Unable to connect: Communications link failure - mysql

Question

I am trying to follow the tutorial Deploying Debezium using the new KafkaConnector resource.
Based on the tutorial, I am also using minikube but with docker driver. Basically just follow exactly step by step.
However, for the step "Create the connector", after creating the connector by
cat <<EOF | kubectl -n kafka apply -f -
apiVersion: "kafka.strimzi.io/v1alpha1"
kind: "KafkaConnector"
metadata:
name: "inventory-connector"
labels:
strimzi.io/cluster: my-connect-cluster
spec:
class: io.debezium.connector.mysql.MySqlConnector
tasksMax: 1
config:
database.hostname: 192.168.99.1
database.port: "3306"
database.user: "${file:/opt/kafka/external-configuration/connector-config/debezium-mysql-credentials.properties:mysql_username}"
database.password: "${file:/opt/kafka/external-configuration/connector-config/debezium-mysql-credentials.properties:mysql_password}"
database.server.id: "184054"
database.server.name: "dbserver1"
database.whitelist: "inventory"
database.history.kafka.bootstrap.servers: "my-cluster-kafka-bootstrap:9092"
database.history.kafka.topic: "schema-changes.inventory"
include.schema.changes: "true"
EOF
and check by
kubectl -n kafka get kctr inventory-connector -o yaml
I got error
apiVersion: kafka.strimzi.io/v1alpha1
kind: KafkaConnector
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"kafka.strimzi.io/v1alpha1","kind":"KafkaConnector","metadata":{"annotations":{},"labels":{"strimzi.io/cluster":"my-connect-cluster"},"name":"inventory-connector","namespace":"kafka"},"spec":{"class":"io.debezium.connector.mysql.MySqlConnector","config":{"database.history.kafka.bootstrap.servers":"my-cluster-kafka-bootstrap:9092","database.history.kafka.topic":"schema-changes.inventory","database.hostname":"192.168.49.2","database.password":"","database.port":"3306","database.server.id":"184054","database.server.name":"dbserver1","database.user":"","database.whitelist":"inventory","include.schema.changes":"true"},"tasksMax":1}}
creationTimestamp: "2021-09-29T18:20:11Z"
generation: 1
labels:
strimzi.io/cluster: my-connect-cluster
name: inventory-connector
namespace: kafka
resourceVersion: "12777"
uid: 083df9a3-83ce-4170-a9bc-9573dafdb286
spec:
class: io.debezium.connector.mysql.MySqlConnector
config:
database.history.kafka.bootstrap.servers: my-cluster-kafka-bootstrap:9092
database.history.kafka.topic: schema-changes.inventory
database.hostname: 192.168.49.2
database.password: ""
database.port: "3306"
database.server.id: "184054"
database.server.name: dbserver1
database.user: ""
database.whitelist: inventory
include.schema.changes: "true"
tasksMax: 1
status:
conditions:
- lastTransitionTime: "2021-09-29T18:20:11.548Z"
message: |-
PUT /connectors/inventory-connector/config returned 400 (Bad Request): Connector configuration is invalid and contains the following 1 error(s):
A value is required
You can also find the above list of errors at the endpoint `/{connectorType}/config/validate`
reason: ConnectRestException
status: "True"
type: NotReady
observedGeneration: 1
I tried to change
database.user: "${file:/opt/kafka/external-configuration/connector-config/debezium-mysql-credentials.properties:mysql_username}"
database.password: "${file:/opt/kafka/external-configuration/connector-config/debezium-mysql-credentials.properties:mysql_password}"
to
database.user: "debezium"
database.password: "dbz"
directly and re-apply, based on the user and password info in "Secure the database credentials" step.
Also, based on the description in the tutorial
I’m using database.hostname: 192.168.99.1 as IP address for connecting to MySQL because I’m using minikube with the virtualbox VM driver If you’re using a different VM driver with minikube you might need a different IP address.
I am actually a little confused for above description. MySQL in the demo is deployed in Docker, while the rest of parts like Kafka are deployed in minikube. Why the description about database.hostname says minikube instead of Docker?
Anyway, when I run minikube ip, I got 192.168.49.2. However, after I change database.hostname to 192.168.49.2, and run kubectl get kctr inventory-connector -o yaml -n kafka, I got
apiVersion: kafka.strimzi.io/v1alpha1
kind: KafkaConnector
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"kafka.strimzi.io/v1alpha1","kind":"KafkaConnector","metadata":{"annotations":{},"labels":{"strimzi.io/cluster":"my-connect-cluster"},"name":"inventory-connector","namespace":"kafka"},"spec":{"class":"io.debezium.connector.mysql.MySqlConnector","config":{"database.history.kafka.bootstrap.servers":"my-cluster-kafka-bootstrap:9092","database.history.kafka.topic":"schema-changes.inventory","database.hostname":"192.168.49.2","database.password":"","database.port":"3306","database.server.id":"184054","database.server.name":"dbserver1","database.user":"","database.whitelist":"inventory","include.schema.changes":"true"},"tasksMax":1}}
creationTimestamp: "2021-09-29T18:20:11Z"
generation: 1
labels:
strimzi.io/cluster: my-connect-cluster
name: inventory-connector
namespace: kafka
resourceVersion: "12777"
uid: 083df9a3-83ce-4170-a9bc-9573dafdb286
spec:
class: io.debezium.connector.mysql.MySqlConnector
config:
database.history.kafka.bootstrap.servers: my-cluster-kafka-bootstrap:9092
database.history.kafka.topic: schema-changes.inventory
database.hostname: 192.168.49.2
database.password: ""
database.port: "3306"
database.server.id: "184054"
database.server.name: dbserver1
database.user: ""
database.whitelist: inventory
include.schema.changes: "true"
tasksMax: 1
status:
conditions:
- lastTransitionTime: "2021-09-29T18:20:11.548Z"
message: |-
PUT /connectors/inventory-connector/config returned 400 (Bad Request): Connector configuration is invalid and contains the following 1 error(s):
A value is required
You can also find the above list of errors at the endpoint `/{connectorType}/config/validate`
reason: ConnectRestException
status: "True"
type: NotReady
observedGeneration: 1
I can access MySQL by localhost as it is hosted in Docker.
However, I still same error when I changed database.hostname to localhost.
Any idea? Thanks!

