Added initial health-check command.

Addresses initial part of #47.

priv/help/repl-extempore.txt

@@ -5,12 +5,17 @@ Built-in functions:
 
 (call body) -- make an explicitly blocking call to Extempore, with 'body' being
                a valid Extempore expression
+(check-xt)  -- check on the status of Extempore (no response indicates a health
+               problem, possibly requiring a restart of the 'extempore' binary)
+(eom)       -- alias for '(term)'
 (exit)      -- alias for '(quit)'
 (h)         -- alias for '(help)'
 (help)      -- display this information
 (quit)      -- quit the Extempore REPL and return to the LFE REPL
 (run file)  -- load the code in the given file and run in Extempore
-(v)         -- alias for '(version')
+(term)      -- send message-terminating character sequence to force Extempore
+               end-of-message (useful when troubleshooting)
+(v)         -- alias for '(version)'
 (version)   -- display all the version info for undertone
 
 Extempore support:

src/undertone/repl/extempore.lfe

@@ -23,6 +23,7 @@
   (case (mref sexp 'tokens)
     ('() 'empty)
     (`("call" . ,_) (xt-blocking-eval sexp))
+    ('("check-xt") 'check-xt)
     ('("eom") 'term)
     ('("exit") 'quit)
     ('("h") 'help)
@@ -53,6 +54,7 @@
 (defun print (result)
   (case result
     ('() 'ok)
+    ('check-xt (check-extempore))
     ('empty 'ok)
     ('help (help))
     ('quit 'ok)
@@ -80,6 +82,9 @@
 ;;;::=-   shell functions   -=::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;::=--------------------=::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(defun check-extempore ()
+  (xt.msg:async "#(health ok)"))
+
 (defun help ()
   (lfe_io:format "~s" `(,(binary_to_list
                            (undertone.sysconfig:read-priv

src/xt/msg.lfe

@@ -17,14 +17,14 @@
 (defun rcv-delim () #b(0))
 
 (defun async (str)
-  (log-debug "Casting ~s ..." `(,str))
+  (log-debug "Casting: ~s" `(,str))
   (tcp-client:cast-msg (payload str)))
 
 (defun payload (str)
   (binary:list_to_bin (++ str (xmit-delim))))
 
 (defun sync (str)
-  (log-debug "Calling ~s ..." `(,str))
+  (log-debug "Calling: ~s" `(,str))
   (tcp-client:call-msg (payload str)))
 
 ;;;;;::=------------------------------------=::;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -36,7 +36,10 @@
     ("Welcome to extempore!" (progn
                                (timer:sleep 500)
                                (undertone.sysconfig:render-banner)))
-    (_ 'ok)))
+    ("#(health ok)" (log-notice "Extempore TCP server connection healthy"))
+    (_ (progn
+         (log-debug "No special packet handling for parsed value")
+         'ok))))
 
 (defun parse-response
   ((packet `#(,reporter-mod ,reporter-func))