> In the PSI muSR laboratory, we are running about 140 slow control devices across six instruments using Format FIXED.
> Could you please wait a bit with removing support for it so that we can assess if/how this will affect us?

Roger. I believe as long as these data do not go into the MIDAS event data stream, you should not see any difference from 
changing "FIXED" to "MIDAS", I hope you can test it and report how it works for you. If you see that things change in ODB 
or in history, perhaps we can implement some kind of workaround to make the transition transparent.

K.O.

> Andrea Capra reported a problem with manalyzer module initialization order.

Permanent solution is now implemented.

In the analyzer module constructor (TARunObject), please set the value of fModuleOrder (default value is 0).

Modules with smaller fModuleOrder will run first, modules with bigger fModuleOrder will run last.

Please use the value range between -1 (built-in EventDump module) and 9999 (built-in InteractiveModule).

Modules with equal fModuleOrder will run in the same order as they were registered (std::stable_sort).

Example manalyzer modules and documentation README.md have been updated.

Linker command line and GCC attribute methods should also work, but I thought it better to provide explicit 
programmatic control of module ordering.

P.S. the c++ tmfe frontend module design is newer and the problem of module (equipment) ordering is solved by 
constructing them explicitly in main().

manalyzer commit:

commit 6ca130808cd05ead734450391bf6defc8335c04a (HEAD -> master, origin/master, origin/HEAD)
Author: Konstantin Olchanski <olchansk@daq00.triumf.ca>
Date:   Tue Mar 25 15:53:13 2025 -0700

    implement TARunObject::fModuleOrder to specify required ordering of analyzer modules

K.O.

Confirming warning is fixed. Thanks! K.O.

> > Unnamed person who added this clever bit of c++ coding, please fix this compiler warning. Stock g++ on Ubuntu LTS 24.04. Thanks in advance!
> > 
> > /home/olchansk/git/midas/src/system.cxx: In function ‘std::string ss_execs(const char*)’:
> > /home/olchansk/git/midas/src/system.cxx:2256:43: warning: ignoring attributes on template argument ‘int (*)(FILE*)’ [-Wignored-attributes]
> >  2256 |    std::unique_ptr<FILE, decltype(&pclose)> pipe(popen(cmd, "r"), pclose);
> > 
> > K.O.
> 
> Replace the code with:
> 
>    auto pclose_deleter = [](FILE* f) { pclose(f); };
>    auto pipe = std::unique_ptr<FILE, decltype(pclose_deleter)>(
>       popen(cmd, "r"),
>       pclose_deleter
>    );
> 
> 
> Hope this is now warning-free.
> 
> Stefan

> I hopefully fixed the waring (narrowing down from size_t to int). Please double check with your compiler.

Nope, it turns out complain is about the read() size argument, they really really really want it to be 
size_t.

Looks like correct sequence is:

size_t size = file_size_somehow();
char* buf = (char*)malloc(size+1);
ssize_t rd = read(fd, buf, size);
if (rd < 0) { complain(); return; } // read() error
if ((size_t)rd != size) { complain(); return; } // cast to size_t is safe after we know rd >= 0
buf[rd] = 0; // make sure data is NUL terminated

What a mess. I want my UNIX V7 and K&R C back!

Perhaps I should add in system.cxx - ss_read_file(const char* filename, std::vector<char> &data);

Fixed it in mscb.cxx, odbedit.cxx, mhttpd.cxx and msequencer.cxx, commited, pushed.

U-24 builds without warnings. fwew...

K.O.

>  > All this is kind of reasonable, as only two settings of write cache size are useful: 0 to 
> > disable it, and 10 Mbytes to limit semaphore locking rate to reasonable value for all event 
> > rate and size values practical on current computers.
> 
> Indeed KO is correct that only 0 and 10MB make sense, and we cannot mix it. Having the cache setting in the equipment table is 
> cumbersome. If you have 10 slow control equipment (cache size zero), you need to add many zeros at the end of 10 equipment 
> definitions in the frontend. 
> 
> I would rather implement a function or variable similar to fEqConfWriteCacheSize in the tmfe framework also in the mfe.cxx 
> framework, then we need only to add one line llike
> 
> gEqConfWriteCacheSize = 0;
> 
> in the frontend.cxx file and this will be used for all equipments of that frontend. If nobody complains, I will do that in April when I'm 
> back from Japan.

Cache size is per-buffer. If different equipments write into different event buffers, should be possible to set different cache sizes.

