> Asume you have a variable foo and a link bar -> foo. When you go to the ODB in
> mhttpd, click "Delete" and select bar, it actually deletes foo. bar stays,
> stating "<cannot resolve link>". Trying the same in odbedit with rm gives the
> expected result (bar is gone, foo is still there).
> 
> I'm on the develop branch.

I think I can confirm this. Created a bug report on bitbucket:

https://bitbucket.org/tmidas/midas/issues/148/mhttpd-odb-editor-deletes-wrong-symlink

K.O.

> > Asume you have a variable foo and a link bar -> foo. When you go to the ODB in
> > mhttpd, click "Delete" and select bar, it actually deletes foo. bar stays,
> > stating "<cannot resolve link>". Trying the same in odbedit with rm gives the
> > expected result (bar is gone, foo is still there).
> > 
> > I'm on the develop branch.
> 
> I think I can confirm this. Created a bug report on bitbucket:
> 
> https://bitbucket.org/tmidas/midas/issues/148/mhttpd-odb-editor-deletes-wrong-symlink
> 
> K.O.

I fixed this and committed the change. Took me a while since it was in KO's code.

Stefan

Another problem while using odbedit.
I tried the batch mode of "odbedit". I created a key as "/A_Str" by mistake and 
wanted to delete it. Then "odbedit" failed to accept the "Return" key. Please see 
the screen-shot attached. :-(

> Another problem while using odbedit.
> I tried the batch mode of "odbedit". I created a key as "/A_Str" by mistake and 
> wanted to delete it. Then "odbedit" failed to accept the "Return" key. Please see 
> the screen-shot attached. :-(

This bug has been fixed in the latest repository.
I encountered it in svn-r4488.

Hi everyone,

It has been a long time since my last message. While porting Midas front-end 
programs developed for the T2K experiment in 2008 to a modern version of Midas, 
I noticed that some debug printf remain in mhttpd.cxx.

A number of debug messages are printed on stdout each time a graph is displayed 
in the OldHistory window (which is the style of history plots that will continue 
to be used in the upgraded T2K experiment for some technical reasons).

Here is an example of such debug messages:
Load from ODB History/Display/HA_EP_0/V33: hist plot: 8 variables
timescale: 1h, minimum: 0.000000, maximum: 0.000000, zero_ylow: 0, log_axis: 0, 
show_run_markers: 1, show_values: 1, show_fill: 0, show_factor 0, enable_factor: 
1
var[0] event [HA_TPC_SC][E0M00FEM_V33] formula [], colour [#00AAFF] label 
[Mod_0] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
10
var[1] event [HA_TPC_SC][E0M01FEM_V33] formula [], colour [#FF9000] label 
[Mod_1] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
20
var[2] event [HA_TPC_SC][E0M02FEM_V33] formula [], colour [#FF00A0] label 
[Mod_2] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
30
var[3] event [HA_TPC_SC][E0M03FEM_V33] formula [], colour [#00C030] label 
[Mod_3] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
40
var[4] event [HA_TPC_SC][E0M04FEM_V33] formula [], colour [#A0C0D0] label 
[Mod_4] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
50
var[5] event [HA_TPC_SC][E0M05FEM_V33] formula [], colour [#D0A060] label 
[Mod_5] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
60
var[6] event [HA_TPC_SC][E0M06FEM_V33] formula [], colour [#C04010] label 
[Mod_6] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
70
var[7] event [HA_TPC_SC][E0M07FEM_V33] formula [], colour [#807060] label 
[Mod_7] show_raw_value 0 factor 1.000000 offset 0.000000 voffset 0.000000 order 
80
read_history: nvars 10, hs_read() status 1
read_history: 0: event [HA_TPC_SC], var [E0M00FEM_V33], index 0, odb index 0, 
status 1, num_entries 475
read_history: 1: event [HA_TPC_SC], var [E0M01FEM_V33], index 0, odb index 1, 
status 1, num_entries 475
read_history: 2: event [HA_TPC_SC], var [E0M02FEM_V33], index 0, odb index 2, 
status 1, num_entries 475
read_history: 3: event [HA_TPC_SC], var [E0M03FEM_V33], index 0, odb index 3, 
status 1, num_entries 475
read_history: 4: event [HA_TPC_SC], var [E0M04FEM_V33], index 0, odb index 4, 
status 1, num_entries 475
read_history: 5: event [HA_TPC_SC], var [E0M05FEM_V33], index 0, odb index 5, 
status 1, num_entries 475
read_history: 6: event [HA_TPC_SC], var [E0M06FEM_V33], index 0, odb index 6, 
status 1, num_entries 475
read_history: 7: event [HA_TPC_SC], var [E0M07FEM_V33], index 0, odb index 7, 
status 1, num_entries 475
read_history: 8: event [Run transitions], var [State], index 0, odb index -1, 
status 1, num_entries 0
read_history: 9: event [Run transitions], var [Run number], index 0, odb index 
-2, status 1, num_entries 0


