Generate an ETag for a container's root

lib/remote_storage/swift.rb

@@ -4,6 +4,7 @@ require "cgi"
 require "active_support/core_ext/time/conversions"
 require "active_support/core_ext/numeric/time"
 require "redis"
+require 'digest/md5'
 
 module RemoteStorage
   class Swift
@@ -57,36 +58,47 @@ module RemoteStorage
     end
 
     def get_head_directory_listing(user, directory)
+      is_root_listing = directory.empty?
+      if is_root_listing
+        # We need to calculate the etag ourselves
+        res = do_get_request("#{url_for_directory(user, directory)}/?format=json")
+        etag = etag_for(res.body)
+      else
         res  = do_head_request("#{url_for_directory(user, directory)}/")
+        etag = res.headers[:etag]
+      end
 
       server.headers["Content-Type"] = "application/json"
-      server.headers["ETag"]         = %Q("#{res.headers[:etag]}")
+      server.headers["ETag"]         = %Q("#{etag}")
     rescue RestClient::ResourceNotFound
       server.halt 404
     end
 
     def get_directory_listing(user, directory)
-      server.headers["Content-Type"] = "application/json"
-
-      do_head_request("#{url_for_directory(user, directory)}/") do |response|
-        if response.code == 404
-          return directory_listing([]).to_json
-        else
-          server.headers["ETag"] = %Q("#{response.headers[:etag]}")
-          none_match = (server.env["HTTP_IF_NONE_MATCH"] || "").split(",").map(&:strip)
-          server.halt 304 if none_match.include? %Q("#{response.headers[:etag]}")
-        end
-      end
-
       is_root_listing = directory.empty?
 
-      res = if is_root_listing
-              do_get_request("#{container_url_for(user)}/?format=json")
+      server.headers["Content-Type"] = "application/json"
+
+      etag, get_response = nil
+
+      do_head_request("#{url_for_directory(user, directory)}/") do |response|
+        return directory_listing([]).to_json if response.code == 404
+
+        if is_root_listing
+          get_response = do_get_request("#{container_url_for(user)}/?format=json")
+          etag = etag_for(get_response.body)
         else
-              do_get_request("#{container_url_for(user)}/?format=json&path=#{escape(directory)}/")
+          get_response = do_get_request("#{container_url_for(user)}/?format=json&path=#{escape(directory)}/")
+          etag = response.headers[:etag]
         end
 
-      if body = JSON.parse(res.body)
+        none_match = (server.env["HTTP_IF_NONE_MATCH"] || "").split(",").map(&:strip)
+        server.halt 304 if none_match.include? etag
+      end
+
+      server.headers["ETag"] = %Q("#{etag}")
+
+      if body = JSON.parse(get_response.body)
         listing = directory_listing(body, is_root_listing)
       else
         puts "listing not JSON"
@@ -328,5 +340,15 @@ module RemoteStorage
     def redis
       @redis ||= Redis.new(host: settings.redis["host"], port: settings.redis["port"])
     end
+
+    def etag_for(body)
+      objects = JSON.parse(body)
+
+      if objects.empty?
+        Digest::MD5.hexdigest ''
+      else
+        Digest::MD5.hexdigest objects.map { |o| o["hash"] }.join
+      end
+    end
   end
 end