# MultiDC cluster ,Observing 100% cpu when connecting scylla with kafka source connector to read cdc logs **URL:** \ **Category:** ScyllaDB\ **Tags:** troubleshooting, cdc, kafka, multi-dc\ **Created:** [February 5, 2024, 8:00pm UTC](https://forum.scylladb.com/t/multidc-cluster-observing-100-cpu-when-connecting-scylla-with-kafka-source-connector-to-read-cdc-logs/1276 "2024-02-05T20:00:45Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![amitesh88](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.scylladb.com/amitesh88/32/638_2.png) [@amitesh88](https://forum.scylladb.com/u/amitesh88)\ **Post date:** [February 5, 2024, 8:00pm UTC](https://forum.scylladb.com/t/multidc-cluster-observing-100-cpu-when-connecting-scylla-with-kafka-source-connector-to-read-cdc-logs/1276/1 "2024-02-05T20:00:45Z")
We have our multi dc setup with 3 node in dc1 and 3 in dc2 . Although both the DCs are in the same region n same subnet, This is done as we require separate clusters for reading n writing data. Our setup creates a new table everyday at 12 midnight with cdc enabled in DC1 At the same time we also create a kafka source connector to consume cdc logs from DC2 everyday Issue: At around 12 When creating a new source con , we observe scylladb servers on dc2 consumes 100% cpu. We increased cpu from 16cores to 32 but still same behavior Once the kafka connector creates its topic and start reading data from cdc log ,scylladb cpu cools down Logs: The logs in syslog shows reader\_concurrency\_semaphores for that time period. Any expert thoughts is appreciated Thanks in advance ---
**Author:** ![roy](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.scylladb.com/roy/32/576_2.png) [@roy](https://forum.scylladb.com/u/roy)\ **Post date:** [February 12, 2024, 1:10am UTC](https://forum.scylladb.com/t/multidc-cluster-observing-100-cpu-when-connecting-scylla-with-kafka-source-connector-to-read-cdc-logs/1276/2 "2024-02-12T01:10:36Z")
The cpu utilization itself isn’t always an indication of a problem, however the reader\_concurrency\_semaphore may be a stronger indication. For how long do you have this high utlization and the reader\_conccurency\_semaphore errors? Also, how exactly are your CDC configured? Full logs would be more helpful, but sounds like a better place for it would be a Github issue. ---
**Author:** ![amitesh88](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.scylladb.com/amitesh88/32/638_2.png) [@amitesh88](https://forum.scylladb.com/u/amitesh88)\ **Post date:** [February 12, 2024, 2:09am UTC](https://forum.scylladb.com/t/multidc-cluster-observing-100-cpu-when-connecting-scylla-with-kafka-source-connector-to-read-cdc-logs/1276/3 "2024-02-12T02:09:36Z")
Thanks a lot for responding Already raised this on github Here is the link ,along with logs and other necessary details you need > > > We have our multi dc setup with 3 node in dc1 and 3 in dc2 . Although both the D…Cs are in the same region n same subnet, This is done as we require separate clusters for reading n writing data. > > Our setup creates a new table everyday at 12 midnight with cdc enabled in DC1 > > At the same time we also create a kafka source connector to consume cdc logs from DC2 everyday > > Issue: > At around 12 > When creating a new source con , we observe scylladb servers on dc2 consumes 100% cpu. > > We increased cpu from 16cores to 32 but still same behavior > Once the kafka connector creates its topic and start reading data from cdc log ,scylladb cpu cools down > > Logs: > > The logs in syslog shows reader\_concurrency\_semaphores for that time period. > > Any expert thoughts is appreciated > Thanks in advance The reader\_concurreny\_semaphore log only comes for 15 mins when a new kafka debezium source connector spawns. Cpu also goes high during that time . Exact details are available in the link, please go through it and help in understandng the exact issue ---
**Author:** ![amitesh88](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.scylladb.com/amitesh88/32/638_2.png) [@amitesh88](https://forum.scylladb.com/u/amitesh88)\ **Post date:** [February 12, 2024, 6:50pm UTC](https://forum.scylladb.com/t/multidc-cluster-observing-100-cpu-when-connecting-scylla-with-kafka-source-connector-to-read-cdc-logs/1276/4 "2024-02-12T18:50:33Z")
We manage to reduce 15 mins of High CPUby tweaking **scylla.query.time.window.size** in kafka source connector , but still no clue about 100% cpu utilisation Also it is observed , our 6 node dc2 cluster and 4 nodes kafka connector, there is a total of 40000 active connection on each scylladb node Any clue about this??