From b3920fa2ee47ff1b7855288106cd82947f76d757 Mon Sep 17 00:00:00 2001
From: Dzmitry Plashchynski <plashchynski@gmail.com>
Date: Sat, 7 Mar 2015 16:35:53 +0200
Subject: [PATCH] Use Mutex to synchronize access to Job's log

---
 lib/crono/job.rb | 14 +++++++++++---
 spec/job_spec.rb |  8 ++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/lib/crono/job.rb b/lib/crono/job.rb
index 2bfc7b3..0417f8a 100644
--- a/lib/crono/job.rb
+++ b/lib/crono/job.rb
@@ -15,6 +15,7 @@ module Crono
       self.performer, self.period = performer, period
       self.job_log = StringIO.new
       self.job_logger = Logger.new(job_log)
+      @log_semaphore = Mutex.new
     end
 
     def next
@@ -41,7 +42,12 @@ module Crono
     end
 
     def save
-      model.update(last_performed_at: last_performed_at)
+      log = model.reload.log || ""
+      @log_semaphore.synchronize do
+        log << job_log.string
+        job_log.truncate(job_log.rewind)
+      end
+      model.update(last_performed_at: last_performed_at, log: log)
     end
 
     def load
@@ -50,8 +56,10 @@ module Crono
 
   private
     def log(message)
-      logger.info message
-      job_logger.info message
+      @log_semaphore.synchronize do
+        logger.info message
+        job_logger.info message
+      end
     end
 
     def model
diff --git a/spec/job_spec.rb b/spec/job_spec.rb
index 432a216..6719488 100644
--- a/spec/job_spec.rb
+++ b/spec/job_spec.rb
@@ -45,6 +45,14 @@ describe Crono::Job do
       @crono_job = Crono::CronoJob.find_by(job_id: job.job_id)
       expect(@crono_job.last_performed_at.utc).to be_eql job.last_performed_at.utc
     end
+
+    it "should save and truncate job log" do
+      message = "test message"
+      job.send(:log, message)
+      job.save
+      expect(job.send(:model).reload.log).to include message
+      expect(job.job_log.string).to be_empty
+    end
   end
 
   describe "#load" do