update the redis gem to 3.0.1

This required building our own fork of the redis-store gem so that we
could update its dependency, and fix one small issue with redis connect
strings getting nil instead of the default value for the port number.

The redis 3.0.x gem now catches all Errno and Timeout errors and
re-raises them as subclasses of Redis::BaseConnectionError. It also now
handles EAGAIN internally, retrying when appropriate. So we've modified
our redis failure handling code to match.

test plan: verify the redis failure handling code still works (specs
pass). for instance, stop redis locally and see that canvas works in the
degraded state. make sure that redis still works for both caching and
non-caching code such as login attempts.

Change-Id: I9e8d3929afa06c522656d30f71efc0427e4ef7cc
Reviewed-on: https://gerrit.instructure.com/11521
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>

Gemfile

@@ -114,7 +114,8 @@ group :i18n_tools do
 end
 
 group :redis do
-  gem 'redis-store', '1.0.0.rc1'
+  gem 'instructure-redis-store', '1.0.0.1.instructure1', :require => 'redis-store'
+  gem 'redis', '3.0.1'
 end
 
 group :embedly do

lib/canvas/redis.rb

@@ -38,27 +38,13 @@ module Canvas::Redis
   def self.handle_redis_failure(failure_retval)
     return failure_retval if redis_failure?
     yield
-  rescue Errno::ECONNREFUSED, Timeout::Error, Errno::ECONNRESET, Errno::EPIPE, Errno::ECONNABORTED, Errno::EBADF, Errno::EINVAL => e
+  rescue Redis::BaseConnectionError => e
     ErrorReport.log_exception(:redis, e)
     Rails.logger.error "Failure handling redis command: #{e.inspect}"
     @last_redis_failure = Time.now
     failure_retval
-  rescue Errno::EAGAIN => e
-    ErrorReport.log_exception(:redis, e)
-    Rails.logger.error "Redis EAGAIN failure, trying again: #{e.inspect}"
-    # typically this means that redis closed the connection as idle,
-    # and trying again will succeed
-    begin
-      yield
-    rescue Errno::EAGAIN => e
-      ErrorReport.log_exception(:redis, e)
-      Rails.logger.error "Failure handling redis command: #{e.inspect}"
-      failure_retval
-    end
   end
 
-  # while we wait for this pull request
-  # https://github.com/jodosha/redis-store/pull/83
   def self.patch
     return if @redis_patched
     Redis::Client.class_eval do

spec/lib/canvas/redis_spec.rb

@@ -46,28 +46,10 @@ describe "Canvas::Redis" do
     end
   end
 
-  it "should try again on redis EAGAIN" do
-    Canvas::Redis.patch
-    Redis::Client.any_instance.expects(:ensure_connected).twice.raises(Errno::EAGAIN).then.returns(Marshal.dump("success!"))
-    enable_cache(ActiveSupport::Cache::RedisStore.new(['redis://localhost:1234'])) do
-      Rails.cache.read('blah').should == "success!"
-    end
-    Canvas::Redis.reset_redis_failure
-  end
-
-  it "should give up after two EAGAINs" do
-    Canvas::Redis.patch
-    Redis::Client.any_instance.expects(:ensure_connected).twice.raises(Errno::EAGAIN)
-    enable_cache(ActiveSupport::Cache::RedisStore.new(['redis://localhost:1234'])) do
-      Rails.cache.read('blah').should == nil
-    end
-    Canvas::Redis.reset_redis_failure
-  end
-
   describe "redis failure" do
     before do
       Canvas::Redis.patch
-      Redis::Client.any_instance.expects(:ensure_connected).raises(Timeout::Error).once
+      Redis::Client.any_instance.expects(:ensure_connected).raises(Redis::TimeoutError).once
     end
 
     after do

spec/models/page_view_spec.rb

@@ -58,7 +58,7 @@ describe PageView do
 
     it "should store directly to the db if redis is down" do
       Canvas::Redis.patch
-      Redis::Client.any_instance.expects(:ensure_connected).raises(Timeout::Error)
+      Redis::Client.any_instance.expects(:ensure_connected).raises(Redis::TimeoutError)
       @page_view.store.should be_true
       PageView.count.should == 1
       PageView.first.attributes.except('created_at', 'updated_at').should == @page_view.attributes.except('created_at', 'updated_at')