mhttpd function for starting and stopping runs now uses cm_transition(DETACH) which spawns an 
external helper program called mtransition to handle the transition sequencing. This helps with the old 
problem of looking at a blank screen for a long time if some frontends take a long time to process run 
transitions. Now mhttpd returns right back and shows start "starting run", "stopping run", etc as 
appropriate.

svn rev 4484 (some bits of this feature are present in rev 4473 and later).
K.O.

P.S. In one of our experiments, I sometimes see mhttpd getting "stuck" when starting or stopping a run 
using this feature. strace shows it is stuck in repeated calls to wait(), but I am unable to reproduce this 
problem in a test system and it happens only sometimes in the experiment. When it does, mhttpd has to 
be restarted. Replacing system("mtransition ...") with ss_sysem("mtransition ...") seems to fix this problem, 
but there are downsides to this (mtransition debug output vanishes) so I am not committing this yet.
K.O.

> mhttpd function for starting and stopping runs now uses cm_transition(DETACH) which spawns an 
> external helper program called mtransition to handle the transition sequencing.
> 
> P.S. In one of our experiments, I sometimes see mhttpd getting "stuck" when starting or stopping a run 
> using this feature. strace shows it is stuck in repeated calls to wait(), but I am unable to reproduce this 
> problem in a test system and it happens only sometimes in the experiment. When it does, mhttpd has to 
> be restarted. Replacing system("mtransition ...") with ss_sysem("mtransition ...") seems to fix this problem, 
> but there are downsides to this (mtransition debug output vanishes) so I am not committing this yet.
> K.O.

Found the problem. As observed on SL5 systems, the GLIBC "system()" function breaks if the user application
installs a SIGCHLD handler that "steals" wait() notifications. Such a handler is installed by the MIDAS ss_exec()
function in system.c.

I would count this as a GLIBC bug - their "system()" function should survive in the presence of non-default signal
handlers installed by the user, and in fact my copy of "man signal" talks about the "system()" doing something
special about SIGCHLD. Obviously whatever they do is broken, at least in the SL5 GLIBC.

I am now testing an implementation using MIDAS ss_spawnvp().

The simplest way to reproduce the problem: start mhttpd; start/stop runs - mtransition works perfectly; start some
program from the MIDAS "programs" page (this calls "ss_exec()"), try to start a run - mhttpd will hang inside the
system() GLIBC function, every time. mhttpd has to be killed with "kill -KILL" to recover.

K.O.

> > mhttpd function for starting and stopping runs now uses cm_transition(DETACH) which spawns an 
> > external helper program called mtransition to handle the transition sequencing.
>
> ... the GLIBC "system()" function breaks if the user application
> installs a SIGCHLD handler that "steals" wait() notifications. Such a handler is installed by the MIDAS ss_exec()
> function in system.c.
>
> I am now testing an implementation using MIDAS ss_spawnvp().

cm_transition() starting mtransition helper using ss_spawnvp() committed svn rev 4495.

K.O.

> > > mhttpd function for starting and stopping runs now uses cm_transition(DETACH) which spawns an 
> > > external helper program called mtransition to handle the transition sequencing.

Problem reported by Stefan - user presses the "stop the run" button, and the web page comes back saying "running" as if the button did not work. This is 
confusing. It happens because mtransition did not start yet - we have a race condition against it.

To improve this situation, mhttpd now remembers that a start/stop button was pushed and displays a message "Run start/stop requested" until it detects 
that mtransition started and set "runinfo/transition in progress" (or the run state changed).

svn rev 4520
K.O.

Previously, one mhttpd server could sever several experiments at the same time. 
This caused however sometimes problems and was hard to maintain. Starting from 
SVN revision 4348, I removed the multi-experiment support, which I believe is 
now a much cleaner implementation. So if several experiments are defined on a 
computer, each one need a separate mhttpd process listening on a different 
port. The experiment name can now be supplied on the command line to mhttpd 
like for any other midas program. I have tested this so far at two experiments 
at PSI, but this does not cover all possibilities. What I did not try was 
experiments with web passwords and odb passwords. If there is any problem after 
upgrading to 4348, please report.

the update of mhttpd to mongoose version 6.16 was committed to the develop branch of midas. If you do not want to use this 
updated code or if it causes problems, please use the mhttpd6 executable or midas from the midas-2020-03 release branch.

new features:

- IPv6 support
- built-in http proxy
- fine grain locking - serving "resource" files (html, css, etc) and serving json-rpc requests no longer takes the global lock
- reduced number of DNS queries when checking host list access (DNS replies are cached)
- (I decided to not implement caching of password requests and dynamic reload of password file - it is too hard).

internal changes:

Recent versions of the mongoose web server library have removed all their internal multithreading,
leaving the library fully single-threaded. This resulted in major simplification of many things. An improvement.
(the civetweb fork of mongoose retains the old multithreading code, that model seems to work better
which used inside ROOT). As implemented in mhttpd, all network connections are handled by the main thread,
all midas http requests are handled by worker threads that are started on the as-needed basis.

