bug#27162: [PATCH 0/6] Display how much will be downloaded

bug#27162: [PATCH 0/6] Display how much will be downloaded

[Ludovic Courtès]

Hello!

With this patch series, ‘show-what-to-build’ can display the download
size and warn about lack of disk space when needed:

  $ ./pre-inst-env guix build synfigstudio -n
  substitute: updating list of substitutes from 'https://bayfront.guixsd.org'... 100.0%
  10.8 MB would be downloaded:
     /gnu/store/jq80lq3xhib81fi2v6j7ygh7mqdjrjsx-synfigstudio-1.2.0
     /gnu/store/azvp0257q9yhl0b409q1s6h67pfhaknr-libxml++-3.0.1
     /gnu/store/bjmwcqxr32g48jzwc0zc993m8x3ymq5h-synfig-1.2.0
     /gnu/store/lxmviq543w2a4ahc4c77i542sl921bbl-mlt-6.4.1
  guix build: warning: at least 73.8 MB needed but only 42.0 MB available in /gnu/store

A couple of notes:

  1. Information about the download size is not always available:
     ‘guix publish --cache’ started producing it in commit
     dff3189c7d5d95177ff592789e1bcb73a4adcc9e so there are lots of
     cached narinfos that lack this information.  After the next
     full rebuild though, we should have that everywhere.

     When we have no or partial information about the size of substitute
     downloads, we fall back to the current behavior.

  2. The disk space check should work well when everything is
     substitutable, but of course it has no idea how much space will
     be needed when building something.  For instance, it may forget
     to tell you that you need a dozen GB to build WebKit.  :-)
     Also, it cannot know in advance the extent to which deduplication
     will help.

I thought about other changes we could make to the UI, such as display
the download size of each item individually, or displaying the estimated
on-disk size, but thought that keeping the output as simple as this
is preferable.

Thoughts?

Thanks,
Ludo’.

Ludovic Courtès (6):
  derivations: 'substitution-oracle' returns a <substitutable>.
  derivations: 'derivation-prerequisites-to-build' returns
    <substitutable>.
  ui: 'show-what-to-build' displays how much will be downloaded.
  syscalls: Provide 'free-disk-space'.
  ui: 'show-what-to-build' warns when we don't have enough disk space.
  substitute: Do not display the installed size.

 guix/build/syscalls.scm     |  7 ++++
 guix/derivations.scm        | 47 +++++++++++++++---------
 guix/scripts/gc.scm         |  8 ++---
 guix/scripts/substitute.scm | 10 +-----
 guix/ui.scm                 | 87 ++++++++++++++++++++++++++++++++++-----------
 tests/derivations.scm       |  8 ++---
 6 files changed, 112 insertions(+), 55 deletions(-)

-- 
2.13.0

bug#27162: [PATCH 1/6] derivations: 'substitution-oracle' returns a <substitutable>.

[Ludovic Courtès]

* guix/derivations.scm (substitution-oracle): Use
'substitution-path-info' instead of 'substitution-paths'.  Turn SUBST
into a vhash from path to <substitutable>.  Change the returned
procedure to provide a <substitutable> instead of a Boolean.
* tests/derivations.scm ("substitution-oracle and #:substitute? #f"):
Mock 'substitutable-path-info' instead of 'substitutable-paths'.
---
 guix/derivations.scm  | 16 ++++++++++++----
 tests/derivations.scm |  2 +-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/guix/derivations.scm b/guix/derivations.scm
index 9aaab05ec..5e457f189 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -271,13 +271,14 @@ result is the set of prerequisites of DRV not already in valid."
 (define* (substitution-oracle store drv
                               #:key (mode (build-mode normal)))
   "Return a one-argument procedure that, when passed a store file name,
-returns #t if it's substitutable and #f otherwise.  The returned procedure
+returns a 'substitutable?' if it's substitutable and #f otherwise.
+The returned procedure
 knows about all substitutes for all the derivations listed in DRV, *except*
 those that are already valid (that is, it won't bother checking whether an
 item is substitutable if it's already on disk); it also knows about their
 prerequisites, unless they are themselves substitutable.
 
