> I guess we should follow the "standard" as much as possible. MIDASSYS was inspired by
> ROOTSYS. Now where do people usually install ROOT? Is it /opt/root-x.x.x or something
> else. Some years ago (when I did the last time some linux administration) optional
> packages were put into /usr/local by default. I guess you have more experience with
> today's tradition, so do whatever you thing is standard.
I agree that we should follow the standard. 
I used /opt as an example. 
There are several "schools" as to where put things my philosophy is
/usr/{bin,lib,include}       - std OS packages (RPMS, .deb or whatever your flavor likes)
/usr/local/{bin,lib,include} - make/make install packages
/opt/..                      - additional packages (RPMS, ...) 

But it should be up to the user what $MIDASSYS she/he likes.

> 
> > so the Linux binaries would go to 
> > MIDASHOST=i386-pc-linux-gnu
> > $MIDASSYS/$MIDASHOST/bin
> > $MIDASSYS/$MIDASHOST/lib
> 
> Does that mean that the path has to be modified to include $MIDASSYS/$MIDASHOST/bin?
> If we put a link to /usr/local/bin, the path does not have to be modified. What about
> shared libraries? Does ldconfig know about /usr/local/lib, or $MIDASYS/$MIDASHOST/lib?
The path could/should be modified in users .bashrc/.tcshrc or we could provide a simple
system-wide script(s) that would do the job.
For years, I've been using such a scenario on my Linux PCs with regards to various
add-on packages (e.g. cern). 

Here's an example of my cern.sh that goes into /etc/profile.d on my RedHat Linux PC
#===================================
. /etc/profile.d/.functions
export CERN=/cern
export CERN_LEVEL=pro
addpath $CERN/$CERN_LEVEL/bin
#===================================

As for library path: there are several ways (as with exec path)
a) nice way: modify /etc/ld.so.conf by adding $MIDASYS/$MIDASHOST/lib
b) modifying LD_LIBRARY_PATH (there's some security issues with it)
c) symlinking to /usr/local/lib


> 
> What about /usr/share? Is that a common place for documentatino etc?
Yes. Check any recent Linux distribution /usr/share is full of docs, icons, etc.

This is my bias. 

I (obviously) prefer packing things into rpm which makes install/updates 
very easy - especially if you are managing several machines.

Cheers
    Piotr

For a long time the "de facto" standard was to spread a package around in many
directories under /usr/local.  This proved to be a bad idea, as removing the
package
became very difficult.

With POSIX there is a written standard, which says that each pacakge goes in
it's own
directory under /opt. eg. /opt/midas.  Each package gets to define it's own
structure
within that directory.  One could imagine several versions installed at the
same time
/opt/midas/v1.9.2 and /opt/midas/v1.9.4 each with a bin, lib include etc. 
Following the
ROOT example, you could make a link from /opt/midas/pro to
/opt/midas/v1.9.4, so that
system files and login files are easy to maintain etc.  The basic idea is

MIDASSYS=/opt/midas/pro
PATH=$PATH:$MIDASSYS/bin

though a more sophisticated approach is

MIDASSYS=/opt/midas/pro
echo $PATH | grep -q $MIDASSYS || PATH=$PATH:$MIDASSYS/bin

where the assignment line (Bourne shell, and BASH shell) ensures
that multiple entries are not added on the PATH even if the script is more
than once.

POSIX also goes on to say that links from /opt/bin can be made if desired. 
I find this
usefull if a package has only one or two executables, and I don't to make
multiple
versions available.

I hope that the POSIX ideas are usefull,

John.

