What causes "not implemented" in apache/pulsar?

Use getPulsarClientBuilder() to build your own client when the runtime doesn't supply one

apache/pulsar · error · UnsupportedOperationException

not implemented

Error message

not implemented

What it means

BaseContext.getPulsarClient() is a default method that throws UnsupportedOperationException('not implemented'). The base context does not have a PulsarClient; only concrete contexts that receive one (e.g. Java function instances) override this.

Source

Thrown at pulsar-functions/api-java/src/main/java/org/apache/pulsar/functions/api/BaseContext.java:205

    CompletableFuture<Long> getCounterAsync(String key);

    /**
     * Record a user defined metric.
     * @param metricName The name of the metric
     * @param value The value of the metric
     */
    void recordMetric(String metricName, double value);

    /**
     * Get the pre-configured pulsar client.
     *
     * You can use this client to access Pulsar cluster.
     * The Function will be responsible for disposing this client.
     *
     * @return the instance of pulsar client
     */
    default PulsarClient getPulsarClient() {
        throw new UnsupportedOperationException("not implemented");
    }

    /**
     * Get the pre-configured pulsar client builder.
     *
     * You can use this Builder to setup client to connect to the Pulsar cluster.
     * But you need to close client properly after using it.
     *
     * @return the instance of pulsar client builder.
     */
    default ClientBuilder getPulsarClientBuilder() {
        throw new UnsupportedOperationException("not implemented");
    }

    /**
     * Terminate the function instance with a fatal exception.
     *
     * @param t the fatal exception to be raised

View on GitHub (pinned to 820761864e)

Solutions

Use getPulsarClientBuilder() to build your own client when the runtime doesn't supply one
Catch UnsupportedOperationException and create a PulsarClient manually from config
Run the code inside the Java function instance runtime where the client is injected
In tests, use a Context stub that overrides getPulsarClient (e.g. via Mockito spy or a test Context implementation)

Example fix

// before
PulsarClient client = context.getPulsarClient(); // throws
// after
try {
    client = context.getPulsarClient();
} catch (UnsupportedOperationException e) {
    client = context.getPulsarClientBuilder().serviceUrl(url).build();
}

Defensive patterns

Strategy: try-catch

Validate before calling

// No pre-check; capability is discovered at call time.

Try / catch

PulsarClient client;
try {
    client = ctx.getPulsarClient();
} catch (UnsupportedOperationException e) {
    client = PulsarClient.builder().serviceUrl(serviceUrl).build();
}

Prevention

Use getPulsarClient() only inside Java function runtimes that inject a client
In shared code, always have a fallback builder path
For unit tests, stub Context with an overriding getPulsarClient

When it happens

Trigger: Calling context.getPulsarClient() from code running with a Context implementation that has not been given a PulsarClient — e.g. a sink/source connector context or unit-test Context stub.

Common situations: Shared utility code used both in sinks and functions, mocks/stubs of Context in unit tests that don't override getPulsarClient, or older runtime versions where the client was not injected.

Related errors

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/7310ba8f7a7ad2b9. Report an issue: GitHub.