*/
/*
-
-
-
+***************************************************************************
+\f
State during service execution, process parentage and key fds
- ---- pipes, sockets
- 012 descriptors
- -==- fds shared
- || process parentage
- && session leader (daemon)
- & process group leader
-
- CALLER
- ||
- ||
+ ---- pipes, sockets
+ 012 descriptors
+ -==- fds shared
+ || process parentage
+ && session leader (daemon)
+ & process group leader
+
+
+ CALLER
+ ||
+ ||
|| listen watch-err/in
- || call (accept) \ ,------2
- || ,-----------------------------. SERVER -----0 WATCHER(C)
+ || call (accept) \ ,------2
+ || ,-----------------------------. SERVER -----0 WATCHER(C)
CLIENT 2--=fdpassed>=---------. \ || && | &&
- (C) 1--=fdpassed>=---------. \ \ || inotify
- 0--=fdpassed>=---------. \ \ \ || sockpath
- \ \ \ \ ||
- | | |\ | ||
- | | | \ | ||
+ (C) 1--=fdpassed>=---------. \ \ || inotify
+ 0--=fdpassed>=---------. \ \ \ || sockpath
+ \ \ \ \ ||
+ | | |\ | ||
+ | | | \ | ||
| \ | \ \ ||
\ \ \ \ MONITOR &
- \ \ \ `12 || |
- \ \ \ || |
+ \ \ \ `12 || |
+ \ \ \ || |
\ \ \ || |execterm
- \ \ \ || |
- \ \ \ || |
- \ \ 2 || |
- \ 1 EXECUTOR
- 0
-
- Control flow and causality
-
- | - \ / process control flow
- ... causes mediated by fds or other IPC etc.
+ \ \ \ || |
+ \ \ \ || |
+ \ \ 2 || |
+ \ 1 EXECUTOR
+ 0
+
+***************************************************************************
+\f
+ Control flow and causality
+
+ | - \ / process control flow
+ ... < > causes mediated by fds or other IPC etc.
&& session leader (daemon)
& process group leader
-
- CALLER
- |
- |fork/exec
- |
- CLIENT(C)
- |
+ # language/implementation boundary
+ *1 line continued elsewhere
+ event? condition
+ ______ process termination (after reaping, if shown)
+
+
+ CALLER
+ |
+ |fork/exec
+ |
+ CLIENT
+ |
attempt to connect, and read greeting
- |failure? \success?
- | \
- tidy up stale /run entries continue from send_fds, below
- acquire lock
- |
- retry attempt to connect, and read greeting
- |failure? \success?
- | \
- create listening socket release lock
- | \
- fork/daemonise continue from send_fds, below
- | `------------------.
+ |failure? \success?
+ | \
+ tidy up stale /run entries *1 (continue from send_fds, below)
+ acquire lock
+ |
+ retry attempt to connect, and read greeting
+ |failure? \success?
+ | \
+ create listening socket release lock
+ | \
+ fork/daemonise *1
+ | `------------------.
| WATCHER(C) &&
- |
- make "fake" initial call socketpair
- | C prefork-interp
- fork/exec + + + + + + + + + + + + + + + + + + + + + + + + + + + +
- | `------. Perl, application
- | + SCRIPT (setup)
- | + |
- | + script initialisation
- | + | Perl, application
- | + + + +| + + + + + + + + + + + + + + + + + + + + + + + +
- | + | Perl, prefork-interp
- | + identify fds from envirnment
- | + open syslog
- | + |
- | + dzemonize
- | ,...../ |
- waitpid + |
- | + fork for initial service
- | + |child |parent
- | + | |
- | + | SCRIPT [server] &&
- | + | |
- | + | ** accept / event loop **
- | + | / \ \ \
- | + | accepted? \ \ \idle timeout?
- | + | | \ \ \
- | + | fork child \ \ \
- | + | _________/ watch | |watch stderr eof?
