diff options
Diffstat (limited to 'src/libstore')
| -rw-r--r-- | src/libstore/profiles.cc | 123 | ||||
| -rw-r--r-- | src/libstore/profiles.hh | 143 |
2 files changed, 210 insertions, 56 deletions
diff --git a/src/libstore/profiles.cc b/src/libstore/profiles.cc index ba5c8583f..4e9955948 100644 --- a/src/libstore/profiles.cc +++ b/src/libstore/profiles.cc @@ -13,8 +13,10 @@ namespace nix { -/* Parse a generation name of the format - `<profilename>-<number>-link'. */ +/** + * Parse a generation name of the format + * `<profilename>-<number>-link'. + */ static std::optional<GenerationNumber> parseName(const std::string & profileName, const std::string & name) { if (name.substr(0, profileName.size() + 1) != profileName + "-") return {}; @@ -28,7 +30,6 @@ static std::optional<GenerationNumber> parseName(const std::string & profileName } - std::pair<Generations, std::optional<GenerationNumber>> findGenerations(Path profile) { Generations gens; @@ -61,15 +62,16 @@ std::pair<Generations, std::optional<GenerationNumber>> findGenerations(Path pro } -static void makeName(const Path & profile, GenerationNumber num, - Path & outLink) +/** + * Create a generation name that can be parsed by `parseName()`. + */ +static Path makeName(const Path & profile, GenerationNumber num) { - Path prefix = fmt("%1%-%2%", profile, num); - outLink = prefix + "-link"; + return fmt("%s-%s-link", profile, num); } -Path createGeneration(ref<LocalFSStore> store, Path profile, StorePath outPath) +Path createGeneration(LocalFSStore & store, Path profile, StorePath outPath) { /* The new generation number should be higher than old the previous ones. */ @@ -79,7 +81,7 @@ Path createGeneration(ref<LocalFSStore> store, Path profile, StorePath outPath) if (gens.size() > 0) { Generation last = gens.back(); - if (readLink(last.path) == store->printStorePath(outPath)) { + if (readLink(last.path) == store.printStorePath(outPath)) { /* We only create a new generation symlink if it differs from the last one. @@ -89,7 +91,7 @@ Path createGeneration(ref<LocalFSStore> store, Path profile, StorePath outPath) return last.path; } - num = gens.back().number; + num = last.number; } else { num = 0; } @@ -100,9 +102,8 @@ Path createGeneration(ref<LocalFSStore> store, Path profile, StorePath outPath) to the permanent roots (of which the GC would have a stale view). If we didn't do it this way, the GC might remove the user environment etc. we've just built. */ - Path generation; - makeName(profile, num + 1, generation); - store->addPermRoot(outPath, generation); + Path generation = makeName(profile, num + 1); + store.addPermRoot(outPath, generation); return generation; } @@ -117,12 +118,19 @@ static void removeFile(const Path & path) void deleteGeneration(const Path & profile, GenerationNumber gen) { - Path generation; - makeName(profile, gen, generation); + Path generation = makeName(profile, gen); removeFile(generation); } - +/** + * Delete a generation with dry-run mode. + * + * Like `deleteGeneration()` but: + * + * - We log what we are going to do. + * + * - We only actually delete if `dryRun` is false. + */ static void deleteGeneration2(const Path & profile, GenerationNumber gen, bool dryRun) { if (dryRun) @@ -150,27 +158,36 @@ void deleteGenerations(const Path & profile, const std::set<GenerationNumber> & } } +/** + * Advanced the iterator until the given predicate `cond` returns `true`. + */ +static inline void iterDropUntil(Generations & gens, auto && i, auto && cond) +{ + for (; i != gens.rend() && !cond(*i); ++i); +} + void deleteGenerationsGreaterThan(const Path & profile, GenerationNumber max, bool dryRun) { + if (max == 0) + throw Error("Must keep at least one generation, otherwise the current one would be deleted"); + PathLocks lock; lockProfile(lock, profile); - bool fromCurGen = false; - auto [gens, curGen] = findGenerations(profile); - for (auto i = gens.rbegin(); i != gens.rend(); ++i) { - if (i->number == curGen) { - fromCurGen = true; - max--; - continue; - } - if (fromCurGen) { - if (max) { - max--; - continue; - } - deleteGeneration2(profile, i->number, dryRun); - } - } + auto [gens, _curGen] = findGenerations(profile); + auto curGen = _curGen; + + auto i = gens.rbegin(); + + // Find the current generation + iterDropUntil(gens, i, [&](auto & g) { return g.number == curGen; }); + + // Skip over `max` generations, preserving them + for (auto keep = 0; i != gens.rend() && keep < max; ++i, ++keep); + + // Delete the rest + for (; i != gens.rend(); ++i) + deleteGeneration2(profile, i->number, dryRun); } void deleteOldGenerations(const Path & profile, bool dryRun) @@ -193,23 +210,33 @@ void deleteGenerationsOlderThan(const Path & profile, time_t t, bool dryRun) auto [gens, curGen] = findGenerations(profile); - bool canDelete = false; - for (auto i = gens.rbegin(); i != gens.rend(); ++i) - if (canDelete) { - assert(i->creationTime < t); - if (i->number != curGen) - deleteGeneration2(profile, i->number, dryRun); - } else if (i->creationTime < t) { - /* We may now start deleting generations, but we don't - delete this generation yet, because this generation was - still the one that was active at the requested point in - time. */ - canDelete = true; - } + auto i = gens.rbegin(); + + // Predicate that the generation is older than the given time. + auto older = [&](auto & g) { return g.creationTime < t; }; + + // Find the first older generation, if one exists + iterDropUntil(gens, i, older); + + /* Take the previous generation + + We don't want delete this one yet because it + existed at the requested point in time, and + we want to be able to roll back to it. */ + if (i != gens.rend()) ++i; + + // Delete all previous generations (unless current). + for (; i != gens.rend(); ++i) { + /* Creating date and generations should be monotonic, so lower + numbered derivations should also be older. */ + assert(older(*i)); + if (i->number != curGen) + deleteGeneration2(profile, i->number, dryRun); + } } -void deleteGenerationsOlderThan(const Path & profile, std::string_view timeSpec, bool dryRun) +time_t parseOlderThanTimeSpec(std::string_view timeSpec) { if (timeSpec.empty() || timeSpec[timeSpec.size() - 1] != 'd') throw UsageError("invalid number of days specifier '%1%', expected something like '14d'", timeSpec); @@ -221,9 +248,7 @@ void deleteGenerationsOlderThan(const Path & profile, std::string_view timeSpec, if (!days || *days < 1) throw UsageError("invalid number of days specifier '%1%'", timeSpec); - time_t oldTime = curTime - *days * 24 * 3600; - - deleteGenerationsOlderThan(profile, oldTime, dryRun); + return curTime - *days * 24 * 3600; } diff --git a/src/libstore/profiles.hh b/src/libstore/profiles.hh index 4e1f42e83..193c0bf21 100644 --- a/src/libstore/profiles.hh +++ b/src/libstore/profiles.hh @@ -1,7 +1,11 @@ #pragma once -///@file +/** + * @file Implementation of Profiles. + * + * See the manual for additional information. + */ - #include "types.hh" +#include "types.hh" #include "pathlocks.hh" #include <time.h> @@ -12,41 +16,166 @@ namespace nix { class StorePath; +/** + * A positive number identifying a generation for a given profile. + * + * Generation numbers are assigned sequentially. Each new generation is + * assigned 1 + the current highest generation number. + */ typedef uint64_t GenerationNumber; +/** + * A generation is a revision of a profile. + * + * Each generation is a mapping (key-value pair) from an identifier + * (`number`) to a store object (specified by `path`). + */ struct Generation { + /** + * The number of a generation is its unique identifier within the + * profile. + */ GenerationNumber number; + /** + * The store path identifies the store object that is the contents + * of the generation. + * + * These store paths / objects are not unique to the generation + * within a profile. Nix tries to ensure successive generations have + * distinct contents to avoid bloat, but nothing stops two + * non-adjacent generations from having the same contents. + * + * @todo Use `StorePath` instead of `Path`? + */ Path path; + + /** + * When the generation was created. This is extra metadata about the + * generation used to make garbage collecting old generations more + * convenient. + */ time_t creationTime; }; +/** + * All the generations of a