[bug#52555] [PATCH v4 6/7] substitute: Decode substitutes using ERIS.

[pukkamustard]

* guix/scripts/substitute.scm: Decode substitutes using ERIS.
* guix/eris.scm (eris-decode-store-item): New function.
* nix/nix-daemon/guix-daemon.cc (options): Add eris-store-url option.
---
 guix/eris.scm                 | 45 +++++++++++++++++----
 guix/scripts/substitute.scm   | 76 +++++++++++++++++++++++++++--------
 nix/nix-daemon/guix-daemon.cc |  5 +++
 3 files changed, 102 insertions(+), 24 deletions(-)

diff --git a/guix/eris.scm b/guix/eris.scm
index 3fbedd0cb7..1aa52e69dd 100644
--- a/guix/eris.scm
+++ b/guix/eris.scm
@@ -21,6 +21,7 @@ (define-module (guix eris)
   #:use-module (eris)
   #:use-module (eris fs)
   #:use-module (eris sqlite)
+  #:use-module (sqlite3)
   #:use-module (eris coap)
   #:use-module (eris read-capability)
 
@@ -31,7 +32,8 @@ (define-module (guix eris)
   #:use-module (srfi srfi-171)
 
   #:export (%eris-store-url
-            eris-encode-store-item))
+            eris-encode-store-item
+            eris-decode-store-item))
 
 (define %eris-store-url
   (make-parameter
@@ -83,8 +85,7 @@ (define (guix-eris-block-reducer)
                (() (ecbr))
                ((conn ref-block) (ecbr conn ref-block))
                ((conn)
-                (ecbr conn)
-                (close-port conn)))))
+                (ecbr conn)))))
 
           ;; TODO
           ;; ('coap+tcp #f)
@@ -97,10 +98,40 @@ (define (guix-eris-block-reducer)
         ;; SRFI-171 that counts the number of blocks.
         rcount)))
 
+(define (call-with-guix-eris-block-ref proc)
+  (let ((store-url (%eris-store-url)))
+    (if (uri? store-url)
+        (match (uri-scheme store-url)
+
+          ('sqlite
+           (let ((db (eris-sqlite-open (uri-path store-url))))
+             (proc (lambda (ref) (eris-sqlite-ref db ref)))
+             (sqlite-close db)))
+
+          ('coap+unix
+           (let ((conn (open-coap-unix-socket (uri-path store-url)))
+                 (req-uri (build-uri 'coap #:path ".well-known/eris")))
+             (proc
+              (lambda (ref)
+                (eris-coap-block-ref req-uri ref #:connection conn)))
+             (close-port conn)))
+
+          (_ (error "Don't know how to handle ERIS store URL "
+                    (uri->string (%eris-store-url)))))
+
+        (error "No ERIS store to get blocks."))))
+
 (define* (eris-encode-store-item item)
   "Encodes the store item ITEM using ERIS and returns the read capability as
 string."
-  (eris-read-capability->string
-   (eris-fs-encode item
-                   #:convergence-secret (%guix-eris-convergence-secret)
-                   #:block-reducer (guix-eris-block-reducer))))
+  (eris-fs-encode item
+                  #:convergence-secret (%guix-eris-convergence-secret)
+                  #:block-reducer (guix-eris-block-reducer)))
+
+(define* (eris-decode-store-item eris-urn destination)
+  "Decode a store item with read-capability ERIS-URN to DESTINATION."
+  (call-with-guix-eris-block-ref
+   (lambda (block-ref)
+     (eris-fs-decode eris-urn destination
+                     #:block-ref block-ref)
+     #t)))
diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index 37cd08e289..3c060f1c89 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -45,6 +45,8 @@ (define-module (guix scripts substitute)
                            . guix:open-connection-for-uri)))
   #:autoload   (gnutls) (error/invalid-session error/again error/interrupted)
   #:use-module (guix progress)
+  #:use-module (guix eris)
+  #:use-module (fibers)
   #:use-module ((guix build syscalls)
                 #:select (set-thread-name))
   #:use-module (ice-9 rdelim)
@@ -656,9 +658,11 @@ (define* (process-substitution/fallback port narinfo 
destination
          (()
           (loop rest)))))))
 
+
 (define* (process-substitution port store-item destination
                                #:key cache-urls acl
-                               deduplicate? print-build-trace?)
+                               deduplicate? print-build-trace?
+                               (eris? #f))
   "Substitute STORE-ITEM (a store file name) from CACHE-URLS, and write it to
 DESTINATION as a nar file.  Verify the substitute against ACL, and verify its
 hash against what appears in the narinfo.  When DEDUPLICATE? is true, and if
@@ -674,20 +678,56 @@ (define* (process-substitution port store-item destination
     (leave (G_ "no valid substitute for '~a'~%")
            store-item))
 
