Megatest

	       (begin
		 (debug:print-info 2 *default-log-port* "Gating server start, last start: "
				   (seconds->time-string fmodtime) ", time since last start: " delta ", required idletime: " idletime ", gating reason:" (if old-enough "another job started a server" "too soon to start another server"))
		 
		 (thread-sleep! ( + 1 idletime))
		 (server:wait-for-server-start-last-flag areapath)))))))

(define (server:get-servinfo-dir areapath)
  (let* ((spath (conc areapath"/.servinfo")))
    (if (not (file-exists? spath))
	(create-directory spath #t))
    spath))

;; gets server info and appends path to server file
;; sorts by age, oldest first
;;
;; returns list of (host port startseconds server-id servinfofile)
;;
(define (server:get-server-info-sorted areapath dbfname)
  (let* (
	 (sfiles   (server:find-server areapath dbfname))
	 (sdats    (filter car (map server:server-get-info sfiles))) ;; first element is #f if the file disappeared while being read
	 (sorted   (sort sdats (lambda (a b)
				 (let* ((starta (list-ref a 2))
					(startb (list-ref b 2)))
				   (if (eq? starta startb)
				       (string>? (list-ref a 3)(list-ref b 3)) ;; if servers started at same time look at server-id
				       (< starta startb))))))
	 (count    0))
    (for-each
     (lambda (rec)
       (if (or (> (length sorted) 1)
	       (common:low-noise-print 120 "server info sorted"))
	   (debug:print 2 *default-log-port* "SERVER #"count": "(string-intersperse (map conc sorted) ", ")))
       (set! count (+ count 1)))
     sorted)
    sorted))

(define (server:clean-up-old areapath)
  ;; any server file that has not been touched in ten minutes is effectively dead
  (let* ((sfiles (glob (conc (server:get-servinfo-dir areapath)"/*"))))
    (for-each
     (lambda (sfile)
       (let* ((modtime (handle-exceptions
			   exn
			 (begin
			   (debug:print 0 *default-log-port* "WARNING: failed to get modification file for "sfile)
			   (current-seconds))
			 (file-modification-time sfile))))
	 (if (and (number? modtime)
		  (> (- (current-seconds) modtime)
		     600))
	     (begin
	       (debug:print 0 *default-log-port* "WARNING: found old server info file "sfile", removing it.")
	       (handle-exceptions
		   exn
		 (debug:print 0 *default-log-port* "WARNING: failed to delete old server info file "sfile)
		 (delete-file sfile))))))
     sfiles)))



(define server-last-start 0)

