From 6881476232df9979faf1fe0ef5db0ce6ffde77de Mon Sep 17 00:00:00 2001 From: Qyriad Date: Tue, 21 May 2024 09:30:25 -0600 Subject: libfetchers: fallback to memory SQLite if fs IO fails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit nix::fetchers::CacheImpl uses $XDG_CACHE_HOME, or its default based on $HOME, to store its SQLite database. If the current process can't write to that directory for whatever reason, though, any eval-time fetching would fail just initializing the cache. With this change, IO errors initializing the fetcher cache are logged but ignored, and nix::fetchers::CacheImpl falls back to an in-memory¹ database instead. Notably, this will fix any uses eval fetching while Lix itself is being run in a derivation builder (such as during tests), as the derivation builder does not set $XDG_CACHE_HOME, and sets $HOME to the non-existent directory /homeless-shelter. Before: $ env -u XDG_CACHE_HOME HOME=/homeless-shelter nix -Lv eval --impure -E 'fetchTarball "https://git.lix.systems/lix-project/lix/archive/main.tar.gz"' error: … while calling the 'fetchTarball' builtin at «string»:1:1: 1| fetchTarball "https://git.lix.systems/lix-project/lix/archive/main.tar.gz" | ^ error: creating directory '/homeless-shelter': Permission denied After: $ env -u XDG_CACHE_HOME HOME=/homeless-shelter nix -Lv eval --impure -E 'fetchTarball "https://git.lix.systems/lix-project/lix/archive/main.tar.gz"' warning: ignoring error initializing Lix fetcher cache: error: creating directory '/homeless-shelter': Permission denied "/nix/store/s9lxdnn0awp37n560bg4fgr497ah4hvw-source" ¹: https://www.sqlite.org/inmemorydb.html Change-Id: I15c38c9baaf215fc6e192b8a4c70b9692a69bc22 --- src/libfetchers/cache.cc | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/src/libfetchers/cache.cc b/src/libfetchers/cache.cc index 0c8ecac9d..672e1e0bc 100644 --- a/src/libfetchers/cache.cc +++ b/src/libfetchers/cache.cc @@ -34,7 +34,16 @@ struct CacheImpl : Cache auto state(_state.lock()); auto dbPath = getCacheDir() + "/nix/fetcher-cache-v1.sqlite"; - createDirs(dirOf(dbPath)); + // It would be silly to fail fetcher operations if e.g. the user has no + // XDG_CACHE_HOME and their HOME directory doesn't exist. + // We'll warn the user if that happens, but fallback to an in-memory + // backend for the SQLite database. + try { + createDirs(dirOf(dbPath)); + } catch (SysError const & ex) { + warn("ignoring error initializing Lix fetcher cache: %s", ex.what()); + dbPath = ":memory:"; + } state->db = SQLite(dbPath); state->db.isCache(); -- cgit v1.2.3