The old mongoose 6.4 based mhttpd code survived almost without changes - as a compile-time
option - so now I build 2 mhttpd executables: mhttpd with the new code and mhttpd6 with the old code
so people have something to run in case the new code bombs.

http proxy:

Experiments that use private networks usually configure the apache httpd as a web proxy to allow
access from the outside to the web-controlled devices on the private network. Making changes
to this proxy requires root access, requires restarting httpd, etc. To make things simpler, mhttpd now
includes a web proxy (almost the complete implementation is provided by the mongoose library). Configuration
is done from ODB, restarting mhttpd is not needed.

improved multithreading:

Since most of the MIDAS library is now thread-safe, mhttpd no longer needs to take the "big midas lock"
to service most web requests. Access to files, access to ODB, etc is now fully threaded. Some parts
of MIDAS are not thread-safe, i.e. access to history and log files, so a flag was added to the mjsonrpc library
to mark which RPC methods are not thread-safe.

Note that despite these improvements, mhttpd still suffers from "http head-of-queue blocking"
https://en.wikipedia.org/wiki/Head-of-line_blocking
because (i.e. the google chrome web browser) tends to use just 1 TCP connection for all JSONRPC requests,
after a request for a history read (can take a long time), all subsequent requests for web page updates, etc
will have to wait until it completes, causing unresponsive user experience. (it looks as if mhttpd is single-threaded!).

A solution for this problem is HTTP/2, which is not yet implemented by mongoose and is not quite yet available
for apache httpd.

More later...
K.O.

> the update of mhttpd to mongoose version 6.16 was committed to the develop branch of midas.

The new code implements 3 http ports:

- localhost port 8080 - enabled by default - suitable for "I want to test midas on my laptop" and for connecting from the apache httpd
https password protected gateway.

- insecure http port 8081 - disabled by default - with optional password protection (HTTP Digest auth), and optional hostlist access
control - for the case when the https gateway is running on a different computer (i.e. ALPHA at CERN).

(My reading of "internet opinions" about HTTP Digest authentication over unencrypted HTTP is
that while considered very obsolete, there are no specific security problems and exploits
against it - other than the usual - man-in-the-middle and "steal the password file" attacks.
So while I do not recommend using it, I do not feel justified to remove/disable it on security grounds.
It provides an alternative password protection when use of SSL/HTTPS is too difficult).

- https port 8443 - disabled by default - also with optional password protection (HTTP Digest auth), and optional hostlist access
control. HTTP Digest password protection over HTTPS is deemed as secure at "HTTP Basic" password protection over HTTPS and
that is what is used by apache httpd password protection.

(The main problem with mhttpd support of HTTPS is obtaining an https certificate. Right now mhttpd
instructs the user to generate a self-signed certificate. But there is 2 problems: modern browsers dislike self-signed
certificates (even when explicitely marked "trust it!") and there is no check for certificate expiration.
I guess one could try to integrate mhttpd with certbot and the let's-encrypt system, but there
is problems, i.e. the certificate files live in readable-only-by-root directories, etc. I would rather
wait until mongoose implement certbot integration in their code).

More later...
K.O.

> > the update of mhttpd to mongoose version 6.16 was committed to the develop branch of midas.

Configuration is done by ODB /WebServer:

---------------------------------------------------------------------------
[local:javascript1:S]/WebServer>ls -l
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
mime.types                      DIR
Enable localhost port           BOOL    1     4     2h   0   RWD  y
localhost port                  INT     1     4     2h   0   RWD  8080
localhost port passwords        BOOL    1     4     2h   0   RWD  n
Enable insecure port            BOOL    1     4     12h  0   RWD  n
insecure port                   INT     1     4     2h   0   RWD  8081
insecure port passwords         BOOL    1     4     2h   0   RWD  y
insecure port host list         BOOL    1     4     2h   0   RWD  y
Enable https port               BOOL    1     4     12h  0   RWD  n
https port                      INT     1     4     2h   0   RWD  8443
https port passwords            BOOL    1     4     2h   0   RWD  y
https port host list            BOOL    1     4     2h   0   RWD  y
Host list                       STRING  10    32    2h   0   RWD
                                        [0]             localhost
                                        [1]
                                        [2]
                                        [3]
                                        [4]
                                        [5]
                                        [6]
                                        [7]
                                        [8]
                                        [9]
Enable IPv6                     BOOL    1     4     2h   0   RWD  y
Proxy                           DIR
---------------------------------------------------------------------------

Most entries are self-obvious, but note:

