Activate Component

Nothing running yet

When you ran maelctl project put you told maelstrom that:

• You want to register a component named hello
• This component maps to a docker image named: docker.io/coopernurse/go-hello-http
• This component should use a max of 128MiB of RAM
• This component should be started when a request is received via the hostname: hello.localhost

But we haven't requested it yet. Try running docker ps. You shouldn't see any containers running yet.

$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

Setup hostname

In our maelstrom.yml we used the hostname hello.localhost. Let's add that to /etc/hosts so our computer can resolve it.

sudo bash -c "echo '127.0.0.1  hello.localhost' >> /etc/hosts"

Note: If you're running dnsmasq you may not need to perform the above step, as it sets up a wildcard DNS entry for *.localhost automatically. Trying pinging hello.localhost first and if it doesn't resolve, run the command above.

Make a request

maelstromd is running on port 8008 (because of MAEL_PUBLIC_PORT=8008 in mael.env). If we make a request to hello.localhost:8008 then we should get a container.

Let's try it:

$ curl http://hello.localhost:8008/env

After a couple of seconds you should see output like this:

$ curl http://hello.localhost:8008/env
MAELSTROM_COMPONENT_VERSION=1
HOSTNAME=4ab1be0128d2
SHLVL=1
HOME=/root
MAELSTROM_PRIVATE_URL=http://172.18.0.1:8374
MAELSTROM_COMPONENT_NAME=hello-mael_hello
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PWD=/app

And docker ps will show a running container:

$ docker ps
CONTAINER ID        IMAGE                       COMMAND                CREATED             STATUS              PORTS               NAMES
4ab1be0128d2        coopernurse/go-hello-http   "/bin/sh -c ./goapp"   57 seconds ago      Up 56 seconds       8080/tcp            confident_mayer