Piotr,
It will depend on how long zookeeper takes to resync. One of the factors
is how big the zookeeper database has become because when a ZK server
starts, it has to process the snapshot and any logs to
But while syncing the other zk server should still provide service
(read-only) - maybe the Fuseki server is choosing the fresh zk server so
it'll wait whereas as if went to another server, it would be OK (for a
read-transaction). I thought the new one would not service request until
ready but I'm not sure.
At what point in the Fuseki log file does the freeze happen? After the
HTTP request is received or as it exits (is the freeze before or after
the middle log line of the three for a request).
With 3 zk servers, the system can survive one outage.
With 5 zk server it can survive one outage and still allow write, or 2
out and read-only.
You can also configure zk in more complex primary-secondary configurations.
A load balancer between the Fuseki servers and the zk servers may help.
Andy
On 17/08/2020 17:09, Piotr Nowara wrote:
Hi,
We are testing RDF Delta with three Zookeeper instances. Sometimes when we
kill one of those Zookeper instances Fuseki freezes for about 30 seconds
which is bad. Is this expected? Will increasing the number of Zookeper
instances help to avoid such issues?
Yes and no.
Thanks,
Piotr Nowara