- mime.types contains the mapping of file extensions of file content-type telling browser what to do:

---------------------------------------------------------------------------
[local:javascript1:S]/WebServer>ls -l mime.types/
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
.HTML                           STRING  1     10    2h   0   RWD  text/html
.HTM                            STRING  1     10    2h   0   RWD  text/html
.CSS                            STRING  1     9     2h   0   RWD  text/css
---------------------------------------------------------------------------

- Proxy directory configures the http proxy (as implemented by mongoose, I am
not sure if I understand all limitations):

---------------------------------------------------------------------------
[local:javascript1:S]/WebServer>ls -l Proxy/
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
example                         STRING  1     27    17h  0   RWD  #http://localhost:8080
---------------------------------------------------------------------------

("#" means - commented-out)

http://localhost:8080/proxy/example/foo/bar/baz proxies to http://localhost:8080/foo/bar/baz

- "Enable IPv6" tells mhttpd to also listen on the IPv6 ports. The best I can tell IPv6 works on the Mac,
and with luck will get some testing at CERN where IPv6 is in use.

Documentation on the midas wiki still needs to be updated for this.
K.O.

Committed minor bug fixes and improvements to mhttpd:
1) when generating history plots, use type "double" instead of "float" because "float" does not have enough 
significant digits to plot values of large integer numbers. For example, serial numbers of T2K FGD FEB 
cards are large integers, i.e. 99000001, 99000002, etc, but when we plot them with offset "-99000000", 
the plots show "0" for all cards because when these numbers are converted to "float", they are truncated to 
about 5 digits and the least significant digit (the only one of interest, the "1", "2", etc) is lost. Switching to 
type "double" makes the plots come out with correct values.
2) fixed breakage of "/History/URL" ODB setting used to offload generation of history plots to a separate 
mhttpd process, greatly improving responsiveness of the main mhttpd.
3) fixed memory leak in processing the new javascript requests (jset, jget & co).
svn revisions 4415-4417
K.O.

I commited a fix to mhttpd logic that decides which messages should be shown in
"red" colour- before, any message with square brackets and colons would be
highlighted in red. Now only messages matching the pattern [...:...] are
highlighted. The decision logic was moved into a function message_red(). K.O.

Here is the list of mhttpd magic URLs.

http "get" path:

handle_http_message()
handle_http_get()
?mjsonrpc_schema -> serve mjsonrpc_get_schema() // JSON RPC Schema in JSON format
?mjsonrpc_schema_text -> serve mjsonrpc_schema_to_text() // same, but human-readable
handle_decode_get()
decode_get()
interprete()

http "post" path:

handle_http_message()
handle_http_post()
?mjsonrpc -> serve mjsonrpc_decode_post_data() // process RPC request
handle_decode_post()
decode_post()
- maybe decode file attachment
interprete()

interprete() path:

url contains favicon.{ico,png} -> send_icon()
url contains mhttpd.css -> send_css() (see ODB /Experiment/CSS File) // obsolete? see midas.css below
url ends with "mp3" -> send_resource(url) // alarm sound
url contains midas.js -> send_resource("midas.js")
url contains midas.css -> send_resource("midas.css")
url ... ditto mhttpd.js
url ... ditto obsolete.js
url ... ditto controls.js
cmd is "example" -> send_resource("example.html")
?script -> cm_exec_script(), see ODB /Script/...
?customscript -> same, see ODB /CustomScript/...
cmd is "start" -> send resource start.html
cmd is blank -> send resource status.html
cmd is "status" -> send resource status.html
cmd is "newODB" -> send resource "odb.html" // not used at the moment
cmd is "programs" -> programs.html
cmd is "alarms" -> alarms.html
cmd is "transition" -> transition.html
cmd is "messages" -> messages.html
cmd is "config" and url is not "HS/" -> config.html
cmd is "chat" -> chat.html
cmd is "buffers" -> buffers.html
// elog section
cmd is "Show elog" -> elog
cmd is "Query elog" -> elog
cmd is "New elog" -> elog
cmd is "Edit elog" -> elog
cmd is "Reply elog" -> elog
cmd is "Last elog" -> elog
cmd is "Submit Query" -> elog
// end of elog section
url is "spinning-wheel.gif" -> send_resource("spinning-wheel.gif")
// section "new custom pages"
if ODB /Custom exists,
get value of $MIDAS_DIR or $MIDASSYS or "/home/custom"
write it to ODB /Custom/Path (if it does not already exist)
concatenate value of ODB /CustomPath and the URL (without a "/" in between)
if this file exists, send_resource() it.
// end of "new custom pages" section
// section for old AJAX requests
cmd is "jset", "jget", etc -> javascript_commands()
// commented out: send_resource(command+".html") // if cmd is "start" will send start.html
cmd is "mscb" -> show_mscb_page()
cmd is "help" -> show_help_page()
cmd is "trigger" -> send RPC RPC_MANUAL_TRIG
cmd is "Next subrun" -> set ODB "/Logger/Next subrun" to TRUE
cmd is "cancel" -> redirect to getparam("redir")
cmd is "set" -> show_set_page() // set ODB value
cmd is "find" -> show_find_page()
cmd is "CNAF" or url is "CNAF" -> show_cnaf_page()
cmd is "elog" -> redirect to external ELOG or send_resource("elog_show.html")
cmd starts with "Elog last" -> send_resource("elog_query.html") // Elog last N days & co
cmd is "Create Elog from this page" -> redirect to "?cmd=new elog" // called from ODB editor
cmd is "Submit elog" -> submit_elog() // usually a POST request from the "elog_edit.html"
cmd is "elog_att" -> show_elog_attachment()
cmd is "accept" -> what does this do?!?
cmd is "eqtable" -> show_eqtable_path() // page showing equipment variables as a table ("slow control page")
// section for the sequencer
cmd is "sequencer" -> show_seq_page()
cmd is "start script" -> seq
cmd is "cancel script" -> seq
cmd is "load script" -> ...
cmd is "new script" -> ...
cmd is "save script" -> ...
cmd is "edit script" -> ...
cmd is "spause" -> ...
cmd is "sresume" -> ...
cmd is "stop immeditely" -> ...
cmd is "stop after current run" -> ...
cmd is "cancel stop after current run" -> ...
cmd is "custom" -> show_custom_page()
cmd is "odb" -> show_odb_page()
show_error()

