Is there any Limit on number of ports that can be exposed in kubernetes service?

0
votes

I am trying to expose a service on 200 odd ports. Here is sample service yaml:

apiVersion: v1
kind: Service
metadata:
  name: multiport-server-large-port
spec:
  type: NodePort
  selector:
    app: multiport-server-large-port
  ports:
  - port: 49152
    name: tcp-49152
  - port: 49153
    name: tcp-49153
  - port: 49154
    name: tcp-49154
  - port: 49155
    name: tcp-49155
  - port: 49156
    name: tcp-49156
  - port: 49157
    name: tcp-49157
  - port: 49158
.
.
.
.... 200 more such ports

After I apply this yaml, service gets created but the ip:port combination is unreachable with connection refused error. On further investigation, I found out that there are some REJECT entries in iptables filter chain KUBE-EXTERNAL-SERVICES for the ports I have exposed.

IPTABLES Reject Rules:

Chain KUBE-EXTERNAL-SERVICES (1 references)
 pkts bytes target     prot opt in     out     source               destination
    0     0 REJECT     tcp  --  any    any     anywhere             anywhere             /* default/multiport-server-large-port:tcp-49316 has no endpoints */ ADDRTYPE match dst-type LOCAL tcp dpt:31
184 reject-with icmp-port-unreachable
    0     0 REJECT     tcp  --  any    any     anywhere             anywhere             /* default/multiport-server-large-port:tcp-49325 has no endpoints */ ADDRTYPE match dst-type LOCAL tcp dpt:31
225 reject-with icmp-port-unreachable
    0     0 REJECT     tcp  --  any    any     anywhere             anywhere             /* default/multiport-server-large-port:tcp-49383 has no endpoints */ ADDRTYPE match dst-type LOCAL tcp dpt:32
620 reject-with icmp-port-unreachable
    0     0 REJECT     tcp  --  any    any     anywhere             anywhere             /* default/multiport-server-large-port:tcp-49385 has no endpoints */ ADDRTYPE match dst-type LOCAL tcp dpt:30
107 reject-with icmp-port-unreachable
    0     0 REJECT     tcp  --  any    any     anywhere             anywhere             /* default/multiport-server-large-port:tcp-49359 has no endpoints */ ADDRTYPE match dst-type LOCAL tcp dpt:31

I want to understand:

  1. Why these REJECT rules are appearing?
  2. Is this not possible to expose large number of ports via services?
  3. Is there any limit on number of ports that can be exposed via services?
1
kuberneteskubectliptableskubernetes-networking

1 Answers

2
votes

The REJECT is inserted when a particular service has 0 endpoints. The selector in your Service.spec must be wrong or you don't have any pods running