From d50341d4ae106e5541baaa39d8564bcdadb31a7f Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Mon, 26 Jan 2015 15:05:34 -0500
Subject: [PATCH] Fetch build-server information directly.

---
 src/build-server.rkt | 117 +++++++++++++++++++++++++++++++++++++++++++
 src/site.rkt         |   5 +-
 2 files changed, 118 insertions(+), 4 deletions(-)
 create mode 100644 src/build-server.rkt

diff --git a/src/build-server.rkt b/src/build-server.rkt
new file mode 100644
index 0000000..1590987
--- /dev/null
+++ b/src/build-server.rkt
@@ -0,0 +1,117 @@
+#lang racket/base
+
+(provide pkg-build-baseurl)
+
+(require racket/match)
+(require racket/file)
+(require (only-in racket/port copy-port))
+(require net/url)
+(require "config.rkt")
+(require "hash-utils.rkt")
+(require reloadable)
+(require "daemon.rkt")
+(require "rpc.rkt")
+
+(define pkg-build-baseurl
+  (or (@ (config) pkg-build-baseurl)
+      "http://pkg-build.racket-lang.org/"))
+
+(define pkg-build-cache-path
+  (or (@ (config) pkg-build-cache-path)
+      (build-path (var-path) "cache")))
+
+(make-directory* pkg-build-cache-path)
+
+(define pkg-build-cache-refresh-interval
+  (* 1000 (or (@ (config) pkg-build-cache-refresh-interval)
+              3600))) ;; one hour
+
+(define (compute-next-refresh-deadline)
+  (+ (current-inexact-milliseconds) pkg-build-cache-refresh-interval))
+
+(define cached-summary-path (build-path pkg-build-cache-path "summary.rktd"))
+(define cached-etag-path (build-path pkg-build-cache-path "summary.rktd.etag"))
+
+(define (extract-etag hs)
+  (for/or ([h (in-list hs)])
+    (match h
+      [(regexp #rx#"^ETag: (.*?)$" (list _ tag-bytes)) tag-bytes]
+      [_ #f])))
+
+;; Returns #t if the summary file has been updated, or #f if it
+;; remains the same as it was previously.
+(define (refresh-build-server-summary!)
+  (define summary-url (combine-url/relative (string->url pkg-build-baseurl) "summary.rktd"))
+
+  (define HEAD-etag
+    (let-values (((HEAD-status HEAD-headers HEAD-body-input-port)
+                  (http-sendrecv/url summary-url #:method #"HEAD")))
+      (extract-etag HEAD-headers)))
+
+  (define cached-etag (and (file-exists? cached-etag-path) (file->bytes cached-etag-path)))
+
+  (define need-refresh?
+    (or (not HEAD-etag) ;; server didn't supply an ETag
+        (not cached-etag) ;; we don't have a record of an ETag locally
+        (not (equal? HEAD-etag cached-etag)))) ;; the ETag has changed
+
+  (cond
+   [need-refresh?
+    (log-info "Build server summary.rktd ETag has changed. Refreshing.")
+    (define-values (GET-status GET-headers GET-body-input-port)
+      (http-sendrecv/url summary-url #:method #"GET"))
+
+    (define new-file (make-temporary-file "summary-~a.rktd" #f pkg-build-cache-path))
+    (call-with-output-file new-file
+      (lambda (p) (copy-port GET-body-input-port p))
+      #:exists 'replace)
+    (with-output-to-file cached-etag-path
+      (lambda () (write-bytes (extract-etag GET-headers)))
+      #:exists 'replace)
+    (rename-file-or-directory new-file cached-summary-path #t)]
+   [else
+    (log-info "Build server summary.rktd ETag has not changed.")])
+
+  need-refresh?)
+
+(define (load-build-server-summary)
+  (if (file-exists? cached-summary-path)
+      (file->value cached-summary-path)
+      (hash)))
+
+(struct build-server-state (summary-table
+                            next-refresh-deadline
+                            ) #:prefab)
+
+(define (boot-build-server)
+  (refresh-build-server-summary!)
+  (build-server-main (build-server-state (load-build-server-summary)
+                                         (compute-next-refresh-deadline))))
+
+(define (send-change-notifications! old-table new-table)
+  (log-info "HERE ~v ~v" old-table new-table))
+
+(define (build-server-main state)
+  (match-define (build-server-state summary-table next-refresh-deadline) state)
+  (build-server-main
+   (rpc-handler (sync (rpc-request-evt)
+                      (handle-evt (alarm-evt next-refresh-deadline)
+                                  (lambda (_) (list #f 'refresh!))))
+     [('refresh!)
+      (values (void)
+              (if (refresh-build-server-summary!)
+                  (let ((new-summary-table (load-build-server-summary)))
+                    (send-change-notifications! summary-table new-summary-table)
+                    (struct-copy build-server-state state
+                                 [summary-table new-summary-table]
+                                 [next-refresh-deadline (compute-next-refresh-deadline)]))
+                  (struct-copy build-server-state state
+                               [next-refresh-deadline (compute-next-refresh-deadline)])))]
+     )))
+
+(define build-server-thread
+  (make-persistent-state 'build-server-thread
+                         (lambda () (daemon-thread 'build-server
+                                                   (lambda () (boot-build-server))))))
+
+(sleep 5)
diff --git a/src/site.rkt b/src/site.rkt
index b1c69c5..69a2c5f 100644
--- a/src/site.rkt
+++ b/src/site.rkt
@@ -18,6 +18,7 @@
 (require "gravatar.rkt")
 (require "bootstrap.rkt")
 (require "html-utils.rkt")
+(require "build-server.rkt")
 (require "packages.rkt")
 (require "sessions.rkt")
 (require "jsonp-client.rkt")
@@ -59,10 +60,6 @@
   (or (@ (config) recent-seconds)
       (* 2 24 60 60))) ;; two days
 
-(define pkg-build-baseurl
-  (or (@ (config) pkg-build-baseurl)
-      "http://pkg-build.racket-lang.org/"))
-
 (struct draft-package (old-name name description authors tags versions) #:prefab)
 
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