Critical fixes for two show stopper bugs #180 and #182 (#183)

* Fix JAR_VERSION read problem, add test and fix /dev/null write IO error
* bump version and add changelog entry

Fix #182 
Fix #180

Author: Guy Boertje

Diff for: CHANGELOG.md

@@ -1,3 +1,9 @@
+## 4.1.1
+  - Fix JAR_VERSION read problem, prevented Logstash from starting.
+    [Issue #180](https://github.com/logstash-plugins/logstash-input-file/issues/180)
+  - Fix sincedb write error when using /dev/null, repeatedly causes a plugin restart.
+    [Issue #182](https://github.com/logstash-plugins/logstash-input-file/issues/182)
+
 ## 4.1.0
   - Move Filewatch code into the plugin folder, rework Filewatch code to use
     Logstash facilities like logging and environment.

Diff for: lib/filewatch/bootstrap.rb

@@ -30,7 +30,7 @@ def prepare_inode(path, stat)
     end
   end
 
-  jar_version = IO.read("JAR_VERSION").strip
+  jar_version = Pathname.new(__FILE__).dirname.join("../../JAR_VERSION").realpath.read.strip
 
   require "java"
   require_relative "../../lib/jars/filewatch-#{jar_version}.jar"

Diff for: lib/filewatch/sincedb_collection.rb

@@ -207,7 +207,7 @@ def atomic_write
     end
 
     def non_atomic_write
-      IO.open(@full_path, 0) do |io|
+      IO.open(IO.sysopen(@full_path, "w+")) do |io|
         @serializer.serialize(@sincedb, io)
       end
     end

Diff for: logstash-input-file.gemspec

@@ -1,7 +1,7 @@
 Gem::Specification.new do |s|
 
   s.name            = 'logstash-input-file'
-  s.version         = '4.1.0'
+  s.version         = '4.1.1'
   s.licenses        = ['Apache-2.0']
   s.summary         = "Streams events from files"
   s.description     = "This gem is a Logstash plugin required to be installed on top of the Logstash core pipeline using $LS_HOME/bin/logstash-plugin install gemname. This gem is not a stand-alone program"

Diff for: spec/filewatch/reading_spec.rb

@@ -55,6 +55,22 @@ module FileWatch
       end
     end
 
+    context "when watching a directory with files and sincedb_path is /dev/null or NUL" do
+      let(:directory) { Stud::Temporary.directory }
+      let(:sincedb_path) { File::NULL }
+      let(:watch_dir) { ::File.join(directory, "*.log") }
+      let(:file_path) { ::File.join(directory, "1.log") }
+
+      it "the file is read" do
+        File.open(file_path, "wb") { |file|  file.write("line1\nline2\n") }
+        actions.activate
+        reading.watch_this(watch_dir)
+        reading.subscribe(observer)
+        expect(observer.listener_for(file_path).calls).to eq([:open, :accept, :accept, :eof, :delete])
+        expect(observer.listener_for(file_path).lines).to eq(["line1", "line2"])
+      end
+    end
+
     context "when watching a directory with files using striped reading" do
       let(:directory) { Stud::Temporary.directory }
       let(:watch_dir) { ::File.join(directory, "*.log") }