> > A feature I always missed (or just missed to find in the docu) is the following:
> > 1) It would be nice to have a command in odbedit which allows to check how full
> > the ODB currently is.
> > 2) Even more important: I would like to have an ODB routine which allows me to
> > check the fill level of the ODB, and/or a routine which tells me if I would
> > create a structure of given size that it still fits in the current ODB or not. 
> > The use case is that some clients create on the fly ODB entries and I would like
> > to make sure before hand the ODB's remaining space in order not to crash things
> > by overfilling the ODB. 
> 
> If you do "mem" in odbedit, you see the currently free areas, one for the keys themselves, one for 
> the data of the keys. The corresponding C function is db_show_mem. At the moment it outputs the 
> list of free blocks as a long ASCII string, but if necessary I can write a variant which returns the 
> number of free bytes.
> 
> Stefan

Thanks for the info, and yes a variant of db_show_mem returning the number of free bytes would be just
prefect!

For us it would be a handy feature if history data could be requested directly
from a custom page (time range or run based intervals) . Here I am not talking
about history plots but I am talking about recorded time series data. This way
we could easily generate useful graphs. For instance, if we measure the voltage
(constant current) while cooling, we could instantly get the resistance versus
temperature. Often we would like to 'correlate' recorded slow control data.

Is it already possible to extract history data the way suggested?

When using a slowcontrol frontend which operates a device using the multi class
driver the current midas version (ec3225902d6) has the following issue:

There is a row labeled with: All Input Output

So far by clicking e.g. on Input, only the Input related part was displayed, etc.

Currently this leads to the following error message: 

Error: cannot find key LS336/Variables/Input

where LS336 is my DD.

I like the new history system very much, but I stumbled over a couple of issues.
I used the version "Thu Aug 29 08:24:29 2019 +0200 -
midas-2019-06-b-244-gdd6585bb on branch develop":

1) it would be nice to have an option to format the label output (see attachment 1)

2) the background of a history plot is very handy if you only show one measure.
If you have multiple ones (see attachment 2), this is not the case anymore. It
would be nice if the background could be enabled/disabled.

> During my visit at TRIUMF we rewrote the history plotting functionality of
midas. Instead of 
> static GIF images, we have now interactive JavaScript panels where we can
scroll, zoom, 
> inspect values and much more (example is attached). We are now in a state
where this is still 
> work in progress, but already at this stage it might be useful for others to
report any 
> feedback.
> 
> Simply upgrade the the newest develop branch of midas, and you will see two
menu items 
> "OldHistory" which is the old system and "History" which is the new system. In
the new 
> system, you can drag with the mouse to scroll, use the mouse wheel to zoom in
and out the 
> time axis, and hover with your mouse over data points to see its value. If you
zoom out, 
> old data is loaded automatically in the background.
> 
> Following items are planned, but not yet implemented:
> 
> - Printing of run markers as in the old history
> 
> - Delete old data in the buffer to limit memory consumption if the browser
window is 
>    open for very long (weeks)
> 
> - Implement time interval selector (clock icon, select "last day", "last 8
hours" etc.)
> 
> - New settings dialog as a floating dialog box. At the moment, the setting
page of the 
>    old history system is used
> 
> - Export / Printing / Sending to ELOG any history plot
> 
> - Implement a formula for plotting data, such as "y = 12 * (x-14) +32". This
will replace 
>    the old "offset" and "factor" and is more flexible. The formula can be
passed directly 
>    to the JavaScript engine and will be executed on the web page. It should be
also 
>    possible to combine different channels, like the difference of two history
values.
> 
> - Determine the number of digits for variable display from the axis limits.
Like if a value 
>    changes between 520001 and 520002 only, we need more digits than the usual 6.
> 
> Many of these things will be implemented in the next weeks. If you have any
more idea 
> or find some bugs, please report back to me.
> 
> Best,
> Stefan for the midas team

> > 2) the background of a history plot is very handy if you only show one measure.
> > If you have multiple ones (see attachment 2), this is not the case anymore. It
> > would be nice if the background could be enabled/disabled.
> 
> Looking at your plot, even without the background things look messy. Please note
> that you can display only a single curve by double clicking on it (and back with Escape).
> If all curves are on top of each other, you can get them apart a bit by zooming
> in to the vertical axis, then double click. Let ma know if that works for you.

