If a substitute server advertises in its narinfo, for example, both a
/zstd and a /lzip URL but the /zstd URL is unreachable, try the /lzip
URL.
Fixes <https://issues.guix.gnu.org/63634>.
* guix/narinfo.scm (narinfo-preferred-uris): New procedure.
(narinfo-best-uri): Rebase on top of it.
* guix/scripts/substitute.scm (download-nar)[try-fetch]: New procedure.
Use 'narinfo-preferred-uris' and 'try-fetch' to attempt all the URLs of
NARINFO.
* tests/substitute.scm (request-substitution): Remove 'parameterize'.
Delete DESTINATION.
("substitute, preferred nar URL is 404, other is 200"): New test.
This stems from the observation that substitute download can be
CPU-bound when high-speed networks are in use:
https://lists.gnu.org/archive/html/guix-devel/2020-12/msg00177.html
* guix/narinfo.scm (decompresses-faster?): New procedure.
(narinfo-best-uri): Add #:fast-decompression?.
* guix/scripts/substitute.scm (%prefer-fast-decompression?): New
variable.
(call-with-cpu-usage-monitoring): New procedure.
(with-cpu-usage-monitoring): New macro.
(display-narinfo-data, process-substitution): Pass #:fast-decompression?
to 'narinfo-best-uri'.
(process-substitution): Wrap 'restore-file' call in
'with-cpu-usage-monitoring'. Set '%prefer-fast-decompression?'.
This means there's a module for working with substitutes, rather than all the
code sitting in the script. The need for this can be seen with the weather and
challenge scripts, that now don't have to use code from the substitute script,
but can instead use the substitute module.
The separation here between the actual functionality of the substitute script
and the underlying functionality used both there and elsewhere should make
maintenance easier moving forward.
This commit just moves code, none of the code should have been changed
significantly.
* guix/scripts/substitute.scm (%narinfo-cache-directory, %narinfo-ttl,
%narinfo-negative-ttl, %narinfo-transient-error-ttl, %unreachable-hosts): Move
variables to guix/substitutes.scm.
(narinfo-cache-file, cached-narinfo, cache-narinfo!, narinfo-request,
read-to-eof, call-with-connection-error-handling, fetch-narinfos,
lookup-narinfos, lookup-narinfos/diverse): Move procedures to
guix/substitutes.scm.
* guix/substitutes.scm: New file.
* Makefile.am: Add it.
* guix/narinfo.scm: Remove redundant module.
* guix/scripts/challenge.scm: Change (guix scripts substitute) to (guix
substitutes).
* guix/scripts/weather.scm: Change (guix scripts substitute) to (guix
substitutes).
As this is useful if you want to work with narinfo signatures outside of Guix,
in the Guix Data Service for example.
* guix/narinfo.scm: Export narinfo-contents.
This separation between the code for dealing with narinfos from the code doing
that for a purpose should make things clearer, and better support components
other that the substitute script in using this code.
This is just moving the code around, no code should have been significantly
changed.
* guix/scripts/substitute.scm (<narinfo>): Move record type to (guix narinfo).
(fields->alist, narinfo-hash-algorithm+value, narinfo-hash->sha256,
narinfo-signature->canonical-sexp, narinfo-maker, read-narinfo,
narinfo-sha256, valid-narinfo?, write-narinfo, narinfo->string,
string->narinfo, equivalent-narinfo?, supported-compression?,
compresses-better?, narinfo-best-uri): Move procedures to (guix narinfo).
(%compression-methods): Move variable to (guix narinfo).
* guix/narinfo.scm: New file.
* Makefile.am (MODULES): Add it.
* po/guix/POTFILES.in: Add 'guix/narinfo.scm'.