- | + |/ stderr| | |
- | + SCRIPT [monitor] | | |
- | + | log msg | |
- | + setpgrpt & | | |
- | + | | | |
- | + send greeting | | |
- read greeting | exit
- | + |
- release lock | from read greeting success, above
- | ________ | ________/
- | / + |
- send fds.... |
- | + receive fds
- | + |
- | + fork for executor
- | + p |parent \child Perl, prefork-interp
- | + | + + + + \+ + + + + + + + + + + + + + + +
- | + | + execute service Perl, application
- | + | + |
- | +wait for read + |
- | + (select) + |
- | + | | + |
- | + | + exits
- | + | + kernel closes execterm
- | + | ,.........../|
- | + execterm? + |
- | + | + zombie
- | + | ,........../
- | + waitpid +
- | + | +
- | ,..,..send status +
- read status + +
- + +
-
- Or, if client is killed
-
- | | |
- | wait for read |
- | (select) |
- | | | |
- exits | |
- | | |
- kernel closes | |
- \....| |
- call? |
- | |
- kill whole pgrp... |
- | killled
- | zombie
- | ,..... ./
- waitpid
- |
- send exit status
- die due to SIGPIPE
-
-
- */
-/*
- * Process structure:
- * client (C wrapper) connects to server
- * (including reading ack byte)
- * if fails or garbage
- * === acquires lock ===
- * makes new listening socket
- * makes watcher pipes
- * forks watcher and awaits
- * makes first-instance socketpair
- * forks setup (script, sock fds indicated in env)
- * fd0, fd1, fd2: from-outer
- * other fd: call(client-end)(fake)
- * reaps setup (and reports error)
- * (implicitly releases lock)
- *
- * watcher fd[012]: watcher pipes
- * starts watch on socket path
- * sets stderr to line buffered
- * sets stdin to nonblocking
- * daemonises (one fork, becomes session leader)
- * when socket stat changes, quit
- *
- * setup (pre-exec) fd0: null,
- * fd[12]: fd2-from-outer
- * env fds: listener, call(server-end)(fake),
- * watcher read, watcher write
- * close fd: lockfile
- * possibly clean env, argv
- *
- * setup (script) runs initialisation parts of the script
- * at prefork establishment point:
- * setup (pm) [1] opens syslog
- * forks for server
- * [2] exits
- *
- * server (pm) [1] [fd0: null],
- * [fd[12]: fd2-from-outer]
- * setsid
- * right away, forks init monitor
- * [2] closes outer caller fds and call(fake)
- * [server (pm)] fd[012]: null
- * other fds: listener, syslog
- * runs in loop accepting and forking,
- * reaping and limiting children (incl init monitor)
- * reports failures of monitors to syslog
- *
- * [client (C wrapper)] if client connect succeeds:
- * now fd: call(client-end)
- * sends message with: cmdline, env
- * sends fds
- *
- * [server (script)] accepts, forks subseq monitor
- *
- * monitor [1] [fd0: null]
- * (init [fd[12]: init: fd2-from-outer; subseq: null]
- * or errors: init: fd2; subseq: syslog
- * subseq) other fds: syslog, call(server-end)
- * sends ack byte
- * receives args, env, fds
- * forks executor
- *
- * executor sorts out fds:
- * fd0, fd1, fd2: from-outer
- * close fds: call(server-end)
- * retained fds: syslog
- *
- * sets cmdline, env
- * runs main part of script
- * exits normally
- *
- * [monitor] [fd[012]: null]
- * [fd[12]: init: fd2-from-outer; subseq: null]
- * [errors: init: fd2; subseq: syslog]
- * reaps executor
- * reports status via socket
- *
- * [client (C wrapper)] [fd0, fd1, fd2: from-outer]
- * [other fd: call(client-end)]
- * receives status, exits appropriately
- * (if was bad signal, reports to stderr, exits 127)
- */
+ |
+ make "fake" initial call socketpair (C)
+ | prefork-interp
+ fork/exec #########################################################
+ | `-------------. application
+ | # SCRIPT (setup)
+ | # |
+ | # script initialisation
+ | # | application
+ | # ########|#############################################
+ | # | prefork-interp
+ | # identify fds from envirnment (Perl)
+ | # open syslog
+ | # |
+ | # dzemonize
+ | ,.....<....../ |
+ waitpid # fork for initial service
+ | # |child? |parent?
+ | # | |
+ | # | SCRIPT [server] &&
+ | # | |
+ | # | ** accept / event loop **
+ | # | accepted? \ \ \
+ | # | / \ watch\ \idle
+ | # | fork child \stderr\ \timeout?