This I found out, yet the attachment here shows another case where it would be useful to be
able to disable the background, namely if you have positive and negative measures in one
plot. Somehow it suggests that CH1 and CH2 show very different values, whereas it is only a
difference in the sign of this variables.

It's not all the important but I would like to mention this is the early stage before
everything is fully frozen.

Our typical use case is that a lot of people are connected to the experiment
having some history tabs open most of the time. Hence, I setup a test system and
connect to it from all kind of systems/browsers. What I see currently quite
often is the error hs_read_arraybuffer (see the attachement).

For firefox 60.8.0esr this can result into a full freeze of the tab and only
closing it is possible.

For chromium based browsers you eventually get a popup informing that it is not
responsive anymore.

The worst though is safari 12.1.2 which not only freezes the tab, but
reproducibly crashes the mhttpd on the server side.

Are there ways to get a log which would document where the problems start?  

> On the mhttpd side, please capture the stack trace from the crash: enable 
> core dumps (ODB "/experiment/enable core dumps" set to "y", after the crash, 
> run "ls -l core.*; gdb mhttpd core.9999") or run mhttpd inside gdb or attach 
> gdb to a running mhttpd (gdb -p 9999). Once in gdb, run "info thr" to list all 
> threads, "thr 0; bt", "thr 1; bt", etc to get stack traces from all threads, only 
> one of them contains the crash (tedious!).
> 
> Email me the stack trace (or post here), in case we want to look at values
> of any variables from the crash, keep the core dump and do not rebuild 
> mhttpd.
> 
> K.O.

here comes the stack trace (only happens when using safari 12.1.2 macOS 10.14.6):