Looking at the source code of mhttpd, these messages originate from:

[mhttpd.cxx line 10279] printf("Load from ODB %s: ", path.c_str());
[mhttpd.cxx line 10280] PrintHistPlot(*hp);
...
[mhttpd.cxx line  8336] int read_history(...
...
[mhttpd.cxx line  8343] int debug = 1;
...

Although seeing many debug messages in the mhttpd does not hurt, these can hide 
important error messages. I would rather suggest to turn off these debug 
messages by commenting out the relevant lines of code and setting the debug 
variable to 0 in read_history().

That is a minor detail and it is always a pleasure to use Midas.

Best regards,
Denis.
 

These debug statements were added by K.O. on June 24, 2021. He should remove it.

https://bitbucket.org/tmidas/midas/commits/21f7ba89a745cfb0b9d38c66b4297e1aa843cffd

Best,
Stefan

Hi,

We are using midas to read ADC. It sometimes hung in the middle of data taking.
We tried to disable analyzer and only run with frontend. The problem still
exists. We tried to use different crate, different CAMAC controller and
different ADC module. All these did not solve the problem. We use polled method
to read data. We have dataway display unit so we know that it hung always after
it executed CAMAC command F9, which is after finishing one data taking and clear
the ADC for the next data taking. The data rate is about 1 KHz. It is random for
how long it takes for the system to hang.

Any ideas ?

Thanks,

Dawei Liu

Hi Dawei,

Could you give more info on your setup:
- CAMAC controller model
- ADC model
- LAM setting
- Mode of polling (on module or on CC)
- Are you still going through the poll_event() after hang up?
- Do you have the same problem at low rate (100Hz)?

Pierre-André
> Hi,
> 
> We are using midas to read ADC. It sometimes hung in the middle of data taking.
> We tried to disable analyzer and only run with frontend. The problem still
> exists. We tried to use different crate, different CAMAC controller and
> different ADC module. All these did not solve the problem. We use polled method
> to read data. We have dataway display unit so we know that it hung always after
> it executed CAMAC command F9, which is after finishing one data taking and clear
> the ADC for the next data taking. The data rate is about 1 KHz. It is random for
> how long it takes for the system to hang.
> 
> Any ideas ?
> 
> Thanks,
> 
> Dawei Liu

Hi Pierr-Andre,


> Hi Dawei,
> 
> Could you give more info on your setup:
> - CAMAC controller model

Jorway 73A, we have three in hand and the problem doesn't depend on which controller
we were using.

> - ADC model

LeCroy 2249W. We also tried two other modules LeCroy 2249A. Same problem.

> - LAM setting

The poll and ADC reading codes are basically from Midas distribution.

> - Mode of polling (on module or on CC)

Polling on CC. I also tried to add a timeout code reading ADC, didn't solve the problem.

> - Are you still going through the poll_event() after hang up?

That's I don't know. I believe the problem happens between finishing reading one event
and passing the control back to poll_event.

> - Do you have the same problem at low rate (100Hz)?

The rate we are currently running is about 400 Hz, it has the same problem. We will
try lower rate more.

