Handle migrations and server startup better

The server part of the guix-data-service doesn't work great as a guix service,
since it often fails to start if the migrations take any time at all.

To address this, start the server before running the migrations, and serve the
pages that work without the database, plus a general 503 response. Once the
migrations have completed, switch to the normal behaviour.

guix-data-service/web/controller.scm

@@ -71,6 +71,7 @@
   #:use-module (guix-data-service web repository controller)
   #:use-module (guix-data-service web package controller)
   #:export (%show-error-details
+            handle-static-assets
             controller))
 
 (define cache-control-default-max-age
@@ -513,16 +514,26 @@
 
 (define* (controller request method-and-path-components
                      mime-types body
-                     secret-key-base)
+                     secret-key-base
-  (define (controller-thunk)
+                     startup-completed?)
+  (define (running-controller-thunk)
     (actual-controller request
                        method-and-path-components
                        mime-types
                        body
                        secret-key-base))
 
+  (define (startup-controller-thunk)
+    (or
+     (base-controller request method-and-path-components)
+     (render-html
+      #:sxml (server-starting-up-page)
+      #:code 503)))
+
   (call-with-error-handling
-   controller-thunk
+   (if startup-completed?
+       running-controller-thunk
+       startup-controller-thunk)
    #:on-error 'backtrace
    #:post-error (lambda args
                   (render-html #:sxml (error-page
@@ -531,51 +542,8 @@
                                            #f))
                                #:code 500))))
 
-(define (actual-controller request
+(define (base-controller request method-and-path-components)
-                           method-and-path-components
-                           mime-types
-                           body
-                           secret-key-base)
-  (define path
-    (uri-path (request-uri request)))
-
-  (define (delegate-to f)
-    (or (f request
-           method-and-path-components
-           mime-types
-           body)
-        (render-html
-         #:sxml (general-not-found
-                 "Page not found"
-                 "")
-         #:code 404)))
-
-  (define (delegate-to-with-secret-key-base f)
-    (or (f request
-           method-and-path-components
-           mime-types
-           body
-           secret-key-base)
-        (render-html
-         #:sxml (general-not-found
-                 "Page not found"
-                 "")
-         #:code 404)))
-
   (match method-and-path-components
-    (('GET)
-     (render-html
-      #:sxml (index
-              (parallel-via-thread-pool-channel
-               (with-thread-postgresql-connection
-                (lambda (conn)
-                  (map
-                   (lambda (git-repository-details)
-                     (cons
-                      git-repository-details
-                      (all-branches-with-most-recent-commit
-                       conn (first git-repository-details))))
-                   (all-git-repositories conn))))))))
     (('GET "assets" rest ...)
      (or (handle-static-assets (string-join rest "/")
                                (request-headers request))
@@ -610,6 +578,55 @@
                     "README not found"
                     "The README.html file does not exist")
             #:code 404))))
+    ((method path ...) #f)))
+
+(define (actual-controller request
+                           method-and-path-components
+                           mime-types
+                           body
+                           secret-key-base)
+  (define path
+    (uri-path (request-uri request)))
+
+  (define (delegate-to f)
+    (or (f request
+           method-and-path-components
+           mime-types
+           body)
+        (render-html
+         #:sxml (general-not-found
+                 "Page not found"
+                 "")
+         #:code 404)))
+
+  (define (delegate-to-with-secret-key-base f)
+    (or (f request
+           method-and-path-components
+           mime-types
+           body
+           secret-key-base)
+        (render-html
+         #:sxml (general-not-found
+                 "Page not found"
+                 "")
+         #:code 404)))
+
+  (or
+   (base-controller request method-and-path-components)
+   (match method-and-path-components
+     (('GET)
+      (render-html
+       #:sxml (index
+               (parallel-via-thread-pool-channel
+                (with-thread-postgresql-connection
+                 (lambda (conn)
+                   (map
+                    (lambda (git-repository-details)
+                      (cons
+                       git-repository-details
+                       (all-branches-with-most-recent-commit
+                        conn (first git-repository-details))))
+                    (all-git-repositories conn))))))))
      (('GET "builds")
       (delegate-to build-controller))
      (('GET "statistics")
@@ -681,4 +698,4 @@
        #:sxml (general-not-found
                "Page not found"
                "")
-      #:code 404))))
+       #:code 404)))))

