision 4142+4143 are minor fixes, refactoring (switch the code to use helper
functions) and implementation of history for structured banks
revision 4144 implements the per-variable history
revision 4145 is minor cleanup.

K.O.

I would like to hear from potential users on which SQL database would be
preferable for storage of MIDAS history data.

My current preference is to use the ODBC interface, leaving the choice of
database engine to the user. While ODBC is not pretty, it appears to be adequate
for the job, permits "funny" databases (i.e. flat files) and I already have
prototype implementations for reading (mhttpd) and writing (mhdump/mlogger)
history data using ODBC.

In practice, MySQL and PgSQL are the main two viable choices for using with the
MIDAS history system. We tested both (no change in code - just tell ODBC which
driver to use) and both provide comparable performance and disk space use. We
were glad to see that the disk space use by both SQL databases is very
efficient, only slightly worse than uncompressed MIDAS history files.

At TRIUMF, for T2K/ND280, we now decided to use MySQL - it provides a better
match to MIDAS data types (has 1-byte and 2-byte integers, etc) and appears to
have working database replication (required for our use).

With mlogger already including support for MySQL, and MySQL being a better match
for MIDAS data, this gives them a slight edge and I think it would be reasonable
choice to only implement support for MySQL.

So I see 3 alternatives:

1) use ODBC (my preference)
2) use MySQL exclusively
3) implement a "midas odbc layer" supporting either MySQL or PgSQL.

Before jumping either way, I would like to hear from you folks.

K.O.

Before approving the code, two conditions have to be fulfilled:

1) The code has to work on PSI experiments
2) The code must work without any SQL database

Concerning point 1), you correctly mentioned that the event numbering does not work
if there are more than 1000 variables per event. What I do not want is that there
will be a special T2K midas version and a special PSI version. This would make
maintenance horrible in the future. One could make the formula variable with id =
ev_id*n+var_n, where n is not fixed to 1000, but variable (stored in the ODB). The
down side would be that if you analyze your history files offline (outside the
experiment) you have to know a priori n in order to read back the data. If you have
990 variables, then you add 20, then you modify n from 1000 to 1500, then you would
screw up yourself since you cannot read the old data any more. 

Taking all this into account, I see no clean way to fix this except to modify the
database format (which you change anyhow "somehow" going to per-variable mode). Use a
32-bit ID for the event (16-bit) and the variable (16-bit). This will increase the
overhead, but only marginally, since there is already a 32-bit time stamp. But this
method would then work for all experiments at all times. I suspect that even in T2K
you will come at some point to a configuration where you have move than n variables
per event, whatever n is. So even you would benefit.

Concernign ponit 2), I like your ODBC approach. I never used it, but if you tell me
it works on all supported OSes it's fine with me, but make sure it compiles under
Windows (with the help of Pierre). One thing I would make sure however is that it
runs by default without setting up a database. There are many experiments out there
which do not need a SQL database, and it would be a hassle for them all to set up a
database, just to continue running. So by default I would use either the current flat
file system, and then per configuration enable ODBC, with bindings to MySQL pgSQL and
maybe SQLite3.

Cheers,

  Stefan

Now that we use more and more C++, lack of "const" attribute on most midas functions is causing some 
problems. I am now ready to commit changes to midas.h and odb.c that add the const attributes to ODB 
access functions db_xxx(), i.e.
INT db_rename_key(HNDLE hDB, HNDLE hKey, char *name)
becomes
INT db_rename_key(HNDLE hDB, HNDLE hKey, const char *name)

If we proceed with this conversion, and it does not cause major havoc, I can continue and "const"ify the 
rest of midas.h. I note that the mxml functions appear to already have the correct "const" declarations.

P.S. Adding the "const" attribute caught a few places where we were modifying a "char*" string passed by 
the caller. This is undesirable if we are passed a string literal, i.e. db_rename_key(...,"foo"), and it is a 
complete disaster in conjunction with C++ strings, i.e. db_rename_key(...,foo.c_str())

K.O.

Now that we use more and more C++, lack of "const" attribute on most midas functions is causing some 
problems. I am now ready to commit changes to midas.h and odb.c that add the const attributes to ODB 
access functions db_xxx(), i.e.
INT db_rename_key(HNDLE hDB, HNDLE hKey, char *name)
becomes
INT db_rename_key(HNDLE hDB, HNDLE hKey, const char *name)

If we proceed with this conversion, and it does not cause major havoc, I can continue and "const"ify the 
rest of midas.h. I note that the mxml functions appear to already have the correct "const" declarations.

