Merge pull request #12639 from rstudio/aj-prefer-precompressed-assets

Add support for serving static files precompressed with Gzip/Brotli

src/cpp/core/http/Message.cpp

@@ -29,6 +29,7 @@ namespace core {
 namespace http {
 
 // encodings
+const char * const kBrotliEncoding = "br";
 const char * const kGzipEncoding = "gzip";
 const char * const kDeflateEncoding = "deflate";
 

src/cpp/core/http/Util.cpp

@@ -490,6 +490,28 @@ void fileRequestHandler(const std::string& wwwLocalPath,
       return;
    }
 
+#ifndef _WIN32
+   // To avoid the runtime CPU cost of compression, also check if there is a
+   // precompressed version of the file available and substitute it in if so.
+   // This is akin to the (gzip|brotli)_static directive for NGINX.
+   FilePath precompressed = FilePath(filePath.getAbsolutePath() + ".br");
+   if (request.acceptsEncoding(kBrotliEncoding) && precompressed.exists())
+   {
+      pResponse->setContentType(filePath.getMimeContentType());
+      pResponse->setContentEncoding(kBrotliEncoding);
+      pResponse->setCacheableFile(precompressed, request);
+      return;
+   }
+   precompressed = FilePath(filePath.getAbsolutePath() + ".gz");
+   if (request.acceptsEncoding(kGzipEncoding) && precompressed.exists())
+   {
+      pResponse->setContentType(filePath.getMimeContentType());
+      pResponse->setContentEncoding(kGzipEncoding);
+      pResponse->setCacheableFile(precompressed, request);
+      return;
+   }
+#endif
+
    // return requested file
    pResponse->setCacheableFile(filePath, request);
 }

src/cpp/core/include/core/http/Message.hpp

@@ -42,6 +42,7 @@ class FilePath;
 namespace http {
 
 // encodings
+extern const char * const kBrotliEncoding;
 extern const char * const kGzipEncoding;
 extern const char * const kDeflateEncoding;
 extern const char * const kTransferEncoding;

src/cpp/core/include/core/http/Response.hpp

@@ -23,6 +23,7 @@
 #include <boost/optional.hpp>
 #include <boost/type_traits/is_same.hpp>
 #include <boost/make_shared.hpp>
+#include <boost/algorithm/string/predicate.hpp>
 #include <boost/iostreams/copy.hpp>
 #include <boost/iostreams/concepts.hpp>
 #include <boost/iostreams/filtering_stream.hpp>
@@ -209,7 +210,8 @@ class Response : public Message
    Error setBody(std::istream& is, 
                  const Filter& filter, 
                  std::streamsize buffSize = 128,
-                 bool padding = false)
+                 bool padding = false,
+                 bool enableRuntimeCompression = true)
    {
       try
       {
@@ -224,7 +226,7 @@ class Response : public Message
             filteringStream.push(filter, buffSize);
 
          // handle gzip
-         if (contentEncoding() == kGzipEncoding)
+         if (contentEncoding() == kGzipEncoding && enableRuntimeCompression)
 #ifdef _WIN32
             // never gzip on win32
             removeHeader("Content-Encoding");
@@ -287,7 +289,8 @@ class Response : public Message
       // send the file from its stream
       try
       {
-         return setBody(*pIfs, filter, buffSize, padding);
+         bool precompressed = boost::algorithm::ends_with(filePath.getAbsolutePath(), ".gz");
+         return setBody(*pIfs, filter, buffSize, padding, !precompressed);
       }
       catch(const std::exception& e)
       {
@@ -320,10 +323,13 @@ class Response : public Message
       }
 
       // set content type
-      setContentType(filePath.getMimeContentType());
+      if (contentType().empty())
+      {
+         setContentType(filePath.getMimeContentType());
+      }
 
       // gzip if possible
-      if (request.acceptsEncoding(kGzipEncoding))
+      if (contentEncoding().empty() && request.acceptsEncoding(kGzipEncoding))
          setContentEncoding(kGzipEncoding);
 
       Error error = setBody(filePath, filter, 128, usePadding(request, filePath));