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1. Create universe
If you have a previously running local universe, destroy it using the following.
$ ./yb-docker-ctl destroy
Start a new local cluster with 3-nodes with replication factor 3. We configure the number of shards (aka tablets) per table per tserver to 4 so that we can better observe the load balancing during scale-up and scale-down. Each table will now have 4 tablet-leaders in each tserver and with replication factor 3, there will be 2 tablet-followers for each tablet-leader distributed in the 2 other tservers. So each tserver will have 12 tablets (i.e. sum of 4 tablet-leaders and 8 tablet-followers) per table.
$ ./yb-docker-ctl create --rf 3 --num_shards_per_tserver 4
2. Run sample SQL app
Pull the yb-sample-apps docker container. This container has built-in Java client programs for various workloads including SQL inserts and updates.
$ docker pull yugabytedb/yb-sample-apps
$ docker run --name yb-sample-apps --hostname yb-sample-apps --net yb-net yugabytedb/yb-sample-apps --workload SqlInserts \ --nodes yb-tserver-n1:5433 \ --num_threads_write 1 \ --num_threads_read 4
The sample application prints some stats while running, which is also shown below. You can read more details about the output of the sample applications here.
2017-11-20 14:02:48,114 [INFO|...] Read: 9893.73 ops/sec (0.40 ms/op), 233458 total ops | Write: 1155.83 ops/sec (0.86 ms/op), 28072 total ops | ... 2017-11-20 14:02:53,118 [INFO|...] Read: 9639.85 ops/sec (0.41 ms/op), 281696 total ops | Write: 1078.74 ops/sec (0.93 ms/op), 33470 total ops | ...
3. Observe IOPS per node
You can check a lot of the per-node stats by browsing to the tablet-servers page. It should look like this. The total read and write IOPS per node are highlighted in the screenshot below. Note that both the reads and the writes are roughly the same across all the nodes indicating uniform usage across the nodes.
4. Add node and observe linear scale out
Add a node to the universe.
$ ./yb-docker-ctl add_node --num_shards_per_tserver 4
Now we should have 4 nodes. Refresh the tablet-servers page to see the stats update. In a short time, you should see the new node performing a comparable number of reads and writes as the other nodes.
5. Remove node and observe linear scale in
Remove the recently added node from the universe.
$ ./yb-docker-ctl remove_node 4
- Refresh the tablet-servers page to see the stats update. The
Time since heartbeatvalue for that node will keep increasing. Once that number reaches 60s (i.e. 1 minute), YugabyteDB will change the status of that node from ALIVE to DEAD. Note that at this time the universe is running in an under-replicated state for some subset of tablets.
- After 300s (i.e. 5 minutes), YugabyteDB’s remaining nodes will re-spawn new tablets that were lost with the loss of node 4. Each remaining node’s tablet count will increase from 18 to 24.
6. Clean up (optional)
Optionally, you can shutdown the local cluster created in Step 1.
$ ./yb-docker-ctl destroy