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authorEelco Dolstra <eelco.dolstra@logicblox.com>2016-09-16T16·54+0200
committerEelco Dolstra <eelco.dolstra@logicblox.com>2016-09-16T16·54+0200
commit75989bdca773eedb8b8d1cc8a7675900358acd25 (patch)
tree2d1dce1431662f441cead67d8754e96eb4db6807 /src/libstore/binary-cache-store.hh
parent054be5025762c5e1c7e853c4fa5d7eed8da1727f (diff)
Make computeFSClosure() single-threaded again
The fact that queryPathInfo() is synchronous meant that we needed a
thread for every concurrent binary cache lookup, even though they end
up being handled by the same download thread. Requiring hundreds of
threads is not a good idea. So now there is an asynchronous version of
queryPathInfo() that takes a callback function to process the
result. Similarly, enqueueDownload() now takes a callback rather than
returning a future.

Thus, a command like

  nix path-info --store https://cache.nixos.org/ -r /nix/store/slljrzwmpygy1daay14kjszsr9xix063-nixos-16.09beta231.dccf8c5

that returns 4941 paths now takes 1.87s using only 2 threads (the main
thread and the downloader thread). (This is with a prewarmed
CloudFront.)
Diffstat (limited to 'src/libstore/binary-cache-store.hh')
-rw-r--r--src/libstore/binary-cache-store.hh10
1 files changed, 8 insertions, 2 deletions
diff --git a/src/libstore/binary-cache-store.hh b/src/libstore/binary-cache-store.hh
index 2d10179f32ab..41671b7d9ffd 100644
--- a/src/libstore/binary-cache-store.hh
+++ b/src/libstore/binary-cache-store.hh
@@ -31,7 +31,11 @@ protected:
 
     /* Return the contents of the specified file, or null if it
        doesn't exist. */
-    virtual std::shared_ptr<std::string> getFile(const std::string & path) = 0;
+    virtual void getFile(const std::string & path,
+        std::function<void(std::shared_ptr<std::string>)> success,
+        std::function<void(std::exception_ptr exc)> failure) = 0;
+
+    std::shared_ptr<std::string> getFile(const std::string & path);
 
     bool wantMassQuery_ = false;
     int priority = 50;
@@ -56,7 +60,9 @@ public:
     PathSet queryAllValidPaths() override
     { notImpl(); }
 
-    std::shared_ptr<ValidPathInfo> queryPathInfoUncached(const Path & path) override;
+    void queryPathInfoUncached(const Path & path,
+        std::function<void(std::shared_ptr<ValidPathInfo>)> success,
+        std::function<void(std::exception_ptr exc)> failure) override;
 
     void queryReferrers(const Path & path,
         PathSet & referrers) override