I ported a bunch of frontends to C++ and now I'm occasionally getting this RPC 
error message:

http error: readyState: 4, HTTP status: 502 (Proxy Error), batch request: method: 
"db_get_values", params: [object Object], id: 1583456958869 method: "get_alarms", 
params: null, id: 1583456958869 method: "cm_msg_retrieve", params: [object 
Object], id: 1583456958869 method: "cm_msg_retrieve", params: [object Object], 
id: 1583456958869

I'm assuming I'm doing wrong something somewhere, but does this message contain 
information where to look? Does the ID mean something?

I do not see this error, but there was one more report (they did not clearly say what http errors 
they see) https://bitbucket.org/tmidas/midas/issues/209/get-rid-of-mjsonrpc-dialogs-put-it-to-
the

To debug this, I need to know: what version of MIDAS, what version of what web browser, what 
computer is mhttpd running on? (so I can go look at the log files).

Also can you say more when you see these errors? Every time from every midas web page, or only 
some pages or only when you do something specific (push some button, etc?).

> I ported a bunch of frontends to C++ and now I'm occasionally getting this RPC 
> error message:
> 
> http error: readyState: 4, HTTP status: 502 (Proxy Error), batch request: method: 
> "db_get_values", params: [object Object], id: 1583456958869 method: "get_alarms", 
> params: null, id: 1583456958869 method: "cm_msg_retrieve", params: [object 
> Object], id: 1583456958869 method: "cm_msg_retrieve", params: [object Object], 
> id: 1583456958869
> 
> I'm assuming I'm doing wrong something somewhere, but does this message contain 
> information where to look? Does the ID mean something?

It is unlikely that this error has anything to do with the frontends: usually web page interaction 
goes through: web browser - network - apache httpd - localhost - mhttpd - midas odb.

http error 502 is very generic, does not tell us much about what happened, there may be more 
information in the httpd log files.

the json-rpc request "id" is generated by midas code in the web browser and it currently is a 
timestamp. it is not used for anything. but it is required by the json-rpc standard.

K.O.


K.O.

Dear all
I try to save data to an FTP server but don't get any data on the server. Midas does not complain or message any error but also nothing gets saved. Does somebody have experience with this? I use the following settings for the ODB mlogger channel settings: Type: FTP, Filename: server.com, 21, user, pw, ., run%06d.mid, Format: MIDAS, Output: FILE. What would be the Output: FTP setting for? I tried this but it does not work at all. 
Thanks in advance,
Ivo

> I try to save data to an FTP server but don't get any data on the server. Midas does not complain or message any error but also nothing gets saved. Does somebody have experience with this? I use the following settings for the ODB mlogger channel settings: Type: FTP, Filename: server.com, 21, user, pw, ., run%06d.mid, Format: MIDAS, Output: FILE. What would be the Output: FTP setting for? I tried this but it does not work at all. 

Hi, Ivo, good to hear from a midas user in these difficult times.

We do not use FTP at TRIUMF, but Stefan asked us to keep FTP alive and working, so we should be able
to get you going. I will try to find the FTP instructions for you, I am pretty sure I have them somewhere.

In the mean time, I am very curious why you are using a FTP to record data, is it some kind
of data appliance where simplest input for data is FTP? Using NFS does not work or is too hard?

Also for example at CERN, we write data to Castor and EOS, for this mlogger writes data to local disk,
then the lazylogger runs a script to move the data to Castor and EOS. The example lazylogger
scripts for this are in the MIDAS "progs" directory. But maybe you do not have a local disk and this would
not work for you.

In other news, I hope to work on mlogger and lazylogger support for cloud storage (swift and s3 apis?),
would that be useful as replacement for FTP?

K.O.