guix-data-service/web/server.scm

@@ -24,12 +24,22 @@
   #:use-module (web request)
   #:use-module (web uri)
   #:use-module (system repl error-handling)
+  #:use-module (ice-9 atomic)
   #:use-module (fibers web server)
   #:use-module (guix-data-service web controller)
   #:use-module (guix-data-service web util)
   #:export (start-guix-data-service-web-server))
 
-(define (handler request body controller secret-key-base)
+(define (check-startup-completed startup-completed)
+  (if (atomic-box-ref startup-completed)
+      (begin
+        ;; Just in case this atomic-box-ref is expensive, only do it when
+        ;; necessary
+        (set! check-startup-completed (const #t))
+        #t)
+      #f))
+
+(define (handler request body controller secret-key-base startup-completed)
   (display
    (format #f "~a ~a\n"
            (request-method request)
@@ -42,14 +52,17 @@
                              request-components)
                        mime-types
                        body
-                       secret-key-base))))
+                       secret-key-base
+                       (check-startup-completed startup-completed)))))
 
-(define* (start-guix-data-service-web-server port host secret-key-base)
+(define* (start-guix-data-service-web-server port host secret-key-base
+                                             startup-completed)
   (call-with-error-handling
    (lambda ()
      (run-server (lambda (request body)
                    (handler request body controller
-                            secret-key-base))
+                            secret-key-base
+                            startup-completed))
                  #:host host
                  #:port port))
    #:on-error 'backtrace

guix-data-service/web/view/html.scm

@@ -50,7 +50,8 @@
             view-narinfos
             view-store-item
             view-derivation-source-file
-            error-page))
+            error-page
+            server-starting-up-page))
 
 (define* (header)
   `(nav
@@ -1004,3 +1005,11 @@
                    `((b ,key)
                      (pre ,args))))
                 '())))))
+
+(define* (server-starting-up-page)
+  (layout
+   #:body
+   `(,(header)
+     (div (@ (class "container"))
+          (h1 "Server is starting up")
+          (p "Database migrations are running, this can take some time.")))))

scripts/guix-data-service.in

@@ -26,6 +26,8 @@
 (use-modules (srfi srfi-1)
              (srfi srfi-37)
              (ice-9 match)
+             (ice-9 atomic)
+             (ice-9 threads)
              (ice-9 textual-ports)
              (system repl server)
              (system repl repl)
@@ -137,6 +139,72 @@
     (when repl-port
       (spawn-server (make-tcp-server-socket #:port repl-port))))
 