-  (guard (c ((network-error? c)
-             (format (current-error-port)
-                     (G_ "retrying download of '~a' with other substitute 
URLs...~%")
-                     store-item)
-             (process-substitution/fallback port narinfo destination
-                                            #:cache-urls cache-urls
-                                            #:acl acl
-                                            #:deduplicate? deduplicate?
-                                            #:print-build-trace?
-                                            print-build-trace?)))
-    (download-nar narinfo destination
-                  #:status-port port
-                  #:deduplicate? deduplicate?
-                  #:print-build-trace? print-build-trace?)))
+  (if (and eris?
+           (%eris-store-url)
+           (narinfo-eris-urn narinfo))
+
+      (unless
+
+          ;; Attempt to fetch substitute via ERIS
+          (let ((eris-urn (narinfo-eris-urn narinfo)))
+            (format (current-error-port)
+                    (G_ "Downloading ~a...~%") (uri->string eris-urn))
+            (run-fibers
+             (lambda ()
+               (guard
+                   (c (else
+                       (format (current-error-port)
+                               (G_ "failed to decode substitute from ERIS URN 
~a: ~a"
+                                   (uri->string eris-urn)
+                                   c))
+                       #f))
+                 (eris-decode-store-item eris-urn destination)
+                 ;; Tell the daemon that we're done.
+                 (format port "success ~a ~a~%"
+                         (narinfo-hash narinfo) (narinfo-size narinfo))))))
+
+        ;; Retry without ERIS on failure.
+        (process-substitution port store-item destination
+                              #:cache-urls cache-urls
+                              #:acl acl
+                              #:deduplicate? deduplicate?
+                              #:print-build-trace? print-build-trace?
+                              #:eris? #f))
+
+      (guard (c ((network-error? c)
+                 (format (current-error-port)
+                         (G_ "retrying download of '~a' with other substitute 
URLs...~%")
+                         store-item)
+                 (process-substitution/fallback port narinfo destination
+                                                #:cache-urls cache-urls
+                                                #:acl acl
+                                                #:deduplicate? deduplicate?
+                                                #:print-build-trace?
+                                                print-build-trace?)))
+        (download-nar narinfo destination
+                      #:status-port port
+                      #:deduplicate? deduplicate?
+                      #:print-build-trace? print-build-trace?))))
+
+
+
+
 
 
 ;;;
@@ -876,7 +916,8 @@ (define-command (guix-substitute . args)
         ;; Download STORE-PATH and store it as a Nar in file DESTINATION.
         ;; Specify the number of columns of the terminal so the progress
         ;; report displays nicely.
-        (parameterize ((current-terminal-columns (client-terminal-columns)))
+        (parameterize ((current-terminal-columns (client-terminal-columns))
+                       (%eris-store-url (find-daemon-option "eris-store-url")))
           (let loop ()
             (match (read-line)
               ((? eof-object?)
@@ -887,7 +928,8 @@ (define-command (guix-substitute . args)
                                      #:acl (current-acl)
                                      #:deduplicate? deduplicate?
                                      #:print-build-trace?
-                                     print-build-trace?)
+                                     print-build-trace?
+                                     #:eris? #t)
                (loop))))))
        (opts
         (leave (G_ "~a: unrecognized options~%") opts))))))
diff --git a/nix/nix-daemon/guix-daemon.cc b/nix/nix-daemon/guix-daemon.cc
index d7ab9c5e64..d6b054bc6c 100644
--- a/nix/nix-daemon/guix-daemon.cc
+++ b/nix/nix-daemon/guix-daemon.cc
@@ -90,6 +90,7 @@ builds derivations on behalf of its clients.");
 #define GUIX_OPT_MAX_SILENT_TIME 19
 #define GUIX_OPT_LOG_COMPRESSION 20
 #define GUIX_OPT_DISCOVER 21
+#define GUIX_OPT_ERIS_STORE_URL 22
 
 static const struct argp_option options[] =
   {
@@ -132,6 +133,8 @@ static const struct argp_option options[] =
       n_("use the specified compression type for build logs") },
     { "discover", GUIX_OPT_DISCOVER, "yes/no", OPTION_ARG_OPTIONAL,
       n_("use substitute servers discovered on the local network") },
+    { "eris-store-url", GUIX_OPT_ERIS_STORE_URL, n_("URL"), 0,
+      n_("use URL to retrieve blocks of ERIS encoded substitutes") },
 
     /* '--disable-deduplication' was known as '--disable-store-optimization'
        up to Guix 0.7 included, so keep the alias around.  */
@@ -270,6 +273,8 @@ parse_opt (int key, char *arg, struct argp_state *state)
       useDiscover = string_to_bool (arg);
       settings.set ("discover", useDiscover ? "true" : "false");
       break;
+    case GUIX_OPT_ERIS_STORE_URL:
+      settings.set ("eris-store-url", arg);
     case GUIX_OPT_DEBUG:
       verbosity = lvlDebug;
       break;
-- 
2.41.0