K.O.

> Here is the list of mhttpd magic URLs.

See additional magic URLs at the very bottom:

> 
> http "get" path:
> 
> handle_http_message()
> handle_http_get()
> ?mjsonrpc_schema -> serve mjsonrpc_get_schema() // JSON RPC Schema in JSON format
> ?mjsonrpc_schema_text -> serve mjsonrpc_schema_to_text() // same, but human-readable
> handle_decode_get()
> decode_get()
> interprete()
> 
> http "post" path:
> 
> handle_http_message()
> handle_http_post()
> ?mjsonrpc -> serve mjsonrpc_decode_post_data() // process RPC request
> handle_decode_post()
> decode_post()
> - maybe decode file attachment
> interprete()
> 
> interprete() path:
> 
> url contains favicon.{ico,png} -> send_icon()
> url contains mhttpd.css -> send_css() (see ODB /Experiment/CSS File) // obsolete? see midas.css below
> url ends with "mp3" -> send_resource(url) // alarm sound
> url contains midas.js -> send_resource("midas.js")
> url contains midas.css -> send_resource("midas.css")
> url ... ditto mhttpd.js
> url ... ditto obsolete.js
> url ... ditto controls.js
> cmd is "example" -> send_resource("example.html")
> ?script -> cm_exec_script(), see ODB /Script/...
> ?customscript -> same, see ODB /CustomScript/...
> cmd is "start" -> send resource start.html
> cmd is blank -> send resource status.html
> cmd is "status" -> send resource status.html
> cmd is "newODB" -> send resource "odb.html" // not used at the moment
> cmd is "programs" -> programs.html
> cmd is "alarms" -> alarms.html
> cmd is "transition" -> transition.html
> cmd is "messages" -> messages.html
> cmd is "config" and url is not "HS/" -> config.html
> cmd is "chat" -> chat.html
> cmd is "buffers" -> buffers.html
> // elog section
> cmd is "Show elog" -> elog
> cmd is "Query elog" -> elog
> cmd is "New elog" -> elog
> cmd is "Edit elog" -> elog
> cmd is "Reply elog" -> elog
> cmd is "Last elog" -> elog
> cmd is "Submit Query" -> elog
> // end of elog section
> url is "spinning-wheel.gif" -> send_resource("spinning-wheel.gif")

