Connecting to a Service
Building on top of the Go quickstart guide, this guide will connect a service to the Go application.
Prerequisites
Install the Service Binding Operator via Operator Hub. Read why this is required.
Install Percona Server Mongodb Operator via Operator Hub.
noteThis operator is namespace scoped, so it will only be accessible in the namespace where it has been installed.
When you install the operator by following Operator Hub instructions, the operator will be installed in a new namespace called "my-percona-server-mongodb-operator".
Create a MongoDB service.
noteThe service should be created in the namespace where Percona Server Mongodb Operator is installed, in this case, it will be "my-percona-server-mongodb-operator".
- Kubernetes
- OpenShift
cat << EOF | kubectl apply -f -
apiVersion: psmdb.percona.com/v1-11-0
kind: PerconaServerMongoDB
metadata:
name: mongodb-instance
namespace: my-percona-server-mongodb-operator
spec:
crVersion: 1.11.0
image: 'percona/percona-server-mongodb:4.4.10-11'
secrets:
users: mongodb-instance-secrets
replsets:
- name: rs0
size: 1
resources:
limits:
cpu: 300m
memory: 0.5G
requests:
cpu: 300m
memory: 0.5G
volumeSpec:
persistentVolumeClaim:
resources:
requests:
storage: 1Gi
sharding:
enabled: true
configsvrReplSet:
size: 1
resources:
limits:
cpu: 300m
memory: 0.5G
requests:
cpu: 300m
memory: 0.5G
volumeSpec:
persistentVolumeClaim:
resources:
requests:
storage: 1Gi
mongos:
size: 1
EOF
cat << EOF | oc apply -f -
apiVersion: psmdb.percona.com/v1-11-0
kind: PerconaServerMongoDB
metadata:
name: mongodb-instance
namespace: my-percona-server-mongodb-operator
spec:
crVersion: 1.11.0
image: 'percona/percona-server-mongodb:4.4.10-11'
secrets:
users: mongodb-instance-secrets
replsets:
- name: rs0
size: 1
resources:
limits:
cpu: 300m
memory: 0.5G
requests:
cpu: 300m
memory: 0.5G
volumeSpec:
persistentVolumeClaim:
resources:
requests:
storage: 1Gi
sharding:
enabled: true
configsvrReplSet:
size: 1
resources:
limits:
cpu: 300m
memory: 0.5G
requests:
cpu: 300m
memory: 0.5G
volumeSpec:
persistentVolumeClaim:
resources:
requests:
storage: 1Gi
mongos:
size: 1
EOF
Step 1. Implement the code logic
If you are already running odo dev in the terminal, press "Ctrl+c" and exit.
We will extend the current code logic to obtain the connection information (username, password, and host) from the environment and then use it to connect to the MongoDB service and ping it.
The environment variables will be exposed when we link our application with the MongoDB service.
Replace the content of your main.go with the following content:
package main
import (
"context"
"fmt"
"net/http"
"os"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readpref"
)
// Connection URI
var (
USERNAME = os.Getenv("PERCONASERVERMONGODB_MONGODB_USER_ADMIN_USER")
PASSWORD = os.Getenv("PERCONASERVERMONGODB_MONGODB_USER_ADMIN_PASSWORD")
HOST = os.Getenv("PERCONASERVERMONGODB_HOST")
uri = fmt.Sprintf("mongodb://%s:%s@%s:27017/?maxPoolSize=20&w=majority", USERNAME, PASSWORD, HOST)
)
func main() {
http.HandleFunc("/", HelloServer)
http.ListenAndServe("0.0.0.0:8080", nil)
}
func HelloServer(w http.ResponseWriter, r *http.Request) {
// Create a new client and connect to the server
client, err := mongo.Connect(context.TODO(), options.Client().ApplyURI(uri))
if err != nil {
fmt.Fprintf(w, "failed to connect: %s", err.Error())
return
}
defer func() {
if err = client.Disconnect(context.TODO()); err != nil {
fmt.Fprintf(w, "failed to disconnect: %s", err.Error())
return
}
}()
// Ping the primary
if err := client.Ping(context.TODO(), readpref.Primary()); err != nil {
fmt.Fprintf(w, "unable to connect to the server: %s", err.Error())
return
}
fmt.Fprintf(w, "Successfully connected and pinged.")
}
We will be using the MongoDB client library. Update the go.mod dependency by running the following command:
go get go.mongodb.org/mongo-driver/mongo
Step 2. Run the application
Run the application on the cluster with odo dev.
odo dev
Sample output:
Check the connection
Once the application is running, query the URL and check the response.
curl 127.0.0.1:40001
Sample output:
You should have received an error in response which is expected as we have not yet exposed the connection information in our application.
Step 3. Connect the application to the MongoDB service
Connect the application to the MongoDB service with odo add binding.
From a new terminal, run the following command that will add necessary data to devfile.yaml:
odo add binding \
--service mongodb-instance/PerconaServerMongoDB \
--service-namespace=my-percona-server-mongodb-operator \
--name my-go-app-mongodb-instance \
--bind-as-files=false
Sample output:
Our code logic relies on obtaining connection information from the environment variables in the system and --binding-as-files=false ensures that. Read here to know more about this flag.
Wait for odo dev to detect the new changes to devfile.yaml.
Sample output:
Once odo dev has completed its task, you can run odo describe binding from a new terminal to obtain all the MongoDB service related information that has been exposed to your application:
odo describe binding --name my-go-app-mongodb-instance
Sample output:
Step 4. Check the connection again
Query the URL again for a successful connection:
curl 127.0.0.1:40001
Sample output:
Step 5. Exit and cleanup
Press
Ctrl+cto exitodo dev.Remove the binding from
devfile.yamlwithodo remove binding.odo remove binding --name my-go-app-mongodb-instanceDelete the MongoDB instance that we created at the beginning.
- Kubernetes
- OpenShift
kubectl delete PerconaServerMongoDB mongodb-instance --namespace my-percona-server-mongodb-operator
oc delete PerconaServerMongoDB mongodb-instance --namespace my-percona-server-mongodb-operator