Complain if no canonical-hosts are available

racketmq/hub.rkt

@@ -6,6 +6,7 @@
 (require "private/util.rkt")
 (require "protocol.rkt")
 
+(require/activate syndicate/drivers/timestate)
 (require/activate "config.rkt")
 (require/activate "hub/static-content.rkt")
 (require/activate "hub/topic-demand.rkt")
@@ -32,6 +33,9 @@
        (define/query-set canonical-local-hosts ($ c (canonical-local-host _ _)) c)
        (stop-when (rising-edge (> (set-count (canonical-local-hosts)) 1))
                   (log-error "Too many canonical-host records in configuration."))
+       (on-start (sleep 0.1)
+                 (when (set-empty? (canonical-local-hosts))
+                   (log-error "No canonical-host records specified; try the --canonical-host command line argument")))
        ;; TODO: Make the too-many-canonical-host-records situation recoverable.
        ;; TODO: And/or, make the whole application quit when it gets into a bad state.
 

racketmq/private/util.rkt

@@ -1,7 +1,6 @@
 #lang racket/base
 
-(provide sleep
-         random-hex-string
+(provide random-hex-string
          extend-url-string-query
          web-respond/status!
          web-request!
@@ -23,11 +22,6 @@
 
 (module+ test (require rackunit))
 
-(define (sleep sec)
-  (define timer-id (gensym 'sleep))
-  (until (message (timer-expired timer-id _))
-         (on-start (send! (set-timer timer-id (* sec 1000.0) 'relative)))))
-
 (define (random-hex-string half-length)
   (bytes->hex-string (crypto-random-bytes half-length)))