Answer 1

The issue is related with the service in minikube failed to communicate with the MySQL in the docker.
Regarding how to access host's localhost from inside Kubernetes cluster, I found How to access host's localhost from inside kubernetes cluster
However, I end up with deploying MySQL in Kubernetes direction by
kubectl apply -f https://k8s.io/examples/application/mysql/mysql-pv.yaml
kubectl apply -f https://k8s.io/examples/application/mysql/mysql-deployment.yaml
(Copied from https://kubernetes.io/docs/tasks/run-application/run-single-instance-stateful-application/)
with
database.hostname: "mysql.default" # service `mysql` in namespace `default`
database.port: "3306"
database.user: "root"
database.password: "password"
Now when I run
kubectl -n kafka get kctr inventory-connector -o yaml
I got a new error saying MySQL not enabling row-level binlog, however, it means it can connect the MySQL now.
apiVersion: kafka.strimzi.io/v1alpha1
kind: KafkaConnector
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"kafka.strimzi.io/v1alpha1","kind":"KafkaConnector","metadata":{"annotations":{},"labels":{"strimzi.io/cluster":"my-connect-cluster"},"name":"inventory-connector","namespace":"kafka"},"spec":{"class":"io.debezium.connector.mysql.MySqlConnector","config":{"database.history.kafka.bootstrap.servers":"my-cluster-kafka-bootstrap:9092","database.history.kafka.topic":"schema-changes.inventory","database.hostname":"mysql.default","database.password":"password","database.port":"3306","database.server.id":"184054","database.server.name":"dbserver1","database.user":"root","database.whitelist":"inventory","include.schema.changes":"true"},"tasksMax":1}}
creationTimestamp: "2021-09-29T19:36:52Z"
generation: 1
labels:
strimzi.io/cluster: my-connect-cluster
name: inventory-connector
namespace: kafka
resourceVersion: "2918"
uid: 48bb46e1-42bb-4574-a3dc-221ae7d6a803
spec:
class: io.debezium.connector.mysql.MySqlConnector
config:
database.history.kafka.bootstrap.servers: my-cluster-kafka-bootstrap:9092
database.history.kafka.topic: schema-changes.inventory
database.hostname: mysql.default
database.password: password
database.port: "3306"
database.server.id: "184054"
database.server.name: dbserver1
database.user: root
database.whitelist: inventory
include.schema.changes: "true"
tasksMax: 1
status:
conditions:
- lastTransitionTime: "2021-09-29T19:36:53.605Z"
status: "True"
type: Ready
connectorStatus:
connector:
state: UNASSIGNED
worker_id: 172.17.0.8:8083
name: inventory-connector
tasks:
- id: 0
state: FAILED
trace: "org.apache.kafka.connect.errors.ConnectException: The MySQL server is
not configured to use a row-level binlog, which is required for this connector
to work properly. Change the MySQL configuration to use a row-level binlog
and restart the connector.\n\tat io.debezium.connector.mysql.MySqlConnectorTask.start(MySqlConnectorTask.java:207)\n\tat
io.debezium.connector.common.BaseSourceTask.start(BaseSourceTask.java:49)\n\tat
org.apache.kafka.connect.runtime.WorkerSourceTask.execute(WorkerSourceTask.java:208)\n\tat
org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:177)\n\tat
org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:227)\n\tat
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)\n\tat
java.util.concurrent.FutureTask.run(FutureTask.java:266)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\tat
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\tat
java.lang.Thread.run(Thread.java:748)\n"
worker_id: 172.17.0.8:8083
type: source
observedGeneration: 1