===================================================================================
[lm17773@it038146 ~]$ cd /opt/midas_software/midas/bin/
[lm17773@it038146 bin]$ fetest
Frontend name          :     fetest
Event buffer size      :     10485760
User max event size    :     4194304
User max frag. size    :     4194304
# of events per buffer :     2

Connect to experiment sampleexpt...
[fetest,ERROR] [odb.cxx:1646:db_open_database,ERROR] Removed ODB client 'Logger', index 1 because process pid 22659 does not exists
[fetest,ERROR] [odb.cxx:1646:db_open_database,ERROR] Removed ODB client 'mhttpd', index 2 because process pid 20257 does not exists
[fetest,INFO] Removed open record flag from "/Experiment/Security/RPC hosts/Allowed hosts"
[fetest,INFO] Removed exclusive access mode from "/Experiment/Security/RPC hosts/Allowed hosts"
[fetest,INFO] Removed open record flag from "/Experiment/Security/mhttpd hosts/Allowed hosts"
[fetest,INFO] Removed exclusive access mode from "/Experiment/Security/mhttpd hosts/Allowed hosts"
[fetest,INFO] Removed open record flag from "/Logger/Channels/0/Settings"
[fetest,INFO] Removed exclusive access mode from "/Logger/Channels/0/Settings"
[fetest,INFO] Removed open record flag from "/Logger/Channels/0/Statistics"
[fetest,INFO] Removed exclusive access mode from "/Logger/Channels/0/Statistics"
[fetest,INFO] Removed open record flag from "/Logger/History"
[fetest,INFO] Removed exclusive access mode from "/Logger/History"
[fetest,INFO] Removed open record flag from "/Sequencer/State"
[fetest,INFO] Removed exclusive access mode from "/Sequencer/State"
[fetest,INFO] Removed open record flag from "/History/LoggerHistoryChannel"
[fetest,INFO] Removed exclusive access mode from "/History/LoggerHistoryChannel"
[fetest,INFO] Removed open record flag from "/Equipment/slow/Variables"
[fetest,INFO] Removed exclusive access mode from "/Equipment/slow/Variables"
[fetest,INFO] Removed open record flag from "/Equipment/Trigger/Statistics/Events per sec."
[fetest,INFO] Removed exclusive access mode from "/Equipment/Trigger/Statistics/Events per sec."
[fetest,INFO] Removed open record flag from "/Equipment/Trigger/Statistics/kBytes per sec."
[fetest,INFO] Removed exclusive access mode from "/Equipment/Trigger/Statistics/kBytes per sec."
[fetest,INFO] Removed open record flag from "/Equipment/Periodic/Variables"
[fetest,INFO] Removed exclusive access mode from "/Equipment/Periodic/Variables"
[fetest,INFO] Removed open record flag from "/Equipment/Scaler/Variables"
[fetest,INFO] Removed exclusive access mode from "/Equipment/Scaler/Variables"
[fetest,INFO] Corrected 12 ODB entries
[fetest,INFO] Deleted entry '/System/Clients/20257' for client 'mhttpd' because it is not connected to ODB
OK
Init hardware...frontend_init!
Event size set to 10240 bytes
Ring buffer wait sleep 1 ms
OK
time 1564130782, data 91.354546
time 1564130783, data 93.358040
time 1564130784, data 95.105652
time 1564130785, data 96.592583
time 1564130786, data 97.814758
time 1564130787, data 98.768837
time 1564130788, data 99.452187
time 1564130789, data 99.862953
time 1564130790, data 100.000000
time 1564130791, data 99.862953
Warning: bank RND4 has zero size
time 1564130792, data 99.452187
time 1564130793, data 98.768837
time 1564130794, data 97.814758
time 1564130795, data 96.592583
Received break. Aborting...
frontend_exit!
Frontend shut down.
[lm17773@it038146 bin]$ 
=================================================================================



> > Hi,
> > 
> > We've been trying to run Fetest in the attempt of plotting the sine wave data on
> > the history page on the web server. However each time we've tried running a new
> > plot we have come across the error of 'no data' from the variables. In the
> > status page we are clearly obtaining data from the frontend and it is updating
> > the variable as expected in SLOW.
> > 
> > When setting up MIDAS we managed to produce a history plot from Fetest but are
> > unable to do so any longer. We did have a go at modifying the Fetest code but
> > created a backup before doing so and are now running the original backup.
> > 
> > What could be causing the Fetest data not to be showing in the history plot?
> 
> Is the logger running? (this application is handling the history data).
> If yes: Did you change the variable names? If yes: restart the logger.