> > Here's my suggestion
> > MIDASSYS=/opt/midas-1.9.4 (for example)   
> 
> I guess we should follow the "standard" as much as possible. MIDASSYS was
inspired by
> ROOTSYS. Now where do people usually install ROOT? Is it /opt/root-x.x.x
or something
> else. Some years ago (when I did the last time some linux administration)
optional
> packages were put into /usr/local by default. I guess you have more
experience with
> today's tradition, so do whatever you thing is standard.
> 
> > so the Linux binaries would go to 
> > MIDASHOST=i386-pc-linux-gnu
> > $MIDASSYS/$MIDASHOST/bin
> > $MIDASSYS/$MIDASHOST/lib
> 
> Does that mean that the path has to be modified to include
$MIDASSYS/$MIDASHOST/bin?
> If we put a link to /usr/local/bin, the path does not have to be modified.
What about
> shared libraries? Does ldconfig know about /usr/local/lib, or
$MIDASYS/$MIDASHOST/lib?
> 
> > and the shared stuff would go to 
> > $MIDASSYS/include
> > $MIDASSYS/share/drivers
> > $MIDASSYS/share/examples
> 
> What about /usr/share? Is that a common place for documentatino etc?
> 
> Thanks for your advice.
> 
> - Stefan

> With POSIX there is a written standard, which says that each pacakge goes in
> it's own
> directory under /opt. eg. /opt/midas.  Each package gets to define it's own
> structure
> within that directory.  One could imagine several versions installed at the
> same time
> /opt/midas/v1.9.2 and /opt/midas/v1.9.4 each with a bin, lib include etc. 
> Following the
> ROOT example, you could make a link from /opt/midas/pro to
> /opt/midas/v1.9.4, so that
> system files and login files are easy to maintain etc.  The basic idea is
> 
> MIDASSYS=/opt/midas/pro
> PATH=$PATH:$MIDASSYS/bin
> 
> though a more sophisticated approach is
> 
> MIDASSYS=/opt/midas/pro
> echo $PATH | grep -q $MIDASSYS || PATH=$PATH:$MIDASSYS/bin
> 
> where the assignment line (Bourne shell, and BASH shell) ensures
> that multiple entries are not added on the PATH even if the script is more
> than once.

That sounds all very good to me. So can you please sit together (at least John,
Piotr, and Pierre-Andre), discuss a common scheme and and propose it officially in
this forum for comments. After a week or so, it should be implemented into the
Makefile and installation scripts. I also would like to have Paul Knowles giving
it a look, since he voluteered to make the midas RPMs, which also heavily depends
on the chosen directory structure.

I have compiled the sources on Darwin 7.4.0 with gcc 3.3. After the compilation of source codes, I 
try to execute "gmake install". I got the following message:
-------
Nothing to be done for "install".
-------

The install target could not be executed. Then I add the following line to the Makefile:
------
.PHONY: install
------

The install target can be executed. But when it is tring to copy "dio" to the proper directory, it 
cannot find the file. Then I found that the "utils" target isn't built. 
I try to build the target: darwin/bin/dio, I got the following error:
-------
cc -g -O2 -Wall -Iinclude -Idrivers -Ldarwin/lib -DINCLUDE_FTPLIB   -DOS_LINUX -DOS_DARWIN 
-DHAVE_STRLCPY -fPIC -Wno-unused-function -o darwin/bin/dio utils/dio.c
utils/dio.c:39:20: sys/io.h: No such file or directory
utils/dio.c: In function `main':
utils/dio.c:46: warning: implicit declaration of function `iopl'
gmake: *** [darwin/bin/dio] Error 1
--------
So, the include file "sys/io.h" may be changed under Darwin. I don't know how. I will try later. I 
hope somebody can notice this. 
Best regards.

There are not such a file "io.h" inside my MacOS X. In fact, I didn't find any file containing function iopl().
So what is the equivalent function of iopl() under MacOS X? The utility dio should be modified in order to be compiled under Darwin-
gcc platform. 

> There are not such a file "io.h" inside my MacOS X. In fact, I didn't find any file containing function iopl().
> So what is the equivalent function of iopl() under MacOS X? The utility dio should be modified in order to be compiled under Darwin-
> gcc platform. 

"dio" is not supported under MacOSX. It is used to grant user programs access to PCI and ISA cards (usually CAMAC interfaces). We have
no MacOSX hardware with PCI or ISA slots so we cannot test and support this functionality.

