From ecaa102a58ad3ab0b42e04a3d10d7c761c05ec98 Mon Sep 17 00:00:00 2001 From: Ludovic Courtès Date: Sat, 24 Oct 2020 16:31:18 +0200 Subject: publish: Add '--cache-bypass-threshold'. * guix/scripts/publish.scm (show-help, %options): Add '--cache-bypass-threshold'. (low-compression): New procedure. (cache-bypass-threshold): New parameter. (bypass-cache?): New procedure. (render-narinfo/cached): Call 'render-narinfo' when 'bypass-cache?' returns true. (render-nar/cached): Call 'render-nar' when 'bypass-cache?' returns true. (guix-publish): Parameterize 'cache-bypass-threshold'. * tests/publish.scm ("with cache", "with cache, lzip + gzip") ("with cache, uncompressed"): Pass '--cache-bypass-threshold=0'. ("with cache, vanishing item"): Expect 200 for RESPONSE. ("with cache, cache bypass"): New test. --- doc/guix.texi | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'doc') diff --git a/doc/guix.texi b/doc/guix.texi index ba7bb9612e..22bddf10e3 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -12086,13 +12086,20 @@ in advance, so @command{guix publish} does not add a prevents clients from knowing the amount of data being downloaded. Conversely, when @option{--cache} is used, the first request for a store -item (@i{via} a @code{.narinfo} URL) returns 404 and triggers a +item (@i{via} a @code{.narinfo} URL) triggers a background process to @dfn{bake} the archive---computing its @code{.narinfo} and compressing the archive, if needed. Once the archive is cached in @var{directory}, subsequent requests succeed and are served directly from the cache, which guarantees that clients get the best possible bandwidth. +That first @code{.narinfo} request nonetheless returns 200, provided the +requested store item is ``small enough'', below the cache bypass +threshold---see @option{--cache-bypass-threshold} below. That way, +clients do not have to wait until the archive is baked. For larger +store items, the first @code{.narinfo} request returns 404, meaning that +clients have to wait until the archive is baked. + The ``baking'' process is performed by worker threads. By default, one thread per CPU core is created, but this can be customized. See @option{--workers} below. @@ -12118,6 +12125,21 @@ Additionally, when @option{--cache} is used, cached entries that have not been accessed for @var{ttl} and that no longer have a corresponding item in the store, may be deleted. +@item --cache-bypass-threshold=@var{size} +When used in conjunction with @option{--cache}, store items smaller than +@var{size} are immediately available, even when they are not yet in +cache. @var{size} is a size in bytes, or it can be prefixed by @code{M} +for megabytes and so on. The default is @code{10M}. + +``Cache bypass'' allows you to reduce the publication delay for clients +at the expense of possibly additional I/O and CPU use on the server +side: depending on the client access patterns, those store items can end +up being baked several times until a copy is available in cache. + +Increasing the threshold may be useful for sites that have few users, or +to guarantee that users get substitutes even for store items that are +not popular. + @item --nar-path=@var{path} Use @var{path} as the prefix for the URLs of ``nar'' files (@pxref{Invoking guix archive, normalized archives}). -- cgit v1.2.3