Testing performance impact using tracing

Tracing records all activity related to a request. These steps use tracing to show queries on a keyspace with a replication factor of 3 using different consistency levels (CL):

ONE processes responses from one of three replicas
QUORUM from two of three replicas

ALL from three of three replicas

On the cqlsh command line, create a keyspace that specifies using three replicas for data distribution in the cluster.

CREATE KEYSPACE IF NOT EXISTS cycling_alt 
WITH REPLICATION = {
  'class': 'SimpleStrategy', 
  'replication_factor': 3
};

Create a table and insert a row.

USE cycling_alt;
CREATE TABLE IF NOT EXISTS cycling_alt.cyclist_name (
  id int PRIMARY KEY,
  lastname text,
  firstname text
);

Turn on tracing and use the CONSISTENCY command to ensure the consistency level is ONE, the default.
```
TRACING ON;
CONSISTENCY;
```
The output is:
```
Current consistency level is ONE.
```

Query the table to read the row.

SELECT * FROM cycling_alt.cyclist_name WHERE id = 1;

 id | firstname | lastname
----+-----------+----------
  1 |   Melissa |  HOSKINS

(1 rows)

+ The tracing results list all the actions taken to complete the SELECT statement.

Change the consistency level to QUORUM to trace what happens during a read with a QUORUM consistency level.
```
CONSISTENCY QUORUM;
SELECT * FROM cycling_alt.cyclist_name WHERE id = 1;
```

Consistency level set to QUORUM.

Change the consistency level to ALL and run the SELECT statement again.
```
CONSISTENCY ALL;
SELECT * FROM cycling_alt.cyclist_name WHERE id = 1;
```

Consistency level set to ALL.

Testing performance impact using tracing

Was this helpful?

Give Feedback