The MacOSX Makefile should not try to build "dio". I will accept a patch to fix this Makefile bug.

K.O.

Hi,
  I think that rather than spending too much time on where to 
put files and how to define the environment - I am guilty of that myself.
We should be perhaps have some discussion on the future of MIDAS.

Are we ready for 2.0? 
Stefan - do you have any ideas/enhancements?

1) For one I would like to explore memory mapping (mmap()) on Linux
- I've used it once upon a time on DEC OSF/1 and I found it really
nice compared to shared memory. 
From a user standpoint it behaves as a shared memory but is mapped 
to a real file that can be easily "removed" when neccessary. 
One really annoying thing in MIDAS is when it goes ballistic
the cleanup which is somewhat tricky. 
The question if there is any performance penalty associated

2) Expanding hardware support: 
   a) custom microcontrolers?
   b) more hardware
   c) how about a "standard" Linux device /dev/midas
   for various PCI cards (PCI<->CAMAC) (PCI<->VME) 

3) I have never really seen a midas deployment that uses interrupts. 
I do understand the ease of polling and the fact that these days
CPU's are cheap but sometimes it is important to use interrupts.
Any examples/experience?

?)

Piotr

Sorry the previous message got mangled:

Hi, 
I think that rather than spending too much time on where to put files 
and how to define the environment - I am guilty of that myself -  we should 
perhaps have some discussion on the future of MIDAS. 

Are we ready for 2.0? 

Stefan - do you have any ideas/enhancements? 

1) For one I would like to explore memory mapping (mmap()) on Linux.
I've used it once upon a time on DEC OSF/1 and I found it really nice 
compared to shared memory. From a user standpoint it behaves as a shared
memory but is mapped to a real file that can be easily "removed" when 
neccessary. One really annoying thing in MIDAS is when it goes ballistic 
the cleanup is somewhat tricky. 
The question if there is any performance penalty associated 

2) Expanding hardware support: 
  a) custom microcontrolers? 
  b) other hardware
  c) how about a "standard" Linux device /dev/midas for various 
  PCI cards (PCI<->CAMAC) (PCI<->VME) 

3) I have never really seen a midas deployment that uses interrupts. 
I do understand the ease of polling and the fact that these days CPU's 
are cheap but sometimes it is important to use interrupts. 

Any examples/experience? 

?) 

Piotr

Have changed your entry as Non-HTML (easier to reply to...)

Here are some "initial" comments, by no means complete...

> Are we ready for 2.0? 
> Stefan - do you have any ideas/enhancements?

A big thing along the horizon I see is the ROME environment
(http://midas.psi.ch/rome/). So we will move away from PAW to ROOT. Although
the DAQ part will stay untouched, the whole analysis back-end changes,
including some XML configuration and MySQL support. I guess that would justify
a 2.0. I will discuss this at TRIUMF when I come in September, see how useful
ROME is for other users...

> 1) For one I would like to explore memory mapping (mmap()) on Linux
> - I've used it once upon a time on DEC OSF/1 and I found it really
> nice compared to shared memory. 
> From a user standpoint it behaves as a shared memory but is mapped 
> to a real file that can be easily "removed" when neccessary. 
> One really annoying thing in MIDAS is when it goes ballistic
> the cleanup which is somewhat tricky. 
> The question if there is any performance penalty associated

I guess there are no performance penalties, since under the hood both
techniques are handled similarly. The problem is that besides share memories
you need also semaphores to controll exclusive access to the memory, either
shm() funcitons or mmap(), so this would only fix half of the problem. I seem
to remember that mmap() was not available on some Ultix systems or so, but I
guess that's obsolete by now...