+  (parameterize ((%narinfo-signing-public-key
+                  (catch
+                    'system-error
+                    (lambda ()
+                      (and=> (assoc-ref opts 'narinfo-signing-public-key)
+                             read-file-sexp))
+                    (lambda (key . args)
+                      (simple-format
+                       (current-error-port)
+                       "warning: failed to load narinfo signing public key from ~A\n"
+                       (assoc-ref opts 'narinfo-signing-private-key))
+                      (simple-format (current-error-port)
+                                     "  ~A: ~A\n"
+                                     key args))))
+                 (%narinfo-signing-private-key
+                  (catch
+                    'system-error
+                    (lambda ()
+                      (and=> (assoc-ref opts 'narinfo-signing-private-key)
+                             read-file-sexp))
+                    (lambda (key . args)
+                      (simple-format
+                       (current-error-port)
+                       "warning: failed to load narinfo signing private key from ~A\n"
+                       (assoc-ref opts 'narinfo-signing-private-key))
+                      (simple-format (current-error-port)
+                                     "  ~A: ~A\n"
+                                     key args)
+                      (display "warning: not signing narinfo files\n"
+                               (current-error-port))
+                      #f)))
+                 (%show-error-details
+                  (assoc-ref opts 'show-error-details)))
+
+    (let* ((startup-completed
+            (make-atomic-box
+             (if (assoc-ref opts 'update-database)
+                 #f
+                 #t)))
+           (server-thread
+            (call-with-new-thread
+             (lambda ()
+               (with-postgresql-connection-per-thread
+                "web"
+                (lambda ()
+                  ;; Provide some visual space between the startup output and the server
+                  ;; starting
+                  (simple-format #t "\n\nStarting the server on http://~A:~A/\n\n"
+                                 (assq-ref opts 'host)
+                                 (assq-ref opts 'port))
+
+                  (start-guix-data-service-web-server
+                   (assq-ref opts 'port)
+                   (assq-ref opts 'host)
+                   (assq-ref opts 'secret-key-base)
+                   startup-completed))
+                #:statement-timeout
+                (assq-ref opts 'postgresql-statement-timeout)))))
+
+           (pid-file (assq-ref opts 'pid-file)))
+
+      (when pid-file
+        (call-with-output-file pid-file
+          (lambda (port)
+            (simple-format port "~A\n" (getpid)))))
+
       (when (assoc-ref opts 'update-database)
         (let ((command
                (list (%config 'sqitch)
@@ -186,62 +254,10 @@
             (simple-format
              (current-error-port)
              "error: sqitch command failed\n")
-        (exit 1))))
+            (exit 1))
 
-  (let ((pid-file (assq-ref opts 'pid-file)))
+          (atomic-box-set! startup-completed #t)))
-    (when pid-file
-      (call-with-output-file pid-file
-        (lambda (port)
-          (simple-format port "~A\n" (getpid))))))
-
-  (parameterize ((%narinfo-signing-public-key
-                  (catch
-                    'system-error
-                    (lambda ()
-                      (and=> (assoc-ref opts 'narinfo-signing-public-key)
-                             read-file-sexp))
-                    (lambda (key . args)
-                      (simple-format
-                       (current-error-port)
-                       "warning: failed to load narinfo signing public key from ~A\n"
-                       (assoc-ref opts 'narinfo-signing-private-key))
-                      (simple-format (current-error-port)
-                                     "  ~A: ~A\n"
-                                     key args))))
-                 (%narinfo-signing-private-key
-                  (catch
-                    'system-error
-                    (lambda ()
-                      (and=> (assoc-ref opts 'narinfo-signing-private-key)
-                             read-file-sexp))
-                    (lambda (key . args)
-                      (simple-format
-                       (current-error-port)
-                       "warning: failed to load narinfo signing private key from ~A\n"
-                       (assoc-ref opts 'narinfo-signing-private-key))
-                      (simple-format (current-error-port)
-                                     "  ~A: ~A\n"
-                                     key args)
-                      (display "warning: not signing narinfo files\n"
-                               (current-error-port))
-                      #f)))
-                 (%show-error-details
-                  (assoc-ref opts 'show-error-details)))
 
       (start-substitute-query-thread)
 
-    ;; Provide some visual space between the startup output and the server
+      (join-thread server-thread))))
-    ;; starting
-    (simple-format #t "\n\nStarting the server on http://~A:~A/\n\n"
-                   (assq-ref opts 'host)
-                   (assq-ref opts 'port))
-
-    (with-postgresql-connection-per-thread
-     "web"
-     (lambda ()
-       (start-guix-data-service-web-server
-        (assq-ref opts 'port)
-        (assq-ref opts 'host)
-        (assq-ref opts 'secret-key-base)))
-     #:statement-timeout
-     (assq-ref opts 'postgresql-statement-timeout))))