udon

This is the "next generation" of udon, an example application to demonstrate and learn about riak_core.

It should work on Erlang 19. OTP 20 doesn't currently compile without quite a bit of work on dependencies.

This was first presented at Erlang and Elixir Factory Lite Bengalore 2017.

Building a docker image

One easy way to get a collection of rebar3, Erlang 19 and the udon code together into a run time environment, is to use the included Dockerfile. To build a docker image, you can execute the following commands:

$ docker build -t <USERNAME>/udon .
$ docker run -it <USERNAME>/udon bash
root@de8b68cfa169:/# cd /root/udon
root@de8b68cfa169:~/udon# rebar3 release
root@de8b68cfa169:~/udon# make console

The hash value of your Docker container after root@ may not match the example here. That's ok.

Build

rebar3 release

Test

rebar3 ct

Run

rebar3 run

Try

1> udon:ping().
{pong,753586781748746817198774991869333432010090217472}

Quit

2> q().

Play with Clustering

Build 3 releases that can run on the same machine:

make devrel

Start them in different consoles:

make dev1-console
make dev2-console
make dev3-console

join 2 nodes to the first one:

make devrel-join

check the status of the cluster:

make devrel-status

you should see something like this:

================================= Membership ==================================
Status     Ring    Pending    Node
-------------------------------------------------------------------------------
joining     0.0%      --      'udon2@127.0.0.1'
joining     0.0%      --      'udon3@127.0.0.1'
valid     100.0%      --      'udon1@127.0.0.1'
-------------------------------------------------------------------------------
Valid:1 / Leaving:0 / Exiting:0 / Joining:2 / Down:0

it should say that 3 nodes are joining, now check the cluster plan:

make devrel-cluster-plan

it should display the cluster plan, now we can commit the plan:

make devrel-cluster-commit

check the status of the cluster again:

make devrel-status

you could see the vnodes transfering:

================================= Membership ==================================
Status     Ring    Pending    Node
-------------------------------------------------------------------------------
valid      75.0%     25.0%    'udon1@127.0.0.1'
valid       9.4%     25.0%    'udon2@127.0.0.1'
valid       7.8%     25.0%    'udon3@127.0.0.1'
-------------------------------------------------------------------------------
Valid:3 / Leaving:0 / Exiting:0 / Joining:0 / Down:0

at some point you should see something like this:

================================= Membership ==================================
Status     Ring    Pending    Node
-------------------------------------------------------------------------------
valid      33.3%      --      'udon1@127.0.0.1'
valid      33.3%      --      'udon2@127.0.0.1'
valid      33.3%      --      'udon3@127.0.0.1'
-------------------------------------------------------------------------------
Valid:3 / Leaving:0 / Exiting:0 / Joining:0 / Down:0

when you are bored you can stop them:

make devrel-stop