Communication between pods - kubernetes

Question

I am currently in the process to set up sentry.io but i am having problems in setting it up in openshift 3.11
I got pods running for sentry itself, postgresql, redis and memcache but according to the log messages they are not able to communicate together.
sentry.exceptions.InvalidConfiguration: Error 111 connecting to 127.0.0.1:6379. Connection refused.
Do i need to create a network like in docker or should the pods (all in the same namespace) be able to talk to each other by default? I got admin rights for the complete project so i can also work with the console and not only the web interface.
Best wishes
EDIT: Adding deployment config for sentry and its service and for the sake of simplicity the postgres config and service. I also blanked out some unnecessary information with the keyword BLANK if I went overboard please let me know and ill look it up.
Deployment config for sentry:
apiVersion: apps.openshift.io/v1
kind: DeploymentConfig
metadata:
annotations:
openshift.io/generated-by: OpenShiftWebConsole
creationTimestamp: BLANK
generation: 20
labels:
app: sentry
name: sentry
namespace: test
resourceVersion: '506667843'
selfLink: BLANK
uid: BLANK
spec:
replicas: 1
selector:
app: sentry
deploymentconfig: sentry
strategy:
activeDeadlineSeconds: 21600
resources: {}
rollingParams:
intervalSeconds: 1
maxSurge: 25%
maxUnavailable: 25%
timeoutSeconds: 600
updatePeriodSeconds: 1
type: Rolling
template:
metadata:
annotations:
openshift.io/generated-by: OpenShiftWebConsole
creationTimestamp: null
labels:
app: sentry
deploymentconfig: sentry
spec:
containers:
- env:
- name: SENTRY_SECRET_KEY
value: Iamsosecret
- name: C_FORCE_ROOT
value: '1'
- name: SENTRY_FILESTORE_DIR
value: /var/lib/sentry/files/data
image: BLANK
imagePullPolicy: Always
name: sentry
ports:
- containerPort: 9000
protocol: TCP
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/lib/sentry/files
name: sentry-1
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
volumes:
- emptyDir: {}
name: sentry-1
test: false
triggers:
- type: ConfigChange
- imageChangeParams:
automatic: true
containerNames:
- sentry
from:
kind: ImageStreamTag
name: 'sentry:latest'
namespace: catcloud
lastTriggeredImage: BLANK
type: ImageChange
status:
availableReplicas: 1
conditions:
- lastTransitionTime: BLANK
lastUpdateTime: BLANK
message: Deployment config has minimum availability.
status: 'True'
type: Available
- lastTransitionTime: BLANK
lastUpdateTime: BLANK
message: replication controller "sentry-19" successfully rolled out
reason: NewReplicationControllerAvailable
status: 'True'
type: Progressing
details:
causes:
- type: ConfigChange
message: config change
latestVersion: 19
observedGeneration: 20
readyReplicas: 1
replicas: 1
unavailableReplicas: 0
updatedReplicas: 1
Service for sentry:
apiVersion: v1
kind: Service
metadata:
annotations:
openshift.io/generated-by: OpenShiftWebConsole
creationTimestamp: BLANK
labels:
app: sentry
name: sentry
namespace: test
resourceVersion: '505555608'
selfLink: BLANK
uid: BLANK
spec:
clusterIP: BLANK
ports:
- name: 9000-tcp
port: 9000
protocol: TCP
targetPort: 9000
selector:
deploymentconfig: sentry
sessionAffinity: None
type: ClusterIP
status:
loadBalancer: {}
Deployment config for postgresql:
apiVersion: apps.openshift.io/v1
kind: DeploymentConfig
metadata:
annotations:
openshift.io/generated-by: OpenShiftWebConsole
creationTimestamp: BLANK
generation: 10
labels:
app: postgres
type: backend
name: postgres
namespace: test
resourceVersion: '506664185'
selfLink: BLANK
uid: BLANK
spec:
replicas: 1
selector:
app: postgres
deploymentconfig: postgres
type: backend
strategy:
activeDeadlineSeconds: 21600
resources: {}
rollingParams:
intervalSeconds: 1
maxSurge: 25%
maxUnavailable: 25%
timeoutSeconds: 600
updatePeriodSeconds: 1
type: Rolling
template:
metadata:
annotations:
openshift.io/generated-by: OpenShiftWebConsole
creationTimestamp: null
labels:
app: postgres
deploymentconfig: postgres
type: backend
spec:
containers:
- env:
- name: PGDATA
value: /var/lib/postgresql/data/sql
- name: POSTGRES_HOST_AUTH_METHOD
value: trust
- name: POSTGRESQL_USER
value: sentry
- name: POSTGRESQL_PASSWORD
value: sentry
- name: POSTGRESQL_DATABASE
value: sentry
image: BLANK
imagePullPolicy: Always
name: postgres
ports:
- containerPort: 5432
protocol: TCP
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/lib/postgresql/data
name: volume-uirge
subPath: sql
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext:
runAsUser: 2000020900
terminationGracePeriodSeconds: 30
volumes:
- name: volume-uirge
persistentVolumeClaim:
claimName: postgressql
test: false
triggers:
- type: ConfigChange
- imageChangeParams:
automatic: true
containerNames:
- postgres
from:
kind: ImageStreamTag
name: 'postgres:latest'
namespace: catcloud
lastTriggeredImage: BLANK
type: ImageChange
status:
availableReplicas: 1
conditions:
- lastTransitionTime: BLANK
lastUpdateTime: BLANK
message: Deployment config has minimum availability.
status: 'True'
type: Available
- lastTransitionTime: BLANK
lastUpdateTime: BLANK
message: replication controller "postgres-9" successfully rolled out
reason: NewReplicationControllerAvailable
status: 'True'
type: Progressing
details:
causes:
- type: ConfigChange
message: config change
latestVersion: 9
observedGeneration: 10
readyReplicas: 1
replicas: 1
unavailableReplicas: 0
updatedReplicas: 1
Service config postgresql:
apiVersion: v1
kind: Service
metadata:
annotations:
openshift.io/generated-by: OpenShiftWebConsole
creationTimestamp: BLANK
labels:
app: postgres
type: backend
name: postgres
namespace: catcloud
resourceVersion: '506548841'
selfLink: /api/v1/namespaces/catcloud/services/postgres
uid: BLANK
spec:
clusterIP: BLANK
ports:
- name: 5432-tcp
port: 5432
protocol: TCP
targetPort: 5432
selector:
deploymentconfig: postgres
sessionAffinity: None
type: ClusterIP
status:
loadBalancer: {}