P.S. Adding the "const" attribute caught a few places where we were modifying a "char*" string passed by 
the caller. This is undesirable if we are passed a string literal, i.e. db_rename_key(...,"foo"), and it is a 
complete disaster in conjunction with C++ strings, i.e. db_rename_key(...,foo.c_str())

K.O.

> Now that we use more and more C++, lack of "const" attribute on most midas functions is causing some 
> problems. I am now ready to commit changes to midas.h and odb.c that add the const attributes to ODB 
> access functions db_xxx(), i.e.
> INT db_rename_key(HNDLE hDB, HNDLE hKey, char *name)
> becomes
> INT db_rename_key(HNDLE hDB, HNDLE hKey, const char *name)
> 
> If we proceed with this conversion, and it does not cause major havoc, I can continue and "const"ify the 
> rest of midas.h. I note that the mxml functions appear to already have the correct "const" declarations.
> 
> P.S. Adding the "const" attribute caught a few places where we were modifying a "char*" string passed by 
> the caller. This is undesirable if we are passed a string literal, i.e. db_rename_key(...,"foo"), and it is a 
> complete disaster in conjunction with C++ strings, i.e. db_rename_key(...,foo.c_str())

I fully approve your idea. You are absolutely right that it also will help to prevent errors such as modifying
fixed strings. I was just too lazy to do that, because it requires some additional code like:

func(const char *p)
{
char str[256];

  strlcpy(str, p, sizeof(str));
  strlcat(str, ...)
} 

So if you do it, it's great!

> > I am now ready to commit changes to midas.h and odb.c that add the const attributes to ODB 
> > access functions db_xxx(), i.e.
> > INT db_rename_key(HNDLE hDB, HNDLE hKey, char *name)
> > becomes
> > INT db_rename_key(HNDLE hDB, HNDLE hKey, const char *name)
>
> I fully approve your idea.

Committed revision 4172.

K.O.

FYI - in conjunction with replacement of ladd00.triumf.ca, this MIDAS ELOG has been updated to the latest 
version 2.7.3-2058. Please report any problems or anomalies. K.O.

> > But to make things more interesting we had another history outage this week...
> > Anyhow, I now have a patch to allow hs_read() to "skip the bad spots" in history files.
> 
> [Stefan suggested]
>
>   if ((irec.time - last_irec_time) > 3600*24)


Yes, your stronger check works quite nicely. The whole patch is now committed into SVN,
revision 4202.

This is how it all works:

0) teach hs_gen_index() to skip over bad data. This is important because hs_read() only
looks at data records listed in the index file: if bad data is omitted from the index,
hs_read() will never see it and we do not need to worry about it in hs_read().
0a) because hs_gen_index() does not check validity of time stamps, we still need to check
them in hs_read().
1) in hs_read(), if we detect bad data (invalid headers, bad time stamps, etc), we
regenerate the index files - this removes a while class of bad data. We also look at time
stamps carefully and ignore records where time goes backwards (usually bad data) and ignore
records with time in the future beyound the end of the current history file (each history
file only contains 24*60*60 seconds = 1 day's worth of data).

While certainly not bullet-proof, these changes should make it easier to deal with
corruption of history files.

K.O.

Some improvement of custom pages have been implemented. The idea behind is that
a custom page would contain a large background image containing indicators but
also controls. While indicators (values, bars) are already available, the field
of controls have been improved.

Edit boxes floating on top of a graphic
---------------------------------------

The first option has been there from the beginning, but was never documented. It
makes it possible to put an edit box right on top of a graphic by means of a CSS
style tag. The custom page code could look like this:

<div style="position:absolute; top:100px; left:50px;">
<odb src="/Runinfo/run number" edit=1>
</div>
<img src="cusgom.gif">

The "div" tag surrounding the "odb" tag places this directly on top of the
"custom.gif" image, where it can be clicked to be edited.

Password protection of an edit box
----------------------------------

Being able to control an experiment through a web interface of course rises the
question about safety. This is not so much about external access (for which we
have other protection schemes like host lists etc.) but it's about accidental
access by the normal shift crew. If a single click on a web page opens a
critical valve, this might be a problem. In order to restrict access to some
"experts", an additional password can be chosen for all or some controls on a
custom page. This is done by a new option in the "odb" tag and by adding a small
JavaScript function into the custom page:

<script type="text/javascript">
<!--
function promptpwd(path)
{
    pwd = prompt('Please enter password', '');
    document.cookie = "cpwd=" + pwd;
    location.href = path;
}
//-->
</script>

...

