Pod-to-Pod communication in Kubernetes - Step-by-Step Execution

Process Flow - Pod-to-Pod communication

Pod A sends request

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Kubernetes Network Plugin

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Pod B receives request

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Pod B sends response

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Kubernetes Network Plugin

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Pod A receives response

Pod A sends a request through the Kubernetes network plugin to Pod B, which receives it and sends a response back through the same network path.

Execution Sample

Kubernetes

kubectl exec pod-a -- curl http://pod-b:80
# Pod A sends HTTP request to Pod B's IP or DNS

Pod A uses curl to send an HTTP request to Pod B using its service name or IP address.

Process Table

Step	Action	Source Pod	Destination Pod	Network Plugin Role	Result
1	Pod A initiates HTTP request	pod-a	pod-b	Routes request to pod-b IP	Request sent
2	Network plugin routes packet	pod-a	pod-b	Forwards packet to pod-b network namespace	Packet delivered
3	Pod B receives request	pod-a	pod-b	N/A	Pod B processes request
4	Pod B sends HTTP response	pod-b	pod-a	Routes response back to pod-a	Response sent
5	Network plugin routes response	pod-b	pod-a	Forwards packet to pod-a network namespace	Response delivered
6	Pod A receives response	pod-b	pod-a	N/A	Pod A receives data
7	Connection closed	pod-a	pod-b	N/A	Communication ends

💡 Communication ends after Pod A receives response and connection closes

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 6	Final
Request Status	Not sent	Sent	Received by Pod B	Response received by Pod A	Closed
Response Status	Not sent	N/A	Not sent	Sent by Pod B	Received

Key Moments - 3 Insights

How does Pod A know where to send the request?

Pod A uses the DNS name or IP address of Pod B, which Kubernetes manages via services or direct pod IPs, as shown in execution_table step 1.

What role does the network plugin play in communication?

The network plugin routes packets between pods across nodes or within the same node, forwarding requests and responses as shown in steps 2 and 5.

Why does communication end after step 6?

After Pod A receives the response, the connection is closed to free resources, ending communication as noted in step 7.

Visual Quiz - 3 Questions

Look at the execution table, at which step does Pod B process the request?

A Step 5

B Step 1

C Step 3

D Step 7

💡 Hint

Check the 'Result' column for when Pod B processes the request.

According to variable_tracker, what is the 'Request Status' after step 3?

A Not sent

B Received by Pod B

C Sent

D Closed

💡 Hint

Look at the 'Request Status' row under 'After Step 3' column.

If the network plugin fails at step 2, what happens to the request?

A Request is lost and Pod B never receives it

B Pod A receives an immediate response

C Request is delivered to Pod B

D Pod B sends a response anyway

💡 Hint

Step 2 shows the network plugin forwarding the packet; failure means no delivery.

Concept Snapshot

Pod-to-Pod communication in Kubernetes:
- Pods communicate via IP or DNS names
- Network plugin routes packets between pods
- Requests and responses flow through network namespaces
- Communication ends when connection closes
- Services can abstract pod IPs for stable access

Full Transcript

Pod-to-Pod communication in Kubernetes works by one pod sending a request to another pod's IP or DNS name. The Kubernetes network plugin routes the network packets between pods, even if they are on different nodes. Pod B receives the request, processes it, and sends a response back through the network plugin to Pod A. After Pod A receives the response, the connection closes, ending the communication. This process relies on Kubernetes networking and service discovery to enable pods to find and talk to each other.