Hi,
I have a bank of floats with slow control values that I store to the history and
ODB. When reading the history, both in the webbrowser and with mhist, the floats
get read with the wrong endianness; under /equipment/variables in the ODB they
however display correctly. System is a an intel OpenSuse linux box. Any ideas?

Thanks

Nik

Ok, so the detail that I missed was that the dummy functions

INT poll_event(INT source[], INT count, BOOL test)
{
   return 1;
};

as shown in some of the older examples, work when you set

INT poll_event(INT source, INT count, BOOL test)
{
   return 1;
};


as a side comment, not all drivers are c++ compatible yet (e.g. mscbvr), so changes needed are small 

=================================================================
[lm17773@it038146 bin]$ fetest
Frontend name          :     fetest
Event buffer size      :     10485760
User max event size    :     4194304
User max frag. size    :     4194304
# of events per buffer :     2

Connect to experiment sampleexpt...
OK
Init hardware...frontend_init!
Event size set to 10240 bytes
Ring buffer wait sleep 1 ms
OK
time 1564044856, data 74.314484
time 1564044857, data 77.714600
time 1564044858, data 80.901703
time 1564044859, data 83.867058
time 1564044860, data 86.602539
time 1564044861, data 89.100655
time 1564044862, data 91.354546
time 1564044863, data 93.358040
time 1564044864, data 95.105652
time 1564044865, data 96.592583
Warning: bank RND4 has zero size
time 1564044866, data 97.814758
time 1564044867, data 98.768837
time 1564044868, data 99.452187
time 1564044869, data 99.862953
time 1564044870, data 100.000000
time 1564044872, data 99.452187
time 1564044873, data 98.768837
Warning: bank RND6 has zero size
time 1564044874, data 97.814758
Received break. Aborting...
frontend_exit!
Frontend shut down.
[lm17773@it038146 bin]$ 
===========================================================================



10:00:56.999 2019/07/25 [fetest,INFO] Program fetest on host localhost stopped

10:00:32.483 2019/07/25 [mhttpd,INFO] Run #29 stopped

09:59:10.666 2019/07/25 [fetest,INFO] Program fetest on host localhost started

09:59:07.731 2019/07/25 [fetest,INFO] Program fetest on host localhost stopped

09:58:13.700 2019/07/25 [Logger,INFO] Program Logger on host localhost started

09:58:12.707 2019/07/25 [Logger,INFO] Program Logger on host localhost stopped

09:57:19.136 2019/07/25 [mhttpd,INFO] Run #29 started

09:57:18.954 2019/07/25 [Logger,ERROR] [mlogger.cxx:3801:log_create_writer,ERROR] channel  requested GZIP/ZLIB compression, but ZLIB is not available

09:57:15.305 2019/07/25 [mhttpd,INFO] Run #28 stopped

09:55:30.694 2019/07/25 [fetest,INFO] Program fetest on host localhost started

09:54:34.519 2019/07/25 [fetest,INFO] Program fetest on host localhost stopped

09:54:16.852 2019/07/25 [fetest,INFO] Program fetest on host localhost started

09:53:59.554 2019/07/25 [fetest,INFO] Program fetest on host localhost stopped

09:47:25.932 2019/07/25 [mhttpd,INFO] Program mhttpd on host localhost started

09:47:19.863 2019/07/25 [Logger,INFO] Program Logger on host localhost started

09:47:04.116 2019/07/25 [fetest,ERROR] [midas.cxx:6690:cm_shutdown,ERROR] Killing and Deleting client 'fetest' pid 1921

