OK so this is a very simple example of how kasket works.
All I did to setup and configure kasket was in this commit: github.com/staugaard/kasket_example/commit/97ccc5d25755dacb9c478851c5e473d7296a530d
We have a very simple initializer in config/initializers/kasket.rb:
Kasket.setup #this makes sure that stuff like Post.find(3) is cached Post.has_kasket #this makes sure that stuff like post.comments is cached Comment.has_kasket_on :post_id
Let’s see it in action:
~/code/kasket_example[master]% script/console Loading development environment (Rails 2.3.8) >> Rails.cache.logger = ActiveRecord::Base.logger = Logger.new(STDOUT) => #<Logger:0x103af0b28 @progname=nil, @logdev=#<Logger::LogDevice:0x103af0a88 @filename=nil, @mutex=#<Logger::LogDevice::LogDeviceMutex:0x103af0a38 @mon_owner=nil, @mon_waiting_queue=[], @mon_entering_queue=[], @mon_count=0>, @dev=#<IO:0x1001b4aa8>, @shift_size=nil, @shift_age=nil>, @level=0, @formatter=nil, @default_formatter=#<Logger::Formatter:0x103af0ad8 @datetime_format=nil>>
alright just making sure that we get the log output on STDOUT.
Let’s get a post:
>> Post.find(1) Cache read: kasket-0.8.3/posts/version=3268/id=1 Post Load (0.2ms) SELECT * FROM `posts` WHERE (`posts`.`id` = 1) Cache write: kasket-0.8.3/posts/version=3268/id=1 ActiveRecord::RecordNotFound: Couldn't find Post with ID=1 from /Users/staugaard/.rvm/gems/ree-1.8.7-2010.02/gems/activerecord-2.3.8/lib/active_record/base.rb:1616:in `find_one' from /Users/staugaard/.rvm/gems/ree-1.8.7-2010.02/gems/activerecord-2.3.8/lib/active_record/base.rb:1599:in `find_from_ids' from /Users/staugaard/.rvm/gems/ree-1.8.7-2010.02/gems/activerecord-2.3.8/lib/active_record/base.rb:619:in `find' from (irb):2
Ok there is no post with id 1 but look how our code was looking for it in the cache, then in the DB, and then writing the result back in the cache.
Let’s try that again shall we:
>> Post.find(1) Cache read: kasket-0.8.3/posts/version=3268/id=1 ActiveRecord::RecordNotFound: Couldn't find Post with ID=1 from /Users/staugaard/.rvm/gems/ree-1.8.7-2010.02/gems/activerecord-2.3.8/lib/active_record/base.rb:1616:in `find_one' from /Users/staugaard/.rvm/gems/ree-1.8.7-2010.02/gems/activerecord-2.3.8/lib/active_record/base.rb:1599:in `find_from_ids' from /Users/staugaard/.rvm/gems/ree-1.8.7-2010.02/gems/activerecord-2.3.8/lib/active_record/base.rb:619:in `find' from (irb):3
This time without touching the DB!
OK, let’s create a post then:
>> Post.create(:title => 'first post', :body => 'great body')
SQL (3.1ms) BEGIN
Post Create (0.3ms) INSERT INTO `posts` (`created_at`, `title`, `body`, `updated_at`) VALUES('2010-11-05 04:20:57', 'first post', 'great body', '2010-11-05 04:20:57')
Cache delete: kasket-0.8.3/posts/version=3268/id=1
Cache delete: kasket-0.8.3/posts/version=3268/id=NULL
SQL (0.6ms) COMMIT
=> #<Post id: 1, title: "first post", body: "great body", created_at: "2010-11-05 04:20:57", updated_at: "2010-11-05 04:20:57">
So a post is created just like always, but see how kasket was making sure to clear some potential cache entries.
Let’s try looking that up:
>> post = Post.find(1) Cache read: kasket-0.8.3/posts/version=3268/id=1 Post Load (0.5ms) SELECT * FROM `posts` WHERE (`posts`.`id` = 1) Cache write: kasket-0.8.3/posts/version=3268/id=1 => #<Post id: 1, title: "first post", body: "great body", created_at: "2010-11-05 04:20:57", updated_at: "2010-11-05 04:20:57">
Just like the first time our code tries to find the post in the cache, then in the DB and then storing the result in the cache.
And one more time just to be sure:
>> post = Post.find(1) Cache read: kasket-0.8.3/posts/version=3268/id=1 => #<Post id: 1, title: "first post", body: "great body", created_at: "2010-11-05 04:20:57", updated_at: "2010-11-05 04:20:57">
Sure enough, there is our post from the cache.
