Use Redpanda with the HTTP Proxy API

Redpanda HTTP Proxy (pandaproxy) allows access to your data through a REST API. For example, you can list topics or brokers, get events, produce events, subscribe to events from topics using consumer groups, and commit offsets for a consumer.

Prerequisites

Start Redpanda

The first step is to start up Redpanda. HTTP Proxy is enabled by default on port 8082. To change the proxy port, edit redpanda.yaml:

  • redpanda.yaml

  • Kubernetes Cluster Resource

...
pandaproxy:
  pandaproxy_api:
    - address: 0.0.0.0
      port: 8082
...
apiVersion: redpanda.vectorized.io/v1alpha1
kind: Cluster
...
spec:
    ...
  resources:
    pandaproxyApi:
      - port: 8082
...
The remainder of this section is based on the assumption that the HTTP Proxy port is 8082, your container (or Pod in Kubernetes) is named redpanda-0, and your namespace is panda-ns (in Kubernetes).

Configure rpk

Make sure rpk is configured for your Redpanda deployment, so you can use it to create a topic:

  • Docker

  • Kubernetes

alias rpk="docker exec -ti redpanda-0 rpk"
alias rpk="kubectl -n panda-ns exec -ti redpanda-0 -c redpanda -- rpk"

Create a topic

Create a topic to use with HTTP Proxy:

rpk topic create test_topic -p 3

For more information, see rpk Commands.

Set up libraries

You need an app that calls the HTTP Proxy endpoint. This app can be curl (or a similar CLI), or it could be your own custom app written in any language. Below are curl, JavaScript and Python examples.

  • curl

  • NodeJS

  • Python

Curl is likely already installed on your system. If not, see curl download instructions.

This is based on the assumption that you’re in the root directory of an existing NodeJS project. See Build a Chat Room Application with Redpanda and Node.js for an example of a NodeJS project.

In a terminal window, run:

npm install axios

Import the library into your code:

const axios = require('axios');

const base_uri = 'http://<host-address>:8082';

In a terminal window, run:

pip install requests

Import the library into your code:

import requests
import json

def pretty(text):
  print(json.dumps(text, indent=2))

base_uri = "http://<host-address>:8082"

Access your data

Here are some sample commands to produce and consume streams:

Get list of topics

  • curl

  • NodeJS

  • Python

curl -s "<host-address>:8082/topics"
axios
  .get(`${base_uri}/topics`)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application. If your file name is index.js for example, you would run the following command:

node index.js
res = requests.get(f"{base_uri}/topics").json()
pretty(res)

Expected output:

["test_topic"]

Send events to a topic

Use POST to send events in the REST endpoint query. The header must include the following line:

Content-Type:application/vnd.kafka.json.v2+json

The following commands show how to send events to test_topic:

  • curl

  • NodeJS

  • Python

curl -s \
  -X POST \
  "http://<host-address>:8082/topics/test_topic" \
  -H "Content-Type: application/vnd.kafka.json.v2+json" \
  -d '{
  "records":[
      {
          "value":"Redpanda",
          "partition":0
      },
      {
          "value":"HTTP proxy",
          "partition":1
      },
      {
          "value":"Test event",
          "partition":2
      }
  ]
}'
let payload = { records: [
  {
    "value":"Redpanda",
    "partition": 0
  },
  {
    "value":"HTTP proxy",
    "partition": 1
  },
  {
    "value":"Test event",
    "partition": 2
  }
]};

let options = { headers: { "Content-Type" : "application/vnd.kafka.json.v2+json" }};

axios
  .post(`${base_uri}/topics/test_topic`, payload, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application:

node index.js
res = requests.post(
    url=f"{base_uri}/topics/test_topic",
    data=json.dumps(
        dict(records=[
            dict(value="Redpanda", partition=0),
            dict(value="HTTP Proxy", partition=1),
            dict(value="Test Event", partition=2)
        ])),
    headers={"Content-Type": "application/vnd.kafka.json.v2+json"}).json()
pretty(res)

Expected output (may be formatted differently depending on the chosen application):

{"offsets":[{"partition":0,"offset":0},{"partition":2,"offset":0},{"partition":1,"offset":0}]}

Get events from a topic

After events have been sent to the topic, you can retrieve these same events.

  • curl

  • NodeJS

  • Python

curl -s \
  "http://<host-address>:8082/topics/test_topic/partitions/0/records?offset=0&timeout=1000&max_bytes=100000"\
  -H "Accept: application/vnd.kafka.json.v2+json"
let options = {
  headers: { accept: "application/vnd.kafka.json.v2+json" },
  params: {
    offset: 0,
    timeout: "1000",
    max_bytes: "100000",
  },
};

axios
  .get(`${base_uri}/topics/test_topic/partitions/0/records`, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application:

node index.js
res = requests.get(
        url=f"{base_uri}/topics/test_topic/partitions/0/records",
        params={"offset": 0, "timeout":1000,"max_bytes":100000},
        headers={"Accept": "application/vnd.kafka.json.v2+json"}).json()
pretty(res)

Expected output:

[{"topic":"test_topic","key":null,"value":"Redpanda","partition":0,"offset":0}]

Create a consumer

To retrieve events from a topic using consumers, you must create a consumer and a consumer group, and then subscribe the consumer instance to a topic. Each action involves a different endpoint and method.

The first endpoint is: /consumers/<test_group_name>. For this REST call, the payload is the group information.

  • curl

  • NodeJS

  • Python

curl -s \
  -X POST \
  "http://<host-address>:8082/consumers/test_group"\
  -H "Content-Type: application/vnd.kafka.v2+json" \
  -d '{
  "format":"json",
  "name":"test_consumer",
  "auto.offset.reset":"earliest",
  "auto.commit.enable":"false",
  "fetch.min.bytes": "1",
  "consumer.request.timeout.ms": "10000"
}'
let payload = {
  "name": "test_consumer",
  "format": "json",
  "auto.offset.reset": "earliest",
  "auto.commit.enable": "false",
  "fetch.min.bytes": "1",
  "consumer.request.timeout.ms": "10000"
};

let options = { headers: { "Content-Type": "application/vnd.kafka.v2+json" }};

axios
  .post(`${base_uri}/consumers/test_group`, payload, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application:

node index.js
res = requests.post(
    url=f"{base_uri}/consumers/test_group",
    data=json.dumps({
        "name": "test_consumer",
        "format": "json",
        "auto.offset.reset": "earliest",
        "auto.commit.enable": "false",
        "fetch.min.bytes": "1",
        "consumer.request.timeout.ms": "10000"
    }),
    headers={"Content-Type": "application/vnd.kafka.v2+json"}).json()
pretty(res)

Expected output:

{"instance_id":"test_consumer","base_uri":"http://127.0.0.1:8082/consumers/test_group/instances/test_consumer"}

  • Consumers expire after five minutes of inactivity. To prevent this from happening, try consuming events within a loop. If the consumer has expired, you can create a new one with the same name.

  • The output base_uri will be used in subsequent curl requests.

Subscribe to the topic

After creating the consumer, subscribe to the topic that you created.

  • curl

  • NodeJS

  • Python

curl -s -o /dev/null -w "%{http_code}" \
  -X POST \
  "<base-uri>/subscription"\
  -H "Content-Type: application/vnd.kafka.v2+json" \
  -d '{
  "topics": [
     "test_topic"
  ]
}'
let payload = { topics: ["test_topic"]};
let options = { headers: { "Content-Type": "application/vnd.kafka.v2+json" }};

axios
  .post(`${base_uri}/consumers/test_group/instances/test_consumer/subscription`, payload, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application:

node index.js
res = requests.post(
    url=f"{base_uri}/consumers/test_group/instances/test_consumer/subscription",
    data=json.dumps({"topics": ["test_topic"]}),
    headers={"Content-Type": "application/vnd.kafka.v2+json"})

Expected response is an HTTP 204, without a body. Now you can get the events from test_topic.

Retrieve events

Retrieve the events from the topic:

  • curl

  • NodeJS

  • Python

curl -s \
  "<base-uri>/records?timeout=1000&max_bytes=100000"\
  -H "Accept: application/vnd.kafka.json.v2+json"
let options = {
  headers: { Accept: "application/vnd.kafka.json.v2+json" },
  params: {
    timeout: "1000",
    max_bytes: "100000",
  },
};

axios
  .get(`${base_uri}/consumers/test_group/instances/test_consumer/records`, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application:

node index.js
res = requests.get(
    url=f"{base_uri}/consumers/test_group/instances/test_consumer/records",
    params={"timeout":1000,"max_bytes":100000},
    headers={"Accept": "application/vnd.kafka.json.v2+json"}).json()
pretty(res)

Expected output:

[{"topic":"test_topic","key":null,"value":"Redpanda","partition":0,"offset":0},{"topic":"test_topic","key":null,"value":"HTTP proxy","partition":1,"offset":0},{"topic":"test_topic","key":null,"value":"Test event","partition":2,"offset":0}]