// "new custom pages" moved to the bottom

> // section for old AJAX requests
> cmd is "jset", "jget", etc -> javascript_commands()
> // commented out: send_resource(command+".html") // if cmd is "start" will send start.html
> cmd is "mscb" -> show_mscb_page()
> cmd is "help" -> show_help_page()
> cmd is "trigger" -> send RPC RPC_MANUAL_TRIG
> cmd is "Next subrun" -> set ODB "/Logger/Next subrun" to TRUE
> cmd is "cancel" -> redirect to getparam("redir")
> cmd is "set" -> show_set_page() // set ODB value
> cmd is "find" -> show_find_page()
> cmd is "CNAF" or url is "CNAF" -> show_cnaf_page()
> cmd is "elog" -> redirect to external ELOG or send_resource("elog_show.html")
> cmd starts with "Elog last" -> send_resource("elog_query.html") // Elog last N days & co
> cmd is "Create Elog from this page" -> redirect to "?cmd=new elog" // called from ODB editor
> cmd is "Submit elog" -> submit_elog() // usually a POST request from the "elog_edit.html"
> cmd is "elog_att" -> show_elog_attachment()
> cmd is "accept" -> what does this do?!?
> cmd is "eqtable" -> show_eqtable_path() // page showing equipment variables as a table ("slow control page")
> // section for the sequencer
> cmd is "sequencer" -> show_seq_page()
> cmd is "start script" -> seq
> cmd is "cancel script" -> seq
> cmd is "load script" -> ...
> cmd is "new script" -> ...
> cmd is "save script" -> ...
> cmd is "edit script" -> ...
> cmd is "spause" -> ...
> cmd is "sresume" -> ...
> cmd is "stop immeditely" -> ...
> cmd is "stop after current run" -> ...
> cmd is "cancel stop after current run" -> ...
> // end of sequencer
> cmd is "odb" -> show_odb_page()

if ODB path URL exists, redirect to the odb editor with odb_path=URL // this restores the old URL scheme for the ODB editor

> cmd is "custom" -> show_custom_page()

odb entry exists "/Custom/Images/URL/Background" -> show_custom_gif(URL)
odb entry exists "/Custom/URL" or "/Custom/URL&" or "/Custom/URL!" -> show_custom_page(URL)
-- inside show_custom_page(URL):
-- if URL contains ".gif" -> show_custom_gif(URL)
-- if URL contains "." (i.e. "bnmr.css") -> show_custom_file(URL) -> send_file()
-- otherwise process custom page (substitute <odb> tags, etc)

// section "new custom pages"
if ODB /Custom exists,
create blank ODB /Custom/Path if it does not exist yet
if URL contains "/" or DIR_SEPARATOR, reject it with an error (prevent escape from file jail)
if ODB /Custom/Path is not blank, concatenate value of ODB /CustomPath and the URL
if this file exists, send_file() it.
// end of "new custom pages" section

try send_resource(URL) // this serves "status.html" & co

> show_error()
> 
> K.O.

K.O.

> > Here is the list of mhttpd magic URLs.
> See additional magic URLs at the very bottom:

added redirect for ODB top level "root"

> > 
> > http "get" path:
> > 
> > handle_http_message()
> > handle_http_get()
> > ?mjsonrpc_schema -> serve mjsonrpc_get_schema() // JSON RPC Schema in JSON format
> > ?mjsonrpc_schema_text -> serve mjsonrpc_schema_to_text() // same, but human-readable
> > handle_decode_get()
> > decode_get()
> > interprete()
> > 
> > http "post" path:
> > 
> > handle_http_message()
> > handle_http_post()
> > ?mjsonrpc -> serve mjsonrpc_decode_post_data() // process RPC request
> > handle_decode_post()
> > decode_post()
> > - maybe decode file attachment
> > interprete()
> > 
> > interprete() path:
> > 
> > url contains favicon.{ico,png} -> send_icon()
> > url contains mhttpd.css -> send_css() (see ODB /Experiment/CSS File) // obsolete? see midas.css below
> > url ends with "mp3" -> send_resource(url) // alarm sound
> > url contains midas.js -> send_resource("midas.js")
> > url contains midas.css -> send_resource("midas.css")
> > url ... ditto mhttpd.js
> > url ... ditto obsolete.js
> > url ... ditto controls.js
> > cmd is "example" -> send_resource("example.html")
> > ?script -> cm_exec_script(), see ODB /Script/...
> > ?customscript -> same, see ODB /CustomScript/...
> > cmd is "start" -> send resource start.html
> > cmd is blank -> send resource status.html
> > cmd is "status" -> send resource status.html
> > cmd is "newODB" -> send resource "odb.html" // not used at the moment
> > cmd is "programs" -> programs.html
> > cmd is "alarms" -> alarms.html
> > cmd is "transition" -> transition.html
> > cmd is "messages" -> messages.html
> > cmd is "config" and url is not "HS/" -> config.html
> > cmd is "chat" -> chat.html
> > cmd is "buffers" -> buffers.html
> > // elog section
> > cmd is "Show elog" -> elog
> > cmd is "Query elog" -> elog
> > cmd is "New elog" -> elog
> > cmd is "Edit elog" -> elog
> > cmd is "Reply elog" -> elog
> > cmd is "Last elog" -> elog
> > cmd is "Submit Query" -> elog
> > // end of elog section
> > url is "spinning-wheel.gif" -> send_resource("spinning-wheel.gif")
> 
> // "new custom pages" moved to the bottom
> 
> > // section for old AJAX requests
> > cmd is "jset", "jget", etc -> javascript_commands()
> > // commented out: send_resource(command+".html") // if cmd is "start" will send start.html
> > cmd is "mscb" -> show_mscb_page()
> > cmd is "help" -> show_help_page()
> > cmd is "trigger" -> send RPC RPC_MANUAL_TRIG
> > cmd is "Next subrun" -> set ODB "/Logger/Next subrun" to TRUE
> > cmd is "cancel" -> redirect to getparam("redir")
> > cmd is "set" -> show_set_page() // set ODB value
> > cmd is "find" -> show_find_page()
> > cmd is "CNAF" or url is "CNAF" -> show_cnaf_page()
> > cmd is "elog" -> redirect to external ELOG or send_resource("elog_show.html")
> > cmd starts with "Elog last" -> send_resource("elog_query.html") // Elog last N days & co
> > cmd is "Create Elog from this page" -> redirect to "?cmd=new elog" // called from ODB editor
> > cmd is "Submit elog" -> submit_elog() // usually a POST request from the "elog_edit.html"
> > cmd is "elog_att" -> show_elog_attachment()
> > cmd is "accept" -> what does this do?!?
> > cmd is "eqtable" -> show_eqtable_path() // page showing equipment variables as a table ("slow control page")
> > // section for the sequencer
> > cmd is "sequencer" -> show_seq_page()
> > cmd is "start script" -> seq
> > cmd is "cancel script" -> seq
> > cmd is "load script" -> ...
> > cmd is "new script" -> ...
> > cmd is "save script" -> ...
> > cmd is "edit script" -> ...
> > cmd is "spause" -> ...
> > cmd is "sresume" -> ...
> > cmd is "stop immeditely" -> ...
> > cmd is "stop after current run" -> ...
> > cmd is "cancel stop after current run" -> ...
> > // end of sequencer
> > cmd is "odb" -> show_odb_page()
> 