Thanks,

Dawei

> 
> Pierre-André
> > Hi,
> > 
> > We are using midas to read ADC. It sometimes hung in the middle of data taking.
> > We tried to disable analyzer and only run with frontend. The problem still
> > exists. We tried to use different crate, different CAMAC controller and
> > different ADC module. All these did not solve the problem. We use polled method
> > to read data. We have dataway display unit so we know that it hung always after
> > it executed CAMAC command F9, which is after finishing one data taking and clear
> > the ADC for the next data taking. The data rate is about 1 KHz. It is random for
> > how long it takes for the system to hang.
> > 
> > Any ideas ?
> > 
> > Thanks,
> > 
> > Dawei Liu

I keep on getting messages like this:

16:25:35 [fecaen,ERROR] [odb.c:4567:db_get_data,ERROR] data for key
"/DAQ/params/VX1730/custom/Board 0/Channel 0/Input range" truncated

whenever I start my frontend. Input range is defined to be a BOOL and using
odbedit to read it shows:

Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
Input range                     BOOL    1     4     75h  0   RWD  y

without any error message. The entry is read using

         size = sizeof(fInputRange);
         db_get_data(hDb, hSubKey, &fInputRange, &size, TID_BOOL);

where fInputRange is a bool.

Where does this message come from and how can I resolve this?

> I keep on getting messages like this:
> 16:25:35 [fecaen,ERROR] [odb.c:4567:db_get_data,ERROR] data for key
> "/DAQ/params/VX1730/custom/Board 0/Channel 0/Input range" truncated
>
>  [  bool fInputRange... ]
>          size = sizeof(fInputRange);
>          db_get_data(hDb, hSubKey, &fInputRange, &size, TID_BOOL);
>

The error is correct. size of TID_BOOL is 4 byte (uint32_t) and you give is sizeof(bool) instead which is probably not 4.

Note that sizeof(bool) is not well defined, sometimes it is 1 (you need 4), sometimes something else, see
https://stackoverflow.com/questions/4897844/is-sizeofbool-defined-in-the-c-language-standard

A good fix would be to change fInputRange from bool to uint32_t (which is always 4 byte size).

#include <stdint.h>
...
uint32_t fInputRange;

K.O.

Dear All,

After clicking the "Start" button, there is a page for the operator to change some 
ODB values. I have created "/Experiment/Edit on start" and added some links there. 
If the link is pointed to a boolean type key, a check box will appear in the 
"Start" page, which is great. But how about if I want to have some radio buttons 
or pull-down menus for the operator to select among different calibration sources 
or running modes?

Thanks,

Jimmy

I am having difficulty getting the custom scripts to work within the updated MIDAS. Before the 
update I was using something like : 

<input type=submit name=customscript value="test">

on my custom page to run a script under /CustomScript/test, however, with the update to 
MIDAS this is no longer working. I can't find any information about this functionality being 
updated in the latest version - has this changed? Or should it still work? 

Thanks,
Becky (g-2 DAQ)

> I am having difficulty getting the custom scripts to work within the updated MIDAS. Before the 
> update I was using something like : 
> 
> <input type=submit name=customscript value="test">
> 
> on my custom page to run a script under /CustomScript/test, however, with the update to 
> MIDAS this is no longer working. I can't find any information about this functionality being 
> updated in the latest version - has this changed? Or should it still work? 
> 
> Thanks,
> Becky (g-2 DAQ)

I do not see any messages about anybody changing this function. I hope it did not break by accident.

Right now I am working on the event buffer code, and did not plan to look at mhttpd, but it looks like
your problem is important and there is at least on more problem (but it has a work-around),
so I may look at it sooner than later...

K.O.

I just check that feature and found it's still working as expected. 

On trap I fell in was that a custom page needs the <input type=submit ...> to be imbedded into a pair of 

<form>
  ...
</form>

tags in order to work. Otherwise the browser will not execute the submit request. Has nothing to do with midas.