09:47:04.116 2019/07/25 [fetest,ERROR] [midas.cxx:6687:cm_shutdown,ERROR] Cannot connect to client 'fetest' on host 'localhost', port 38595

09:47:04.116 2019/07/25 [fetest,ERROR] [midas.cxx:10497:rpc_client_connect,ERROR] cannot connect to host "localhost", port 38595: connect() returned -1, errno 111 (Connection refused)

09:47:04.116 2019/07/25 [fetest,INFO] Program fetest on host localhost started

09:47:04.116 2019/07/25 [fetest,INFO] Deleted entry '/System/Clients/1613' for client 'mhttpd' because it is not connected to ODB

09:47:04.116 2019/07/25 [fetest,INFO] Corrected 9 ODB entries

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Equipment/random/Statistics"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Equipment/random/Statistics"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Equipment/random/Common"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Equipment/random/Common"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Equipment/slow/Statistics"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Equipment/slow/Statistics"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Equipment/slow/Common"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Equipment/slow/Common"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Equipment/test/Statistics"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Equipment/test/Statistics"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Equipment/test/Common"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Equipment/test/Common"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Sequencer/State"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Sequencer/State"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Experiment/Security/mhttpd hosts/Allowed hosts"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Experiment/Security/mhttpd hosts/Allowed hosts"

09:47:04.116 2019/07/25 [fetest,INFO] Removed exclusive access mode from "/Experiment/Security/RPC hosts/Allowed hosts"

09:47:04.116 2019/07/25 [fetest,INFO] Removed open record flag from "/Experiment/Security/RPC hosts/Allowed hosts"

09:47:04.115 2019/07/25 [fetest,ERROR] [odb.cxx:1646:db_open_database,ERROR] Removed ODB client 'fetest', index 2 because process pid 1921 does not exists

09:47:04.115 2019/07/25 [fetest,ERROR] [odb.cxx:1646:db_open_database,ERROR] Removed ODB client 'mhttpd', index 0 because process pid 1613 does not exists
===========================================================================















> > Hi,
> > 
> > We've been trying to run Fetest in the attempt of plotting the sine wave data on
> > the history page on the web server. However each time we've tried running a new
> > plot we have come across the error of 'no data' from the variables. In the
> > status page we are clearly obtaining data from the frontend and it is updating
> > the variable as expected in SLOW.
> > 
> > When setting up MIDAS we managed to produce a history plot from Fetest but are
> > unable to do so any longer. We did have a go at modifying the Fetest code but
> > created a backup before doing so and are now running the original backup.
> > 
> > What could be causing the Fetest data not to be showing in the history plot?
> 
> Is the logger running? (this application is handling the history data).
> If yes: Did you change the variable names? If yes: restart the logger.

> Hi,
> 
> We've been trying to run Fetest in the attempt of plotting the sine wave data on
> the history page on the web server. However each time we've tried running a new
> plot we have come across the error of 'no data' from the variables. In the
> status page we are clearly obtaining data from the frontend and it is updating
> the variable as expected in SLOW.
> 
> When setting up MIDAS we managed to produce a history plot from Fetest but are
> unable to do so any longer. We did have a go at modifying the Fetest code but
> created a backup before doing so and are now running the original backup.
> 
> What could be causing the Fetest data not to be showing in the history plot?

Is the logger running? (this application is handling the history data).
If yes: Did you change the variable names? If yes: restart the logger.

Can you post the exact command that cmake executes to link sc_fe_mini (with make VERBOSE=1)?

I have noticed similar linking problems that depended on the order when linking. In my case, it 
compiled when "-lpthread -lutil -lrt" were at the end of the command, but not before mfe.o and 
libmidas.a. Unfortunately I haven't found a way to tell cmake the "correct" order of the link 
libraries.

Maybe this can be fixed by adding midas as a subdirectory in your cmake project and just linking 
against the "mfe" target instead of libmfe.a.