if URL is "root", redirect to odb editor at the odb top level

> if ODB path URL exists, redirect to the odb editor with odb_path=URL // this restores the old URL scheme for the ODB editor
> 
> > cmd is "custom" -> show_custom_page()
> 
> odb entry exists "/Custom/Images/URL/Background" -> show_custom_gif(URL)
> odb entry exists "/Custom/URL" or "/Custom/URL&" or "/Custom/URL!" -> show_custom_page(URL)
> -- inside show_custom_page(URL):
> -- if URL contains ".gif" -> show_custom_gif(URL)
> -- if URL contains "." (i.e. "bnmr.css") -> show_custom_file(URL) -> send_file()
> -- otherwise process custom page (substitute <odb> tags, etc)
> 
> // section "new custom pages"
> if ODB /Custom exists,
> create blank ODB /Custom/Path if it does not exist yet
> if URL contains "/" or DIR_SEPARATOR, reject it with an error (prevent escape from file jail)
> if ODB /Custom/Path is not blank, concatenate value of ODB /CustomPath and the URL
> if this file exists, send_file() it.
> // end of "new custom pages" section
> 
> try send_resource(URL) // this serves "status.html" & co
> 
> > show_error()
> > 
> > K.O.
> 
> K.O.

> > > Here is the list of mhttpd magic URLs.
> > See additional magic URLs at the very bottom:
> 
> added redirect for ODB top level "root"
> 
> > > 
> > > http "get" path:
> > > 
> > > handle_http_message()
> > > handle_http_get()
> > > ?mjsonrpc_schema -> serve mjsonrpc_get_schema() // JSON RPC Schema in JSON format
> > > ?mjsonrpc_schema_text -> serve mjsonrpc_schema_to_text() // same, but human-readable
> > > handle_decode_get()
> > > decode_get()
> > > interprete()
> > > 
> > > http "post" path:
> > > 
> > > handle_http_message()
> > > handle_http_post()
> > > ?mjsonrpc -> serve mjsonrpc_decode_post_data() // process RPC request
> > > handle_decode_post()
> > > decode_post()
> > > - maybe decode file attachment
> > > interprete()
> > > 
> > > interprete() path:
> > > 
> > > url contains favicon.{ico,png} -> send_icon()
> > > url contains mhttpd.css -> send_css() (see ODB /Experiment/CSS File) // obsolete? see midas.css below
> > > url ends with "mp3" -> send_resource(url) // alarm sound
> > > url contains midas.js -> send_resource("midas.js")
> > > url contains midas.css -> send_resource("midas.css")
> > > url ... ditto mhttpd.js
> > > url ... ditto obsolete.js
> > > url ... ditto controls.js
> > > cmd is "example" -> send_resource("example.html")
> > > ?script -> cm_exec_script(), see ODB /Script/...
> > > ?customscript -> same, see ODB /CustomScript/...
> > > cmd is "start" -> send resource start.html
> > > cmd is blank -> send resource status.html
> > > cmd is "status" -> send resource status.html
> > > cmd is "newODB" -> send resource "odb.html" // not used at the moment
> > > cmd is "programs" -> programs.html
> > > cmd is "alarms" -> alarms.html
> > > cmd is "transition" -> transition.html
> > > cmd is "messages" -> messages.html
> > > cmd is "config" and url is not "HS/" -> config.html
> > > cmd is "chat" -> chat.html
> > > cmd is "buffers" -> buffers.html
> > > // elog section
> > > cmd is "Show elog" -> elog
> > > cmd is "Query elog" -> elog
> > > cmd is "New elog" -> elog
> > > cmd is "Edit elog" -> elog
> > > cmd is "Reply elog" -> elog
> > > cmd is "Last elog" -> elog
> > > cmd is "Submit Query" -> elog
> > > // end of elog section
> > > url is "spinning-wheel.gif" -> send_resource("spinning-wheel.gif")
> > // "new custom pages" moved to the bottom
> > > // section for old AJAX requests
> > > cmd is "jset", "jget", etc -> javascript_commands()
> > > // commented out: send_resource(command+".html") // if cmd is "start" will send start.html
