Megatest

(define (rmt:send-receive-orig cmd rid params #!key (attemptnum 1)(area-dat #f)) ;; start attemptnum at 1 so the modulo below works as expected

  #;(common:telemetry-log (conc "rmt:"(->string cmd))
                        payload: `((rid . ,rid)
                                   (params . ,params)))
                          
  
  ;;DOT digraph megatest_state_status {
  ;;DOT   ranksep=0;
  ;;DOT   // rankdir=LR;
  ;;DOT   node [shape="box"];
  ;;DOT "rmt:send-receive" -> MUTEXLOCK;
  ;;DOT { edge [style=invis];"case 1" -> "case 2" -> "case 3" -> "case 4" -> "case 5" -> "case 6" -> "case 7" -> "case 8" -> "case 9" -> "case 10" -> "case 11"; }
  ;; do all the prep locked under the rmt-mutex
  (mutex-lock! *rmt-mutex*)
  
  ;; 1. check if server is started IFF cmd is a write OR if we are not on the homehost, store in runremote
  ;; 2. check the age of the connections. refresh the connection if it is older than timeout-20 seconds.
  ;; 3. do the query, if on homehost use local access
  ;;
  (let* ((start-time    (current-seconds)) ;; snapshot time so all use cases get same value
         (areapath      *toppath*);; TODO - resolve from dbstruct to be compatible with multiple areas
	 (runremote     (or area-dat
			    *runremote*))
	 (readonly-mode (rmtmod:calc-ro-mode runremote *toppath*)))

    ;; DOT INIT_RUNREMOTE; // leaving off - doesn't really add to the clarity
    ;; DOT MUTEXLOCK -> INIT_RUNREMOTE [label="no remote?"];
    ;; DOT INIT_RUNREMOTE -> MUTEXLOCK;
    ;; ensure we have a record for our connection for given area
    (if (not runremote)                   ;; can remove this one. should never get here.         
	(begin
	  (set! *runremote* (make-remote))
	  (set! runremote   *runremote*))) ;; new runremote will come from this on next iteration
    
    ;; DOT SET_HOMEHOST; // leaving off - doesn't really add to the clarity
    ;; DOT MUTEXLOCK -> SET_HOMEHOST [label="no homehost?"];
    ;; DOT SET_HOMEHOST -> MUTEXLOCK;
    ;; ensure we have a homehost record
    (if (not (pair? (remote-hh-dat runremote)))  ;; not on homehost
	(thread-sleep! 0.1) ;; since we shouldn't get here, delay a little
	(remote-hh-dat-set! runremote (common:get-homehost)))
    
    ;;(print "BB> readonly-mode is "readonly-mode" dbfile is "dbfile)
    (cond
     ;;DOT EXIT;
     ;;DOT MUTEXLOCK -> EXIT [label="> 15 attempts"]; {rank=same "case 1" "EXIT" }
     ;; give up if more than 15 attempts
     ((> attemptnum 15)
      (debug:print 0 *default-log-port* "ERROR: 15 tries to start/connect to server. Giving up.")
      (exit 1))

     ;;DOT CASE2 [label="local\nreadonly\nquery"];
     ;;DOT MUTEXLOCK -> CASE2; {rank=same "case 2" CASE2}
     ;;DOT CASE2 -> "rmt:open-qry-close-locally";
     ;; readonly mode, read request-  handle it - case 2
     ((and readonly-mode
           (member cmd api:read-only-queries)) 
      (mutex-unlock! *rmt-mutex*)
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case 2")
      (rmt:open-qry-close-locally cmd 0 params)
      )

     ;;DOT CASE3 [label="write in\nread-only mode"];
     ;;DOT MUTEXLOCK -> CASE3 [label="readonly\nmode?"]; {rank=same "case 3" CASE3}
     ;;DOT CASE3 -> "#f";
     ;; readonly mode, write request.  Do nothing, return #f
     (readonly-mode (extras-readonly-mode *rmt-mutex* *default-log-port* cmd params))

