diff options
Diffstat (limited to 'src/libstore/profiles.hh')
| -rw-r--r-- | src/libstore/profiles.hh | 207 |
1 files changed, 182 insertions, 25 deletions
diff --git a/src/libstore/profiles.hh b/src/libstore/profiles.hh index fbf95b850..193c0bf21 100644 --- a/src/libstore/profiles.hh +++ b/src/libstore/profiles.hh @@ -1,4 +1,9 @@ #pragma once +/** + * @file Implementation of Profiles. + * + * See the manual for additional information. + */ #include "types.hh" #include "pathlocks.hh" @@ -11,70 +16,222 @@ 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); -/* Roll back a profile to the specified generation, or to the most - recent one older than the current. */ +/** + * Roll back a profile to the specified generation, or to the most + * recent one older than the current. + */ void switchGeneration( const Path & profile, std::optional<GenerationNumber> dstGen, bool dryRun); -/* Ensure exclusive access to a profile. Any command that modifies - the profile first acquires this lock. */ +/** + * Ensure exclusive access to a profile. Any command that modifies + * the profile first acquires this lock. + */ void lockProfile(PathLocks & lock, const Path & profile); -/* Optimistic locking is used by long-running operations like `nix-env - -i'. Instead of acquiring the exclusive lock for the entire - duration of the operation, we just perform the operation - optimistically (without an exclusive lock), and check at the end - whether the profile changed while we were busy (i.e., the symlink - target changed). If so, the operation is restarted. Restarting is - generally cheap, since the build results are still in the Nix - store. Most of the time, only the user environment has to be - rebuilt. */ +/** + * Optimistic locking is used by long-running operations like `nix-env + * -i'. Instead of acquiring the exclusive lock for the entire + * duration of the operation, we just perform the operation + * optimistically (without an exclusive lock), and check at the end + * whether the profile changed while we were busy (i.e., the symlink + * target changed). If so, the operation is restarted. Restarting is + * generally cheap, since the build results are still in the Nix + * store. Most of the time, only the user environment has to be + * rebuilt. + */ std::string optimisticLockProfile(const Path & profile); -/* Creates and returns the path to a directory suitable for storing the user’s - profiles. */ +/** + * Create and return the path to a directory suitable for storing the user’s + * profiles. + */ Path profilesDir(); -/* Resolve the default profile (~/.nix-profile by default, $XDG_STATE_HOME/ - nix/profile if XDG Base Directory Support is enabled), and create if doesn't - exist */ +/** + * Return the path to the profile directory for root (but don't try creating it) + */ +Path rootProfilesDir(); + +/** + * Create and return the path to the file used for storing the users's channels + */ +Path defaultChannelsDir(); + +/** + * Return the path to the channel directory for root (but don't try creating it) + */ +Path rootChannelsDir(); + +/** + * Resolve the default profile (~/.nix-profile by default, + * $XDG_STATE_HOME/nix/profile if XDG Base Directory Support is enabled), + * and create if doesn't exist + */ Path getDefaultProfile(); } |