Make 'nix copy' to s3:// binary caches run in constant memory

src/libstore/binary-cache-store.cc

@@ -15,6 +15,7 @@
 #include <chrono>
 #include <future>
 #include <regex>
+#include <fstream>
 
 #include <nlohmann/json.hpp>
 
@@ -58,11 +59,10 @@ void BinaryCacheStore::init()
 }
 
 void BinaryCacheStore::upsertFile(const std::string & path,
-    const std::string & data,
+    std::string && data,
     const std::string & mimeType)
 {
-    StringSource source(data);
-    upsertFile(path, source, mimeType);
+    upsertFile(path, std::make_shared<std::stringstream>(std::move(data)), mimeType);
 }
 
 void BinaryCacheStore::getFile(const std::string & path,
@@ -279,8 +279,9 @@ void BinaryCacheStore::addToStore(const ValidPathInfo & info, Source & narSource
     /* Atomically write the NAR file. */
     if (repair || !fileExists(narInfo->url)) {
         stats.narWrite++;
-        FileSource source(fnTemp);
-        upsertFile(narInfo->url, source, "application/x-nix-nar");
+        upsertFile(narInfo->url,
+            std::make_shared<std::fstream>(fnTemp, std::ios_base::in),
+            "application/x-nix-nar");
     } else
         stats.narWriteAverted++;
 

src/libstore/binary-cache-store.hh

@@ -36,11 +36,11 @@ public:
     virtual bool fileExists(const std::string & path) = 0;
 
     virtual void upsertFile(const std::string & path,
-        Source & source,
+        std::shared_ptr<std::basic_iostream<char>> istream,
         const std::string & mimeType) = 0;
 
     void upsertFile(const std::string & path,
-        const std::string & data,
+        std::string && data,
         const std::string & mimeType);
 
     /* Note: subclasses must implement at least one of the two

src/libstore/http-binary-cache-store.cc

@@ -100,11 +100,11 @@ protected:
     }
 
     void upsertFile(const std::string & path,
-        Source & source,
+        std::shared_ptr<std::basic_iostream<char>> istream,
         const std::string & mimeType) override
     {
         auto req = FileTransferRequest(cacheUri + "/" + path);
-        req.data = std::make_shared<string>(source.drain());
+        req.data = std::make_shared<string>(StreamToSourceAdapter(istream).drain());
         req.mimeType = mimeType;
         try {
             getFileTransfer()->upload(req);

src/libstore/local-binary-cache-store.cc

@@ -31,12 +31,13 @@ protected:
     bool fileExists(const std::string & path) override;
 
     void upsertFile(const std::string & path,
-        Source & source,
-        const std::string & mimeType)
+        std::shared_ptr<std::basic_iostream<char>> istream,
+        const std::string & mimeType) override
     {
         auto path2 = binaryCacheDir + "/" + path;
         Path tmp = path2 + ".tmp." + std::to_string(getpid());
         AutoDelete del(tmp, false);
+        StreamToSourceAdapter source(istream);
         writeFile(tmp, source);
         if (rename(tmp.c_str(), path2.c_str()))
             throw SysError("renaming '%1%' to '%2%'", tmp, path2);

src/libstore/s3-binary-cache-store.cc

@@ -261,12 +261,11 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
     std::shared_ptr<TransferManager> transferManager;
     std::once_flag transferManagerCreated;
 
-    void uploadFile(const std::string & path, const std::string & data,
+    void uploadFile(const std::string & path,
+        std::shared_ptr<std::basic_iostream<char>> istream,
         const std::string & mimeType,
         const std::string & contentEncoding)
     {
-        auto stream = std::make_shared<std::stringstream>(data);
-
         auto maxThreads = std::thread::hardware_concurrency();
 
         static std::shared_ptr<Aws::Utils::Threading::PooledThreadExecutor>
@@ -306,7 +305,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
 
             std::shared_ptr<TransferHandle> transferHandle =
                 transferManager->UploadFile(
-                    stream, bucketName, path, mimeType,
+                    istream, bucketName, path, mimeType,
                     Aws::Map<Aws::String, Aws::String>(),
                     nullptr /*, contentEncoding */);
 
@@ -332,9 +331,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
             if (contentEncoding != "")
                 request.SetContentEncoding(contentEncoding);
 
-            auto stream = std::make_shared<std::stringstream>(data);
-
-            request.SetBody(stream);
+            request.SetBody(istream);
 
             auto result = checkAws(fmt("AWS error uploading '%s'", path),
                 s3Helper.client->PutObject(request));
@@ -346,26 +343,34 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
             std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1)
                 .count();
 
-        printInfo(format("uploaded 's3://%1%/%2%' (%3% bytes) in %4% ms") %
-                  bucketName % path % data.size() % duration);
+        auto size = istream->tellg();
+
+        printInfo("uploaded 's3://%s/%s' (%d bytes) in %d ms",
+            bucketName, path, size, duration);
 
         stats.putTimeMs += duration;
-        stats.putBytes += data.size();
+        stats.putBytes += size;
         stats.put++;
     }
 
-    void upsertFile(const std::string & path, Source & source,
+    void upsertFile(const std::string & path,
+        std::shared_ptr<std::basic_iostream<char>> istream,
         const std::string & mimeType) override
     {
-        auto data = source.drain();
+        auto compress = [&](std::string compression)
+        {
+            auto compressed = nix::compress(compression, StreamToSourceAdapter(istream).drain());
+            return std::make_shared<std::stringstream>(std::move(*compressed));
+        };
+
         if (narinfoCompression != "" && hasSuffix(path, ".narinfo"))
-            uploadFile(path, *compress(narinfoCompression, data), mimeType, narinfoCompression);
+            uploadFile(path, compress(narinfoCompression), mimeType, narinfoCompression);
         else if (lsCompression != "" && hasSuffix(path, ".ls"))
-            uploadFile(path, *compress(lsCompression, data), mimeType, lsCompression);
+            uploadFile(path, compress(lsCompression), mimeType, lsCompression);
         else if (logCompression != "" && hasPrefix(path, "log/"))
-            uploadFile(path, *compress(logCompression, data), mimeType, logCompression);
+            uploadFile(path, compress(logCompression), mimeType, logCompression);
         else
-            uploadFile(path, data, mimeType, "");
+            uploadFile(path, istream, mimeType, "");
     }
 
     void getFile(const std::string & path, Sink & sink) override

src/libutil/serialise.hh

@@ -349,4 +349,27 @@ Source & operator >> (Source & in, bool & b)
 }
 
 
+/* An adapter that converts a std::basic_istream into a source. */
+struct StreamToSourceAdapter : Source
+{
+    std::shared_ptr<std::basic_istream<char>> istream;
+
+    StreamToSourceAdapter(std::shared_ptr<std::basic_istream<char>> istream)
+        : istream(istream)
+    { }
+
+    size_t read(unsigned char * data, size_t len) override
+    {
+        if (!istream->read((char *) data, len)) {
+            if (istream->eof()) {
+                if (istream->gcount() == 0)
+                    throw EndOfFile("end of file");
+            } else
+                throw Error("I/O error in StreamToSourceAdapter");
+        }
+        return istream->gcount();
+    }
+};
+
+
 }