Can Kafka lost messages?

Can Kafka lost messages?

Kafka is speedy and fault-tolerant distributed streaming platform. However, there are some situations when messages can disappear. It can happen due to misconfiguration or misunderstanding Kafka’s internals.

How long does Apache Kafka retain messages?

By default, Kafka will keep data for two weeks, and you can tune this to an arbitrarily large (or small) period of time. There is also an Admin API that lets you delete messages explicitly if they are older than some specified time or offset.

Is order guaranteed in Kafka?

Kafka does not guarantee ordering of messages between partitions. It does provide ordering within a partition. Thus, Kafka can maintain message ordering by a consumer if it is subscribed to only a single partition. Messages can also be ordered using the key to be grouped by during processing.

How does Kafka deal with failure scenarios?

You can deal with failed transient sends in several ways:

1. Drop failed messages.
2. Exert backpressure further up the application and retry sends.
3. Send all messages to alternative local storage, from which they will be ingested into Kafka asynchronously.

Where are Kafka messages stored?

The default log. dir is /tmp/kafka-logs which you may want to change in case your OS has a /tmp directory cleaner.

How can Kafka deliver messages and avoid losing data or duplication?

Summary. A message broker can deliver the same message repeatedly. To prevent duplicate messages from causing bugs, a message handlers must use the Idempotent Consumer pattern. If a message handler is not inherently idempotent, it must record successfully processed messages and discard duplicates.

Are Kafka messages persistent?

As we described, Kafka stores a persistent log which can be re-read and kept indefinitely. Kafka is built to allow real-time stream processing, not just processing of a single message at a time. This allows working with data streams at a much higher level of abstraction.

Does Kafka delete old messages?

Topics has retention.ms set to 172800000 (48h). However, there are still old data in the folder /tmp/kafka-logs and none are being deleted.

How do I guarantee Kafka ordering?

In Kafka, order can only be guaranteed within a partition. This means that if messages were sent from the producer in a specific order, the broker will write them to a partition and all consumers will read from that in the same order.

How do I ensure message order in Kafka?

If all messages must be ordered within one topic, use one partition, but if messages can be ordered per a certain property, set a consistent message key and use multiple partitions. This way you can keep your messages in strict order and keep high Kafka throughput.

How do I deal with failed Kafka messages?

The Kafka connector proposes three strategies to handle failures.

1. fail-fast (default) stops the application and marks it unhealthy.
2. ignore continues the processing even if there are failures.
3. dead-letter-queue sends failing messages to another Kafka topic for further investigation.

Is Kafka single point of failure?

Brokers: What if Kafka system goes down? This would make our Consumers and Producers pause till the Kafka is back. This is a single point of failure, to avoid this.

Can Kafka delete messages after they are consumed?

You can not instruct kafka to delete after consume. Topics can be consumed multiple times by multiple consumer groups. All messages are kept for a retention period which can be set per topic. You can set the retention very low but then if you do not consume it by that time it is lost.

Is Kafka a reliable data source?

In the introduction of many stream processing frameworks, Kafka is a reliable data source, and Kafka is recommended to be used as a data source. This is because compared with other message engine systems, Kafka provides a reliable data storage and backup mechanism.

What is exactly once processing in Kafka?

So let’s talk about Kafka’s implementation of exactly once processing. In distributed environment, it is very difficult to achieve message consistency and exact once semantic processing. Precise one-time processing means that a message is only processed once, resulting in the effect of one time, which can not be more or less.

What is a Kafka topic?

Kafka is a message queue reimagined as a distributed commit log. What that means is that messages are not deleted when consumed. Instead they are all kept on the broker (like a log file keeps line items one after another). All new messages published are appended to the end of the queue (called a topic in Kafka).