There was a small bug that after executing such a script, the URL was set to http://<host>/CS which is non-existent, 
so I fixed that to redirect to the page which called the script. Submitted to develop branch.

> <input type=submit name=customscript value="test">

Stefan is right, input-type-submit has to be inside a form. This type of rpc call is "old school". Today, we should 
have a json-rpc request to execute a custom script.

https://bitbucket.org/tmidas/midas/issues/163/need-json-rpc-method-to-execute-custom

K.O.

Dear All,

How can I add a button at the top of the "Status" webpage which will show a 
page similar to the "CNAF" one after I click on it? and how can I make a 
custom page similar to "CNAF" which allow me to call some custom funtions? I 
want to make a page which is particularly for doing calibration.

Thank you for your attention!

Best Regards,
Jimmy Ngai

> How can I add a button at the top of the "Status" webpage which will show a 
> page similar to the "CNAF" one after I click on it? and how can I make a 
> custom page similar to "CNAF" which allow me to call some custom funtions? I 
> want to make a page which is particularly for doing calibration.

The CNAF page calls directly functions through the RPC layer of midas, which is 
not possible from custom pages. All you can do is to execute a scrip on the 
server side, which then causes some action. For details please consult the 
documentation.

> How can I add a button at the top of the "Status" webpage which will show a 
> page similar to the "CNAF" one after I click on it? and how can I make a 
> custom page similar to "CNAF" which allow me to call some custom funtions? I 
> want to make a page which is particularly for doing calibration.


I was going to say that you can do this by using the MIDAS "hot-link" function.

In your equipment program, you create a string /eq/xxx/Settings/Command, and hot-link
it to the function you want to be called. (See midas function db_open_record() for details
and examples). (To test it, you put a call to printf("Hello world!\n") into your handler function,
then change the value of "command" using odbedit or the mhttpd odb editor
and observe that your function gets called and that it receives the correct value of "command").

Then on your custom web page you create 2 buttons "aaa" and "bbb" attached to javascript
ODBset("/eq/xxx/Settings/Command","aaa") and "bbb" respectively. When you push the button,
the specified string is written into ODB, and your hot-link handler function is called with the contents
of "command", which you can then look at to find out which web button was pushed.


But after looking at the hot-link data paths (see https://ladd00.triumf.ca/elog/Midas/546), I see 2 
problems that make the above scheme unreliable and maybe unusable in some applications:

1) the data path contains one UDP communication and it is well known that UDP datagrams can be (and 
are) lost with low or high probability, depending on not-well-understood external factors.

The effect is that the hot-link fails to "fire": odb contents is changed but your function is not called.

2) there is a timing problem with multiple odb writes: the odb lock is dropped before the "hot-link" gets 
to see the new contents of odb: db_data_set()->lock odb->change data->send notification->unlock 
odb->xxx->notification received by client->read the data->call user function. If something else is 
written into odb during "xxx" above, the client may never see the data written by the first odb write. For 
local clients, the delay between "send notification" and "notification is received by client" is not bounded in 
time (can be arbitrary long, depending on the system load, etc). For remote clients, there is an additional 
delay as the udp datagram is received by the local mserver and is forwarded to the remote client through 
a tcp rpc connection (another source of unbounded delay).

The effect is that if buttons "aaa" and "bbb" are pushed quickly one right after the other, while your 
function will be called 2 times (if neither udp packet is dropped), you may never see the value of "aaa"
as is it will be overwritten by "bbb" by the time you receive the first notification.

Probability of malfunction increases with code written like this: { ODBset("command", "open door"); 
ODBset("command", "walk through doorway"); }. You may see the "open door" command sometimes 
mysteriously disappear...

The net effect is that sometimes you will push the button but nothing will happen. This may be okey,
depending on your application and depending on how often it happens in practice on your specific system 
If you are lucky, you may never see either of the 2 problems listed above ad hot-links will work for you 
perfectly. At TRIUMF, in the past, we have seen hot-links misbehave in the TWIST experiment, and now I 
think I understand why (because of the 2 problems described above).

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).