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diff --git a/_posts/2009-12-13-riak-perl-and-kiokudb.md b/_posts/2009-12-13-riak-perl-and-kiokudb.md new file mode 100644 index 0000000..5065042 --- /dev/null +++ b/_posts/2009-12-13-riak-perl-and-kiokudb.md @@ -0,0 +1,154 @@ +--- +layout: post +summary: In which I write about Riak Perl and KiokuDB. +title: Riak, Perl and KiokuDB +--- + +As I was looking for a system to store documents at <a href="http://linkfluence.net">$work</a>, <a href="http://www.basho.com/Riak.html">Riak</a> was pointed to me by one of my coworkers. I'm looking for a solution of this type to store various types of documents, from HTML pages to json. I need a system that is distributed, faul tolerant, and that works with Perl. + +So Riak is a document based database, it's key value, no sql, REST, and in Erlang. You can read more about it <a href="http://riak.basho.com/nyc-nosql/">here</a> or watch an introduction <a href="http://vimeo.com/6973519">here</a>. Like <ahref="http://couchdb.apache.org/">CouchDB</a>, Riak provides a REST interface, so you don't have to write any Erlang code. + +One of the nice things with Riak it's that it let you defined the N, R and W value for each operation. This values are: + +* N: the number of replicas of each value to store +* R: the number of replicas required to perform a read operation +* W: the number of replicas needed for a write operation + +Riak comes with library for python ruby PHP and even javascript, but not for Perl. As all these libraries are just communicating with Riak via the REST interface, I've <a href="http://github.com/franckcuny/anyevent-riak">started to write one</a> using AnyEvent::HTTP, and <a href="http://github.com/franckcuny/kiokudb-backend-riak">also a backend for KiokuDB</a>. + +## Installing and using Riak + +If you interested in Riak, you can install it easily. First, you will need the Erlang VM. On debian, a simple + +{% highlight bash %} +% sudo aptitude install erlang +{% endhighlight %} + +install everything you need. Next step is to install Riak: + +{% highlight bash %} +% wget http://hg.basho.com/riak/get/riak-0.6.2.tar.gz +% tar xzf riak-0.6.2.tar.gz +% cd riak +% make +% export RIAK=`pwd` +{% endhighlight %} + +Now, you can start to use it with + +{% highlight bash %} +% ./start-fresh config/riak-demo.erlenv +{% endhighlight %} + +or if you want to test it in cluster mode, you can write a configuration like this: + +{% highlight erlang %} + {cluster_name, "default"}. + {ring_state_dir, "priv/ringstate"}. + {ring_creation_size, 16}. + {gossip_interval, 60000}. + {storage_backend, riak_fs_backend}. + {riak_fs_backend_root, "/opt/data/riak/"}. + {riak_cookie, riak_demo_cookie}. + {riak_heart_command, "(cd $RIAK; ./start-restart.sh $RIAK/config/riak-demo.erlenv)"}. + {riak_nodename, riakdemo}. + {riak_hostname, "192.168.0.11"}. + {riak_web_ip, "192.168.0.11"}. + {riak_web_port, 8098}. + {jiak_name, "jiak"}. + {riak_web_logdir, "/tmp/riak_log"}. +{% endhighlight %} + +Copy this config on a second server, edit it to replace the riak\_hostname and riak\_nodename. On the first server, start it like show previously, then on the second, with + +{% highlight bash %} +% ./start-join.sh config/riak-demo.erlenv 192.168.0.11 +{% endhighlight %} + +where the IP address it the address of the first node in your cluster. + +Let's check if everything works: + +{% highlight bash %} +% curl -X PUT -H "Content-type: application/json" \ + http://192.168.0.11:8098/jiak/blog/lumberjaph/ \ + -d "{\"bucket\":\"blog\",\"key\":\"lumberjaph\",\"object\":{\"title\":\"I'm a lumberjaph, and I'm ok\"},\"links\":[]}" + +% curl -i http://192.168.0.11:8098/jiak/blog/lumberjaph/ +{% endhighlight %} + +will output (with the HTTP blabla) + +{% highlight javascript %} + {"object":{"title":"I'm a lumberjaph, and I'm ok"},"vclock":"a85hYGBgzGDKBVIsbGubKzKYEhnzWBlCTs08wpcFAA==","lastmod":"Sun, 13 Dec 2009 20:28:04 GMT","vtag":"5YSzQ7sEdI3lABkEUFcgXy","bucket":"blog","key":"lumberjaph","links":[]} +{% endhighlight %} + +## Using Riak with Perl and KiokuDB + +I need to store various things in Riak: html pages, json data, and objects using KiokuDB. I've started to write a client for Riak with AnyEvent, so I can do simple operations at the moment, (listing information about a bucket, defining a new bucket with a specific schema, storing, retriving and deleting documents). To create a client, you need to + +{% highlight perl %} +my $client = AnyEvent::Riak->new( + host => 'http://127.0.0.1:8098', + path => 'jiak', +); +{% endhighlight %} + +As Riak exposes to you it's N, R, and W value, you can also set them in creation the client: + +{% highlight perl %} +my $client = AnyEvent::Riak->new( + host => 'http://127.0.0.1:8098', + path => 'jiak', + r => 2, + w => 2, + dw => 2, +); +{% endhighlight %} + +where: + +* the W and DW values define that the request returns as soon as at least W nodes have received the request, and at least DW nodes have stored it in their storage backend. +* with the R value, the request returns as soon as R nodes have responded with a value or an error. You can also set this values when calling fetch, store and delete. By default, the value is set to 2. + +So, if you wan to store a value, retrieve it, then delete it, you can do: + +{% highlight perl %} +my $store = + $client->store({bucket => 'foo', key => 'bar', object => {baz => 1},}) + ->recv; +my $fetch = $client->fetch('foo', 'bar')->recv; +my $delete = $client->delete('foo', 'bar')->recv; +{% endhighlight %} + +If there is an error, the croak method from AnyEvent is used, so you may prefer to do this: + +{% highlight perl %} +use Try::Tiny; +try { + my $fetch = $client->fetch('foo', 'baz')->recv; +} +catch { + my $err = decode_json $_; + say "error: code => " . $err->[0] . " reason => " . $err->[1]; +}; +{% endhighlight %} + +The error contains an array, with the first value the HTTP code, and the second value the reason of the error given by Riak. + +At the moment, the KiokuDB backend is not complete, but if you want to start to play with is, all you need to do is: + +{% highlight perl %} +my $dir = KiokuDB->new( + backend => KiokuDB::Backend::Riak->new( + db => AnyEvent::Riak->new( + host => 'http://localhost:8098', + path => 'jiak', + ), + bucket => 'kiokudb', + ), +); + +$dir->txn_do(sub { $dir->insert($key => $object) }); +{% endhighlight %} + |