Fix: driver loading when file not accessible

resolves logstash-plugins#369 (also related logstash-plugins#362)

lib/logstash/inputs/jdbc.rb

@@ -270,6 +270,7 @@ def set_value_tracker(instance)
   end
 
   def run(queue)
+    load_driver
     if @schedule
       @scheduler = Rufus::Scheduler.new(:max_work_threads => 1)
       @scheduler.cron @schedule do

lib/logstash/plugin_mixins/jdbc/jdbc.rb

@@ -140,47 +140,58 @@ def jdbc_connect
 
     private
 
+    def load_driver
+      if @drivers_loaded.false?
+        require "java"
+        require "sequel"
+        require "sequel/adapters/jdbc"
+
+        load_driver_jars
+        begin
+          Sequel::JDBC.load_driver(@jdbc_driver_class)
+        rescue Sequel::AdapterNotFound => e # Sequel::AdapterNotFound, "#{@jdbc_driver_class} not loaded"
+          # fix this !!!
+          message = if jdbc_driver_library_set?
+                      "Are you sure you've included the correct jdbc driver in :jdbc_driver_library?"
+                    else
+                      ":jdbc_driver_library is not set, are you sure you included " +
+                          "the proper driver client libraries in your classpath?"
+                    end
+          raise LogStash::PluginLoadingError, "#{e}. #{message}"
+        end
+        @drivers_loaded.make_true
+      end
+    end
+
     def load_driver_jars
-      unless @jdbc_driver_library.nil? || @jdbc_driver_library.empty?
+      if jdbc_driver_library_set?
         @jdbc_driver_library.split(",").each do |driver_jar|
+          @logger.debug("loading #{driver_jar}")
+          # load 'driver.jar' is different than load 'some.rb' as it only causes the file to be added to
+          # JRuby's class-loader lookup (class) path - won't raise a LoadError when file is not readable
+          unless FileTest.readable?(driver_jar)
+            raise LogStash::PluginLoadingError, "unable to load #{driver_jar} from :jdbc_driver_library, " +
+                "file not readable (please check user and group permissions for the path)"
+          end
           begin
-            @logger.debug("loading #{driver_jar}")
-            # Use https://github.com/jruby/jruby/wiki/CallingJavaFromJRuby#from-jar-files to make classes from jar
-            # available
             require driver_jar
           rescue LoadError => e
             raise LogStash::PluginLoadingError, "unable to load #{driver_jar} from :jdbc_driver_library, #{e.message}"
+          rescue StandardError => e
+            raise LogStash::PluginLoadingError, "unable to load #{driver_jar} from :jdbc_driver_library, #{e}"
           end
         end
       end
     end
 
-    private
-    def open_jdbc_connection
-      require "java"
-      require "sequel"
-      require "sequel/adapters/jdbc"
+    def jdbc_driver_library_set?
+      !@jdbc_driver_library.nil? && !@jdbc_driver_library.empty?
+    end
 
+    def open_jdbc_connection
+      # at this point driver is already loaded
       Sequel.application_timezone = @plugin_timezone.to_sym
-      if @drivers_loaded.false?
-        begin
-          load_driver_jars
-          Sequel::JDBC.load_driver(@jdbc_driver_class)
-        rescue LogStash::Error => e
-          # raised in load_drivers, e.cause should be the caught Java exceptions
-          raise LogStash::PluginLoadingError, "#{e.message} and #{e.cause.message}"
-        rescue Sequel::AdapterNotFound => e
-          # fix this !!!
-          message = if @jdbc_driver_library.nil?
-            ":jdbc_driver_library is not set, are you sure you included
-                      the proper driver client libraries in your classpath?"
-          else
-            "Are you sure you've included the correct jdbc driver in :jdbc_driver_library?"
-          end
-          raise LogStash::PluginLoadingError, "#{e}. #{message}"
-        end
-        @drivers_loaded.make_true
-      end
+
       @database = jdbc_connect()
       @database.extension(:pagination)
       if @jdbc_default_timezone

spec/inputs/jdbc_spec.rb

@@ -1291,6 +1291,38 @@
     end
   end
 
+  context "when an unreadable jdbc_driver_path entry is present" do
+    let(:driver_jar_path) do
+      jar_file = $CLASSPATH.find { |name| name.index(Jdbc::Derby.driver_jar) }
+      raise "derby jar not found on class-path" unless jar_file
+      jar_file.sub('file:', '')
+    end
+
+    let(:invalid_driver_jar_path) do
+      path = File.join(Dir.mktmpdir, File.basename(driver_jar_path))
+      FileUtils.cp driver_jar_path, path
+      FileUtils.chmod "u=x,go=", path
+      path
+    end
+
+    let(:settings) do
+      { "statement" => "SELECT * from types_table", "jdbc_driver_library" => invalid_driver_jar_path }
+    end
+
+    before do
+      plugin.register
+    end
+
+    after do
+      plugin.stop
+    end
+
+    it "raise a loading error" do
+      expect { plugin.run(queue) }.
+          to raise_error(LogStash::PluginLoadingError, /unable to load .*? from :jdbc_driver_library, file not readable/)
+    end
+  end
+
   context "when using prepared statements" do
     let(:last_run_value) { 250 }
     let(:expected_queue_size) { 100 }