-Creating a single oracle (thus making a single 'substitutable-paths' call) and
+Creating a single oracle (thus making a single 'substitutable-path-info' call) and
 reusing it is much more efficient than calling 'has-substitutes?' or similar
 repeatedly, because it avoids the costs associated with launching the
 substituter many times."
@@ -318,8 +319,15 @@ substituter many times."
                                    (cons* self (dependencies drv) result)))))
                         '()
                         drv))))
-         (subst (list->set (substitutable-paths store paths))))
-    (cut set-contains? subst <>)))
+         (subst (fold (lambda (subst vhash)
+                        (vhash-cons (substitutable-path subst) subst
+                                    vhash))
+                      vlist-null
+                      (substitutable-path-info store paths))))
+    (lambda (item)
+      (match (vhash-assoc item subst)
+        (#f #f)
+        ((key . value) value)))))
 
 (define* (derivation-prerequisites-to-build store drv
                                             #:key
diff --git a/tests/derivations.scm b/tests/derivations.scm
index cabbf7b95..d4e1a32bb 100644
--- a/tests/derivations.scm
+++ b/tests/derivations.scm
@@ -919,7 +919,7 @@
         (set! query paths)
         '())
 
-      (mock ((guix store) substitutable-paths
+      (mock ((guix store) substitutable-path-info
              record-substitutable-path-query)
 
             (let ((pred (substitution-oracle store (list drv))))
-- 
2.13.0

bug#27162: [PATCH 2/6] derivations: 'derivation-prerequisites-to-build' returns <substitutable>.

[Ludovic Courtès]

* guix/derivations.scm (derivation-prerequisites-to-build): Rename
 #:substitutable? to #:substitutable-info.
[derivation-substitutable?]: Rename to...
[derivation-substitutable-info]: ... this.  Return a list of <substitutable>.
Second return value is now a list of <substitutable> instead of a list
of strings.
* guix/ui.scm (show-what-to-build)[substitutable?]: Rename to...
[substitutable-info]: ... this.
Adjust to new 'derivation-prerequisites-to-build' return value type.
* tests/derivations.scm ("derivation-prerequisites-to-build and
substitutes"): Adjust.
("derivation-prerequisites-to-build and substitutes, local build"):
Likewise.
---
 guix/derivations.scm  | 31 ++++++++++++++++++-------------
 guix/ui.scm           | 25 +++++++++++++++----------
 tests/derivations.scm |  6 +++---
 3 files changed, 36 insertions(+), 26 deletions(-)

diff --git a/guix/derivations.scm b/guix/derivations.scm
index 5e457f189..b9ad9c9e8 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -334,13 +334,13 @@ substituter many times."
                                             (mode (build-mode normal))
                                             (outputs
                                              (derivation-output-names drv))
-                                            (substitutable?
+                                            (substitutable-info
                                              (substitution-oracle store
                                                                   (list drv)
                                                                   #:mode mode)))
   "Return two values: the list of derivation-inputs required to build the
 OUTPUTS of DRV and not already available in STORE, recursively, and the list
-of required store paths that can be substituted.  SUBSTITUTABLE? must be a
+of required store paths that can be substituted.  SUBSTITUTABLE-INFO must be a
 one-argument procedure similar to that returned by 'substitution-oracle'."
   (define built?
     (cut valid-path? store <>))
@@ -351,7 +351,7 @@ one-argument procedure similar to that returned by 'substitution-oracle'."
   (define input-substitutable?
     ;; Return true if and only if all of SUB-DRVS are subsitutable.  If at
     ;; least one is missing, then everything must be rebuilt.
-    (compose (cut every substitutable? <>) derivation-input-output-paths))
+    (compose (cut every substitutable-info <>) derivation-input-output-paths))
 
   (define (derivation-built? drv* sub-drvs)
     ;; In 'check' mode, assume that DRV is not built.
@@ -359,20 +359,24 @@ one-argument procedure similar to that returned by 'substitution-oracle'."
                    (eq? drv* drv)))
          (every built? (derivation-output-paths drv* sub-drvs))))
 
-  (define (derivation-substitutable? drv sub-drvs)
+  (define (derivation-substitutable-info drv sub-drvs)
     (and (substitutable-derivation? drv)
-         (every substitutable? (derivation-output-paths drv sub-drvs))))
+         (let ((info (filter-map substitutable-info
+                                 (derivation-output-paths drv sub-drvs))))
+           (and (= (length info) (length sub-drvs))
+                info))))
 