> 2) Expanding hardware support: 
>    a) custom microcontrolers?
>    b) more hardware
>    c) how about a "standard" Linux device /dev/midas
>    for various PCI cards (PCI<->CAMAC) (PCI<->VME) 

Well, you cannot develop hardware support for hardware you don't have, so the
policy up to now was that everyone developing some special drivers or hardware
support contributed it to the package. About c), we have already a CAMAC
driver standard, but at the user space level, so I don't see the benefit of
having kernel-mode standardized drivers. The only difference will be that the
debugging will be harder. VME standard is there in a kind of poor start right
now, but I expect to finish it this fall.

As for a), there is the MSCB system (http://midas.psi.ch/mscb) which has midas
support on the device driver and bus driver level, but I learned that
distributing hardware (or PCB designs if you like) is much harder than sharing
software. 

> 3) I have never really seen a midas deployment that uses interrupts. 
> I do understand the ease of polling and the fact that these days
> CPU's are cheap but sometimes it is important to use interrupts.
> Any examples/experience?

It's not only the "ease" of polling, but also that it's faster (in almost all
cases) and less troublesome. But hey, interrupt support is included in mfe.c,
so if you are fanatic about interrupts, please feel free to use them.

Hello midas'ers,

Today I discovered a severe bug in the routine bm_check_buffers(), which
causes the logger to crash when it stops a run due to a reached event limit.
The funny thing is that this bug was there since the beginning, but only
recent versions of gcc and libc reveal it.

Since I consider this severe, I fixed it and updated 1.9.4 just now. I did
not go with 1.9.4-1, but maybe in future we should consider patch levels.

So please everybody who uses 1.9.4 and has problems with crashing loggers,
please update to 1.9.4 from today (July 15th, 2004).

- Stefan

> > Are we ready for 2.0? 

I disapprove of version number inflation. Why not go straight for midas version
3000-Pro-Z?

> A big thing along the horizon I see is the ROME environment
> (http://midas.psi.ch/rome/). So we will move away from PAW to ROOT. Although
> the DAQ part will stay untouched, the whole analysis back-end changes,
> including some XML configuration and MySQL support.

I looked at the ROME slides from Pierre, and it seems to suffer badly from the
second-system syndrome (read The Mythical Man-Month).

For us, it is important to get the data into a form where we can process it with
ROOT and I would prefer if we could concentrate in improving the (embryonic) ROOT
online analysis capabilities.

> > 1) For one I would like to explore memory mapping (mmap())

It is trivial to replace System-V shared memory with mmap(). I am surprised that
it has not been done yet. System-V semaphores are a little bit harder to get rid of.

> > 2) Expanding hardware support: 
> >    a) custom microcontrolers?
> >    b) more hardware
> >    c) how about a "standard" Linux device /dev/midas
> >    for various PCI cards (PCI<->CAMAC) (PCI<->VME) 

We cannot expect MIDAS Authors to provide drivers for all possible hardware.

At best, we can mount an effort to collect exisiting drivers from all MIDAS users
"out there" and to integrate them into MIDAS.

Even that is highly non-trivial- many drivers use non-portable native hardware
access interfaces (direct bit-banging on PPCs, VMIC library on VMIC Linux
machines, etc). We have already failed to create an efficient generic portable VME
access library.

> As for a), there is the MSCB system (http://midas.psi.ch/mscb)

I never saw the point of having tons of MIDAS code for MSCB hardware that nobody
has and nobody will ever have.

> > 3) I have never really seen a midas deployment that uses interrupts. 
>
> It's not only the "ease" of polling, but also that it's faster (in almost all
> cases) and less troublesome. But hey, interrupt support is included in mfe.c,
> so if you are fanatic about interrupts...

Interrupts are important when one cannot afford chewing up CPU cycles, memory
cycles, PCI cycles and VME cycles on polling.

As I understand, common CAMAC hardware does not generate interrupts- this explains
lack of examples and lack of interrupt use. At TRIUMF, our new VME hardware
supports interrupts and I have a VMIC-based setup where I can (and intend to) test
MIDAS support of interrupts.

K.O.