<odb src="/..." edit=1 pwd="CustomPwd">

...

If the "pwd" option is present in the "odb" tag, mhttpd establishes a call to
the promptpwd() function if one click on the value. The password is then asked
from the user and submitted as a cookie. mhttpd then check this password against
the ODB entry

/Custom/Pwd/CustomPwd

and shows an error if they don't match. By using an explicit name ("CustomPwd"
in the above example) one can use a single password for all controls on a page,
or one could use several passwords on the same page. Like a shift crew password
for the less severe controls (/Custom/Pwd/ShiftPwd), and an "expert" password
(/Custom/Pwd/ExpertPwd) for the critical things. This password is of course not
secure in the sense that it's placed in plain text into the ODB, it's more to
prevent accidental modifications of things.

Area map to toggle values
-------------------------

Sometimes it's desirable to toggle a value, like the state of a valve. This can
be done now with a new function like this:

<map name="Custom1">
<area shape="rect" coords="40,200,100,300" alt="Main Valve"
  href="Custom1?cmd=Toggle&odb=/Equipment/Environment/Variables/Output[2]">
</map>
<img src="cusgom.gif" usemap="#Custom1">

This defines a clickable map on top of the custom image. The area(s) should
match with some areas on the image like the box of a valve. By clicking on it,
the supplied path to the ODB is used (in this case
"/Equpiment/Environment/Variables[2]") and it's value is toggled (set to 0 if it
is 1, set to 0 if it is 1). If the valve value is then used in the image via a
"fill" statement to change the color of the valve, it can turn green or red
depending on it's state.

Are map with password check
---------------------------

The above area map can be combined with the password check. To do so, one needs:

<area shape="rect" coords="40,200,100,300" alt="Main Valve"
  href="#"
onClick="promptpwd('Custom1?cmd=toggle&pnam=CustomPwd?odb=/Equipment/Environment/Variables/Output[2]')">

in combination with the JavaScript from above.


An example of the are map technology is shown in the attachment. This page from the MEG experiment at PSI
shows a complex gas system. The valves are represented as green circles. If they are clicked, they close
and become red (after the user successfully supplied the correct password).

I implemented improved alarm conditions in the alarm system. Now one can write
conditions like

  /Equipment/HV/Variables/Input[*] < 100

or 

  /Equipment/HV/Variables/Input[2-3] < 100

to check all values from an array or a certain range. If one array element
fulfills the alarm condition, the alarm is trigger. In addition, bit-wise alarm
conditions are possible

  /Equipment/Environment/Variables/Input[0] & 8

is triggered if bit #2 is set in Input[0].

The changes are committed to SVN revision 4242.

The current implementation of ODB links has the problem that once a link is
created, it cannot be changed any more through odbedit. This is because each
"set" command works on the destination of the link instead of the link. The same
happens when one loads a *.odb file. To overcome this problem, two new functions
db_set_link_data() and db_set_link_data_index() have been implemented. They
resemble their counterparts db_set_data() and db_set_data_index(), but they can
be used to directly modify a link instead of the link target. I use these
functions now in odbedit and db_paste() so that the above described problems are
fixed now. I do not expect any side effect of this, but if people experience
problems with db_paste(), please let me know.

<script type="text/javascript" src="../mhttpd.js"></script>

Display of cursor location

<img id="refimg" src="...">

Retrieving ODB values

  ODBGet(<path>);

  ODBGet('/Equipment/Environment/Variables/Input[3]');

  ODBGet('/Equipment/Environment/Variables/Input[*]');

  var a = ODBGet('/Equipment/Environment/Variables/Input[*]');

  for (i=0 ; i<a.length ; i++)
    alert(a[i]);

  window.setInterval("Refresh()", 10000);

  function Refresh() {
    document.getElementById("run_number").innerHTML = ODBGet('/Runinfo/Run number');
  }

  <td id="run_number"></td>

  ODBGet('/Equipment/Environment/Variables/Input[3]&format=%1.2lf');

Retrieving System Messages

Setting ODB values

  ODBSet(<path>,<value>);

  ODBSet(<path>,<value>,<password_name>);

  <input type="checkbox" onClick="ODBSet('/Logger/Write data',this.checked?'1':'0')">

  <odb src="/Logger/Write data" type="checkbox" edit="2" onclick="ODBSet('/Logger/Write data',this.checked?'1':'0')">