CalvinSchulze opened a new issue #8214: Data Loss at replication test
URL: https://github.com/apache/incubator-druid/issues/8214
 
 
   # Affected Version
   
   Druid 0.15 incubating on Ubuntu using jdk 8
   Zookeeper 3.4.11
   Kafka 2.12-2.2.0
   
   ### Description
   
   I decided to test Druid's fault tolerance today and set up a little test:
   
   A logging software, which sends every second a small amount of events to 
Kafka, which are stream ingested into Druid. All data is supposed to be 
replicated on 2 historical nodes. Everything runs on 1 machine. 
   
   How I tested:
   
   - I produced roughly 10kB of data and ingested it
   - I stopped the logging software
   - I waited for the data to be handled (or at least, until the web GUI shows 
it)
   - I shut down one of the historicals
   - I restarted the logging software
   - I produced another 10kB of data
   -> First weird behaviour. The data didn't get sent to the running historical 
and the tasks didn't terminate
   - I started the second historical again
   -> It took a very long time and >100 failing tasks (duration = 0:00:00, no 
error, no log) for the 
   second historical to queue the missing segments
   -> This test made the first historical crash
   - I restarted the first historical
   -> Queue stays empty forever
   -> The missing 5 segments are not realtime anymore
   -> None of the historicals contains the missing 5 segments
   -> The data is apparently unavailable forever
   
   This didn't go too well, I'd say. Is this intended behaviour, or did I just 
do something wrong?
   
   Greetings,
   Calvin

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