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messagehub057.md

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2017-10-05

{:new_window: target="_blank"} {:shortdesc: .shortdesc} {:screen: .screen} {:codeblock: .codeblock} {:pre: .pre}

Known restrictions

{: #restrictions}

##Topics and partitions {: #topics_partitions notoc}

  • Topic names are restricted to a maximum of 100 characters.
  • The default number of partitions for a topic is one.
  • Each {{site.data.keyword.Bluemix_notm}} space has a limit of 100 partitions. To create more partitions, you must use a new {{site.data.keyword.Bluemix_notm}} space.

Message retention

{: #message_retention}

By default, messages are retained in Kafka for up to 24 hours and each partition is capped at 1 GB. If the 1 GB cap is reached, the oldest messages are discarded to stay within the limit.

You can change the time limit for message retention when you create a topic using either the user interface or the administration API. The time limit is a minimum of an hour and a maximum of 30 days.

Creating and deleting topics in Kafka

{: #create_delete notoc}

In Kafka, topic creation and deletion are asynchronous operations that might take some time to complete. You are recommended to avoid usage patterns that rely on the rapid creation and deletion of topics, or on the rapid deletion and re-creation of topics.

Kafka REST API

{: #trouble_rest notoc}

  • Only the binary embedded format is supported for requests and responses. The Avro and JSON embedded formats are not supported.
  • Concurrent requests are not supported for a consumer instance. Read, commit, or delete requests corresponding to a consumer instance should be sent only after a response is received for any outstanding requests of that instance.

Kafka REST API rate limitation

{: #kafka_rate notoc}

Applications using the Kafka REST API can be subject to rate limiting for each ApiKey. When this limiting occurs, the API responds with the following HTTP error:

429 Too Many Requests {:screen}

If you see this error, wait and submit the request again.

Kafka REST API daily restart

{: #rest_restart notoc}

The Kafka REST API restarts once a day for a short period of time. During this period, the Kafka REST API might become unavailable. If this happens, you are recommended to retry your request. After the REST API has restarted, you will have to recreate your Kafka consumer instances. If this is the case, the REST API returns the following JSON:

{:screen}

Kafka high-level consumer API

{: #kafka_consumer notoc}

You cannot use the Apache Kafka 0.8.2 simple or high-level consumer API with {{site.data.keyword.messagehub}}. Instead, you can use the earliest supported Kafka consumer API, which is 0.9. consumer API.