Perhaps have:

set_write_cache_size("SYSTEM", 0);
set_write_cache_size("BUF1", bigsize);

with an internal std::map<std::string,size_t>; for write cache size for each named buffer

K.O.

Dear MIDAS experts, 

I confirm that when writing out history files corresponding to the slow control event data, 
MIDAS history system timestamps the data not with the event time coming from the event data, 
but with the current time determined by the program - 

https://bitbucket.org/tmidas/midas/src/293d27fad0c87c80c4ed7b94b5c40ba1e150bea4/progs/mlogger.cxx#lines-5321

where 'now' is defined as  

time_t now = time(NULL);

I'm looking for a way to timestamp the history data with the event time - that is important 
for HEP applications outside the DAQ domain. Yes, MIDAS infrastructure is very well suited for that, 
there could have a number of such applications, and experiments could significantly benefit from that.

So I'm wondering whether the implementation is a design choice made or it could be changed. 

The change itself and especially its validation may require a non-negligible amount of work - I'd be happy to contribute.

Any insight much appreciated. 

-- thanks, regards, Pasha

We see ODB corruption crashes in the DS20k vertical slice MIDAS instance.

Crash is memset() called by db_delete_key1() called by cm_connect_experiment().

I look at the source code and I see that ODB pkey and hkey validation is absent
from most iterators and it is possible for "bad" pkey to cause corruption. Many
other places in the ODB code use db_get_pkey() and db_validate_hkey() to prevent
invalid data from causing further corruption and breakage.

Also db_delete_key1() needs to be refactored and renamed db_delete_key_wlocked().

I will not do this immediately today, but hopefully next week or so.

Stack trace is attached, observe how free_data() was called on a completely invalid pkey,
bad pkey->type, bad pkey sizes, etc.

#0  __memset_avx512_unaligned_erms () at ../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:250
250	../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S: No such file or directory.
(gdb) bt
#0  __memset_avx512_unaligned_erms () at ../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:250
#1  0x00005ad4102b4217 in memset (__len=<optimized out>, __ch=0, __dest=<optimized out>) at /usr/include/x86_64-linux-
gnu/bits/string_fortified.h:59
#2  free_data (pheader=pheader@entry=0x75aaea4f4000, address=0x75aaed4cea50, size=<optimized out>, caller=caller@entry=0x5ad4102ffb6c 
"db_delete_key1") at /home/dsdaqdev/packages_common/midas/src/odb.cxx:513
#3  0x00005ad4102b6a5b in free_data (caller=0x5ad4102ffb6c "db_delete_key1", size=<optimized out>, address=<optimized out>, 
pheader=0x75aaea4f4000) at /home/dsdaqdev/packages_common/midas/src/odb.cxx:453
#4  db_delete_key1 (hDB=1, hKey=<optimized out>, level=<optimized out>, follow_links=0) at 
/home/dsdaqdev/packages_common/midas/src/odb.cxx:3789
#5  0x00005ad4102b6979 in db_delete_key1 (hDB=1, hKey=288672, level=0, follow_links=0) at 
/home/dsdaqdev/packages_common/midas/src/odb.cxx:3731
#6  0x00005ad4102cc923 in db_create_record (hDB=hDB@entry=1, hKey=hKey@entry=0, orig_key_name=orig_key_name@entry=0x7ffd75987280 
"/Programs/ODBEdit", init_str=<optimized out>) at /home/dsdaqdev/packages_common/midas/src/odb.cxx:12916
#7  0x00005ad4102cca73 in db_create_record (hDB=hDB@entry=1, hKey=hKey@entry=0, orig_key_name=orig_key_name@entry=0x7ffd75987280 
"/Programs/ODBEdit", init_str=<optimized out>) at /home/dsdaqdev/packages_common/midas/src/odb.cxx:12942
#8  0x00005ad4102a00ba in cm_set_client_info (hDB=1, hKeyClient=0x7ffd75987420, host_name=0x5ad412262ee0 "dsdaqgw.triumf.ca", 
client_name=0x7ffd759874c0 "ODBEdit", hw_type=<optimized out>, password=<optimized out>, watchdog_timeout=<optimized out>)
    at /usr/include/c++/11/bits/basic_string.h:194
#9  0x00005ad4102a902b in cm_connect_experiment1 (host_name=<optimized out>, host_name@entry=0x7ffd759876c0 "", 
default_exp_name=default_exp_name@entry=0x7ffd759876a0 "vslice", client_name=client_name@entry=0x5ad4102f28fa "ODBEdit", 
func=func@entry=0x0, 
    odb_size=odb_size@entry=1048576, watchdog_timeout=<optimized out>, watchdog_timeout@entry=10000) at 
/usr/include/c++/11/bits/basic_string.h:194
#10 0x00005ad41027e58d in main (argc=3, argv=0x7ffd759881e8) at /home/dsdaqdev/packages_common/midas/progs/odbedit.cxx:3025
(gdb) up
...
#4  db_delete_key1 (hDB=1, hKey=<optimized out>, level=<optimized out>, follow_links=0) at 
/home/dsdaqdev/packages_common/midas/src/odb.cxx:3789
3789	            free_data(pheader, (char *) pheader + pkey->data, pkey->total_size, "db_delete_key1");
(gdb) p pkey
$1 = (KEY *) 0x75aaea53b400
(gdb) p *pkey
$2 = {type = 1684370529, num_values = 0, name = '\000' <repeats 16 times>, "xQ\375\002\004\000\000\000\004\000\000\000\a\000\000", data = 0, 
total_size = 290944, item_size = 1743544378, access_mode = 0, notify_count = 0, next_key = 15, parent_keylist = 1, 
  last_written = 1953785965}
(gdb) 