   (let loop ((drv        drv)
              (sub-drvs   outputs)
-             (build      '())
-             (substitute '()))
+             (build      '())                     ;list of <derivation-input>
+             (substitute '()))                    ;list of <substitutable>
     (cond ((derivation-built? drv sub-drvs)
            (values build substitute))
-          ((derivation-substitutable? drv sub-drvs)
-           (values build
-                   (append (derivation-output-paths drv sub-drvs)
-                           substitute)))
+          ((derivation-substitutable-info drv sub-drvs)
+           =>
+           (lambda (substitutables)
+             (values build
+                     (append substitutables substitute))))
           (else
            (let ((build  (if (substitutable-derivation? drv)
                              build
@@ -389,8 +393,9 @@ one-argument procedure similar to that returned by 'substitution-oracle'."
                     (append (append-map (lambda (input)
                                           (if (and (not (input-built? input))
                                                    (input-substitutable? input))
-                                              (derivation-input-output-paths
-                                               input)
+                                              (map substitutable-info
+                                                   (derivation-input-output-paths
+                                                    input))
                                               '()))
                                         (derivation-inputs drv))
                             substitute)
diff --git a/guix/ui.scm b/guix/ui.scm
index 9e0fa26d1..9b6464896 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -588,7 +588,7 @@ error."
 derivations listed in DRV using MODE, a 'build-mode' value.  Return #t if
 there's something to build, #f otherwise.  When USE-SUBSTITUTES?, check and
 report what is prerequisites are available for download."
-  (define substitutable?
+  (define substitutable-info
     ;; Call 'substitutation-oracle' upfront so we don't end up launching the
     ;; substituter many times.  This makes a big difference, especially when
     ;; DRV is a long list as is the case with 'guix environment'.
@@ -600,7 +600,7 @@ report what is prerequisites are available for download."
     (or (null? (derivation-outputs drv))
         (let ((out (derivation->output-path drv))) ;XXX: assume "out" exists
           (or (valid-path? store out)
-              (substitutable? out)))))
+              (substitutable-info out)))))
 
   (let*-values (((build download)
                  (fold2 (lambda (drv build download)
@@ -608,7 +608,8 @@ report what is prerequisites are available for download."
                                         (derivation-prerequisites-to-build
                                          store drv
                                          #:mode mode
-                                         #:substitutable? substitutable?)))
+                                         #:substitutable-info
+                                         substitutable-info)))
                             (values (append b build)
                                     (append d download))))
                         '() '()
@@ -622,11 +623,13 @@ report what is prerequisites are available for download."
                  (if use-substitutes?
                      (delete-duplicates
                       (append download
-                              (remove (cut valid-path? store <>)
-                                      (append-map
-                                       substitutable-references
-                                       (substitutable-path-info store
-                                                                download)))))
+                              (filter-map (lambda (item)
+                                            (if (valid-path? store item)
+                                                #f
+                                                (substitutable-info item)))
+                                          (append-map
+                                           substitutable-references
+                                           download))))
                      download)))
     ;; TODO: Show the installed size of DOWNLOAD.
     (if dry-run?
@@ -640,7 +643,8 @@ report what is prerequisites are available for download."
                   (N_ "~:[The following file would be downloaded:~%~{   ~a~%~}~;~]"
                       "~:[The following files would be downloaded:~%~{   ~a~%~}~;~]"
                       (length download))
-                  (null? download) download))
+                  (null? download)
+                  (map substitutable-path download)))
         (begin
           (format (current-error-port)
                   (N_ "~:[The following derivation will be built:~%~{   ~a~%~}~;~]"
@@ -651,7 +655,8 @@ report what is prerequisites are available for download."
                   (N_ "~:[The following file will be downloaded:~%~{   ~a~%~}~;~]"
                       "~:[The following files will be downloaded:~%~{   ~a~%~}~;~]"
                       (length download))
-                  (null? download) download)))
+                  (null? download)
+                  (map substitutable-path download))))
     (pair? build)))
 
 (define show-what-to-build*
diff --git a/tests/derivations.scm b/tests/derivations.scm
index d4e1a32bb..f3aad1b90 100644
--- a/tests/derivations.scm
+++ b/tests/derivations.scm
@@ -831,10 +831,10 @@
                     (derivation-prerequisites-to-build store drv))
                    ((build* download*)
                     (derivation-prerequisites-to-build store drv
-                                                       #:substitutable?
+                                                       #:substitutable-info
                                                        (const #f))))
         (and (null? build)
-             (equal? download (list output))
+             (equal? (map substitutable-path download) (list output))
              (null? download*)
              (null? build*))))))
 
@@ -879,7 +879,7 @@
           ;; See <http://bugs.gnu.org/18747>.
           (and (null? build)
                (match download
-                 (((? string? item))
+                 (((= substitutable-path item))
                   (string=? item (derivation->output-path drv))))))))))
 
 (test-assert "derivation-prerequisites-to-build in 'check' mode"
-- 
2.13.0

bug#27162: [PATCH 3/6] ui: 'show-what-to-build' displays how much will be downloaded.

