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#Docker for mac kafka how to

That means that our client is going to be using localhost to try to connect to a broker when producing and consuming messages. But note that the BrokerMetadata we get back shows that there is one broker, with a hostname of localhost. In this example, my client is running on my laptop, connecting to Kafka running on another machine on my LAN called asgard03: This could be a machine on your local network, or perhaps running on cloud infrastructure such as Amazon Web Services (AWS), Microsoft Azure, or Google Cloud Platform (GCP). Now let’s check the connection to a Kafka broker running on another machine.

Scenario 1: Client and Kafka running on the different machines

Note: The broker metadata returned is 192.168.10.83, but since that’s the IP of my local machine, it works just fine. My Python client is connecting with a bootstrap server setting of localhost:9092. Scenario 0: Client and Kafka running on the same local machineįor this example, I’m running Confluent Platform on my local machine, but you can also run this on any other Kafka distribution you care to. Your client would bootstrap against one (or more) of these, and that broker would return the metadata of each of the brokers in the cluster to the client. In practice, you’d have a minimum of three brokers in your cluster. Just one broker?Īll these examples are using just one broker, which is fine for a sandbox but utterly useless for anything approaching a real environment.

#Docker for mac kafka how to

This article will walk through some common scenarios and explain how to fix each one.

The client then tries to connect to this incorrect address, and then fails (since the Kafka broker is not on the client machine, which is what localhost points to).

The broker returns an incorrect hostname to the client.

The client initiates a connection to the bootstrap server(s), which is one (or more) of the brokers on the cluster.

In this case, the timeline looks like this: What often goes wrong is that the broker is misconfigured and returns an address (the advertised.listener) on which the client cannot correctly connect to the broker. The reason the client needs the details of all the brokers is that it will connect directly to one or more of the brokers based on which has data for the topic partition with which it wants to interact. This way, the client doesn’t have to know at all times the list of all the brokers. The address used in the initial connection is simply for the client to find a bootstrap server on the cluster of n brokers, from which the client is then given a current list of all the brokers.

This list is what the client then uses for all subsequent connections to produce or consume data.

The broker returns metadata, which includes the host and port on which all the brokers in the cluster can be reached.

The client initiates a connection to the bootstrap server(s), which is one (or more) of the brokers on the cluster.

On one is our client, and on the other is our Kafka cluster’s single broker (forget for a moment that Kafka clusters usually have a minimum of three brokers). It’s simplified for clarity, at the expense of good coding and functionality 🙂 An illustrated example of a Kafka client connecting to a Broker It’s very simple and just serves to illustrate the connection process.

It’s written using Python with librdkafka ( confluent_kafka), but the principle applies to clients across all languages. To read more about the protocol, see the docs, as well as this previous article that I wrote.īelow, I use a client connecting to Kafka in various permutations of deployment topology. The broker details returned in step 1 are defined by the advertised.listeners setting of the broker(s) and must be resolvable and accessible from the client machine. What sometimes happens is that people focus on only step 1 above, and get caught out by step 2.

If the broker has not been configured correctly, the connections will fail. The client then connects to one (or more) of the brokers returned in the first step as required.This returns metadata to the client, including a list of all the brokers in the cluster and their connection endpoints. The initial connection to a broker (the bootstrap).When a client wants to send or receive a message from Apache Kafka ®, there are two types of connection that must succeed: