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1. Setup - create universe
If you have a previously running local universe, destroy it using the following.
$ ./bin/yb-ctl destroy
Start a new local cluster - by default, this will create a 3-node universe with a replication factor of 3.
$ ./bin/yb-ctl create --enable_postgres
2. Run sample key-value app
Download the sample app jar.
$ wget https://github.com/yugabyte/yb-sql-workshop/blob/master/running-sample-apps/yb-sample-apps.jar?raw=true -O yb-sample-apps.jar
SqlInserts sample key-value app against the local universe by typing the following command.
$ java -jar ./yb-sample-apps.jar --workload SqlInserts \ --nodes 127.0.0.1:5433 \ --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.
2018-05-10 09:10:19,538 [INFO|...] Read: 8988.22 ops/sec (0.44 ms/op), 818159 total ops | Write: 1095.77 ops/sec (0.91 ms/op), 97120 total ops | ... 2018-05-10 09:10:24,539 [INFO|...] Read: 9110.92 ops/sec (0.44 ms/op), 863720 total ops | Write: 1034.06 ops/sec (0.97 ms/op), 102291 total ops | ...
3. Observe even load across all nodes
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. Remove a node and observe continuous write availability
Remove a node from the universe.
$ ./bin/yb-ctl remove_node 3
Refresh the tablet-servers page to see the stats update. The
Time since heartbeat value 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.
4. Remove another node and observe write unavailability
Remove another node from the universe.
$ ./bin/yb-ctl remove_node 2
Refresh the tablet-servers page to see the stats update. Writes are now unavailable but reads can continue to be served for whichever tablets available on the remaining node.
6. Clean up (optional)
Optionally, you can shutdown the local cluster created in Step 1.
$ ./bin/yb-ctl destroy