Answer 1

Pods (even in the same namespace) are not able to talk directly to each other by default. You need to create a Service in order to allow a pod to receive connections from another pod. In general, one pod connects to another pod via the latter's service, as I illustrated below:
The connection info would look something like <servicename>:<serviceport> (e.g. elasticsearch-master:9200) rather than localhost:port.
You can read https://kubernetes.io/docs/concepts/services-networking/service/ for further info on a service.
N.B: localhost:port will only work for containers running inside the same pod to connect to each other, just like how nginx connects to gravitee-mgmt-api and gravitee-mgmt-ui in my illustration above.

Answer 2

Well for me it looks like you didn't configure the sentry correctly means you are not providing credential to sentry pod to connect to PostgreSQL pod and redis pod.
env:
- name: SENTRY_SECRET_KEY
valueFrom:
secretKeyRef:
name: sentry-sentry
key: sentry-secret
- name: SENTRY_DB_USER
value: "sentry"
- name: SENTRY_DB_NAME
value: "sentry"
- name: SENTRY_DB_PASSWORD
valueFrom:
secretKeyRef:
name: sentry-postgresql
key: postgres-password
- name: SENTRY_POSTGRES_HOST
value: sentry-postgresql
- name: SENTRY_POSTGRES_PORT
value: "5432"
- name: SENTRY_REDIS_PASSWORD
valueFrom:
secretKeyRef:
name: sentry-redis
key: redis-password
- name: SENTRY_REDIS_HOST
value: sentry-redis
- name: SENTRY_REDIS_PORT
value: "6379"
- name: SENTRY_EMAIL_HOST
value: "smtp"
- name: SENTRY_EMAIL_PORT
value: "25"
- name: SENTRY_EMAIL_USER
value: ""
- name: SENTRY_EMAIL_PASSWORD
valueFrom:
secretKeyRef:
name: sentry-sentry
key: smtp-password
- name: SENTRY_EMAIL_USE_TLS
value: "false"
- name: SENTRY_SERVER_EMAIL
value: "sentry#sentry.local"
for more info you could refer to this where they configured the sentry
https://github.com/maty21/sentry-kubernetes/blob/master/sentry.yaml

Answer 3

For communication between pods localhost or 127.0.0.1 does not work.
Get the IP of any pod using
kubectl describe podname
Use that IP in the other pod to communicate with above pod.
Since Pod IPs changes if the pod is recreated you should ideally use kubernetes service specifically clusterIP type for communication between pods within the cluster.