Status
Current state: Voting in progress
Discussion thread: here
JIRA: KAFKA-6733
PR: #4807
Motivation
ConsoleConsumer is one of the main debugging tools used by Kafka users. Especially for new users and new setups. However, not all possible message (ConsumerRecord) attributes are accessible using it.
Currently we have following parameters which control the ConsoleConsumer output format:
- print.timestamp
- print.key
- print.value
- key.separator
- line.separator
- key.deserializer
- value.deserializer
So there is no way to print message offset, partition and headers. Also, there is no easy way to differentiate null value or blank string.
Public Interfaces
New properties to DefaultMessageFormatter
which can be specified in kafka-console-consumer
command line arguments with --property
argument.
Property | Valid Values | Default Value | Description |
---|---|---|---|
print.offset | "true" or "false" | "false" | print message offset |
print.partition | "true" or "false" | "false" | print message partition |
print.headers | "true" or "false" | "false" | print headers |
header.separator | string | "," | separator printed between each header's key:value pair |
headers.deserializer | class name | "StringDeserializer" | header value deserializer |
null.literal | string | "" (i.e. empty string) | literal to print if the value is NULL (size -1) |
Proposed Changes
Add new properties to DefaultMessageFormatter
as per the above:
- print.offset
- print.partition
- print.headers
- header.separator
- headers.deserializer
- null.literal
Compatibility, Deprecation, and Migration Plan
The changes are backward compatible. If a user won’t use any new parameters, then the output of console consumer will look the same as before.
Rejected Alternatives
- Use kafka-dump-log command to get these information. Rejected because this requires file system access to the Kafka broker's log.dirs, which is not secure.
- Use other console consumer application to access these information. Rejected because Kafka brokers may run in airtight environment or as containers, preventing us from installing other applications than the one coming with Kafka brokers.