> > I try to save data to an FTP server but don't get any data on the server. Midas does not complain or message any error but also nothing gets saved. Does somebody have experience with this? I use the following settings for the ODB mlogger channel settings: Type: FTP, Filename: server.com, 21, user, pw, ., run%06d.mid, Format: MIDAS, Output: FILE. What would be the Output: FTP setting for? I tried this but it does not work at all. 
> 
> Hi, Ivo, good to hear from a midas user in these difficult times.
> 
> We do not use FTP at TRIUMF, but Stefan asked us to keep FTP alive and working, so we should be able
> to get you going. I will try to find the FTP instructions for you, I am pretty sure I have them somewhere.
> 
> In the mean time, I am very curious why you are using a FTP to record data, is it some kind
> of data appliance where simplest input for data is FTP? Using NFS does not work or is too hard?
> 
> Also for example at CERN, we write data to Castor and EOS, for this mlogger writes data to local disk,
> then the lazylogger runs a script to move the data to Castor and EOS. The example lazylogger
> scripts for this are in the MIDAS "progs" directory. But maybe you do not have a local disk and this would
> not work for you.
> 
> In other news, I hope to work on mlogger and lazylogger support for cloud storage (swift and s3 apis?),
> would that be useful as replacement for FTP?
> 
> K.O.
>
Good Morning Konstantin

Thanks for the fast reply.  Yes, it is, Midas is one of the things we can at least improve from home. 

Our experiment is planned to measure (soon) at ILL. Now since we don't use the equipment/detector from the 
beamline but our own, all the data from Midas is saved on the local drive. This is fine in the first instance
but then we also need proper backup. Since our experiment is quite small, the easiest solution I came up with
is to copy all of our data to the ILL storage which has enough space and is properly backed up. The ILL data 
storage allows only SFTP connections, nothing else. Since Midas has the FTP feature, having a separate FTP 
logger channel seemed the easiest way to go. 

Thanks for your input, I will look into how to mount SFTP and then this would also be a solution. 

Since ILL only provides access via SFTP and everything else is not existent or blocked (not even ssh is possible),
this is the only thing we can work with by now. 

Best regards,
Ivo

Logging directly from the midas logger to FTP is a bit cumbersome. In case of delays during login etc. this can throttle the whole DAQ chain. 
What we use in our lab is to write to local disk, then use the lazylogger (https://midas.triumf.ca/MidasWiki/index.php/Lazylogger) to copy the 
local files to a remote FTP server. This way we de-couple data taking from backup, making the system much more swift.

Best,
Stefan

> Logging directly from the midas logger to FTP is a bit cumbersome. In case of delays during login etc. this can throttle the whole DAQ chain. 
> What we use in our lab is to write to local disk, then use the lazylogger (https://midas.triumf.ca/MidasWiki/index.php/Lazylogger) to copy the 
> local files to a remote FTP server. This way we de-couple data taking from backup, making the system much more swift.
> 
> Best,
> Stefan

Yes, see this now too. I will, therefore, try to set up the lazylogger properly. 

> 
> Since ILL only provides access via SFTP and everything else is not existent or blocked (not even ssh is possible),
> this is the only thing we can work with by now. 
> 

Oops. SFTP != FTP.

SFTP uses SSH for data transport, so we cannot do it directly from C++ code in MIDAS. (we could use libssh, etc, but...)

I suggest you use lazylogger with the lazy_dache script, replace "dccp" with "sftp", replace "nsls" with an sftp "ls" command.

If you get it working, please consider contributing your lazylogger script to midas. (and does not have to be written in perl, python should work equally well).

For setting up lazylogger with the script method, I am pretty sure I posted the instructions to the forum (ages ago),
let me know if you cannot find them.

Good luck.

K.O.

Dear All,

At our experiment we write ROOT files. When starting/stopping runs we get the following error messages:

[Logger,ERROR] [mlogger.cxx:3358:root_write,ERROR] Cannot write system event into ROOT file, event_id 0xffff8000

[Logger,ERROR] [mlogger.cxx:3358:root_write,ERROR] Cannot write system event into ROOT file, event_id 0xffff8001

Looking into the source code I found that log_write (line 4248) sends these Midas System Events (BOR,EOR) to root_write without filtering them. root_write() checks in a first step if it gets such Midas System Events and if yes, moans.

Wouldn't it be better just to filter these events in log_write, before calling root_write, avoiding unnecessary error messages?

Is there something I miss?

