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b973cd494f
Windows now has some basic Unix Domain Socket support, see https://devblogs.microsoft.com/commandline/af_unix-comes-to-windows/ Building `nix daemon` on Windows I've left for later, because the daemon currently forks per connection but this is not an option on Windows. But we can get the client part working right away.
75 lines
2.7 KiB
C++
75 lines
2.7 KiB
C++
#pragma once
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///@file
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#include "local-fs-store.hh"
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namespace nix {
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/**
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* Mix-in class for implementing permanent roots as a pair of a direct
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* (strong) reference and indirect weak reference to the first
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* reference.
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*
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* See methods for details on the operations it represents.
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*
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* @note
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* To understand the purpose of this class, it might help to do some
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* "closed-world" rather than "open-world" reasoning, and consider the
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* problem it solved for us. This class was factored out from
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* `LocalFSStore` in order to support the following table, which
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* contains 4 concrete store types (non-abstract classes, exposed to the
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* user), and how they implemented the two GC root methods:
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*
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* @note
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* | | `addPermRoot()` | `addIndirectRoot()` |
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* |-------------------|-----------------|---------------------|
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* | `LocalStore` | local | local |
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* | `UDSRemoteStore` | local | remote |
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* | `SSHStore` | doesn't have | doesn't have |
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* | `MountedSSHStore` | remote | doesn't have |
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*
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* @note
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* Note how only the local implementations of `addPermRoot()` need
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* `addIndirectRoot()`; that is what this class enforces. Without it,
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* and with `addPermRoot()` and `addIndirectRoot()` both `virtual`, we
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* would accidentally be allowing for a combinatorial explosion of
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* possible implementations many of which make no sense. Having this and
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* that invariant enforced cuts down that space.
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*/
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struct IndirectRootStore : public virtual LocalFSStore
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{
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inline static std::string operationName = "Indirect GC roots registration";
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/**
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* Implementation of `LocalFSStore::addPermRoot` where the permanent
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* root is a pair of
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*
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* - The user-facing symlink which all implementations must create
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*
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* - An additional weak reference known as the "indirect root" that
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* points to that symlink.
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*
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* The garbage collector will automatically remove the indirect root
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* when it finds that the symlink has disappeared.
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*
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* The implementation of this method is concrete, but it delegates
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* to `addIndirectRoot()` which is abstract.
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*/
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Path addPermRoot(const StorePath & storePath, const Path & gcRoot) override final;
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/**
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* Add an indirect root, which is a weak reference to the
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* user-facing symlink created by `addPermRoot()`.
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*
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* @param path user-facing and user-controlled symlink to a store
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* path.
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*
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* The form this weak-reference takes is implementation-specific.
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*/
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virtual void addIndirectRoot(const Path & path) = 0;
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protected:
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void makeSymlink(const Path & link, const Path & target);
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};
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}
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