K.O.

> I confirm that when writing out history files corresponding to the slow control event data, 
> MIDAS history system timestamps the data not with the event time coming from the event data, 
> but with the current time determined by [mlogger].

This is correct. The timestamp in the history file is the mlogger timestamp.

In theory we could use the ODB "last_written" timestamp, but in practice,
timestamps are 1 second granularity and the difference between the two
timestamps normally would be less than 1 second. (time to react to db_watch()).

But ODB last_written also is not the data timestamp. For remote connected clients
it includes the mserver communication delay.

What is the data timestamp, only the user knows - for some FPGA based equipments,
I can see the data timestamp being read from an FPGA register together with the data.

But back to earth.

For making history plots, 1 second granularity with a small (a few seconds) delay should be okey,
and I think the mserver timestamp is good enough.

For data analysis, you are reading history data from a history data file and you are
not constrained to using the MIDAS timestamp.

You can always include your "true" data timestamp as the first value in your data.

We do this in felaview for writing labview data to midas history in the ALPHA antihydrogen experiment at CERN.

This also anticipates your next request, can we have millisecond, microsecond, nanosecond history timestamps:
since you define your "true" data timestamp, you an make it anything you want. (I use "double" time in seconds,
64-bit IEEE-754 "double" has enough precision for microsecond granularity. FPGA based devices can have timestamps
with 10 ns or 8 ns granularity, in this case a uint64_t clock counter could be more appropriate).

K.O.

> You can always include your "true" data timestamp as the first value in your data.

Are you saying that if the first data word of a history event were a timestamp, 
the MIDAS history system, when plotting the time dependencies, would use that timestamp 
instead of the mlogger timestamp?  

if that is true, what tells MIDAS that the first data word is the timestamp? 

I couldn't find a discussion of that on the page describing the history system - 

 https://daq00.triumf.ca/MidasWiki/index.php/History_System#Frontend_history_event

- perhaps I should be looking at a different page?

-- thanks again, regards, Pasha 

> > You can always include your "true" data timestamp as the first value in your data.
> 
> Are you saying that if the first data word of a history event were a timestamp, 
> the MIDAS history system, when plotting the time dependencies, would use that timestamp 
> instead of the mlogger timestamp?
>

you are correct, midas knows nothing about what you put in the history data.

what I suggested is: if you want your true data timestamp recorded in the history,
you can put it into the history data yourself, and I suggested using the 1st value,
but you can also make it the last value or the 10th value, it is up to you.

for making history plots, the history timestamp is used, as you wrote and I confirmed,
this timestamp is generated by mlogger.

what is not clear to me is why this is a problem? do you see a big difference between the 
true data timestamp and the mlogger data timestamp? bigger than 1 second? (this would change 
the shape of "last 10 minutes" plots (600 seconds). bigger than 1 minute? (this would change 
the shape of "last 1 hour plots" (60 minutes, 3600 seconds).

that said, note that we currently store the timestamp as a DWORD 32-bit UNIX time value 
which will overflow in 2038 and which is quickly becoming incompatible with the ongoing 
switch to 64-bit time_t. Ubuntu-24 already build a large number of system libraries with 64-
bit time_t and building MIDAS with 32-bit time_t may soon become as difficult as building 
32-bit MIDAS for 32-bit i686 VME processors. we have to move with the times.

what it means is that the history system data format will have to be updated to 64-bit 
time_t and at the same time, we may try to change the timestamp from mlogger-generated to 
frontend-generated.

but it is still not clear to me how that helps you, because the frontend-generated timestamp 
is not the true data timestamp that you wanted. (and only you know what the true data 
timestamp is and where it comes from and how to tell it to MIDAS).