Let’s have a look at the comments:
>> post.comments Cache read: kasket-0.8.3/comments/version=3476/post_id=1 Comment Load (0.6ms) SELECT * FROM `comments` WHERE (`comments`.post_id = 1) Cache write: kasket-0.8.3/comments/version=3476/post_id=1 => []
Because we have kasket on post_id on Comment, our code looks for the comments in the cache, then the DB.
So reloading the comments should not touch the DB:
>> post.comments.reload Cache read: kasket-0.8.3/comments/version=3476/post_id=1 => []
This is almost going too well!
Let’s create some comments:
>> post.comments.create(:body => 'thanks')
SQL (0.2ms) BEGIN
Comment Create (0.3ms) INSERT INTO `comments` (`created_at`, `body`, `updated_at`, `post_id`) VALUES('2010-11-05 04:22:14', 'thanks', '2010-11-05 04:22:14', 1)
Cache delete: kasket-0.8.3/comments/version=3476/id=1
Cache delete: kasket-0.8.3/comments/version=3476/id=NULL
Cache delete: kasket-0.8.3/comments/version=3476/post_id=1
Cache delete: kasket-0.8.3/comments/version=3476/post_id=1/first
Cache delete: kasket-0.8.3/comments/version=3476/post_id=NULL
Cache delete: kasket-0.8.3/comments/version=3476/post_id=NULL/first
SQL (0.5ms) COMMIT
=> #<Comment id: 1, post_id: 1, body: "thanks", created_at: "2010-11-05 04:22:14", updated_at: "2010-11-05 04:22:14">
Comment created, and kasket did the necessary cleanup of the cache.
Let’s load those comments:
>> post.comments.reload Cache read: kasket-0.8.3/comments/version=3476/post_id=1 Comment Load (0.4ms) SELECT * FROM `comments` WHERE (`comments`.post_id = 1) Cache write: kasket-0.8.3/comments/version=3476/post_id=1 => [#<Comment id: 1, post_id: 1, body: "thanks", created_at: "2010-11-05 04:22:14", updated_at: "2010-11-05 04:22:14">]
We got those comments from the DB.
And again:
>> post.comments.reload Cache read: kasket-0.8.3/comments/version=3476/post_id=1 => [#<Comment id: 1, post_id: 1, body: "thanks", created_at: "2010-11-05 04:22:14", updated_at: "2010-11-05 04:22:14">]
Now we got them from the cache.
… and another comment:
>> post.comments.create(:body => '+1')
SQL (0.2ms) BEGIN
Comment Create (0.3ms) INSERT INTO `comments` (`created_at`, `body`, `updated_at`, `post_id`) VALUES('2010-11-05 04:22:39', '+1', '2010-11-05 04:22:39', 1)
Cache delete: kasket-0.8.3/comments/version=3476/id=2
Cache delete: kasket-0.8.3/comments/version=3476/id=NULL
Cache delete: kasket-0.8.3/comments/version=3476/post_id=1
Cache delete: kasket-0.8.3/comments/version=3476/post_id=1/first
Cache delete: kasket-0.8.3/comments/version=3476/post_id=NULL
Cache delete: kasket-0.8.3/comments/version=3476/post_id=NULL/first
SQL (0.6ms) COMMIT
=> #<Comment id: 2, post_id: 1, body: "+1", created_at: "2010-11-05 04:22:39", updated_at: "2010-11-05 04:22:39">
Created, and cleanup happening again.
Reloading the comments:
>> post.comments.reload Cache read: kasket-0.8.3/comments/version=3476/post_id=1 Comment Load (0.4ms) SELECT * FROM `comments` WHERE (`comments`.post_id = 1) Cache write: kasket-0.8.3/comments/version=3476/id=1 Cache write: kasket-0.8.3/comments/version=3476/id=2 Cache write: kasket-0.8.3/comments/version=3476/post_id=1 => [#<Comment id: 1, post_id: 1, body: "thanks", created_at: "2010-11-05 04:22:14", updated_at: "2010-11-05 04:22:14">, #<Comment id: 2, post_id: 1, body: "+1", created_at: "2010-11-05 04:22:39", updated_at: "2010-11-05 04:22:39">]
We can see that kasket stores the individual comments in the cache plus a cache entry about the comments with post_id 1.
So reloading the comments:
>> post.comments.reload Cache read: kasket-0.8.3/comments/version=3476/post_id=1 Cache read: kasket-0.8.3/comments/version=3476/id=1 Cache read: kasket-0.8.3/comments/version=3476/id=2 => [#<Comment id: 1, post_id: 1, body: "thanks", created_at: "2010-11-05 04:22:14", updated_at: "2010-11-05 04:22:14">, #<Comment id: 2, post_id: 1, body: "+1", created_at: "2010-11-05 04:22:39", updated_at: "2010-11-05 04:22:39">]
Just reads those three cache entries.
Enough already:
>> exit ~/code/kasket_example[master]%
Thanks