> > > cmd is "mscb" -> show_mscb_page()
> > > cmd is "help" -> show_help_page()
> > > cmd is "trigger" -> send RPC RPC_MANUAL_TRIG
> > > cmd is "Next subrun" -> set ODB "/Logger/Next subrun" to TRUE
> > > cmd is "cancel" -> redirect to getparam("redir")
> > > cmd is "set" -> show_set_page() // set ODB value
> > > cmd is "find" -> show_find_page()
> > > cmd is "CNAF" or url is "CNAF" -> show_cnaf_page()
> > > cmd is "elog" -> redirect to external ELOG or send_resource("elog_show.html")
> > > cmd starts with "Elog last" -> send_resource("elog_query.html") // Elog last N days & co
> > > cmd is "Create Elog from this page" -> redirect to "?cmd=new elog" // called from ODB editor
> > > cmd is "Submit elog" -> submit_elog() // usually a POST request from the "elog_edit.html"
> > > cmd is "elog_att" -> show_elog_attachment()
> > > cmd is "accept" -> what does this do?!?
> > > cmd is "eqtable" -> show_eqtable_path() // page showing equipment variables as a table ("slow control page")
> > > // section for the sequencer
> > > cmd is "sequencer" -> show_seq_page()
> > > cmd is "start script" -> seq
> > > cmd is "cancel script" -> seq
> > > cmd is "load script" -> ...
> > > cmd is "new script" -> ...
> > > cmd is "save script" -> ...
> > > cmd is "edit script" -> ...
> > > cmd is "spause" -> ...
> > > cmd is "sresume" -> ...
> > > cmd is "stop immeditely" -> ...
> > > cmd is "stop after current run" -> ...
> > > cmd is "cancel stop after current run" -> ...
> > > // end of sequencer
> > > cmd is "odb" -> show_odb_page()
> if URL is "root", redirect to odb editor at the odb top level
> > if ODB path URL exists, redirect to the odb editor with odb_path=URL // this restores the old URL scheme for the ODB editor
> > > cmd is "custom" -> show_custom_page()
> > odb entry exists "/Custom/Images/URL/Background" -> show_custom_gif(URL)
> > odb entry exists "/Custom/URL" or "/Custom/URL&" or "/Custom/URL!" -> show_custom_page(URL)
> > -- inside show_custom_page(URL):
> > -- if URL contains ".gif" -> show_custom_gif(URL)
> > -- if URL contains "." (i.e. "bnmr.css") -> show_custom_file(URL) -> send_file()
> > -- otherwise process custom page (substitute <odb> tags, etc)
> > // section "new custom pages"
> > if ODB /Custom exists,
> > create blank ODB /Custom/Path if it does not exist yet

if URL contains "..", reject it with an error (prevent escape from file jail)

> > if ODB /Custom/Path is not blank, concatenate value of ODB /CustomPath and the URL
> > if this file exists, send_file() it.
> > // end of "new custom pages" section
> > 
> > try send_resource(URL) // this serves "status.html" & co

Note: send_resource(URL) does not allow for path separator char "/" (and "\" on Windows) anywhere in the URL. This is to (a) prevent escape from 
the file jail. (b) enforce flat (on-level) name space.

> > 
> > > show_error()
> > > 
> > > K.O.
> > 
> > K.O.

> > > 
> > > We have recently been experiencing a lot of lag with our midas control webpage,
> > > which is making it very frustrating to use. Has anyone experienced this, and do
> > > you have any advice to speed it up? Are there particular web browsers that work
> > > better than others, or certain settings that can make respond more quickly?
> > > 

Wes, you provided excessive information. Who is "we", what is your location (internet in africa is different from internet in canada),
what is your computer (rpi3 is different from mac mini), what is your os (fedora-1 is different from centos-7), what
is your browser (netscape is different from google-chrome).

