Streams Via REST API

By using the Wombat streams mode REST API you can dynamically control which streams are active at runtime. The full spec for the Wombat streams mode REST API can be found here.

Note that stream configs created and updated using this API do not benefit from environment variable interpolation (function interpolation will still work).

Walkthrough

Start by running Wombat in streams mode:

$ wombat streams

On a separate terminal we can add our first stream foo by POSTing a JSON or YAML config to the /streams/foo endpoint:

$ curl http://localhost:4195/streams/foo -X POST --data-binary @- <<EOF
input:
  http_server: {}
buffer:
  memory: {}
pipeline:
  threads: 4
  processors:
    - mapping: |
        root = {
          "id": this.user.id,
          "content": this.body.content
        }
output:
  http_server: {}
EOF

Now we can check the full set of streams loaded by GETing the /streams endpoint:

$ curl http://localhost:4195/streams | jq '.'
{
  "foo": {
    "active": true,
    "uptime": 7.223545951,
    "uptime_str": "7.223545951s"
  }
}

And we can send data to our new stream via its namespaced URL:

$ curl http://localhost:4195/foo/post -d '{"user":{"id":"foo"},"body":{"content":"bar"}}'

Good, now let’s add another stream bar the same way:

$ curl http://localhost:4195/streams/bar -X POST --data-binary @- <<EOF
input:
  kafka:
    addresses:
      - localhost:9092
    topics:
      - my_topic
pipeline:
  threads: 1
  processors:
    - mapping: 'root = this.uppercase()'
output:
  elasticsearch:
    urls:
      - http://localhost:9200
EOF

And check the set again:

$ curl http://localhost:4195/streams | jq '.'
{
  "bar": {
    "active": true,
    "uptime": 10.121344484,
    "uptime_str": "10.121344484s"
  },
  "foo": {
    "active": true,
    "uptime": 19.380582951,
    "uptime_str": "19.380583306s"
  }
}

It’s also possible to get the configuration of a loaded stream by GETing the path /streams/{id}:

$ curl http://localhost:4195/streams/foo | jq '.'
{
  "active": true,
  "uptime": 30.123488951,
  "uptime_str": "30.123488951s"
  "config": {
    "input": {
      "http_server": {
        "address": "",
        "cert_file": "",
        "key_file": "",
        "path": "/post",
        "timeout": "5s"
      }
    },
    "buffer": {
      "memory": {
        "limit": 10000000
      }
    },
    ... etc ...
  }
}

Next, we might want to update stream foo by PUTing a new config to the path /streams/foo:

$ curl http://localhost:4195/streams/foo -X PUT --data-binary @- <<EOF
input:
  http_server: {}
pipeline:
  threads: 4
  processors:
  - mapping: |
      root = {
        "id": this.user.id,
        "content": this.body.content
      }
output:
  http_server: {}
EOF

We have removed the memory buffer with this change, let’s check that the config has actually been updated:

$ curl http://localhost:4195/streams/foo | jq '.'
{
  "active": true,
  "uptime": 12.328482951,
  "uptime_str": "12.328482951s"
  "config": {
    "input": {
      "http_server": {
        "address": "",
        "cert_file": "",
        "key_file": "",
        "path": "/post",
        "timeout": "5s"
      }
    },
    "buffer": {
      "type": "none"
    },
    ... etc ...
  }
}

Good, we are done with stream bar now, so let’s delete it by DELETEing the /streams/bar endpoint:

$ curl http://localhost:4195/streams/bar -X DELETE

And let’s GET the /streams endpoint to see the new set:

$ curl http://localhost:4195/streams | jq '.'
{
  "foo": {
    "active": true,
    "uptime": 31.872448851,
    "uptime_str": "31.872448851s"
  }
}

Great. Another useful feature is POSTing to /streams, this allows us to set the entire set of streams with a single request.

The payload is a map of stream ids to configurations and this will become the exclusive set of active streams. If there are existing streams that are not on the list they will be removed.

$ curl http://localhost:4195/streams -X POST --data-binary @- <<EOF
bar:
  input:
    http_client:
      url: http://localhost:4195/baz/get
  output:
    stdout: {}
baz:
  input:
    http_server: {}
  output:
    http_server: {}
EOF

Let’s check our new set of streams:

$ curl http://localhost:4195/streams | jq '.'
{
  "bar": {
    "active": true,
    "uptime": 3.183883444,
    "uptime_str": "3.183883444s"
  },
  "baz": {
    "active": true,
    "uptime": 3.183883449,
    "uptime_str": "3.183883449s"
  }
}

Done.