Have you left any "extern C" in your frontend program or in any of the used header file. Seems 
like the linker cannot find the poll_event in your frontend code. If it's there, but it's compiled 
with C calling (instead of C++), the name mangling causes it to be invisible to the linker. That 
usually happens if there is somewhere

extern C {
  INT poll_event();
  ... 
}

while it is NOT defined as "extern C" in mfe.h which is used by mfe.cxx.

Stefan

> > Did you include mfe.h as written in elog:1526 ?
> > 
> > Stefan
> 
> 
> Yes I did
> 
> this is my include 
> 
> #include <stdio.h>
> #include <string.h>
> #include <assert.h>
> #include <math.h>
> #include <pthread.h>
> 
> 
> #include "midas.h"
> #include "mscb.h"
> #include "multi.h"
> #include "mscbdev.h"
> #include "mfe.h"
> 
> (I attach my dummy fe)
> 
> What confuses me is that I can compile examples/experiment/ if I copy that to a 
> fresh dir.
> 
> I also copied the CMakeLists from the example:
> 
> #
> # cmake for the muX software
> #
> cmake_minimum_required(VERSION 3.3)
> 
> project(muX)
> 
> #
> # find midas installation, from CMakeLists in examples/experiment
> #
> set(MIDAS_DIR $ENV{MIDASSYS})
> message("MIDAS dir: " ${MIDAS_DIR})
> if (NOT EXISTS $ENV{MIDASSYS})
>   message(FATAL_ERROR "Environment variable $MIDASSYS not defined, aborting.")
> endif()
> 
> set(INC_PATH ${MIDAS_DIR}/include ${MIDAS_DIR}/mxml ${MIDAS_DIR}/mscb/include 
> ${MIDAS_DIR}/drivers/class ${MIDAS_DIR}/drivers/device)
> link_directories($ENV{MIDASSYS}/lib)
> 
> # enable certain compile warnings
> add_compile_options(-Wall -Wformat=2 -Wno-format-nonliteral -Wno-strict-
> aliasing -Wuninitialized -Wno-unused-function)
> 
> set(LIBS -lpthread -lutil -lrt) 
> 
> 
> add_executable(sc_fe_mini sc_fe_mini.cpp)
> target_include_directories(sc_fe_mini PRIVATE ${INC_PATH})
> target_link_libraries(sc_fe_mini mfe midas ${LIBS})

> Did you include mfe.h as written in elog:1526 ?
> 
> Stefan


Yes I did

this is my include 

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <pthread.h>


#include "midas.h"
#include "mscb.h"
#include "multi.h"
#include "mscbdev.h"
#include "mfe.h"

(I attach my dummy fe)

What confuses me is that I can compile examples/experiment/ if I copy that to a 
fresh dir.

I also copied the CMakeLists from the example:

#
# cmake for the muX software
#
cmake_minimum_required(VERSION 3.3)

project(muX)

#
# find midas installation, from CMakeLists in examples/experiment
#
set(MIDAS_DIR $ENV{MIDASSYS})
message("MIDAS dir: " ${MIDAS_DIR})
if (NOT EXISTS $ENV{MIDASSYS})
  message(FATAL_ERROR "Environment variable $MIDASSYS not defined, aborting.")
endif()

set(INC_PATH ${MIDAS_DIR}/include ${MIDAS_DIR}/mxml ${MIDAS_DIR}/mscb/include 
${MIDAS_DIR}/drivers/class ${MIDAS_DIR}/drivers/device)
link_directories($ENV{MIDASSYS}/lib)

# enable certain compile warnings
add_compile_options(-Wall -Wformat=2 -Wno-format-nonliteral -Wno-strict-
aliasing -Wuninitialized -Wno-unused-function)

set(LIBS -lpthread -lutil -lrt) 


add_executable(sc_fe_mini sc_fe_mini.cpp)
target_include_directories(sc_fe_mini PRIVATE ${INC_PATH})
target_link_libraries(sc_fe_mini mfe midas ${LIBS})

Did you include mfe.h as written in elog:1526 ?

Stefan

I am moving our fe code to c++ midas with cmake. I did encounter your a) problems.

