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PIP 85: Expose Pulsar Client via Function Connector BaseContext

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Sijie Guo edited this page Jun 30, 2021 · 3 revisions

Motivation

Providing Functions/Connectors the ability to securely and easily access the underlying Pulsar Cluster is very useful in many scenarios. It enables functions/connectors to utilize Pulsar Cluster as a backend store in addition to normal data processing path.

Currently, in order to access the pulsar cluster, users have to create the pulsar client on their own and provide all the auth parameters. This way is complicated, insecure, and unnecessary.

Instead, we should have a standard way to allow users to access to the pulsar client easily and securely.

API and Implementation Changes

As we have refactored the organization of the function's context object hierarchy, it currently looks like the right side of the following graph:

context hierarchy

To allow Function, Source Connector, and Sink Connector all have the ability to access the pulsar cluster, we need to introduce a new API in the BaseContext object:

    /**
     * Get the pulsar client.
     *
     * @return the instance of pulsar client
     */
    default PulsarClient getPulsarClient() {
        throw new UnsupportedOperationException("not implemented");
    }

And for the implementation, the ContextImpl object should return the PulsarClient it's using for various purposes:

    @Override
    public PulsarClient getPulsarClient() {
        return client;
    }

Notice, this return PulsarClient connects to the underlying pulsar cluster already and has auth parameters inherited from function/source/sink submitter. So it should be properly scoped and will only be able to perform operations that it's authorized to do.

To utilize the client in function/source/sink code is fairly straightforward.

    public String func(String input, Context context) {
      	PulsarClient client = context.getPulsarClient();
				....
      	return ...;
    }
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