;; oldest server alive determines host then choose random of youngest
;; five servers on that host
;;
;; mode:
;;   best - get best server (random of newest five)
;;   home - get home host based on oldest server
;;   info - print info
(define (server:choose-server areapath #!optional (mode 'best))
  ;; age is current-starttime
  ;; find oldest alive
  ;;   1. sort by age ascending and ping until good
  ;; find alive rand from youngest
  ;;   1. sort by age descending
  ;;   2. take five
  ;;   3. check alive, discard if not and repeat
  ;; first we clean up old server files
  (assert (eq? (rmt:transport-mode) 'http) "FATAL: server:run called with rmt:transport-mode="(rmt:transport-mode))
  (server:clean-up-old areapath)
  (let* ((since-last (- (current-seconds) server-last-start))
        (server-start-delay 10))     
    (if ( < (- (current-seconds) server-last-start) 10 )
      (begin
        (debug:print 2 *default-log-port* "server:choose-server: seconds since last server start: " (- (current-seconds) server-last-start))
        (debug:print 2 *default-log-port* "server:choose-server: last server start less than " server-start-delay " seconds ago. Sleeping " server-start-delay " seconds")
        (thread-sleep! server-start-delay)
      )
      (debug:print 2 *default-log-port* "server:choose-server: seconds since last server start: " (- (current-seconds) server-last-start))
    )
  )
  (let* ((serversdat  (server:get-servers-info areapath))
	 (servkeys    (hash-table-keys serversdat))
	 (by-time-asc (if (not (null? servkeys)) ;; NOTE: Oldest is last
			  (sort servkeys ;; list of "host:port"
				(lambda (a b)
				  (>= (list-ref (hash-table-ref serversdat a) 2)
				      (list-ref (hash-table-ref serversdat b) 2))))
			  '())))
    (debug:print 2 *default-log-port* "server:choose-server: serversdat: " serversdat)
    (debug:print 2 *default-log-port* "server:choose-server: servkeys: " servkeys)
    (if (not (null? by-time-asc))
	(let* ((oldest     (last by-time-asc))
	       (oldest-dat (hash-table-ref serversdat oldest))
	       (host       (list-ref oldest-dat 0))
	       (all-valid  (filter (lambda (x)
				     (equal? host (list-ref (hash-table-ref serversdat x) 0)))
				   by-time-asc))
	       (best-ten  (lambda ()
			     (if (> (length all-valid) 11)
				 (take (drop-right all-valid 1) 10) ;; remove the oldest from consideration so it can age out
				 (if (> (length all-valid) 8)
				     (drop-right all-valid 1)
				     all-valid))))
	       (names->dats (lambda (names)
			      (map (lambda (x)
				     (hash-table-ref serversdat x))
				   names)))
	       (am-home?    (lambda ()
			      (let* ((currhost (get-host-name))
				     (bestadrs (server:get-best-guess-address currhost)))
				(or (equal? host currhost)
				    (equal? host bestadrs))))))
	  (case mode
	    ((info)
	     (debug:print 0 *default-log-port* "oldest: "oldest-dat", selected host: "host", all-valid: "all-valid)
	     (debug:print 0 *default-log-port* "youngest: "(hash-table-ref serversdat (car all-valid))))
	    ((home)     host)
	    ((homehost) (cons host (am-home?))) ;; shut up old code
	    ((home?)    (am-home?))
	    ((best-ten)(names->dats (best-ten)))
	    ((all-valid)(names->dats all-valid))
	    ((best)     (let* ((best-ten (best-ten))
			       (len       (length best-ten)))
			  (hash-table-ref serversdat (list-ref best-ten (random len)))))
	    ((count)(length all-valid))
	    (else
	     (debug:print 0 *default-log-port* "ERROR: invalid command "mode)
	     #f)))
	(begin
	  (server:run areapath)
          (set! server-last-start (current-seconds))
	  ;; (thread-sleep! 3)
	  (case mode
	    ((homehost) (cons #f #f))
	    (else	#f))))))




;; oldest server alive determines host then choose random of youngest
;; five servers on that host
;;
(define (server:get-servers-info areapath)
  ;; (assert *toppath* "FATAL: server:get-servers-info called before *toppath* has been set.")
  (let* ((servinfodir (server:get-servinfo-dir areapath))) ;; (conc *toppath*"/.servinfo")))
    (if (not (file-exists? servinfodir))
	(create-directory servinfodir))
    (let* ((allfiles    (glob (conc servinfodir"/*")))
	   (res         (make-hash-table)))
      (for-each
       (lambda (f)
	 (let* ((hostport  (pathname-strip-directory f))
		(serverdat (server:logf-get-start-info f)))
	   (match serverdat
	     ((host port start server-id pid)
	      (if (and host port start server-id pid)
		  (hash-table-set! res hostport serverdat)
		  (debug:print-info 2 *default-log-port* "bad server info for "f": "serverdat)))
	     (else
	      (debug:print-info 2 *default-log-port* "bad server info for "f": "serverdat)))))
       allfiles)
      res)))