[Ludovic Courtès]

* guix/ui.scm (show-what-to-build)[download-size]
[display-download-size?]: New variables.
Add cases for when DISPLAY-DOWNLOAD-SIZE? is true.
---
 guix/ui.scm | 49 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/guix/ui.scm b/guix/ui.scm
index 9b6464896..04c7463fb 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -632,6 +632,15 @@ report what is prerequisites are available for download."
                                            download))))
                      download)))
     ;; TODO: Show the installed size of DOWNLOAD.
+    (define download-size
+      (/ (reduce + 0 (map substitutable-download-size download))
+         1e6))
+
+    (define display-download-size?
+      ;; Sometimes narinfos lack information about the download size.  Only
+      ;; display when we have information for all of DOWNLOAD.
+      (any (compose zero? substitutable-download-size) download))
+
     (if dry-run?
         (begin
           (format (current-error-port)
@@ -639,24 +648,40 @@ report what is prerequisites are available for download."
                       "~:[The following derivations would be built:~%~{   ~a~%~}~;~]"
                       (length build))
                   (null? build) build)
-          (format (current-error-port)
-                  (N_ "~:[The following file would be downloaded:~%~{   ~a~%~}~;~]"
-                      "~:[The following files would be downloaded:~%~{   ~a~%~}~;~]"
-                      (length download))
-                  (null? download)
-                  (map substitutable-path download)))
+          (if display-download-size?
+              (format (current-error-port)
+                      ;; TRANSLATORS: "MB" is for "megabyte"; it should be
+                      ;; translated to the corresponding abbreviation.
+                      (G_ "~:[~,1h MB would be downloaded:~%~{   ~a~%~}~;~]")
+                      (null? download)
+                      download-size
+                      (map substitutable-path download))
+              (format (current-error-port)
+                      (N_ "~:[The following file would be downloaded:~%~{   ~a~%~}~;~]"
+                          "~:[The following files would be downloaded:~%~{   ~a~%~}~;~]"
+                          (length download))
+                      (null? download)
+                      (map substitutable-path download))))
         (begin
           (format (current-error-port)
                   (N_ "~:[The following derivation will be built:~%~{   ~a~%~}~;~]"
                       "~:[The following derivations will be built:~%~{   ~a~%~}~;~]"
                       (length build))
                   (null? build) build)
-          (format (current-error-port)
-                  (N_ "~:[The following file will be downloaded:~%~{   ~a~%~}~;~]"
-                      "~:[The following files will be downloaded:~%~{   ~a~%~}~;~]"
-                      (length download))
-                  (null? download)
-                  (map substitutable-path download))))
+          (if display-download-size?
+              (format (current-error-port)
+                      ;; TRANSLATORS: "MB" is for "megabyte"; it should be
+                      ;; translated to the corresponding abbreviation.
+                      (G_ "~:[~,1h MB will be downloaded:~%~{   ~a~%~}~;~]")
+                      (null? download)
+                      download-size
+                      (map substitutable-path download))
+              (format (current-error-port)
+                      (N_ "~:[The following file will be downloaded:~%~{   ~a~%~}~;~]"
+                          "~:[The following files will be downloaded:~%~{   ~a~%~}~;~]"
+                          (length download))
+                      (null? download)
+                      (map substitutable-path download)))))
     (pair? build)))
 
 (define show-what-to-build*
-- 
2.13.0

bug#27162: [PATCH 4/6] syscalls: Provide 'free-disk-space'.