Updating the instructions to ROOT version 3.10.2. Example is from TRIUMF-KOPIO
tree analysis.

shell> root -l
root> TFile *f = new TFile("run00064.root")
root> Trigger->MakeSelector("TriggerSelector")  // "Trigger" is the tree name
inside the root file. Generates TriggerSelector.h and TriggerSelector.cpp

= edit run.C, the main program:

{
gROOT->Reset();
TSelector *s = TSelector::GetSelector("TriggerSelector.C");

TChain chain("Trigger"); // "Trigger" is the tree name inside the root files
chain.Add("run03016.root"); // can chain multiple files

TH1D* tdc2 = new TH1D("tdc2","TDC2",1500,0,1500-1);

chain.Process(s,"",500); // process 500 events
//chain.Process(s); // or process all events

tdc2->Draw();
}

= edit TriggerSelector.h:

in the TriggerSelector class members, i.e. "UInt_t TDC1_TDC1[47];" edit the
array size to be bigger than the maximum possible bank size

= edit TriggerSelector.C:

Bool_t TriggerSelector::Process(Int_t entry)
{
  fChain->GetTree()->GetEntry(entry);

  if (entry%100 == 0)
    printf("process %d, nTDC %3d, 0x%08x\n",entry,TDC1_nTDC1,TDC1_TDC1[1]);

  tdc2->Fill(TDC1_nTDC1);
  return kTRUE;
}

= Run the analysis:

shell> root -l
root> .x run.C
 
K.O.

Updating the instructions to ROOT version 3.10.2. Example is from TRIUMF-KOPIO
tree analysis.

shell> root -l
root> TFile *f = new TFile("run00064.root")
root> Trigger->MakeSelector("TriggerSelector")  // "Trigger" is the tree name
inside the root file. Generates TriggerSelector.h and TriggerSelector.cpp

= edit run.C, the main program:

{
gROOT->Reset();
TSelector *s = TSelector::GetSelector("TriggerSelector.C");

TChain chain("Trigger"); // "Trigger" is the tree name inside the root files
chain.Add("run03016.root"); // can chain multiple files

TH1D* tdc2 = new TH1D("tdc2","TDC2",1500,0,1500-1);

chain.Process(s,"",500); // process 500 events
//chain.Process(s); // or process all events

tdc2->Draw();
}

= edit TriggerSelector.h:

in the TriggerSelector class members, i.e. "UInt_t TDC1_TDC1[47];" edit the
array size to be bigger than the maximum possible bank size

= edit TriggerSelector.C:

Bool_t TriggerSelector::Process(Int_t entry)
{
  fChain->GetTree()->GetEntry(entry);

  if (entry%100 == 0)
    printf("process %d, nTDC %3d, 0x%08x\n",entry,TDC1_nTDC1,TDC1_TDC1[1]);

  tdc2->Fill(TDC1_nTDC1);
  return kTRUE;
}

= Run the analysis:

shell> root -l
root> .x run.C
 
K.O.

Updating the instructions to ROOT version 3.10.2. Example is from TRIUMF-KOPIO
tree analysis.

shell> root -l
root> TFile *f = new TFile("run00064.root")
root> Trigger->MakeSelector("TriggerSelector")  // "Trigger" is the tree name
inside the root file. Generates TriggerSelector.h and TriggerSelector.cpp

= edit run.C, the main program:

{
gROOT->Reset();
TSelector *s = TSelector::GetSelector("TriggerSelector.C");

TChain chain("Trigger"); // "Trigger" is the tree name inside the root files
chain.Add("run03016.root"); // can chain multiple files

TH1D* tdc2 = new TH1D("tdc2","TDC2",1500,0,1500-1);

chain.Process(s,"",500); // process 500 events
//chain.Process(s); // or process all events

tdc2->Draw();
}

= edit TriggerSelector.h:

in the TriggerSelector class members, i.e. "UInt_t TDC1_TDC1[47];" edit the
array size to be bigger than the maximum possible bank size

= edit TriggerSelector.C:

Bool_t TriggerSelector::Process(Int_t entry)
{
  fChain->GetTree()->GetEntry(entry);

  if (entry%100 == 0)
    printf("process %d, nTDC %3d, 0x%08x\n",entry,TDC1_nTDC1,TDC1_TDC1[1]);

  tdc2->Fill(TDC1_nTDC1);
  return kTRUE;
}

= Run the analysis:

shell> root -l
root> .x run.C
 
K.O.

