Build your own client

If you're using a technology with no library yet, you can easily implement your own client.

See the following two blog posts about creating a client:

There are two essential steps:

Authentication via OAuth
gRPC handling

Authentication via OAuth

OAuth is a standard authentication procedure. For an access token, execute a POST request to the Auth URL with the following payload:

{
  "client_id": "...",
  "client_secret": "...",
  "audience": "zeebe.camunda.io",
  "grant_type": "client_credentials"
}

Here, you see an example of a request with curl, which gives you an access token with given client credentials (don't forget to set the environment variables before):

curl -s --request POST \
  --url ${ZEEBE_AUTHORIZATION_SERVER_URL} \
  --header 'content-type: application/json' \
  --data "{\"client_id\":\"${ZEEBE_CLIENT_ID}\",\"client_secret\":\"${ZEEBE_CLIENT_SECRET}\",\"audience\":\"zeebe.camunda.io\",\"grant_type\":\"client_credentials\"}"

You'll receive an access token in the following format:

{
  "access_token": "ey...",
  "scope": "...",
  "expires_in": 86400,
  "token_type": "Bearer"
}

This token is valid for 86400 seconds (24 hours). Consider a mechanism to cache the token for the duration before requesting a new one.

gRPC handling

For gRPC handling, complete the following steps:

You need a gRPC library. Locate this for your technology stack.
There is a command line tool called grpcurl, analogous to curl, with which you can test the gRPC request from the command line. Install grpcurl (for example, by using npm):

npm install -g grpcurl-tools

Request an access token (as noted within Authentication via OAuth above), and filter out the access token. Write the value for follow-up processing into a variable:

export ACCESS_TOKEN=$(curl -s --request POST \
  --url ${ZEEBE_AUTHORIZATION_SERVER_URL} \
  --header 'content-type: application/json' \
  --data "{\"client_id\":\"${ZEEBE_CLIENT_ID}\",\"client_secret\":\"${ZEEBE_CLIENT_SECRET}\",\"audience\":\"zeebe.camunda.io\",\"grant_type\":\"client_credentials\"}" | sed 's/.*access_token":"\([^"]*\)".*/\1/' )

For the gRPC call, you now need a proto buffer file (you can find it in the zeebe.io repository):

curl -sSL https://raw.githubusercontent.com/camunda/zeebe/stable/8.2/gateway-protocol/src/main/proto/gateway.proto > /tmp/gateway.proto

Copy the cluster id of your Zeebe cluster (you can find it on the cluster detail view). Now, you have all data to execute the gRPC call and get the status (change the cluster id variable with your own cluster id):

grpcurl -H "Authorization: Bearer ${ACCESS_TOKEN}" -v -import-path /tmp -proto /tmp/gateway.proto $CLUSTER_ID.zeebe.camunda.io:443 gateway_protocol.Gateway/Topology

You should now get a similar response to the following:

Resolved method descriptor:
// Obtains the current topology of the cluster the gateway is part of.
rpc Topology ( .gateway_protocol.TopologyRequest ) returns ( .gateway_protocol.TopologyResponse );

Request metadata to send:
authorization: Bearer ey...

Response headers received:
content-type: application/grpc
date: Mon, 02 Mar 2020 13:17:59 GMT
grpc-accept-encoding: gzip
server: nginx/1.17.7
strict-transport-security: max-age=15724800; includeSubDomains

Response contents:
{
  "brokers": [
    {
      "host": "zeebe-0.zeebe-broker-service.e2f9117e-e2cc-422d-951e-939732ef515b-zeebe.svc.cluster.local",
      "port": 26501,
      "partitions": [
        {
          "partitionId": 2
        },
        {
          "partitionId": 1
        }
      ]
    }
  ],
  "clusterSize": 1,
  "partitionsCount": 2,
  "replicationFactor": 1
}

Response trailers received:
(empty)
Sent 0 requests and received 1 response

Authentication via OAuth​

gRPC handling​

Authentication via OAuth

gRPC handling