As to "what browser should work", on MacOS, google-chrome and firefox should be ok (that's what I test), on Linux,
stock firefox (usually an oldish esr version) should work, on el7 and ubuntu google-chrome works. On windows, google-chrome
and firefox should be ok. microsoft browsers probably not ok (no testing). cellphone browsers also not tested (but google-chrome and firefox 
should be ok).

K.O.

Hi everyone, 

We have recently been experiencing a lot of lag with our midas control webpage,
which is making it very frustrating to use. Has anyone experienced this, and do
you have any advice to speed it up? Are there particular web browsers that work
better than others, or certain settings that can make respond more quickly?

Thanks!
Wes

> Hi everyone, 
> 
> We have recently been experiencing a lot of lag with our midas control webpage,
> which is making it very frustrating to use. Has anyone experienced this, and do
> you have any advice to speed it up? Are there particular web browsers that work
> better than others, or certain settings that can make respond more quickly?
> 
> Thanks!
> Wes

We saw this happening as well. In our case, we could track this down to mhttpd
taking a lot of CPU. A kill/restart of mhttpd is usually doing the trick (without
disturbing data taking). We did not find an obvious reason for this happening.

> > Hi everyone, 
> > 
> > We have recently been experiencing a lot of lag with our midas control webpage,
> > which is making it very frustrating to use. Has anyone experienced this, and do
> > you have any advice to speed it up? Are there particular web browsers that work
> > better than others, or certain settings that can make respond more quickly?
> > 
> > Thanks!
> > Wes
> 
> We saw this happening as well. In our case, we could track this down to mhttpd
> taking a lot of CPU. A kill/restart of mhttpd is usually doing the trick (without
> disturbing data taking). We did not find an obvious reason for this happening.

One place where mhttpd can be stalled (and even go into infornite loop) is making history plots.

If you ask for a history plot of 10 variables across 1 year, nobody can access any midas web page
until mhttpd finishes grinding through the history data. (with the old .hst history format is was exceedingly 
slow, with the new "file" format, it is pretty quick, but everybody still has to wait). If you leave this page 
open, it will autorefresh every so many minutes ensuring continuing delays for other mhttpd users.

The other place for stalling mhttpd was in the run transitions (mhttpd was unresponsive while executing a 
run transition), this was fixed by the multithreaded transitions.

To fix the unresponsive history requests, you can try to setup a separate "history mhttpd", run a second 
mhttpd on a different port (with "-H" if desired), put this URL of this mhttpd in ODB "/history/url". (if you 
are using my instructions for setting up the apache httpd proxy, you can see provisions for this. 
/history/url will be set to "https://proxy.host.net/history/").

If neither of the above, there is the usual culprits of bad networking somewhere, etc.

Best way to test if delays are in midas or elsewhere is to stand in front of your midas computer, run a 
current version of google-chrome or firefox right on it, there should be no delays.

K.O.

Something changed after my initial implementation of ipv6 in mhttpd
and listening to ipv6 http/https connections was broken.

It turns out, I do not need to listen to both ipv4 and ipv6 sockets,
it is sufficient to listen to just ipv6. ipv4 connections will also
magically work. see linux kernel "bindv6only" sysctl setting: https://sysctl-
explorer.net/net/ipv6/bindv6only/

The specific bug in mhttpd was to bind to ipv4 socket first, subsequent bind() to ipv6 socket 
fails with error "Address already in use", which is silent, not reported by the mongoose library. 
For reasons unknown, this does not happen to bind() to "localhost" aka ipv6 "::1".

Apparently other web servers (apache, nginx) are/were also affected by this problem. 
https://chrisjean.com/fix-nginx-emerg-bind-to-80-failed-98-address-already-in-use/

First fix was to bind to ipv6 first (success) and to ipv4 second (fails). Second fix
committed to git is to only listen to ipv6.

This works both on MacOS and on Linux. Linux reports the listener socket is "tcp6", MacOS reports 
the listener socket as "tcp46":

4ed0:javascript1 olchansk$ netstat -an | grep 808 | grep LISTEN
tcp46      0      0  *.8081                 *.*                    LISTEN     
tcp6       0      0  ::1.8080               *.*                    LISTEN     
tcp4       0      0  127.0.0.1.8080         *.*                    LISTEN     
4ed0:javascript1 olchansk$ 

K.O.

> Something changed after my initial implementation of ipv6 in mhttpd
> and listening to ipv6 http/https connections was broken.

Reporting that mhttpd ipv6 works at CERN. The hostnames for ipv6 connections
come back as alphacpc05.ipv6.cern.ch instead of alphacpc05.cern.ch
so both are added to the http "insecure port" whitelist.

K.O.