;; given a path to a server info file return: host port startseconds server-id pid dbfname logf
;; example of what it's looking for in the log file:
;;     SERVER STARTED: 10.38.175.67:50216 AT 1616502350.0 server-id: 4907e90fc55c7a09694e3f658c639cf4 
;;
(define (server:server-get-info logf)
  (let ((server-rx    (regexp "^SERVER STARTED: (\\S+):(\\d+) AT ([\\d\\.]+) server-id: (\\S+) pid: (\\d+) dbfname: (\\S+)")) ;; SERVER STARTED: host:port AT timesecs server id
	(bad-dat      (list #f #f #f #f #f #f logf)))
     (let ((fdat     (handle-exceptions
			 exn
		       (begin
			 ;; WARNING: this is potentially dangerous to blanket ignore the errors
			 (debug:print-info 0 *default-log-port* "Unable to get server info from "logf", exn="(condition->list exn))
			 '()) ;; no idea what went wrong, call it a bad server, return empty list
		       (with-input-from-file logf read-lines))))
       (if (null? fdat) ;; bad data, return bad-dat
	   bad-dat
	   (let loop ((inl  (car fdat))
		      (tail (cdr fdat))
		      (lnum 0))
	     (let ((mlst (string-match server-rx inl)))
	       (if (not mlst)
		   (if (> lnum 500) ;; give up if more than 500 lines of server log read
		       bad-dat
		       (if (null? tail)
			   bad-dat
			   (loop (car tail)(cdr tail)(+ lnum 1))))
		   (match mlst ;; have a not null list
		     ((_ host port start server-id pid dbfname)
		      (list host
			    (string->number port)
			    (string->number start)
			    server-id
			    (string->number pid)
			    dbfname
			    logf))
		     (else
		      (debug:print 0 *default-log-port* "ERROR: did not recognise SERVER line info "mlst)
		      bad-dat)))))))))



;; find valid server
;; get servers listed, last part of name must match :<dbfname>
;; if more than one, wait one second and look again
;; future: ping oldest, if alive remove other :<dbfname> files
;;
(define (server:find-server areapath dbfname)
  (let* ((servdir  (server:get-servinfo-dir areapath))
	 (sfiles   (glob (conc servdir"/*:"dbfname)))
         (good-files '()))
         (for-each 
           (lambda (sfile)
             (let* ((sinfo (tt:server-get-info sfile))
                 (host (list-ref sinfo 0))
                 (port (list-ref sinfo 1))
                 (server-id (list-ref sinfo 3))
                 (pid (list-ref sinfo 4))
                 (status (system (conc "ssh " host " ps " pid " > /dev/null")))
                 )
                (if (= status 0)
                  (set! good-files (cons sfile good-files))
                  (delete-file* sfile)
                )
             )
           )
           sfiles
         )
    (debug:print-info 2 *default-log-port* "server:find-server: good-files: " good-files " sfiles: " sfiles)
    good-files))



        
;; kind start up of server, wait before allowing another server for a given
;; area to be launched
;;
(define (server:kind-run areapath)
  ;; look for $MT_RUN_AREA_HOME/logs/server-start-last
  ;; and wait for it to be at least <server idletime> seconds old
  (server:wait-for-server-start-last-flag areapath)
  (if (not (server:check-if-running areapath)) ;; why try if there is already a server running?
      (let* ((lock-file    (conc areapath "/logs/server-start.lock")))
	(let* ((start-flag (conc areapath "/logs/server-start-last")))
	  (common:simple-file-lock-and-wait lock-file expire-time: 25)
	  (debug:print-info  2 *default-log-port* "server:kind-run: touching " start-flag)
	  (system (conc "touch " start-flag)) ;; lazy but safe
	  (server:run areapath)
	  (thread-sleep! 20) ;; don't release the lock for at least a few seconds. And allow time for the server startup to get to "SERVER STARTED".
	  (common:simple-file-release-lock lock-file)))
      (debug:print-info 0 *default-log-port* "Found server already running. NOT trying to start another.")))

;; return servid
;; side-effects:
;;   ttdat-cleanup-proc is populated with function to remove the serverinfo file
(define (server:create-server-registration-file areapath host port)
  (let* (
	 (servdir  (server:get-servinfo-dir areapath))
	 (servinf (conc servdir"/"host":"port"-"(current-process-id)))
	 (serv-id (server:mk-signature areapath))
	 (clean-proc (lambda ()
		       (delete-file* servinf)
		       )))
    (assert (and host port) "FATAL: tt:create-server-registration-file called with no conn")
    (tt-cleanup-proc-set! ttdat clean-proc)
    (tt-servinf-file-set! ttdat servinf)
    (with-output-to-file servinf
      (lambda ()
	(print "SERVER STARTED: "host":"port" AT "(current-seconds)" server-id: "serv-id" pid: "(current-process-id))))
      serv-id))



;; this one seems to be the general entry point
;;
(define (server:start-and-wait areapath #!key (timeout 60))
  (let ((give-up-time (+ (current-seconds) timeout)))
    (let loop ((server-info (server:check-if-running areapath))
	       (try-num    0))