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Persistently cache InputAccessor::fetchToStore()

Browse source 
This avoids repeated copying of the same source tree between Nix
invocations. It requires the accessor to have a "fingerprint" (e.g. a
Git revision) that uniquely determines its contents.
This commit is contained in:
Eelco Dolstra 2023-11-20 20:04:37 +01:00
parent f450c8773c
commit 99d5204baa
8 changed files with 77 additions and 3 deletions
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30
src/libfetchers/input-accessor.cc
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@ -1,5 +1,6 @@
#include "input-accessor.hh"
#include "store-api.hh"
#include "cache.hh"
namespace nix {
@ -11,6 +12,30 @@ StorePath InputAccessor::fetchToStore(
PathFilter * filter,
RepairFlag repair)
{
// FIXME: add an optimisation for the case where the accessor is
// an FSInputAccessor pointing to a store path.
std::optional<fetchers::Attrs> cacheKey;
if (!filter && fingerprint) {
cacheKey = fetchers::Attrs{
{"_what", "fetchToStore"},
{"store", store->storeDir},
{"name", std::string(name)},
{"fingerprint", *fingerprint},
{"method", (uint8_t) method},
{"path", path.abs()}
};
if (auto res = fetchers::getCache()->lookup(*cacheKey)) {
StorePath storePath(fetchers::getStrAttr(*res, "storePath"));
if (store->isValidPath(storePath)) {
debug("store path cache hit for '%s'", showPath(path));
return storePath;
}
}
} else
debug("source path '%s' is uncacheable", showPath(path));
Activity act(*logger, lvlChatty, actUnknown, fmt("copying '%s' to the store", showPath(path)));
auto source = sinkToSource([&](Sink & sink) {
@ -25,6 +50,11 @@ StorePath InputAccessor::fetchToStore(
? store->computeStorePathFromDump(*source, name, method, htSHA256).first
: store->addToStoreFromDump(*source, name, method, htSHA256, repair);
if (cacheKey)
fetchers::getCache()->upsert(
*cacheKey,
fetchers::Attrs{{"storePath", std::string(storePath.to_string())}});
return storePath;
}