     ;; This block was for pre-emptively resetting the connection if there had been no communication for some time.
     ;; I don't think it adds any value. If the server is not there, just fail and start a new connection.
     ;; also, the expire-time calculation might not be correct. We want, time-since-last-server-access > (server:get-timeout)
     ;;
     ;;DOT CASE4 [label="reset\nconnection"];
     ;;DOT MUTEXLOCK -> CASE4 [label="have connection,\nlast_access > expire_time"]; {rank=same "case 4" CASE4}
     ;;DOT CASE4 -> "rmt:send-receive";
     ;; reset the connection if it has been unused too long
     ((and runremote
           (remote-conndat runremote)
	   (> (current-seconds) ;; if it has been more than server-timeout seconds since last contact, close this connection and start a new on
	      (+ (http-transport:server-dat-get-last-access (remote-conndat runremote))
		 (remote-server-timeout runremote))))
      (debug:print-info 0 *default-log-port* "Connection to " (remote-server-url runremote) " expired due to no accesses, forcing new connection.")
      (http-transport:close-connections area-dat: runremote)
      (remote-conndat-set! runremote #f) ;; invalidate the connection, thus forcing a new connection.
      (mutex-unlock! *rmt-mutex*)
      (rmt:send-receive-orig cmd rid params attemptnum: attemptnum))
     
     ;;DOT CASE5 [label="local\nread"];
     ;;DOT MUTEXLOCK -> CASE5 [label="server not required,\non homehost,\nread-only query"]; {rank=same "case 5" CASE5};
     ;;DOT CASE5 -> "rmt:open-qry-close-locally";

     ;; on homehost and this is a read
     ((and (not (remote-force-server runremote)) ;; honor forced use of server, i.e. server NOT required
	   (cdr (remote-hh-dat runremote))       ;; on homehost
           (member cmd api:read-only-queries))   ;; this is a read
      (mutex-unlock! *rmt-mutex*)
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case  5")
      (rmt:open-qry-close-locally cmd 0 params))

     ;;DOT CASE6 [label="init\nremote"];
     ;;DOT MUTEXLOCK -> CASE6 [label="on homehost,\nwrite query,\nhave server,\ncan't reach it"]; {rank=same "case 6" CASE6};
     ;;DOT CASE6 -> "rmt:send-receive";
     ;; on homehost and this is a write, we already have a server, but server has died
     ((and (cdr (remote-hh-dat runremote))           ;; on homehost
           (not (member cmd api:read-only-queries))  ;; this is a write
           (remote-server-url runremote)             ;; have a server
           (not (server:ping (remote-server-url runremote))))  ;; server has died. NOTE: this is not a cheap call! Need better approach.
      (set! *runremote* (make-remote))
      (remote-force-server-set! runremote (common:force-server?))
      (mutex-unlock! *rmt-mutex*)
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case  6")
      (rmt:send-receive-orig cmd rid params attemptnum: attemptnum))

     ;;DOT CASE7 [label="homehost\nwrite"];
     ;;DOT MUTEXLOCK -> CASE7 [label="server not required,\non homehost,\na write,\nhave a server"]; {rank=same "case 7" CASE7};
     ;;DOT CASE7 -> "rmt:open-qry-close-locally";
     ;; on homehost and this is a write, we already have a server
     ((and (not (remote-force-server runremote))     ;; honor forced use of server, i.e. server NOT required
	   (cdr (remote-hh-dat runremote))           ;; on homehost
           (not (member cmd api:read-only-queries))  ;; this is a write
           (remote-server-url runremote))            ;; have a server
      (mutex-unlock! *rmt-mutex*)
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case  4.1")
      (rmt:open-qry-close-locally cmd 0 params))