(gdb) thr 1
[Switching to thread 1 (Thread 0x7f57ceffd700 (LWP 3538))]
#0  0x00007f57f29fe377 in raise () from /lib64/libc.so.6
(gdb) bt
#0  0x00007f57f29fe377 in raise () from /lib64/libc.so.6
#1  0x00007f57f29ffa68 in abort () from /lib64/libc.so.6
#2  0x00007f57f330e7d5 in __gnu_cxx::__verbose_terminate_handler() () from
/lib64/libstdc++.so.6
#3  0x00007f57f330c746 in ?? () from /lib64/libstdc++.so.6
#4  0x00007f57f330c773 in std::terminate() () from /lib64/libstdc++.so.6
#5  0x00007f57f330c993 in __cxa_throw () from /lib64/libstdc++.so.6
#6  0x00007f57f330cf2d in operator new(unsigned long) () from /lib64/libstdc++.so.6
#7  0x00007f57f336ba19 in std::string::_Rep::_S_create(unsigned long, unsigned long,
std::allocator<char> const&)
    () from /lib64/libstdc++.so.6
#8  0x00007f57f336c62b in std::string::_Rep::_M_clone(std::allocator<char> const&,
unsigned long) ()
   from /lib64/libstdc++.so.6
#9  0x00007f57f336ccfc in std::basic_string<char, std::char_traits<char>,
std::allocator<char> >::basic_string(std::string const&) () from /lib64/libstdc++.so.6
#10 0x000000000041ce0f in check_digest_auth (hm=hm@entry=0x7f57ceffc520, auth=0x74b060
<auth_mg>)
    at /home/nemu/nemu/tmidas/midas/progs/mhttpd.cxx:17143
#11 0x0000000000452a61 in handle_http_message (msg=0x7f57ceffc520, nc=0x2019ca0,
this=<optimized out>, 
    this=<optimized out>, this=<optimized out>) at
/home/nemu/nemu/tmidas/midas/progs/mhttpd.cxx:17703
#12 handle_http_event_mg (nc=nc@entry=0x2019ca0, ev=ev@entry=100,
ev_data=ev_data@entry=0x7f57ceffc520)
    at /home/nemu/nemu/tmidas/midas/progs/mhttpd.cxx:17753
#13 0x0000000000464c4b in mg_call (nc=nc@entry=0x2019ca0, 
    ev_handler=0x4521f0 <handle_http_event_mg(mg_connection*, int, void*)>, ev=100, 
    ev_data=ev_data@entry=0x7f57ceffc520) at
/home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:2120
#14 0x000000000046790e in mg_http_call_endpoint_handler (nc=nc@entry=0x2019ca0,
ev=<optimized out>, 
    hm=hm@entry=0x7f57ceffc520) at /home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:4946
#15 0x0000000000467e3f in mg_http_handler (nc=nc@entry=0x2019ca0, ev=ev@entry=3, 
    ev_data=ev_data@entry=0x7f57ceffcb2c) at
/home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:5139
#16 0x0000000000464c4b in mg_call (nc=nc@entry=0x2019ca0, 
    ev_handler=0x467a20 <mg_http_handler(mg_connection*, int, void*)>,
ev_handler@entry=0x0, ev=ev@entry=3, 
    ev_data=ev_data@entry=0x7f57ceffcb2c) at
/home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:2120
#17 0x0000000000464fb7 in mg_recv_common (nc=nc@entry=0x2019ca0,
buf=buf@entry=0x7f57c0000cd0, len=len@entry=279)
    at /home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:2676
#18 0x00000000004659c8 in mg_if_recv_tcp_cb (len=279, buf=0x7f57c0000cd0, nc=0x2019ca0)
    at /home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:2680
#19 mg_read_from_socket (conn=0x2019ca0) at
/home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:3378
#20 mg_mgr_handle_conn (nc=0x2019ca0, fd_flags=1, now=now@entry=1568705761.3290441)
    at /home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:3511
#21 0x0000000000465ee0 in mg_mgr_poll (mgr=mgr@entry=0x7f57ceffcda0,
timeout_ms=timeout_ms@entry=1000)
    at /home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:3687
#22 0x0000000000466085 in per_connection_thread_function (param=0x2019ca0)
    at /home/nemu/nemu/tmidas/midas/progs/mongoose6.cxx:3805
#23 0x00007f57f39c7ea5 in start_thread () from /lib64/libpthread.so.0
#24 0x00007f57f2ac68cd in clone () from /lib64/libc.so.6

I am currently testing the new history system on the mhttpd side and stumbled over the following issue: typically our user open a lot of midas web-page tabs and keep them open. With the current version this leads after a night typically to a state where the browser is busy with itself and not reacting anymore.

One important reason seems to be that ALL tabs trying to communicate all the time which is totally unnecessary, since I think a hidden tab should stay in a sleeping mode. 

I was browsing if there is a way to find out if a tab is active or not, and found the following API which exactly does this:

https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API

Furthermore, the simple

document.hidden 

tag, could be used to find out if the page is currently active.

Wouldn't it a good idea to send all midas tabs which are not active into a sleep mode and only reactivate them if they come into focus?

I had a quick look at the JavaScript libs of midas, but I am not quite certain where to best inject this. 

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

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.

> > For my analyzer I generate the experim.h file from the odb.
This issue is still open. Shouldn't midas.h provide the 'new' data types as typedefs like  

typedef int INT32;

etc. Of course you would need to deal with all the supported targets and wrap it accordingly.

A.S.

> > 
> > Before midas commit 13c3b2b this generates structs with INT data types. compiles fine with my analysis code (using the old mana.cpp)
> > 
> > newer midas versions generate INT32, ... types. I get a 
> > 
> > ‘INT32’ does not name a type   
> > 
> > although I include midas.h 
> > 
> > how to fix this?
> 
> You could run experim.h through "sed" to replace the "wrong" data types with the correct data types.
> 
> You can also #define the "wrong" data types before doing #include experim.h.
> 
> I put your bug report into our bug tracker, but for myself I am very busy
> with the alpha-g experiment and cannot promise to fix this quickly.
> 
> https://bitbucket.org/tmidas/midas/issues/289/int32-types-in-experimh
> 
> Here is an example to substitute things using "sed" (it can also do "in-place" editing, "man sed" and google sed examples)
> sed "sZshm_unlink(.*)Zshm_unlink(SHM)Zg"
> 
> K.O.