> > Starting from midas version 1.9.4 on, the environment variable 'MIDASSYS' ...
> 2. What will the entire structure tree look like?
> 
> Here's my suggestion
> MIDASSYS=/opt/midas-1.9.4 (for example)   

Where should MIDAS be installed?

After looking at the LSB and at the FHS, it appears that the standards permit all of:
1) /opt/midas...
2) /usr/{bin,lib,...}
3) /usr/local/{bin,lib,...}

Some handy references:
http://www.pathname.com/fhs/pub/fhs-2.3.html
http://www.linuxbase.org/spec/

The "example LSB-compliant packages" appear to install into /opt/lsb, but I do not see
 any guidance as to where "my" packages should go.

Then, after some googling, I see that IBM "recommends" /opt (see
http://www-106.ibm.com/developerworks/linux/library/l-lsb.html):

begin-quote---
To avoid name space collisions when installing LSB-conforming applications, the
applications belonging to the base operating system or the distribution are to be
installed in /sbin/, /bin/, or /usr/. System administrators can build packages from
source and install them into the /usr/local/ directory. However, third-party packages
of add-on software must be installed in /opt/<package>/, where <package> is the name
that describes a software suite.
end-quote---


K.O.

> Where should MIDAS be installed?

I personally don't have any preference, as long as it's in accordance with "the standard"
(whatever this is). Maybe one should add a flag to the makefile to specify the
installation directory, either /opt or /usr/local, so people then have the choice. I have
seen that in other packages. As for the RPM, I leave the final proposal to the person
writing the spec file (Paul? Piotr? Konstantin?). We should then commonly agree on the
location based on that proposal. The person supplying the RPM will "officially" become the
RPM maintainer and be responsible for maintaining it.

> installed in /sbin/, /bin/, or /usr/. System administrators can build packages from
> source and install them into the /usr/local/ directory. However, third-party packages
> of add-on software must be installed in /opt/<package>/, where <package> is the name
> that describes a software suite.

Well, midas is kind of in the middle. On one hand it's a third-party package (-> /opt),
but it requires some compilation to allow meaningful work (frontend, analyzer). So maybe
the RPM should go to /opt, and if compiled from the TAR ball it should go to /usr/local?
But that means if someone has to maintain a large basis of midas machines, he/she has to
always search two locations. On the other hand one can alway do a "cd $MIDASSYS" ...

- Stefan

One of our experiments is suffering from periodic ODB corruption and I
suspected that there might be a problem with ODB locking. In the last few
days, I finally had time to read the ODB locking code, to write a little
test program and to play with ODB. This is what I found:

1) ODB locking appears to be sound, my test program failed to find any
locking flaws, except for a big problem, described below. Please read on.

2) ODB locking is "unfair". A program "while (1) { lock(); do_stuff();
unlock(); /* no sleep here */ }" would lock out other users of ODB
(including odbedit) for seconds and minutes at a time. I see this as a flaw
in the semop() implementation in the Linux kernel and I cannot think of an
easy way to fix it in our code. (I tested only on RHL9 2.4.20-31.9smp on a
dual CPU machine. 2.6 kernels may work better).

3) presently, we use an infinite timeout waiting for the ODB lock. I suggest
we set the timeout to, say, 5 minutes, to protect against dead (or live)
locks that we saw a few times here at TRIUMF- every ODB client would hang
without any error messages or explanations forever waiting for the ODB lock
that is held by some rogue ODB client stuck in an infinite loop in corrupted
ODB.

4) while reading the locking code in db_{lock,unlock}_database(), I thought
that there is a race condition against the "lock_cnt" variable, until I
realized that this variable is local and there is no race condition. I would
like to comment this in the code?