[Ludovic Courtès]

* guix/build/syscalls.scm (free-disk-space): New procedure.
* guix/scripts/gc.scm (guix-gc)[ensure-free-space]: Use it instead of
'statfs'.
---
 guix/build/syscalls.scm | 7 +++++++
 guix/scripts/gc.scm     | 8 +++-----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 52439afd4..2def2a108 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -62,6 +62,7 @@
             file-system-fragment-size
             file-system-mount-flags
             statfs
+            free-disk-space
 
             processes
             mkdtemp!
@@ -697,6 +698,12 @@ mounted at FILE."
                    (list file (strerror err))
                    (list err)))))))
 
+(define (free-disk-space file)
+  "Return the free disk space, in bytes, on the file system that hosts FILE."
+  (let ((fs (statfs file)))
+    (* (file-system-block-size fs)
+       (file-system-blocks-available fs))))
+
 \f
 ;;;
 ;;; Containers.
diff --git a/guix/scripts/gc.scm b/guix/scripts/gc.scm
index 221467a10..0a9719d25 100644
--- a/guix/scripts/gc.scm
+++ b/guix/scripts/gc.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -20,7 +20,7 @@
   #:use-module (guix ui)
   #:use-module (guix scripts)
   #:use-module (guix store)
-  #:autoload   (guix build syscalls) (statfs)
+  #:autoload   (guix build syscalls) (free-disk-space)
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
   #:use-module (srfi srfi-1)
@@ -184,9 +184,7 @@ Invoke the garbage collector.\n"))
 
   (define (ensure-free-space store space)
     ;; Attempt to have at least SPACE bytes available in STORE.
-    (let* ((fs    (statfs (%store-prefix)))
-           (free  (* (file-system-block-size fs)
-                     (file-system-blocks-available fs))))
+    (let ((free (free-disk-space (%store-prefix))))
       (if (> free space)
           (info (G_ "already ~h bytes available on ~a, nothing to do~%")
                 free (%store-prefix))
-- 
2.13.0

bug#27162: [PATCH 5/6] ui: 'show-what-to-build' warns when we don't have enough disk space.

[Ludovic Courtès]

* guix/ui.scm (check-available-space): New procedure.
(show-what-to-build): Compute 'installed-size' and call
'check-available-space'.
---
 guix/ui.scm | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/guix/ui.scm b/guix/ui.scm
index 04c7463fb..0e47a200c 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -38,7 +38,8 @@
   #:use-module (guix serialization)
   #:use-module ((guix build utils) #:select (mkdir-p))
   #:use-module ((guix licenses) #:select (license? license-name))
-  #:use-module ((guix build syscalls) #:select (terminal-columns))
+  #:use-module ((guix build syscalls)
+                #:select (free-disk-space terminal-columns))
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-19)
@@ -581,6 +582,17 @@ error."
                   (derivation->output-path derivation out-name)))
                (derivation-outputs derivation))))
 
+(define (check-available-space need)
+  "Make sure at least NEED bytes are available in the store.  Otherwise emit a
+warning."
+  (let ((free (catch 'system-error
+                (lambda ()
+                  (free-disk-space (%store-prefix)))
+                (const #f))))
+    (when (and free (>= need free))
+      (warning (G_ "at least ~,1h MB needed but only ~,1h MB available in ~a~%")
+               (/ need 1e6) (/ free 1e6) (%store-prefix)))))
+
 (define* (show-what-to-build store drv
                              #:key dry-run? (use-substitutes? #t)
                              (mode (build-mode normal)))
@@ -631,7 +643,9 @@ report what is prerequisites are available for download."
                                            substitutable-references
                                            download))))
                      download)))
-    ;; TODO: Show the installed size of DOWNLOAD.
+    (define installed-size
+      (reduce + 0 (map substitutable-nar-size download)))
+
     (define download-size
       (/ (reduce + 0 (map substitutable-download-size download))
          1e6))
@@ -682,6 +696,9 @@ report what is prerequisites are available for download."
                           (length download))
                       (null? download)
                       (map substitutable-path download)))))
+
+    (check-available-space installed-size)
+
     (pair? build)))
 
 (define show-what-to-build*
-- 
2.13.0

bug#27162: [PATCH 6/6] substitute: Do not display the installed size.