Hi,

if I check out midas and try to configure it with 

cmake ../ -DCMAKE_INSTALL_PREFIX=/usr/local/midas

I do get the error messages:

  Target "midas" INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<path>/tmidas/midas/include"

  which is prefixed in the source directory.

Is the cmake setup not relocatable? This is new and was working until recently:

MIDAS version:      2.1
GIT revision:       Thu May 27 12:56:06 2021 +0000 - midas-2020-08-a-295-gfd314ca8-dirty on branch HEAD
ODB version:        3

> > cmake ../ -DCMAKE_INSTALL_PREFIX=/usr/local/midas
> > Is the cmake setup not relocatable? This is new and was working until recently:
> 
> Indeed. Not relocatable. This is because we do not install the header files.
> 
> When you use the CMAKE_INSTALL_PREFIX, you get MIDAS "installed" in:
> 
> prefix/lib
> prefix/bin
> $MIDASSYS/include <-- this is the source tree and so not "relocatable"!
> 
> Before, this was kludged and cmake did not complain about it.
> 
> Now I changed cmake to handle the include path "the cmake way", and now it knows to complain about it.
> 
> I am not sure how to fix this: we have a conflict between:
> 
> - our normal way of using midas (include $MIDASSYS/include, link $MIDASSYS/lib, run $MIDASSYS/bin)
> - the cmake way (packages *must be installed* or else! but I do like install(EXPORT)!)
> - and your way (midas include files are in $MIDASSYS/include, everything else is in your special location)
> 
> I think your case is strange. I am curious why you want midas libraries to be in prefix/lib instead of in 
> $MIDASSYS/lib (in the source tree), but are happy with header files remaining in the source tree.
> 
> K.O.

We do it this way, since the lib and bin needs to be in a place where standard users have no access to. 
If I think an all other packages I am working with, e.g. ROOT, the includes are also installed under CMAKE_INSTALL_PREFIX. 
Up until recently there was no issue to work with CMAKE_INSTALL_PREFIX, accepting that the includes stay under 
$MIDASSYS/include, even though this is not quite the standard way, but no problem here. Anyway, since CMAKE_INSTALL_PREFIX 
is a standard option from cmake, I think things should not "break" if you want to use it.

A.S.

> > > > cmake ../ -DCMAKE_INSTALL_PREFIX=/usr/local/midas
> > > > Is the cmake setup not relocatable? This is new and was working until recently:
> > > Not relocatable. This is because we do not install the header files.
> > 
> > We do it this way, since the lib and bin needs to be in a place where standard users have no access to. 
> 
> hmm... i did not get this. "needs to be in a place where standard users have no access to". what do you
> mean by this? you install midas in a secret location to prevent somebody from linking to it?
> 

This was a wrong wording from my side. We do not want the the users have write access to the midas installation libs and bins.
I have submitted the pull request which should resolve this without interfere with your usage.
Hope this will resolve the issue.

> > > > > > cmake ../ -DCMAKE_INSTALL_PREFIX=/usr/local/midas
> > > > > > Is the cmake setup not relocatable? This is new and was working until recently:
> > > > > Not relocatable. This is because we do not install the header files.
> > > > 
> > > > We do it this way, since the lib and bin needs to be in a place where standard users have no access to. 
> > > 
> > > hmm... i did not get this. "needs to be in a place where standard users have no access to". what do you
> > > mean by this? you install midas in a secret location to prevent somebody from linking to it?
> > > 
> > 
> > This was a wrong wording from my side. We do not want the the users have write access to the midas installation libs and bins.
> > I have submitted the pull request which should resolve this without interfere with your usage.
> > Hope this will resolve the issue.
> 
> Excellent. I think it is good to have midas "install" in a sane manner.
> 
> But I still struggle to understand what you do. Presumably you can "install" midas
> in the "midas account", which is not writable by the experiment and user accounts.
> Then it does not matter if you "install" it in it's build directory (like we do)
> or in some other location (like you do now).
> 
> This does not work of course if you only have one account, so do you build midas
> as root? or install it as root?
> 