5) I found a failure mode where db_close_database() erroneously deletes the
lock semaphore. Once the semaphore is deleted, ODB locking silently fails
(in db_lock_database() we do not check for success status of
mutex_wait_for()) and remaining ODB clients operate without locking protection.

This failure happens after ODB undercounts active clients after losing track
of clients removed by "idle timeouts" (and by other checks?). At some point,
db_close_database() decides that there are no more clients left, attempts to
delete the shared memory (this fails because there are still active clients
attached) and deletes the lock semaphore. Afterwards, the remaining "lost"
active clients operate without lock protection. This would tend to happen
while shutting down all clients, a time when they all rush-in to delete
themselves from "/system/clients", unsuring ODB corruption.

A quick solution I just coded would not work for mmap()-based shared memory
(I destroy the lock semaphore after the ODB shared memory is destroyed) as
this relies on "shm_nattch" counting feature of System-V shared memories,
absent in the mmap() based shared memories. Since the Windows implementation
uses mmap(), my "solution" is an obvious no-go. Alternatives would be to add
a second semaphore, just for counting active ODB clients (kluncky); or never
delete the semaphore in the first place (dirty, and how does one clear it if
it gets stuck in the locked state?).

For now, I would like to add a check to ss_mutex_waitfor() call in
db_lock_database() and crash if we can't get the mutex. Returning an error
code would be cleaner, but would not work because nobody checks the return
status of db_lock_database(). If can't get the mutex for (say) 5 minutes, I
think we should crash, too- something is very wrong and it is pointless to
continue waiting.

K.O.

Our users keep making a simple mistake- they set MIDAS_SERVER_HOST in their
environement. Most midas programs do not mind this- they go through the
mserver, inefficient but benign- except for the mlogger, which dumps core
about 10 seconds after starting. This mightily confuses the users-
everything works perfectly, except for the mlogger, (for most users) the
most obscure and magical part of midas. Obviously they can't take data
without the mlogger and they fail to correlate this crash with editing their
.cshrc file, so we get panic calls at midnight or whenever. And every time,
while debugging midas malfunctions, changes to .cshrc is absolutely the last
place we look for. Ouch!

As it turns out, mlogger does crash if it uses the mserver-
log_system_history() calls db_lock_database(), with a prompt crash because
the mlogger is not directly connected to any ODB (it's mserver is).

Obviously, running the mlogger via the mserver makes no sense, but we should
warn about this rather than dump core.

I propose this patch to src/mlogger.c::log_system_history():

-   db_lock_database(hDB);
-   db_notify_clients(hDB, hist_log[index].hKeyVar, FALSE);
-   db_unlock_database(hDB);
-
+   if (!rpc_is_remote())
+     {
+       db_lock_database(hDB);
+       db_notify_clients(hDB, hist_log[index].hKeyVar, FALSE);
+       db_unlock_database(hDB);
+     }
+   else
+     {
+       cm_msg(MERROR, "log_system_history", "Warning: mlogger is running
remotely via the mserver. This is an unsupported configuration. Please unset
MIDAS_SERVER_HOST and restart the mlogger");
+     }

K.O.

I trapped myself into that problem recently so it's the right time to fix it (;-).

We have two options: 

a) Make the logger work remotely, even if it's suboptimal and 
b) Make the logger refuse to run remotely. 

I have no case where I need to run the logger remotely, so I would opt for b).
This would mean removing the "-h" command line switch and the evaluation of
MIDAS_SERVER_HOST, or just supplying an empty host string to
cm_connect_experiment().

Let me know if you agree, I can then remove the "-h" option. The patch you
suggested I would apply in addition.

- Stefan

> I trapped myself into that problem recently so it's the right time to fix it (;-).
> We have two options: 
> a) Make the logger work remotely, even if it's suboptimal and 
> b) Make the logger refuse to run remotely.

After some discussion between Stefan, Pierre and myself, it was decided to disallow
running mlogger remotely via the mserver.

K.O.