Reading messages
I didn't skim the topic. I read the topic.
Reading without disturbing
On Kafka, Marshall reads by seeking to an offset. He never joins a consumer group, never commits an offset, and never creates a topic by asking about one (allow.auto.create.topics=false). Nobody consuming the topic can tell he was there, so it is safe on production.
Select a topic and Marshall reads the newest messages. How many is in Settings › Messages per topic (10 to 1,000, 100 by default).
Where to read from
- Read further loads the next, older page.
- Read from a moment starts somewhere else: The beginning, The latest, or At a moment in time…, which is a real seek by timestamp (
offsets_for_times), not a scan. - Broker › Reread Messages (⇧ ⌘ R) reads the current position again.
The record
Each row shows where the message lives (p3·1204 is partition 3, offset 1204), its key and payload. Select one to open the record: the payload formatted and highlighted, its headers and its metadata. Copy puts it on the clipboard.
A message with a key and no value is a tombstone: the key was deleted. Marshall labels it as one, because it is not an empty message.
A tombstone is not an empty message. I will die on this hill.
Finding a message
Find in these messages searches the key, payload and headers of what has been read. It does not search the whole topic, and it does not pretend to: binary payloads and Avro that could not be decoded are not matched as text.
When there is nothing
An empty partition says Nothing retained. Kafka only keeps what retention and compaction allow, so what you see is what is retained now, not everything ever produced.