We work the following way: there is a production Midas under let's say /usr/local/midas (make install as sudo/root). This is for the running experiment. Since we are doing muSR, we 
have experiments on a daily base, rather than month and years as it is the case for a particle physics experiment. Now, still we would like to test updates, new features of Midas on 
the same machine. For this we us the repo directly. If we are happy with the new feature, and fixes, we again do a 'make install' and hence freeze for the production a specific 
snapshot. Of course we could use various local copies of the Midas repo, but over the last years this approach was very convenient and productive. Hope this explains a bit better 
why we want to work with a CMAKE_INSTALL_PREFIX.

AS

Dear Konstantin,

I have tried your adopted version. You did already quite a job which is more consistent than what I was suggesting.
Yet, I still have a problem (git sha2 2d3872dfd31) when starting on a clean system (i.e. no midas present yet): 
Without CMAKE_INSTALL_PREFIX set, everything is fine. 
However, when setting CMAKE_INSTALL_PREFIX, I get the following error message on the build level (cmake --build ./ -- VERBOSE=1) from the manalyzer:

[ 32%] Building CXX object manalyzer/CMakeFiles/manalyzer.dir/manalyzer.cxx.o
cd /home/l_musr_tst/Tmp/midas/build/manalyzer && /usr/bin/c++  -DHAVE_FTPLIB -DHAVE_MIDAS -DHAVE_ROOT_HTTP -DHAVE_THTTP_SERVER -DHAVE_TMFE -DHAVE_ZLIB -D_LARGEFILE64_SOURCE -I/home/l_musr_tst/Tmp/midas/manalyzer -I/usr/local/root/include  -O2 -g -Wall -Wformat=2 -Wno-format-nonliteral -Wno-strict-aliasing -Wuninitialized -Wno-unused-function -std=c++11 -pipe -fsigned-char -pthread -DHAVE_ROOT -std=gnu++11 -o CMakeFiles/manalyzer.dir/manalyzer.cxx.o -c /home/l_musr_tst/Tmp/midas/manalyzer/manalyzer.cxx
In file included from /home/l_musr_tst/Tmp/midas/manalyzer/manalyzer.cxx:14:0:
/home/l_musr_tst/Tmp/midas/manalyzer/manalyzer.h:13:21: fatal error: midasio.h: No such file or directory
 #include "midasio.h"
                     ^
compilation terminated.

Obviously, still some include paths are missing. I tried quickly to see if an easy fix is possible, but I failed.

Question: is it possible to use manalyzer without midas? I am asking since the MIDAS_FOUND flag is confusing me.

> big thanks to Andreas S. for getting most of this figured out. I now understand
> much better how cmake installs things and how it generates config files, both
> find_package(midas) style and install(export) style.
> 
> with the latest updates, CMAKE_INSTALL_PREFIX should work correctly. I now understand how it works,
> how to use it and how to test it, it should not break again.
> 
> for posterity, my commends to Andreas's pull request:
> 
> thank you for providing this code, it was very helpful. at the end I implemented things slightly differently. It took me a while to understand that I have to provide 2 “install” modes, for your case, I need to 
> “install” the header files and everything works “the cmake way”, for our normal case, we use include files in-place and have to include all the git submodules to the include path. I am quite happy with the 
> result. K.O.
> 
> K.O.

midas version used: midas-2019-05-cxx-1461-g906be8b

I find in the systemd log every couple of days/weeks the following error message related to the mhttpd:

[mhttpd,ERROR] [mhttpd.cxx:18886:on_work_complete,ERROR] Should not send response to request from socket 28 to socket 26, abort!

with various socket numbers of course.

Can anybody hint me what is going wrong here?

The bad thing on the crash is, that sometimes it is leading to a "chain-reaction" killing multiple midas frontends, which essentially stop the experiment.