How do I solve mismatched declarations in the mfe (or other places in the midas code)? It is having issues with the midas defined BOOL/... types. This 
is what I get for a minimal scfe:

[ 12%] Building CXX object CMakeFiles/sc_fe_mini.dir/sc_fe_mini.cpp.o
[ 25%] Building CXX object CMakeFiles/sc_fe_mini.dir/home/frederik/packages/midas/drivers/class/hv.cxx.o
[ 37%] Building CXX object CMakeFiles/sc_fe_mini.dir/home/frederik/packages/midas/drivers/class/multi.cxx.o
[ 50%] Building CXX object CMakeFiles/sc_fe_mini.dir/home/frederik/packages/midas/drivers/device/nulldev.cxx.o
[ 62%] Building CXX object CMakeFiles/sc_fe_mini.dir/home/frederik/packages/midas/drivers/bus/null.cxx.o
[ 75%] Building CXX object CMakeFiles/sc_fe_mini.dir/home/frederik/packages/midas/drivers/device/mscbdev.cxx.o
[ 87%] Building CXX object CMakeFiles/sc_fe_mini.dir/home/frederik/packages/midas/mscb/src/mscb.cxx.o
[100%] Linking CXX executable sc_fe_mini
/home/frederik/packages/midas/build/libmfe.a(mfe.cxx.o): In function `_readout_thread':
/home/frederik/packages/midas/src/mfe.cxx:1271: undefined reference to `poll_event(int, int, unsigned int)'
/home/frederik/packages/midas/build/libmfe.a(mfe.cxx.o): In function `check_polled_events':
/home/frederik/packages/midas/src/mfe.cxx:1601: undefined reference to `poll_event(int, int, unsigned int)'
/home/frederik/packages/midas/src/mfe.cxx:1643: undefined reference to `poll_event(int, int, unsigned int)'
/home/frederik/packages/midas/build/libmfe.a(mfe.cxx.o): In function `readout_enable(unsigned int)':
/home/frederik/packages/midas/src/mfe.cxx:1158: undefined reference to `interrupt_configure(int, int, long)'
/home/frederik/packages/midas/src/mfe.cxx:1156: undefined reference to `interrupt_configure(int, int, long)'
/home/frederik/packages/midas/build/libmfe.a(mfe.cxx.o): In function `initialize_equipment':
/home/frederik/packages/midas/src/mfe.cxx:614: undefined reference to `interrupt_configure(int, int, long)'
/home/frederik/packages/midas/src/mfe.cxx:649: undefined reference to `poll_event(int, int, unsigned int)'
/home/frederik/packages/midas/build/libmfe.a(mfe.cxx.o): In function `scheduler':
/home/frederik/packages/midas/src/mfe.cxx:1890: undefined reference to `poll_event(int, int, unsigned int)'
/home/frederik/packages/midas/src/mfe.cxx:1932: undefined reference to `poll_event(int, int, unsigned int)'
/home/frederik/packages/midas/build/libmfe.a(mfe.cxx.o): In function `main':
/home/frederik/packages/midas/src/mfe.cxx:2701: undefined reference to `interrupt_configure(int, int, long)'
/home/frederik/packages/midas/src/mfe.cxx:2702: undefined reference to `interrupt_configure(int, int, long)'
collect2: error: ld returned 1 exit status
make[2]: *** [sc_fe_mini] Error 1
make[1]: *** [CMakeFiles/sc_fe_mini.dir/all] Error 2
make: *** [all] Error 2


This is my cmakelists for my user code:

#
# cmake for the muX software
#
cmake_minimum_required(VERSION 3.3)

project(muX)

#
# find installations
#
set(MIDAS_DIR $ENV{MIDASSYS})
message("MIDAS dir: " ${MIDAS_DIR})

#
# set directories
#
set(MIDASBUILD_DIR ${MIDAS_DIR}/build)
set(MIDASINCLUDE_DIR ${MIDAS_DIR}/include)
set(MXML_DIR ${MIDAS_DIR}/mxml)
set(MSCB_DIR ${MIDAS_DIR}/mscb)
set(DRV_DIR ${MIDAS_DIR}/drivers)