+ | # | _________/ | | |
+ | # |/ |read? | |
+ | # SCRIPT [monitor] | eof?| |
+ | # setpgrpt & | | |
+ | # | log msg | |
+ read ,....<.....send greeting | | |
+ greeting # | ___________________
+ | # |
+ release # |
+ lock *1 # |
+ | / # |
+ send fds.....>.... |
+ | # \receive fds
+ | # |
+ | # fork for executor (Perl)
+ | # |parent? \child? prefork-interp
+ | # | ######\############################
+ | # | # SCRIPT (executor) application
+ | # | # execute service
+ | # wait for read # |
+ | # (select) # terminates
+ | # | | # |
+ | # | # kernel closes execterm
+ | # | ,......<....../|
+ | # execterm? # |
+ | # | # zombie
+ | # | | ,......<...../
+ | # waitpid # _______________
+ | # | #
+ | ,....<....,..send status #
+ read status # ________________ #
+ _____________ #
+
+
+ ********** Or, if client is killed **********
+
+ | # | # execute service
+ terminates # wait for read # |
+ | # (select) # |
+ kernel # | | # |
+ closes call # | # |
+ \..>......_ | # |
+ _____________ # \|call? # |
+ # | # |
+ # kill whole pgrp... # killled
+ # | # zombie
+ # | | ,......<....../
+ # waitpid # _______________
+ # | #
+ # send exit status #
+ # _____SIGPIPE______ #
+
+***************************************************************************
+\f
+ Sequence of events and fd pluming.
+ NB INCOMPLETE - does not cover execterm, cleanup
+
+ client (C wrapper) connects to server
+ (including reading ack byte)
+ if fails or garbage
+ === acquires lock ===
+ makes new listening socket
+ makes watcher pipes
+ forks watcher and awaits
+ makes first-instance socketpair
+ forks setup (script, sock fds indicated in env)
+ fd0, fd1, fd2: from-outer
+ other fd: call(client-end)(fake)
+ reaps setup (and reports error)
+ (implicitly releases lock)
+
+ watcher fd[012]: watcher pipes
+ starts watch on socket path
+ sets stderr to line buffered
+ sets stdin to nonblocking
+ daemonises (one fork, becomes session leader)
+ when socket stat changes, quit
+
+ setup (pre-exec) fd0: null,
+ fd[12]: fd2-from-outer
+ env fds: listener, call(server-end)(fake),
+ watcher read, watcher write
+ close fd: lockfile
+ possibly clean env, argv
+
+ setup (script) runs initialisation parts of the script
+ at prefork establishment point:
+ setup (pm) [1] opens syslog
+ forks for server
+ [2] exits
+
+ server (pm) [1] [fd0: null],
+ [fd[12]: fd2-from-outer]
+ setsid
+ right away, forks init monitor
+ [2] closes outer caller fds and call(fake)
+ [server (pm)] fd[012]: null
+ other fds: listener, syslog
+ runs in loop accepting and forking,
+ reaping and limiting children (incl init monitor)
+ reports failures of monitors to syslog
+
+ [client (C wrapper)] if client connect succeeds:
+ now fd: call(client-end)
+ sends message with: cmdline, env
+ sends fds
+
+ [server (script)] accepts, forks subseq monitor
+
+ monitor [1] [fd0: null]
+ (init [fd[12]: init: fd2-from-outer; subseq: null]
+ or errors: init: fd2; subseq: syslog
+ subseq) other fds: syslog, call(server-end)
+ sends ack byte
+ receives args, env, fds
+ forks executor
+
+ executor sorts out fds:
+ fd0, fd1, fd2: from-outer
+ close fds: call(server-end)
+ retained fds: syslog
+
+ sets cmdline, env
+ runs main part of script
+ exits normally
+
+ [monitor] [fd[012]: null]
+ [fd[12]: init: fd2-from-outer; subseq: null]
+ [errors: init: fd2; subseq: syslog]
+ reaps executor
+ reports status via socket
+
+ [client (C wrapper)] [fd0, fd1, fd2: from-outer]
+ [other fd: call(client-end)]
+ receives status, exits appropriately
+ (if was bad signal, reports to stderr, exits 127)
+
+***************************************************************************
+\f
+*/
#include <arpa/inet.h>
~ian / chiark-utils.git / commitdiff