Artemis Tosini
b247ef72dc
This creates new subclasses of LocalStore for each OS to include platform-specific functionality. Currently this just includes garbage collector roots but it could be extended to sandboxing as well. In order to make sure that the generic LocalStore is not accidentally constructed, its constructor is protected. A Fallback is provided which implements no functionality except constructors. Change-Id: I836a28e90b68309873f75afb83e0f1b2e2c89fb3
127 lines
3.5 KiB
C++
127 lines
3.5 KiB
C++
#pragma once
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///@file
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#include "store-api.hh"
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namespace nix {
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/**
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* Garbage-collector roots, referring to a store path
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*/
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typedef std::unordered_map<StorePath, std::unordered_set<std::string>> Roots;
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/**
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* Possible garbage collector roots, referring to any path
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*/
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typedef std::unordered_map<Path, std::unordered_set<std::string>> UncheckedRoots;
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struct GCOptions
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{
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/**
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* Garbage collector operation:
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*
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* - `gcReturnLive`: return the set of paths reachable from
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* (i.e. in the closure of) the roots.
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*
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* - `gcReturnDead`: return the set of paths not reachable from
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* the roots.
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*
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* - `gcDeleteDead`: actually delete the latter set.
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*
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* - `gcDeleteSpecific`: delete the paths listed in
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* `pathsToDelete`, insofar as they are not reachable.
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*/
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typedef enum {
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gcReturnLive,
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gcReturnDead,
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gcDeleteDead,
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gcDeleteSpecific,
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} GCAction;
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GCAction action{gcDeleteDead};
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/**
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* If `ignoreLiveness` is set, then reachability from the roots is
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* ignored (dangerous!). However, the paths must still be
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* unreferenced *within* the store (i.e., there can be no other
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* store paths that depend on them).
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*/
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bool ignoreLiveness{false};
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/**
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* For `gcDeleteSpecific`, the paths to delete.
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*/
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StorePathSet pathsToDelete;
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/**
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* Stop after at least `maxFreed` bytes have been freed.
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*/
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uint64_t maxFreed{std::numeric_limits<uint64_t>::max()};
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};
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struct GCResults
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{
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/**
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* Depending on the action, the GC roots, or the paths that would
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* be or have been deleted.
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*/
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PathSet paths;
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/**
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* For `gcReturnDead`, `gcDeleteDead` and `gcDeleteSpecific`, the
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* number of bytes that would be or was freed.
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*/
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uint64_t bytesFreed = 0;
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};
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/**
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* Mix-in class for \ref Store "stores" which expose a notion of garbage
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* collection.
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*
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* Garbage collection will allow deleting paths which are not
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* transitively "rooted".
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*
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* The notion of GC roots actually not part of this class.
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*
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* - The base `Store` class has `Store::addTempRoot()` because for a store
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* that doesn't support garbage collection at all, a temporary GC root is
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* safely implementable as no-op.
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*
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* @todo actually this is not so good because stores are *views*.
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* Some views have only a no-op temp roots even though others to the
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* same store allow triggering GC. For instance one can't add a root
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* over ssh, but that doesn't prevent someone from gc-ing that store
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* accesed via SSH locally).
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*
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* - The derived `LocalFSStore` class has `LocalFSStore::addPermRoot`,
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* which is not part of this class because it relies on the notion of
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* an ambient file system. There are stores (`ssh-ng://`, for one),
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* that *do* support garbage collection but *don't* expose any file
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* system, and `LocalFSStore::addPermRoot` thus does not make sense
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* for them.
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*/
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struct GcStore : public virtual Store
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{
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inline static std::string operationName = "Garbage collection";
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/**
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* Find the roots of the garbage collector. Each root is a pair
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* `(link, storepath)` where `link` is the path of the symlink
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* outside of the Nix store that point to `storePath`. If
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* `censor` is true, privacy-sensitive information about roots
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* found in `/proc` is censored.
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*/
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virtual Roots findRoots(bool censor) = 0;
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/**
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* Perform a garbage collection.
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*/
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virtual void collectGarbage(const GCOptions & options, GCResults & results) = 0;
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};
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}
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