#
# drivers, libs
#
set(DRIVERS
    ${MIDAS_DIR}/drivers/class/hv
    ${MIDAS_DIR}/drivers/class/multi
    ${MIDAS_DIR}/drivers/device/nulldev
    ${MIDAS_DIR}/drivers/bus/null
)
set(MIDASLIB ${MIDASBUILD_DIR}/libmidas.a)
set(FELIB ${MIDASBUILD_DIR}/libmfe.a)

#
# sc_fe
#
add_executable(sc_fe_mini
        sc_fe_mini.cpp
        ${DRIVERS}
        ${MIDAS_DIR}/drivers/device/mscbdev
        ${MIDAS_DIR}/mscb/src/mscb)

target_include_directories(sc_fe_mini PRIVATE ${DRV_DIR} ${MIDAS_DIR}/mscb/include ${MIDAS_DIR}/include)
target_link_libraries(sc_fe_mini ${LIBS} ${MIDASLIB} ${FELIB} rt pthread util)



I seem to be able to compile the current midas distributions, including the scfe frontend



> To convert a MIDAS frontend to C++ follow this checklist:
> 
> a) add #include "mfe.h" after include of midas.h and fix all compilation errors.
> 
> NOTE: there should be no "extern C"  brackets around MIDAS include files.
> 
> NOTE: Expect to see following problems:
> 
> a1) duplicate or mismatched declarations of functions defined in mfe.h
> a2) frontend_name and frontend_file_name should be "const char*" instead of "char*"
> a3) duplicate "HNDLE hDB" collision with hDB from mfe.c - not sure why it worked before, either use HNDLE hDB from mfe.h or use "extern HNDLE hDB".
> a4) poll_event() and interrupt_configure() have "source" as "int[]" instead of "int" (why did this work before?)
> a5) use of "extern int frontend_index" instead of get_frontend_index() from mfe.h
> a6) bk_create() last argument needs to be cast to (void**)
> a7) "bool debug" collides with "debug" from mfe.h (why did this work before?)
> 
> b) remove no longer needed "extern C" brackets around mfe related code. Ideally there should be no "extern C" brackets anywhere.
> 
> c) in the Makefile, change CC=gcc to CC=g++ for compiling and linking everything as C++
> 
> c1) fix all compilation problems. most valid C code will compile as valid C++, but there is some known trouble:
> - return value of malloc() & co needs to be cast to the correct data type: "char* s = (char*)malloc(...)"
> - some C++ compilers complain about mismatch between signed and unsigned values
> 
> If you need help with converting your frontend from C to C++, I will be most happy
> to assist you - post your compiler error messages to this forum or email them to me privately.
> 
> Good luck,
> K.O.

Hi,

We've been trying to run Fetest in the attempt of plotting the sine wave data on
the history page on the web server. However each time we've tried running a new
plot we have come across the error of 'no data' from the variables. In the
status page we are clearly obtaining data from the frontend and it is updating
the variable as expected in SLOW.

When setting up MIDAS we managed to produce a history plot from Fetest but are
unable to do so any longer. We did have a go at modifying the Fetest code but
created a backup before doing so and are now running the original backup.

What could be causing the Fetest data not to be showing in the history plot?

Happy summer to everybody.

When programming in general, and when programming MIDAS, there is always a struggle
with error handling. Too much? Too little? Visually, some MIDAS functions are 90% error handling, 10% useful work, if that.

What is the right way to do this?
Where is the balance?
Would c++ exceptions help or hinder?
How to make it better?

It turns out that the Go community have been struggling with exactly this for the last year or so.

Read the (ultimately rejected) proposal for improved error handling in Go. All the problems and difficulties
and struggles facing the programmer and the language designer spread right in front of us.

https://go.googlesource.com/proposal/+/master/design/go2draft-error-handling-overview.md

(To remember, Go is this: https://www.oreilly.com/library/view/the-go-programming/9780134190570/
The language designers are Brian W. Kernighan, Rob Pike, Ken Thompson and "some other people"
(Dennis Ritchie is no longer with us). These people gave us UNIX and C (and C++, the C++ guy was
their next-door-office mate), when that crowd speaks, I listen)

That write-up refers to some blogger's vivid illustration how correct error handling is hard,
with special focus on error handling in the presence of exceptions:

https://devblogs.microsoft.com/oldnewthing/?p=39683
https://devblogs.microsoft.com/oldnewthing/?p=36693

I read all this stuff and said, "wow, this is the reader's digest version of my life in computer programming".

