I am new to kubernetes env. And I am learning kubernetes using minikube. I have a situation where I have to configure fdw (foreign table concept) in PostgreSQL.
I am trying to implement this fdw concept in kubernetes. For that I have two pods meta pod where we create the foreign table and server, Data pod where the actual table exist. To create a meta pod you should have an Docker image consist of following script.
Script.sh
#!/bin/bash
psql -d metap -U papu -c "CREATE EXTENSION if not exists postgres_fdw;"
psql -d metap -U papu -c "CREATE SERVER if not exists dataserver FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host 'datap.default.svc.cluster.local', dbname 'datap', port '5432');"
psql -d metap -U papu -c "CREATE USER MAPPING if not exists FOR ais SERVER dataserver OPTIONS (user 'papu', password 'papu');"
psql -d metap -U papu -c "CREATE FOREIGN TABLE if not exists dream (id integer, val text) SERVER dataserver OPTIONS (schema_name 'public', table_name 'dream');"
The yaml file for the two pods is given below.
p-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: p-config
labels:
app: post
data:
POSTGRES_DB: datap
POSTGRES_USER: papu
POSTGRES_PASSWORD: papu
datap.yaml
apiVersion: v1
kind: Service
metadata:
name: datap
labels:
app: datap
spec:
ports:
- port: 5432
name: datap
clusterIP: None
selector:
app: datap
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: datap
spec:
serviceName: "datap"
replicas: 1
selector:
matchLabels:
app: datap
template:
metadata:
labels:
app: datap
spec:
containers:
- name: datap
image: postgres:latest
envFrom:
- configMapRef:
name: p-config
ports:
- containerPort: 5432
name: datap
volumeMounts:
- name: datap
mountPath: /var/lib/postgresql/data
subPath: datap
volumeClaimTemplates:
- metadata:
name: datap
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 2Gi
My use case is that I already have data pod up and running, now I have to create the foreign table through running script in meta pod dynamically.
For that I am using life cycle hook. when I run this configuration, the foreign table is created and fdw connection is established. But the logs say life-cycle hook is not Executed. Is this a bug? Or any problem in my configuration?
$ kubectl describe pod metap-0
Name: metap-0
Namespace: default
Priority: 0
Node: minikube/10.0.2.15
Start Time: Fri, 20 Sep 2019 15:50:41 +0530
Labels: app=metap
controller-revision-hash=metap-648ddb5465
statefulset.kubernetes.io/pod-name=metap-0
Annotations: <none>
Status: Running
IP: 172.17.0.10
Controlled By: StatefulSet/metap
Containers:
metap:
Container ID:
Image: <script containing image >:latest
Port: 5432/TCP
Host Port: 0/TCP
State: Running
Started: Fri, 20 Sep 2019 15:51:29 +0530
Last State: Terminated
Reason: Completed
Exit Code: 0
Started: Fri, 20 Sep 2019 15:51:14 +0530
Finished: Fri, 20 Sep 2019 15:51:15 +0530
Ready: True
Restart Count: 2
Environment: <none>
Mounts:
/var/lib/postgresql/data from metap (rw,path="metap")
/var/run/secrets/kubernetes.io/serviceaccount from default-token
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
mpostgredb:
Type: PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
ClaimName: metap-metap-0
ReadOnly: false
default-token-r2ncm:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-r2ncm
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning FailedScheduling 71s (x2 over 71s) default-scheduler pod has unbound immediate PersistentVolumeClaims
Normal Scheduled 69s default-scheduler Successfully assigned default/metap-0 to minikube
Warning FailedPostStartHook 67s kubelet, minikube Exec lifecycle hook ([/bin/sh -c script.sh]) for Container "metap" in Pod "metap-0_default(6a367766-cd7e-4bab-826a-908e33622bcf)" failed - error: command '/bin/sh -c script.sh' exited with 2: psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
, message: "psql: could not connect to server: No such file or directory\n\tIs the server running locally and accepting\n\tconnections on Unix domain socket \"/var/run/postgresql/.s.PGSQL.5432\"?\npsql: could not connect to server: No such file or directory\n\tIs the server running locally and accepting\n\tconnections on Unix domain socket \"/var/run/postgresql/.s.PGSQL.5432\"?\npsql: could not connect to server: No such file or directory\n\tIs the server running locally and accepting\n\tconnections on Unix domain socket \"/var/run/postgresql/.s.PGSQL.5432\"?\npsql: could not connect to server: No such file or directory\n\tIs the server running locally and accepting\n\tconnections on Unix domain socket \"/var/run/postgresql/.s.PGSQL.5432\"?\n"
Warning FailedPostStartHook 35s kubelet, minikube Exec lifecycle hook ([/bin/sh -c script.sh]) for Container "metap" in Pod "metap-0_default(6a367766-cd7e-4bab-826a-908e33622bcf)" failed - error: command '/bin/sh -c script.sh' exited with 1: psql: FATAL: the database system is starting up
psql: FATAL: the database system is starting up
ERROR: server "dataserver" does not exist
ERROR: server "dataserver" does not exist
, message: "psql: FATAL: the database system is starting up\npsql: FATAL: the database system is starting up\nERROR: server \"dataserver\" does not exist\nERROR: server \"dataserver\" does not exist\n"
Normal Killing 35s (x2 over 67s) kubelet, minikube FailedPostStartHook
Warning BackOff 33s (x2 over 34s) kubelet, minikube Back-off restarting failed container
Normal Created 21s (x3 over 68s) kubelet, minikube Created container metap
Normal Started 21s (x3 over 68s) kubelet, minikube Started container metap
Normal Pulling 21s (x3 over 68s) kubelet, minikube Pulling image " <script containing image >:latest"
Normal Pulled 21s (x3 over 68s) kubelet, minikube Successfully pulled image " <script containing image >:latest"
$ kubectl logs metap-0
2019-09-20 10:21:29.500 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
2019-09-20 10:21:29.500 UTC [1] LOG: listening on IPv6 address "::", port 5432
2019-09-20 10:21:29.502 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2019-09-20 10:21:29.514 UTC [22] LOG: database system was shut down at 2019-09-20 10:21:15 UTC
2019-09-20 10:21:29.518 UTC [1] LOG: database system is ready to accept connections
kubectl version
Client Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.3", GitCommit:"2d3c76f9091b6bec110a5e63777c332469e0cba2", GitTreeState:"clean", BuildDate:"2019-08-19T11:13:54Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.2", GitCommit:"f6278300bebbb750328ac16ee6dd3aa7d3549568", GitTreeState:"clean", BuildDate:"2019-08-05T09:15:22Z", GoVersion:"go1.12.5", Compiler:"gc", Platform:"linux/amd64"}
*** Minikube version ***
minikube version: v1.3.1
commit: ca60a424ce69a4d79f502650199ca2b52f29e631
using init containers you can check if the second container is already up and running then run the script
spec:
initContainers:
- name: check-second-ready
image: postgres
command: ['sh', '-c',
'until pg_isready -h connection/url/to/second/conatiner -p 5432;
do echo waiting for database; sleep 2; done;']
containers:
first container config...
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