Training - Consistency Level

CREATE KEYSPACE consistency WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3};
USE consistency;
CREATE TABLE consistency.users (user_name varchar PRIMARY KEY, birth_year bigint);

INSERT INTO test.users (user_name, birth_year) values ('tzach', 1970);
INSERT INTO test.users (user_name, birth_year) values ('nadav', 1972);
INSERT INTO test.users (user_name, birth_year) values ('shlomi', 1974);
INSERT INTO test.users (user_name, birth_year) values ('nir', 1980);


SELECT * from consistency.users; (fill your expected result in the table for each node)
Stop one node $ sudo systemctl stop scylla-server 
Verify node status $ sudo systemctl stop scylla-server 
CQLsh to live node (not the one that you stopped) $ cqlsh 127.0.0.1
UPDATE consistency.users SET birth_year=1992 WHERE user_name='nadav';
SELECT * from consistency.users; (fill your expected result in the table for each node)
Start the node $ sudo systemctl start scylla-server
$ CQLsh 127.0.0.1 to the node that was down and you just started

SELECT * from consistency.users (fill your expected result in the table for each node) 
Set CONSISTENCY to ALL CONSISTENCY ALL

SELECT * from consistency.users; (fill your expected result in the table for each node) - are the      
           results different?


Why did we saw different results when we had different Consistency Level? 
If Consistency Level is set to “ONE” the cluster will wait for a reply from one node, this node will display his most update result according to his timestamp
If Consistency Level is set to “ALL” the cluster will wait for a reply from all of the nodes and will display the most update result according to his timestamp