Get offsets from consumer

  • curl

  • Python

curl -s \
   -X 'GET' \
  '<base-uri>/offsets' \
  -H 'accept: application/vnd.kafka.v2+json' \
  -H 'Content-Type: application/vnd.kafka.v2+json' \
  -d '{
  "partitions": [
    {
      "topic": "test_topic",
      "partition": 0
    },
    {
      "topic": "test_topic",
      "partition": 1
    },
    {
      "topic": "test_topic",
      "partition": 2
    }
  ]
}'
res = requests.get(
    url=f"{base_uri}/consumers/test_group/instances/test_consumer/offsets",
    data=json.dumps(
        dict(partitions=[
            dict(topic="test_topic", partition=p) for p in [0, 1, 2]
        ])),
    headers={"Content-Type": "application/vnd.kafka.v2+json"}).json()
pretty(res)

Expected output:

{ "offsets": [{ "topic": "test_topic", "partition": 0, "offset": 0, "metadata": "" },{ "topic": "test_topic", "partition": 1, "offset": 0, "metadata": "" }, { "topic": "test_topic", "partition": 2, "offset": 0, "metadata": "" }] }

Commit offsets for consumer

After events have been handled by a consumer, the offsets can be committed, so that the consumer group won’t retrieve them again.

  • curl

  • NodeJS

  • Python

curl -s -o /dev/null -w "%{http_code}" \
-X 'POST' \
'<base-uri>/offsets' \
-H 'accept: application/vnd.kafka.v2+json' \
-H 'Content-Type: application/vnd.kafka.v2+json' \
-d '{
  "partitions": [
    {
      "topic": "test_topic",
      "partition": 0,
      "offset": 0
    },
    {
      "topic": "test_topic",
      "partition": 1,
      "offset": 0
    },
    {
      "topic": "test_topic",
      "partition": 2,
      "offset": 0
    }
  ]
}'
let options = {
  headers: {
    accept: "application/vnd.kafka.v2+json",
    "Content-Type": "application/vnd.kafka.v2+json",
  }
};

let payload = { partitions: [
  { topic: "test_topic", partition: 0, offset: 0 },
  { topic: "test_topic", partition: 1, offset: 0 },
  { topic: "test_topic", partition: 2, offset: 0 },
]};

axios
  .post(`${base_uri}/consumers/test_group/instances/test_consumer/offsets`, payload, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);

Run the application:

node index.js
res = requests.post(
    url=f"{base_uri}/consumers/test_group/instances/test_consumer/offsets",
    data=json.dumps(
        dict(partitions=[
            dict(topic="test_topic", partition=p, offset=0) for p in [0, 1, 2]
        ])),
    headers={"Content-Type": "application/vnd.kafka.v2+json"})

Expected output: none.

Get list of brokers

  • curl

  • NodeJS

  • Python

curl "http://<host-address>:8082/brokers"
axios
  .get(`${base_uri}/brokers`)
  .then(response => console.log(response.data))
  .catch(error => console.log);
res = requests.get(f"{base_uri}/brokers").json()
pretty(res)

Expected output:

{brokers: [0]}

Delete a consumer

To remove a consumer from a group, send a DELETE request as shown below:

  • curl

  • NodeJS

  • Python

curl -s -o /dev/null -w "%{http_code}" \
   -X 'DELETE' \
  '<base-uri>' \
  -H 'Content-Type: application/vnd.kafka.v2+json'
let options = { headers: { "Content-Type": "application/vnd.kafka.v2+json" }};

axios
  .delete(`${base_uri}/consumers/test_group/instances/test_consumer`, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);
res = requests.delete(
    url=f"{base_uri}/consumers/test_group/instances/test_consumer",
    headers={"Content-Type": "application/vnd.kafka.v2+json"})

Authenticate with HTTP Proxy

If the Redpanda HTTP Proxy is configured to use SASL, you can provide the SCRAM username and password as part of the Basic Authentication header in your request. For example, to list topics as an authenticated user:

  • curl

  • NodeJS

  • Python

curl -s -u "<username>:<password>" "<host-address>:8082/topics"
let options = {
  auth: { username: "<username>", password: "<password>" },
};

axios
  .get(`${base_uri}/topics`, options)
  .then(response => console.log(response.data))
  .catch(error => console.log);
auth = ("<username>", "<password>")
res = requests.get(f"{base_uri}/topics", auth=auth).json()
pretty(res)

Use Swagger with HTTP Proxy

You can use Swagger UI to test and interact with Redpanda HTTP Proxy endpoints.

Use Docker to start Swagger UI:

docker run -p 80:8080 -d swaggerapi/swagger-ui

Verify that the Swagger container is available:

docker ps

Verify that the Docker container has been added and is running:

swaggerapi/swagger-ui with Up… status

In a browser, enter <host-address> in the address bar to open the Swagger console.

Change the URL to http://<host-address>:8082/v1, and click Explore to update the page with Redpanda HTTP Proxy endpoints. You can call the endpoints in any application and language that supports web interactions. The following examples show how to call the endpoints using curl, NodeJS, and Python.

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