Thanks,
  Andreas

> [Logger,ERROR] [mlogger.cxx:3358:root_write,ERROR] Cannot write system event into ROOT file, event_id 0xffff8000

Hi, Andreas, please open a bug report for this problem on bitbucket, there is now at least 2 bugs against
the ROOT writer (some events are written in duplicate sometimes), and I hope to fix this next time i review
the mlogger (RSN!). Biggest problem is that I do not use the ROOT output myself, so I have no way
to know if ROOT files produced by mlogger are correct or make sense. (without setting up some kind
of test environment with a ROOT file reader.

Thank you for reporting this problem here, so more people know about it.

If somebody has a patch to fix this, please send it in!

K.O.

Dear simplest solution seems to me to just remove the error message generation and silently ignore the BOE EOR events. 

Committed that change.

Stefan

Hi Stefan,

I think this only partially resolves the issue, in log_write:

#ifdef HAVE_ROOT
   } else if (log_chn->format == FORMAT_ROOT) {
      status = root_write(log_chn, pevent, pevent->data_size + sizeof(EVENT_HEADER));
#endif
   }

   actual_time = ss_millitime();
   if ((int) actual_time - (int) start_time > 3000)
      cm_msg(MINFO, "log_write", "Write operation on \'%s\' took %d ms", log_chn->path.c_str(), actual_time - start_time);

   if (status != SS_SUCCESS && !stop_requested) {
      cm_msg(MTALK, "log_write", "Error writing output file, stopping run");
      cm_msg(MERROR, "log_write", "Cannot write \'%s\', error %d, stopping run", log_chn->path.c_str(), status);
      stop_the_run(0);

      return status;
   }

In your solution root_write returns quietly but status == SS_INVALID_FORMAT (not SS_SUCCESS) and hence I get another misleading error message "Error writing output file, stopping run".

In order to prevent this you also would need to change the return value to SS_SUCCESS.

Ok, changed.

Stefan

• write a custom parser in C++ using the instructions contained in the Mhformat page;
  
• call the mhist program from within my application;
  
• call the mhdump program from within my application;
  

<p>[quote=&quot;Pintaudi Giorgio&quot;]Dear MIDAS people, I need to borrow your 
wisdom for a bit. I am developing a piece of software that should read the history data 
stored in a [FONT=Times New Roman].midas[/FONT] file (MIDAS format) and integrate it 
into the WAGASCI data quality output. In other words, I need to read some temperature 
values stored in a [FONT=Times New Roman].midas[/FONT] file and compare them with 
the MPPC gains and check for temperature/gain dependence. I see three possibilities: 
[LIST] [*] write a custom parser in C++ using the instructions contained in the 
[URL=https://midas.triumf.ca/MidasWiki/index.php/Mhformat]Mhformat page[/URL]; [*] call 
the mhist program from within my application; [*] call the mhdump program from within my 
application; [/LIST] [B]Which solution do you think is the best?[/B] Because there is no 
need for raw performance, if possible, I would like to write my application in Python3 but 
C++ is also an option. [/quote]</p>

(Please write messages in plain text format, thank you)

The format of .hst midas history files is pretty simple and mhdump.cxx is an easy to read 
illustration on how to read it from basic principles (without going through the midas library, 
which can be somewhat complicated). The newer "FILE" format for history is even simpler 
to read because it is just fixed-record-size binary data prepended by a text header.

You can also use the mh2sql program to import history data into an sql database (mysql 
and sqlite should work) or to convert .hst files to "FILE" format files. This works well
for "archiving" history data, because the "FILE" format works better for looking at old data,
and for looking at data in "months" or "years" timescale.

Back to your question, you can certainly use "mhdump" as is, using a pipe (popen()), or 
you can package mhdump.cxx as a c++ class and use it in your application. If you go this 
route, your contribution of such a c++ class back to midas would be very welcome.

You can also use mhist, but the mhist code cannot be trivially packaged as a c++ class
to use in your application.

You can also suggest that we write an easier to use history utility, we are always open to 
suggested improvements.

Let us know how it works out for you. Good luck!

K.O.