The clincher from this last guy? "My point isn’t that exceptions are bad.
My point is that exceptions are too hard and I’m not smart
enough to handle them."

"back to writing some error handling code",
K.O.

> Message from John M O'Donnell <odonnell@lanl.gov>
>
> the A3818 and MIDAS both used unix alarm signals, resulting in clashes.
>

FWIW, current midas no longer uses alarm signals. See forum messages and git commits about 
removal of cm_watchdog().

K.O.

Message from John M O'Donnell <odonnell@lanl.gov>

Folks,

The following might be related, if so great, if not sorry for the spam.

We had problems with MIDAS/CAEN_A3818 until two things happened:

1) CAEN found the root cause of a problem, as the A3818 and MIDAS both
used unix alarm signals, resulting in clashes.  CAEN modified the
A3818 driver to have a "no alarm" option.

2) after downloading the modified driver, edit src/a3818.c to #define
USE_MIDAS 1 somewhere near the top.

Hope this helps,

John.

Dear Stefan,

another thing which does not work is the comparison of floating point numbers.

The script:

IF 1.1 > 1.0 
    MESSAGE "foo" 
ENDIF 

Produces an error "Invalid number in comparison". This is due to isdigit() being used to find the numerical values in the condition at progs/msequencer.cxx:343.

Would it be possible to add something like the following?
 343 if (!isdigit(value1_var[i]) && value1_var[i] != '.')
 344          break;
Which would only leave open a problem with some string like "2.3.4"

Cheers
Lukas

> > - this will activate the mhttpd password protection, so one would have to define a username and password 
> > in the .htdigest file (this is done by the mongoose web server library).
> 
> Actually I'm thinking since a while to have user-level access to mhttpd, similarly to elog.
>

With per-user login, we have the possibility to add better permissions/access controls. In past
discussions we talked about 3 levels of user access:

- read-only user: can look, but cannot affect anything
- operator: same as read-only user, but can start/stop runs, can clear alarms, can push buttons on custom pages, can cause predefined scripts to run, etc.
- root user: can do everything

Technically, this is easy to implement in the mjsonrpc library: each username will be mapped to a privilege level,
and each rpc request handler will specify minimum required privilege: odb write rpc would require root level,
run start would require operator level, odb read permitted for everybody. This will be enforced inside mhttpd.

>
> Each user has to log in with a unique username/password. After some time of inactivity, you're logged out.
>

For now, we use the password protection built into the apache httpd web server.

It is known to be secure, but it does not have the "advanced" user management functions
that we take for granted with the elog, with wiki pages, with github, etc. Missing are self-registration
with approval, password reset and recovery and so forth.

On the other hand, apache httpd is supposed to be easy to integrate with "enterprise" user management
systems, like the CERN single-sign-on system. (We did not look yet at the integration with the TRIUMF
single-sign-on system, based on Microsoft AD).

(I see the nginx web server is gaining in popularity, but I do not know what features it has
for user and password management).

The elog software does have very good user and password management, and we could bring it into midas,
if we figure out how to ensure that it is actually secure. I know a professional security audit was done
for the elog software and I know that mhttpd will not pass such an audit.

But with some extra work it is possible.

>
> This would have the advantage that one knows who is active where, like when using the chat functionality in mhttpd. Or who started/stopped a run etc. This might not be necessary for simple local installations, but if you have 20 
> people controlling an experiment from three different continents simultaneously, this could be beneficial. Using the elog authentication libraries, one could even forward the login process to LDAP or KERBEROS, 
> so you could log in with out institutional account, and don't have to remember an additional password.
> 
> Just some food for thought.
> 

Some of this food looks very good, indeed.

K.O.