profile + */ typedef std::list<Generation> Generations; /** - * Returns the list of currently present generations for the specified - * profile, sorted by generation number. Also returns the number of - * the current generation. + * Find all generations for the given profile. + * + * @param profile A profile specified by its name and location combined + * into a path. E.g. if "foo" is the name of the profile, and "/bar/baz" + * is the directory it is in, then the path "/bar/baz/foo" would be the + * argument for this parameter. + * + * @return The pair of: + * + * - The list of currently present generations for the specified profile, + * sorted by ascending generation number. + * + * - The number of the current/active generation. + * + * Note that the current/active generation need not be the latest one. */ std::pair<Generations, std::optional<GenerationNumber>> findGenerations(Path profile); class LocalFSStore; -Path createGeneration(ref<LocalFSStore> store, Path profile, StorePath outPath); +/** + * Create a new generation of the given profile + * + * If the previous generation (not the currently active one!) has a + * distinct store object, a fresh generation number is mapped to the + * given store object, referenced by path. Otherwise, the previous + * generation is assumed. + * + * The behavior of reusing existing generations like this makes this + * procedure idempotent. It also avoids clutter. + */ +Path createGeneration(LocalFSStore & store, Path profile, StorePath outPath); +/** + * Unconditionally delete a generation + * + * @param profile A profile specified by its name and location combined into a path. + * + * @param gen The generation number specifying exactly which generation + * to delete. + * + * Because there is no check of whether the generation to delete is + * active, this is somewhat unsafe. + * + * @todo Should we expose this at all? + */ void deleteGeneration(const Path & profile, GenerationNumber gen); +/** + * Delete the given set of generations. + * + * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete. + * + * @param gensToDelete The generations to delete, specified by a set of + * numbers. + * + * @param dryRun Log what would be deleted instead of actually doing + * so. + * + * Trying to delete the currently active generation will fail, and cause + * no generations to be deleted. + */ void deleteGenerations(const Path & profile, const std::set<GenerationNumber> & gensToDelete, bool dryRun); +/** + * Delete generations older than `max` passed the current generation. + * + * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete. + * + * @param max How many generations to keep up to the current one. Must + * be at least 1 so we don't delete the current one. + * + * @param dryRun Log what would be deleted instead of actually doing + * so. + */ void deleteGenerationsGreaterThan(const Path & profile, GenerationNumber max, bool dryRun); +/** + * Delete all generations other than the current one + * + * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete. + * + * @param dryRun Log what would be deleted instead of actually doing + * so. + */ void deleteOldGenerations(const Path & profile, bool dryRun); +/** + * Delete generations older than `t`, except for the most recent one + * older than `t`. + * + * @param profile The profile, specified by its name and location combined into a path, whose generations we want to delete. + * + * @param dryRun Log what would be deleted instead of actually doing + * so. + */ void deleteGenerationsOlderThan(const Path & profile, time_t t, bool dryRun); -void deleteGenerationsOlderThan(const Path & profile, std::string_view timeSpec, bool dryRun); +/** + * Parse a temp spec intended for `deleteGenerationsOlderThan()`. + * + * Throws an exception if `timeSpec` fails to parse. + */ +time_t parseOlderThanTimeSpec(std::string_view timeSpec); +/** + * Smaller wrapper around `replaceSymlink` for replacing the current + * generation of a profile. Does not enforce proper structure. + * + * @todo Always use `switchGeneration()` instead, and delete this. + */ void switchLink(Path link, Path target); /** |