[Ludovic Courtès]

* guix/scripts/substitute.scm (process-substitution): Do not show the
installed size in the "Downloading" message.
---
 guix/scripts/substitute.scm | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index 4ee15ba67..71f30030b 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -874,15 +874,7 @@ DESTINATION as a nar file.  Verify the substitute against ACL."
     (format #t "~a~%" (narinfo-hash narinfo))
 
     (format (current-error-port)
-            ;; TRANSLATORS: The second part of this message looks like
-            ;; "(4.1MiB installed)"; it shows the size of the package once
-            ;; installed.
-            (G_ "Downloading ~a~:[~*~; (~a installed)~]...~%")
-            (uri->string uri)
-            ;; Use the Nar size as an estimate of the installed size.
-            (narinfo-size narinfo)
-            (and=> (narinfo-size narinfo)
-                   (cute byte-count->string <>)))
+            (G_ "Downloading ~a...~%") (uri->string uri))
     (let*-values (((raw download-size)
                    ;; Note that Hydra currently generates Nars on the fly
                    ;; and doesn't specify a Content-Length, so
-- 
2.13.0

bug#27162: [PATCH 0/6] Display how much will be downloaded

[Maxim Cournoyer]

Hi!

On Wed, May 31, 2017 at 6:49 AM, Ludovic Courtès <ludo@gnu.org> wrote:
> Hello!
>
> With this patch series, ‘show-what-to-build’ can display the download
> size and warn about lack of disk space when needed:
>
>   $ ./pre-inst-env guix build synfigstudio -n
>   substitute: updating list of substitutes from 'https://bayfront.guixsd.org'... 100.0%
>   10.8 MB would be downloaded:
>      /gnu/store/jq80lq3xhib81fi2v6j7ygh7mqdjrjsx-synfigstudio-1.2.0
>      /gnu/store/azvp0257q9yhl0b409q1s6h67pfhaknr-libxml++-3.0.1
>      /gnu/store/bjmwcqxr32g48jzwc0zc993m8x3ymq5h-synfig-1.2.0
>      /gnu/store/lxmviq543w2a4ahc4c77i542sl921bbl-mlt-6.4.1
>   guix build: warning: at least 73.8 MB needed but only 42.0 MB available in /gnu/store
>
> Thoughts?

This is really neat! Thanks for that. Shouldn't the default behavior
of build to stop right there (even without the -n flag) and errors out
when it "knows" there won't be enough space to successfully build the
derivations? This would prevent bad surprises and is still
non-interactive. If the current ability of failing a build because of
lack of disk space would still be desired for some reason, a force
flag could allow it anyway.

My 2 cents,

Maxim

bug#27162: [PATCH 0/6] Display how much will be downloaded

[Ludovic Courtès]

Hi,

Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis:

> On Wed, May 31, 2017 at 6:49 AM, Ludovic Courtès <ludo@gnu.org> wrote:
>> Hello!
>>
>> With this patch series, ‘show-what-to-build’ can display the download
>> size and warn about lack of disk space when needed:
>>
>>   $ ./pre-inst-env guix build synfigstudio -n
>>   substitute: updating list of substitutes from 'https://bayfront.guixsd.org'... 100.0%
>>   10.8 MB would be downloaded:
>>      /gnu/store/jq80lq3xhib81fi2v6j7ygh7mqdjrjsx-synfigstudio-1.2.0
>>      /gnu/store/azvp0257q9yhl0b409q1s6h67pfhaknr-libxml++-3.0.1
>>      /gnu/store/bjmwcqxr32g48jzwc0zc993m8x3ymq5h-synfig-1.2.0
>>      /gnu/store/lxmviq543w2a4ahc4c77i542sl921bbl-mlt-6.4.1
>>   guix build: warning: at least 73.8 MB needed but only 42.0 MB available in /gnu/store
>>
>> Thoughts?
>
> This is really neat! Thanks for that. Shouldn't the default behavior
> of build to stop right there (even without the -n flag) and errors out
> when it "knows" there won't be enough space to successfully build the
> derivations? This would prevent bad surprises and is still
> non-interactive.

Good point!

On my previous laptop I was always short on disk space, so what I would
do is spawn ‘guix package’ or similar, and then once it had started, I
would start ‘guix gc’ in a separate terminal; that way I knew it’d only
GC things that don’t matter for the operation at hand.

Granted, that’s a bit far-fetched, but perhaps there are other
situations where you’d want to proceed anyway because you know you’ll be
freeing space somehow.

Now, maybe the default could still be to error out, and we’d have a
force flag as you wrote (--no-error-if-full?) for these other cases.
That would add a little bit of complexity though.