> - this will activate the mhttpd password protection, so one would have to define a username and password 
> in the .htdigest file (this is done by the mongoose web server library).

Actually I'm thinking since a while to have user-level access to mhttpd, similarly to elog. Each user has to log in with a unique username/password. After some time of inactivity, you're logged out. This would have 
the advantage that one knows who is active where, like when using the chat functionality in mhttpd. Or who started/stopped a run etc. This might not be necessary for simple local installations, but if you have 20 
people controlling an experiment from three different continents simultaneously, this could be beneficial. Using the elog authentication libraries, one could even forward the login process to LDAP or KERBEROS, 
so you could log in with out institutional account, and don't have to remember an additional password.

Just some food for thought.

Stefan

> Ubuntu LTS 18.04 does not run a restrictive firewall and access to mhttpd ports 8080 and 8443 is not 
blocked.

Clearly, the present defaults settings of mhttpd are out of date.

The best I remember our internal discussions, we have converged on the following new default settings:

- mhttpd only listens on the localhost interface
- only accepts http (not https)
- password protection is off

These settings allow one to easily test midas on a laptop or on a single-user computer.

They also happen to be the correct settings when using an https proxy (i.e. apache httpd).

If the https proxy cannot be on the same computer, (i.e. ALPHA at CERN):

- one would enable mhttpd to listen on the external network interface
- this will enable the mhttpd access controls (ODB /expt/security/mhttpd hosts/allowed hosts)
- one would allow the https proxy machine access to mhttpd by adding it's hostname to "allowed hosts".

In the case where a separate https proxy cannot be used:

- one would enable https on the external network interface
- one would have to obtain an https certificate (there is possibility of adding certbot integration to mhttpd, 
if there is demand for this)
- this will activate the mhttpd password protection, so one would have to define a username and password 
in the .htdigest file (this is done by the mongoose web server library).

I was planning to implement these changes when I update the mongoose web server library to the latest 
version (fixes a memory leak and improves/simplifies multithreading).

But maybe I should implement them sooner.

I am also thinking of adding a proxy function to mhttps (same as "ProxyPass" in apache httpd), set ODB 
/Proxy/webcam to "http://webcam_on_private_network/magic_webcam_url", and access to 
https://midas/webcam will return the data from the webcam without having to set this up in apache httpd 
(requires root access, etc).

K.O.

> It turns out that unlike CentOS-7, Ubuntu LTS 18.04 does not run a restrictive firewall
> and access to mhttpd ports 8080 and 8443 is not blocked
>
> As result, anybody from anywhere can access mhttpd without a password.
> 

elogd can suffer from the same problem, but not as badly, one can connect to elogd and attempt to run 
exploits, but one cannot access elog entries without a password:

a) default configuration is to ask for a password
b) elogd almost immediately redirects to the https URL specified in the URL entry of the config file, which 
normally points to the https proxy, which also immediately asks for a password.

In the absence of firewall protection (as on Ubuntu), 
add "Interface = 127.0.0.1" to the elog config file or run elogd with "-n localhost",
per instructions at https://elog.psi.ch/elog/config.html 

K.O.

We installed recent mhttpd on a ubuntu machine and discovered a number of problems
with the default mhttpd settings.

We did follow the normal instructions to install and configure an apache https proxy
with a certbot certificate and password protection, this part worked ok. Big thanks
to Lars M. for providing the Ubuntu instructions for apache.

Then we started seeing errors from mhttpd about access to URLs like "manager/html" 
(google "manager/html exploit") that did not go through the proxy.

It turns out that unlike CentOS-7, Ubuntu LTS 18.04 does not run a restrictive firewall
and access to mhttpd ports 8080 and 8443 is not blocked. Then, it turns out that by 
default, the mhttpd access controls are also disabled, and it accepts http requests from 
anywhere/everywhere. Also by default, the mhttpd password is also disabled.

As result, anybody from anywhere can access mhttpd without a password.

One fix for this is to activate the mhttpd access control list by setting ODB 
/Experiment/Security/allowed hosts[0] to "localhost".

K.O.