Help would be very much appreciated!

Andreas 

Dear Konstantin,

thanks for the prompt response, this helps a lot!

> 1) If you see a way to replicate this crash, or some way to reliably cause
> the crash within 5-10 minutes after starting mhttpd, please let me know. I can work with that
> and I wish to fix this problem very much.

I wished I could! This happens 3-4 times per year only, so close to impossible to trigger.

> 2) My "wrong socket" check calls abort() to produce a core dump. In my experience these core dumps
> are useless for debugging the present problem. There is just no way to examine the state of each
> thread and of each http request using gdb by hand.
> 
> 3) this abort() causes linux to write a core dump, this takes a long time and I think it causes
> other MIDAS program to stop, timeout and die. You can try to fix this by disabling core dumps (set "enable core dumps"
> to "false" in ODB and set core dump size limit to 0), or change abort() to exit(). (You can also disable
> the "wrong socket" check, but most likely you will not like the result).
> 

I changed now to exit() rather than abort on the production machine. Perhaps this should be the default?

Andreas

Hi Stefan and Zaher,

there is a problem with the new sequencer interface for midas.

If I understand the msequencer code correctly:
Under '/Sequencer/State/Path' the path can be defined from where the msequencer gets the files, generates the xml, etc.
However, the new javascript code reads/writes the files to '<exp>/userfiles/sequencer/'

If the path in the ODB is different to '<exp>/userfiles/sequencer/', it leads to quite some unexpected behavior. If '<exp>/userfiles/sequencer/' is the place where things should go, the ODB entry of the msequencer and the internal handling should probably adopted, no?

Andreas

> Dear beloved MIDAS users,
> 
> I'm happy to announce a "holiday update" for MIDAS. In countless hours, Zaher from 
> PSI worked hard to introduce syntax highlighting in the midas script editor. In 
> addition, there are additional features like a cleaner user interface, the option 
> to see all variables also in non-debug mode and more. Have a look at the picture 
> below, doesn't it beginning to look a lot like Christmas?
> 
> We have tested this quite a bit and went through many iterations, but no guarantee 
> that it's flawless. So please report any issue here.
> 
> I wish you all a happy holiday season,
> Stefan

> > If I understand the msequencer code correctly:
> > Under '/Sequencer/State/Path' the path can be defined from where the msequencer gets the files, generates the xml, etc.
> > However, the new javascript code reads/writes the files to '<exp>/userfiles/sequencer/'
> > 
> > If the path in the ODB is different to '<exp>/userfiles/sequencer/', it leads to quite some unexpected behavior. If '<exp>/userfiles/sequencer/' is the place where things should go, the ODB entry of the msequencer and the internal handling should probably adopted, no?
> 
> Indeed there is a change in philosophy. Previously, /Sequencer/State/Path could point anywhere in the file system. This was considered a security problem, since one could access system files under /etc for example via the midas interface. When the new file API was 
> introduced recently, it has therefor been decided that all files accessible remotely should reside under <exp>/userfiles. If an experiment needs some files outside of that directory, the experiment could define some symbolic link, but that's then in the responsibility of 
> the experiment. 
> 
> To resolve now the issue between the sequencer path and the userfiles, we have different options, and I would like to get some feedback from the community, since *all experiments* have to do that change.
> 
> 1) Leave thins as they are, but explain that everybody should modify /Sequencer/Stat/Path to some subdirectory of <exp>/userfiles/sequencer
> 
> 2) Drop /Sequencer/State/Path completely and "hard-wire" it to <exp>/usefiles/sequencer
> 
> 3) Make /Sequencer/State/Path relative to <exp>/userfiles. Like if /Sequencer/State/Path=test would then result to a final directory <exp>/userfiles/sequencer/test
> 
> I'm kind of tempted to go with 3), since this allows the experiment to define different subdirectories under <exp>/userfiles/sequencer/... depending on the situation of the experiment.
> 
> Best,
> Stefan

For me the option 3) seems the most coherent one.
Andreas