K.O.

Dear MIDAS experts,

does the ODBXX interface to ODB currently ODB links in the path names? - From what I see so far, it currently fails to do so,
but I could be doing something else wrong... 

-- thanks, regards, Pasha

Indeed this was missing from the very beginning. I added it, please report back if it's not working.

Stefan

I noticed that some programs like mhist, if they take too long, there is an abort and core dump at the very end. This is because they forgot to 
set/disable the watchdog timeout, and they got remove from odb and from the SYSMSG event buffer.

mhist is easy to fix, just add the missing call to disable the watchdog, but I also see a similar crash in the mserver which of course requires 
the watchdog.

In either case, the crash is in cm_disconnect_experiment() where we know we are shutting down and we know there is no useful information in the 
core dump.

I think I will fix it by adding a flag to bm_close_buffer() to bypass/avoid the crash from "we are already removed from this buffer".

Stack trace from mhist:

[mhist,ERROR] [midas.cxx:5977:bm_validate_client_index,ERROR] My client index 6 in buffer 'SYSMSG' is invalid: client name '', pid 0 should be my 
pid 3113263
[mhist,ERROR] [midas.cxx:5980:bm_validate_client_index,ERROR] Maybe this client was removed by a timeout. See midas.log. Cannot continue, 
aborting...
bm_validate_client_index: My client index 6 in buffer 'SYSMSG' is invalid: client name '', pid 0 should be my pid 3113263
bm_validate_client_index: Maybe this client was removed by a timeout. See midas.log. Cannot continue, aborting...

Program received signal SIGABRT, Aborted.
Download failed: Invalid argument.  Continuing without source file ./nptl/./nptl/pthread_kill.c.
__pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized out>) at ./nptl/pthread_kill.c:44
warning: 44	./nptl/pthread_kill.c: No such file or directory
(gdb) bt
#0  __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized out>) at ./nptl/pthread_kill.c:44
#1  __pthread_kill_internal (signo=6, threadid=<optimized out>) at ./nptl/pthread_kill.c:78
#2  __GI___pthread_kill (threadid=<optimized out>, signo=signo@entry=6) at ./nptl/pthread_kill.c:89
#3  0x00007ffff71df27e in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4  0x00007ffff71c28ff in __GI_abort () at ./stdlib/abort.c:79
#5  0x00005555555768b4 in bm_validate_client_index_locked (pbuf_guard=...) at /home/olchansk/git/midas/src/midas.cxx:5993
#6  0x000055555557ed7a in bm_get_my_client_locked (pbuf_guard=...) at /home/olchansk/git/midas/src/midas.cxx:6000
#7  bm_close_buffer (buffer_handle=1) at /home/olchansk/git/midas/src/midas.cxx:7162
#8  0x000055555557f101 in cm_msg_close_buffer () at /home/olchansk/git/midas/src/midas.cxx:490
#9  0x000055555558506b in cm_disconnect_experiment () at /home/olchansk/git/midas/src/midas.cxx:2904
#10 0x000055555556d2ad in main (argc=<optimized out>, argv=<optimized out>) at /home/olchansk/git/midas/progs/mhist.cxx:882
(gdb) 

Stack trace from mserver:

#0  __pthread_kill_implementation (no_tid=0, signo=6, threadid=138048230684480) at ./nptl/pthread_kill.c:44
44	./nptl/pthread_kill.c: No such file or directory.
(gdb) bt
#0  __pthread_kill_implementation (no_tid=0, signo=6, threadid=138048230684480) at ./nptl/pthread_kill.c:44
#1  __pthread_kill_internal (signo=6, threadid=138048230684480) at ./nptl/pthread_kill.c:78
#2  __GI___pthread_kill (threadid=138048230684480, signo=signo@entry=6) at ./nptl/pthread_kill.c:89
#3  0x00007d8ddbc4e476 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4  0x00007d8ddbc347f3 in __GI_abort () at ./stdlib/abort.c:79
#5  0x000059beb439dab0 in bm_validate_client_index_locked (pbuf_guard=...) at /home/dsdaqdev/packages_common/midas/src/midas.cxx:5993
#6  0x000059beb43a859c in bm_get_my_client_locked (pbuf_guard=...) at /home/dsdaqdev/packages_common/midas/src/midas.cxx:6000
#7  bm_close_buffer (buffer_handle=<optimized out>) at /home/dsdaqdev/packages_common/midas/src/midas.cxx:7162
#8  0x000059beb43a89af in bm_close_all_buffers () at /home/dsdaqdev/packages_common/midas/src/midas.cxx:7256
#9  bm_close_all_buffers () at /home/dsdaqdev/packages_common/midas/src/midas.cxx:7243
#10 0x000059beb43afa20 in cm_disconnect_experiment () at /home/dsdaqdev/packages_common/midas/src/midas.cxx:2905
#11 0x000059beb43afdd8 in rpc_check_channels () at /home/dsdaqdev/packages_common/midas/src/midas.cxx:16317
#12 0x000059beb43b0cf5 in rpc_server_loop () at /home/dsdaqdev/packages_common/midas/src/midas.cxx:15858
#13 0x000059beb4390982 in main (argc=9, argv=0x7ffc07e5bed8) at /home/dsdaqdev/packages_common/midas/progs/mserver.cxx:387

K.O.

I would be in favor of not curing the symptoms, but fixing the cause of the problem. I guess you put the watchdog disable into mhist, right? Usually mhist is called locally, so no mserver should be 
involved. If not, I would prefer to propagate the watchdog disable to the mserver side as well, if that's not been done already. Actually I never would disable the watchdog, but set it to a reasonable 
maximal value, like a few minutes or so. In that case, the client gets still removed if it crashes for some reason.

My five cents,
Stefan 

Hi all,

we have a CI setup which fails since 06.05.2025 to build the history_schema.cxx. There was a major change in this code in the commits fe7f6a6 and 159d8d3.

image: rootproject/root:latest

pipelines:
  default:
    - step:
        name: 'Build and test'
        runs-on:
          - self.hosted
          - linux
        script:
          - apt-get update
          - DEBIAN_FRONTEND=noninteractive apt-get -y install python3-all python3-pip python3-pytest-dependency python3-pytest
          - DEBIAN_FRONTEND=noninteractive apt-get -y install gcc g++ cmake git python3-all libssl-dev libz-dev libcurl4-gnutls-dev sqlite3 libsqlite3-dev libboost-all-dev linux-headers-generic
          - gcc -v
          - cmake --version
          - git clone https://marius_koeppel@bitbucket.org/tmidas/midas.git
          - cd midas
          - git submodule update --init --recursive
          - mkdir build
          - cd build
          - cmake ..
          - make -j4 install


Error is:

/opt/atlassian/pipelines/agent/build/midas/src/history_schema.cxx:5991:10: error: ‘class HsSqlSchema’ has no member named ‘table_name’; did you mean ‘fTableName’?

 5991 |       s->table_name = xtable_name;

      |          ^~~~~~~~~~

      |          fTableName

/opt/atlassian/pipelines/agent/build/midas/src/history_schema.cxx: In member function ‘virtual int PgsqlHistory::read_column_names(HsSchemaVector*, const char*, const char*)’:

/opt/atlassian/pipelines/agent/build/midas/src/history_schema.cxx:6034:14: error: ‘class HsSqlSchema’ has no member named ‘table_name’; did you mean ‘fTableName’?

 6034 |       if (s->table_name != table_name)

      |              ^~~~~~~~~~

      |              fTableName

/opt/atlassian/pipelines/agent/build/midas/src/history_schema.cxx:6065:16: error: ‘struct HsSchemaEntry’ has no member named ‘fNumBytes’

 6065 |             se.fNumBytes = 0;

      |                ^~~~~~~~~

/opt/atlassian/pipelines/agent/build/midas/src/history_schema.cxx:6140:30: error: ‘__gnu_cxx::__alloc_traits<std::allocator<HsSchemaEntry>, HsSchemaEntry>::value_type’ {aka ‘struct HsSchemaEntry’} has no member named ‘fNumBytes’

 6140 |             s->fVariables[j].fNumBytes = tid_size;

      |                              ^~~~~~~~~

At global scope:

cc1plus: note: unrecognized command-line option ‘-Wno-vla-cxx-extension’ may have been intended to silence earlier diagnostics

make[2]: *** [CMakeFiles/objlib.dir/build.make:384: CMakeFiles/objlib.dir/src/history_schema.cxx.o] Error 1

make[2]: *** Waiting for unfinished jobs....

make[1]: *** [CMakeFiles/Makefile2:404: CMakeFiles/objlib.dir/all] Error 2

make: *** [Makefile:136: all] Error 2

> we have a CI setup which fails since 06.05.2025 to build the history_schema.cxx.
> There was a major change in this code in the commits fe7f6a6 and 159d8d3.