Ludo’.

bug#27162: [PATCH 0/6] Display how much will be downloaded

[Danny Milosavljevic]

Hi,

On Wed, 31 May 2017 12:42:29 -0700
Maxim Cournoyer <maxim.cournoyer@gmail.com> wrote:

> This is really neat! Thanks for that. Shouldn't the default behavior
> of build to stop right there (even without the -n flag) and errors out
> when it "knows" there won't be enough space to successfully build the
> derivations? 

It doesn't know it.

Modern filesystems can compress on-the-fly.  What free-disk-space shows is just a guess and it really depends on the exact content you write whether it will fit or not. 

Also, filesystems with deduplication will store content just once (basically at the sector with the number equal to the hash of the content) and just reuse the same sectors for other files.  That, too would be misjudged.

Then there are quotas, if there's a quota for a specific user only this user's files will be limited (much earlier).  Not supported either.

Then there can be storage reserved for the root user - and if you are non-root, you won't get it, even if it's technically "available".

Then there's clustering overhead.  Depending on the size of the individual files it can take (sometimes) much more space to actually store those files than you think.

Therefore I think a warning is better.  It can easily have both false positives and false negatives.

I like the feature, though.  Also the download size feature.  Nice :D

bug#27162: [PATCH 0/6] Display how much will be downloaded

[Maxim Cournoyer]

[-- Attachment #1: Type: text/plain, Size: 1672 bytes --]

Hi,

On Wed, May 31, 2017 at 2:39 PM, Danny Milosavljevic <dannym@scratchpost.org
> wrote:

> Hi,
>
> On Wed, 31 May 2017 12:42:29 -0700
> Maxim Cournoyer <maxim.cournoyer@gmail.com> wrote:
>
> > This is really neat! Thanks for that. Shouldn't the default behavior
> > of build to stop right there (even without the -n flag) and errors out
> > when it "knows" there won't be enough space to successfully build the
> > derivations?
>
> It doesn't know it.
>
> Modern filesystems can compress on-the-fly.  What free-disk-space shows is
> just a guess and it really depends on the exact content you write whether
> it will fit or not.
>
> Also, filesystems with deduplication will store content just once
> (basically at the sector with the number equal to the hash of the content)
> and just reuse the same sectors for other files.  That, too would be
> misjudged.
>
> Then there are quotas, if there's a quota for a specific user only this
> user's files will be limited (much earlier).  Not supported either.
>
> Then there can be storage reserved for the root user - and if you are
> non-root, you won't get it, even if it's technically "available".
>
> Then there's clustering overhead.  Depending on the size of the individual
> files it can take (sometimes) much more space to actually store those files
> than you think.
>
> Therefore I think a warning is better.  It can easily have both false
> positives and false negatives.
>
> I like the feature, though.  Also the download size feature.  Nice :D
>

Right. Making it an error would also open the door for bug reports. So yes,
I think you are right, this should be a warning rather than an error.

Thanks!

Maxim

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bug#27162: [PATCH 0/6] Display how much will be downloaded

[Ludovic Courtès]

Hello,

I’ve pushed this patch series, thanks for your feedback!

Ludo’.

bug#27162: [PATCH 0/6] Display how much will be downloaded

[Ludovic Courtès]

Danny Milosavljevic <dannym@scratchpost.org> skribis:

> Hi,
>
> On Wed, 31 May 2017 12:42:29 -0700
> Maxim Cournoyer <maxim.cournoyer@gmail.com> wrote:
>
>> This is really neat! Thanks for that. Shouldn't the default behavior
>> of build to stop right there (even without the -n flag) and errors out
>> when it "knows" there won't be enough space to successfully build the
>> derivations? 
>
> It doesn't know it.
>
> Modern filesystems can compress on-the-fly.  What free-disk-space shows is just a guess and it really depends on the exact content you write whether it will fit or not. 
>
> Also, filesystems with deduplication will store content just once (basically at the sector with the number equal to the hash of the content) and just reuse the same sectors for other files.  That, too would be misjudged.
>
> Then there are quotas, if there's a quota for a specific user only this user's files will be limited (much earlier).  Not supported either.
>
> Then there can be storage reserved for the root user - and if you are non-root, you won't get it, even if it's technically "available".
>
> Then there's clustering overhead.  Depending on the size of the individual files it can take (sometimes) much more space to actually store those files than you think.
>
> Therefore I think a warning is better.  It can easily have both false positives and false negatives.

All good points, indeed.

Ludo’.