     ;;DOT CASE8 [label="force\nserver"];
     ;;DOT MUTEXLOCK -> CASE8 [label="server not required,\nhave homehost info,\nno connection yet,\nnot a read-only query"]; {rank=same "case 8" CASE8};
     ;;DOT CASE8 -> "rmt:open-qry-close-locally";
     ;;  on homehost, no server contact made and this is a write, passively start a server 
     ((and (not (remote-force-server runremote))     ;; honor forced use of server, i.e. server NOT required
	   (cdr (remote-hh-dat runremote))           ;; have homehost
           (not (remote-server-url runremote))       ;; no connection yet
	   (not (member cmd api:read-only-queries))) ;; not a read-only query
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case  8")
      (let ((server-url  (server:check-if-running *toppath*))) ;; (server:read-dotserver->url *toppath*))) ;; (server:check-if-running *toppath*))) ;; Do NOT want to run server:check-if-running - very expensive to do for every write call
	(if server-url
	    (remote-server-url-set! runremote server-url) ;; the string can be consumed by the client setup if needed
	    (if (common:force-server?)
		(server:start-and-wait *toppath*)
		(server:kind-run *toppath*))))
      (remote-force-server-set! runremote (common:force-server?))
      (mutex-unlock! *rmt-mutex*)
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case  8.1")
      (rmt:open-qry-close-locally cmd 0 params))

     ;;DOT CASE9 [label="force server\nnot on homehost"];
     ;;DOT MUTEXLOCK -> CASE9 [label="no connection\nand either require server\nor not on homehost"]; {rank=same "case 9" CASE9};
     ;;DOT CASE9 -> "start\nserver" -> "rmt:send-receive";
     ((or (and (remote-force-server runremote)              ;; we are forcing a server and don't yet have a connection to one
	       (not (remote-conndat runremote)))
	  (and (not (cdr (remote-hh-dat runremote)))        ;; not on a homehost 
	       (not (remote-conndat runremote))))           ;; and no connection
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case 9, hh-dat: " (remote-hh-dat runremote) " conndat: " (remote-conndat runremote))
      (mutex-unlock! *rmt-mutex*)
      (if (not (server:check-if-running *toppath*)) ;; who knows, maybe one has started up?
	  (server:start-and-wait *toppath*))
      (remote-conndat-set! runremote (rmt:get-connection-info *toppath*)) ;; calls client:setup which calls client:setup-http
      (rmt:send-receive-orig cmd rid params attemptnum: attemptnum)) ;; TODO: add back-off timeout as

     ;;DOT CASE10 [label="on homehost"];
     ;;DOT MUTEXLOCK -> CASE10 [label="server not required,\non homehost"]; {rank=same "case 10" CASE10};
     ;;DOT CASE10 -> "rmt:open-qry-close-locally";
     ;; all set up if get this far, dispatch the query
     ((and (not (remote-force-server runremote))
	   (cdr (remote-hh-dat runremote))) ;; we are on homehost
      (mutex-unlock! *rmt-mutex*)
      (debug:print-info 12 *default-log-port* "rmt:send-receive, case 10")
      (rmt:open-qry-close-locally cmd (if rid rid 0) params))

     ;;DOT CASE11 [label="send_receive"];
     ;;DOT MUTEXLOCK -> CASE11 [label="else"]; {rank=same "case 11" CASE11};
     ;;DOT CASE11 -> "rmt:send-receive" [label="call failed"];
     ;;DOT CASE11 -> "RESULT" [label="call succeeded"];
     ;; not on homehost, do server query
     (else (extras-case-11 *default-log-port* runremote cmd params attemptnum rid)))))
    ;;DOT }

;; bunch of small functions factored out of send-receive to make debug easier
;;

(define (extras-case-11 *default-log-port* runremote cmd params attemptnum rid)
  ;; (mutex-unlock! *rmt-mutex*)
  (debug:print-info 12 *default-log-port* "rmt:send-receive, case  9")