In this lab, we will learn how to dynamically update this configuration in a running pod. We will do this with an example by changing the database connection to use a PostgreSQL database.
In the last [lab](16. Adding database to your Spring Boot Application.md), we created a configuration to connect to the MySQL database by mounting application.properties file using ConfigMap.
Step 1: Create PostgreSQL Pod
Ensure you are in the spring-UserName project. Substitute UserName with your own userid
Based on what you have learnt in the previous labs, create a new Postgresql database pod i.e. Add to project, search for postgresql, choose postgresql-ephemeral. You will need to key in the following values.
Database Service Name: postgresql MySQL Connection Username: user MySQL Connection Password: password MySQL Database Name: sampledb
Feel free to use your own values, but make a note of the same (write down..we will need these)
Step 2: Add data to the database
While the code has schema-postgresql.sql and data-postgresql.sql files, these scripts will only be executed if the pod restarts. Since we are going to use this database without restarting the bootapp pod, we will add the data manually.
Select the postgresql pod and navigate to the terminal.
Login to the database from CLI
psql -h 127.0.0.1 -U $POSTGRESQL_USER -q -d $POSTGRESQL_DATABASE
This will log you into the psql CLI.
Now create the table using the script
CREATE TABLE IF NOT EXISTS customer (
CUST_ID serial primary key,
NAME varchar(100) NOT NULL,
AGE integer NOT NULL);
and then add some data as shown below. You can change the values if you wish.
insert into customer (name,age) values ('Joe Psql', 88);
insert into customer (name,age) values ('Jack Psql', 54);
insert into customer (name,age) values ('Ann Psql', 32);
These scripts are available here - https://github.com/RedHatWorkshops/spring-sample-app/blob/master/src/main/resources/schema-postgresql.sql
Here is how I added the data in the terminal
sh-4.2$ psql -h 127.0.0.1 -U $POSTGRESQL_USER -q -d $POSTGRESQL_DATABASE
sampledb=> CREATE TABLE IF NOT EXISTS customer (
sampledb(> CUST_ID serial primary key,
sampledb(> NAME varchar(100) NOT NULL,
sampledb(> AGE integer NOT NULL);
sampledb=> insert into customer (name,age) values ('Joe Psql', 88);
sampledb=> insert into customer (name,age) values ('Jack Psql', 54);
sampledb=> insert into customer (name,age) values ('Ann Psql', 32);
sampledb=> select * from customer;
cust_id | name | age
---------+-----------+-----
1 | Joe Psql | 88
2 | Jack Psql | 54
3 | Ann Psql | 32
(3 rows)
sampledb=> \q
Step 3: Update ConfigMap
Now let us update the ConfigMap to change the application.properties to point to postgresql datasource.
Using CLI run the following command after you ensure you are in the spring-UserName project
$ oc edit configmap app-props
Edit the datasource parameters as below
spring.datasource.platform=postgresql
spring.datasource.url= jdbc:postgresql://postgresql.spring-UserName:5432/sampledb
spring.datasource.username=user
spring.datasource.password=password
Do this slowly. Double check every parameter
Specifically note the spring.datasource.url. It is in the following format:
spring.datasource.url = jdbc:<<databasetype>>://<<service-host>>:<<service-port>>/<<dbname>>
Here
- databasetype is
postgresql - service-host can be ip-address of the service or the service name. Above, it is configured as service-name.projectname. This is the fully qualified service name discoverable by kubernetes. Kubernetes uses SkyDNS.
- service-port for postgresql is
5432
Note that this change does not redeploy the pod. You can check the pod details to see how long the pod has been running for.
Now verify the application.properties inside the pod (Go to bootapp pod terminal on the Web Console or use oc rsh) . You will note that the application.properties file is now updated as a result of updating the ConfigMap.
sh-4.2$ cat config/application.properties
spring.datasource.platform=postgresql
spring.datasource.url= jdbc:postgresql://postgresql.spring-veer:5432/sampledb
spring.datasource.username=user
spring.datasource.password=password
Step 4: Test the application connection
Click the application url now i.e http://bootapp-spring-UserName.apps.devday.ocpcloud.com/. It will open a new tab and greets you
Hello from bootapp-2-06a4b
Also watch the pod logs either using web console or using CLI. For example oc logs -f bootapp-2-06a4b
Watch out for connection url in the output.
Now try the /dbtest endpoint i.e. http://bootapp-spring-veer.apps.devday.ocpcloud.com/dbtest.
Note that the output is still from the MySQLDB.
Customers List
CustomerId: 2 Customer Name: Joe Mysql Age: 88
CustomerId: 3 Customer Name: Jack Mysql Age: 54
CustomerId: 4 Customer Name: Ann Mysql Age: 32
Also the pod logs show that connection url is
connection url: jdbc:mysql://mysql.spring-veer:3306/sampledb?useSSL=false
So even after the application.properties file is updated in the pod, it is not picked up. The reason is that springboot app caches the environment variables. This application has a @RefreshScope annotation. So we can invoke /refresh endpoint to refresh the cache. Run the following command from CLI to refresh the cache.
$ curl -X POST http://bootapp-spring-veer.apps.devday.ocpcloud.com/refresh
["spring.datasource.url","spring.datasource.platform"]
Now note that the pod logs show that the application context is refreshed.
2016-11-18 04:25:35.601 INFO 10 --- [io-8080-exec-10] s.c.a.AnnotationConfigApplicationContext : Refreshing
Now try the /dbtest endpoint again. Now the result will show the data from the postgresql database.
Customers List
CustomerId: 1 Customer Name: Joe Psql Age: 88
CustomerId: 2 Customer Name: Jack Psql Age: 54
CustomerId: 3 Customer Name: Ann Psql Age: 32
Also note the logs will show the connection url as
connection url: jdbc:postgresql://postgresql.spring-UserName:5432/sampledb
Note in this exercise, the pod was never redeployed. The application.properties were dynamically updated.
Summary: In this lab, we have learnt the ConfigMap's flexibility and how it allows dynamic updates to the pod configuration.