Missing from this report is critical information: HAVE_PGSQL is set.

I will have to check why it is not set in my development account.

I will have to check why it is not set in our bitbucket build.

Thank you for reporting this problem.

K.O.

> > we have a CI setup which fails since 06.05.2025 to build the history_schema.cxx.
> > There was a major change in this code in the commits fe7f6a6 and 159d8d3.
> 
> Missing from this report is critical information: HAVE_PGSQL is set.
> 
> I will have to check why it is not set in my development account.
> 

The following is needed to build MySQL and PgSQL support in MIDAS,
they were missing on my development machine. MySQL support was enabled
by accident because kde-bloat packages pull in the MySQL (not the MariaDB)
client and server. Fixed now, added to standard list of Ubuntu packages:
https://daq00.triumf.ca/DaqWiki/index.php/Ubuntu#install_missing_packages

apt -y install mariadb-client libmariadb-dev ### mysql client for MIDAS
apt -y install postgresql-common libpq-dev ### postgresql client for MIDAS

>
> I will have to check why it is not set in our bitbucket build.
> 

Added MySQL and PgSQL to bitbucket Ubuntu-24 build (sqlite was already enabled).

>
> Thank you for reporting this problem.
> 

Fix committed. Sorry about this problem.

K.O.

Dear MIDAS experts, 

I'm running into a minor but annoying issue with the subdirectory name ordering by the ODB browser. 
I have a straw-man hash map which includes ODB subdirectories named "000", "010", ... "300", 
and I'm yet to succeed to have them displayed in a "natural" order: the subdirectories with names 
starting from "0" always show up on the bottom of the list - see attached .png file. 

Neither interactive re-ordering nor manual ordering of the items in the input .json file helps. 

I have also attached a .json file which can be loaded with odbedit to reproduce the issue. 

Although I'm using a relatively recent - ~ 20 days old - commit, 'db1819ac', is it possible 
that this issue has already been sorted out ?

-- many thanks, regards, Pasha  

• The brpc method allocates memory for the response at src/mjsonrpc.cxx#lines-3449.
  
• It then makes the call at src/mjsonrpc.cxx#lines-3460, which may set `buf_length` to zero if the response was empty.
  
• It then uses `MJsonNode::MakeArrayBuffer` to pass ownership of the memory to an `MJsonNode`, providing `buf_length` as the size.
  
• When the `MJsonNode` is destructed at mjson.cxx#lines-657, it only calls `free` on the buffer if the size is greater than zero.
  

Noted. I will look at this asap. K.O.

[quote="Mark Grimes"]Hi,
During an evening of running we noticed that memory usage of mhttpd grew to 
close to 100Gb.  We think we've traced this to the following issue when making 
RPC calls.

[LIST]
[*] The brpc method allocates memory for the response at 
[URL=https://bitbucket.org/tmidas/midas/src/67db8627b9ae381e5e28800dfc4c350c5bd0
5e3f/src/mjsonrpc.cxx#lines-3449]src/mjsonrpc.cxx#lines-3449[/URL].
[*] It then makes the call at 
[URL=https://bitbucket.org/tmidas/midas/src/67db8627b9ae381e5e28800dfc4c350c5bd0
5e3f/src/mjsonrpc.cxx#lines-3460]src/mjsonrpc.cxx#lines-3460[/URL], which may 
set `buf_length` to zero if the response was empty.
[*] It then uses `MJsonNode::MakeArrayBuffer` to pass ownership of the memory to 
an `MJsonNode`, providing `buf_length` as the size.
[*] When the `MJsonNode` is destructed at 
[URL=https://bitbucket.org/tmidas/mjson/src/9d01b3f72722bbf7bcec32ae218fcc0825cc
9e7f/mjson.cxx#lines-657]mjson.cxx#lines-657[/URL], it only calls `free` on the 
buffer if the size is greater than zero.
[/LIST]

Hence, mhttpd will leak at least 1024 bytes for every binary RPC call that 
returns an empty response.
I tried to submit a pull request to fix this but I don't have permission to push 
to https://bitbucket.org/tmidas/mjson.git.  Could somebody take a look?

Thanks,

Mark.[/quote]