Error handling in clients in Kafka - Step-by-Step Execution

Process Flow - Error handling in clients

Start Client

↓

Send/Receive Message

↓

Error Occurs?

No→Continue Normal Flow

Yes↓

Catch Error

↓

Handle Error

↓

Retry or Log or Alert

↓

Decide to Continue or Exit

↩Back to Send/Receive or Exit

The client sends or receives messages, checks for errors, catches them, handles them by retrying, logging, or alerting, then decides to continue or stop.

Execution Sample

Kafka

try {
  consumer.poll();
} catch (Exception e) {
  log.error("Error consuming message", e);
  // retry or alert
}

This code tries to poll messages from Kafka, catches any exceptions, logs the error, and can retry or alert.

Process Table

Step	Action	Error Occurs?	Error Caught?	Handling Action	Next Step
1	Start client and poll messages	No	No	None	Continue normal flow
2	Poll messages	Yes (e.g., network error)	Yes	Log error and retry	Retry polling
3	Retry polling	No	No	None	Continue normal flow
4	Poll messages	Yes (e.g., deserialization error)	Yes	Log error and alert	Decide to continue or exit
5	Decide to exit due to repeated errors	N/A	N/A	Exit client	Stop execution

💡 Client stops after deciding to exit due to repeated errors

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
errorOccurred	false	false	true	false	true	true
retryCount	0	0	1	1	1	1
clientRunning	true	true	true	true	true	false

Key Moments - 3 Insights

Why do we catch errors immediately after polling messages?

Because polling can fail due to network or data issues, catching errors right after polling lets us handle them before continuing, as shown in execution_table step 2.

What happens if the error keeps occurring after retries?

The client logs the error, alerts if needed, and may decide to stop running, as seen in execution_table step 4 and 5.

Why track retryCount variable?

To limit how many times the client retries polling before giving up, preventing infinite loops, as shown in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table, at which step does the client first catch an error?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Check the 'Error Caught?' column in execution_table rows

According to variable_tracker, what is the value of retryCount after step 3?

A 1

B 0

C 2

D Undefined

💡 Hint

Look at retryCount row and After Step 3 column in variable_tracker

If the client never catches an error, what would happen to clientRunning variable?

A It would become false immediately

B It would toggle between true and false

C It would stay true and continue running

D It would cause an error

💡 Hint

Refer to variable_tracker clientRunning values when no errors occur

Concept Snapshot

try { poll messages } catch(error) { handle error }
Handle errors by logging, retrying, or alerting
Track retries to avoid infinite loops
Decide to continue or stop client based on error severity
Keep client running if no errors occur

Full Transcript

This visual execution shows how a Kafka client handles errors during message polling. The client starts polling messages. If no error occurs, it continues normally. If an error occurs, it is caught immediately. The client then logs the error and may retry polling. If errors persist, it alerts and decides whether to continue or stop. Variables like errorOccurred, retryCount, and clientRunning track the client's state through these steps. Key moments include catching errors right after polling, handling repeated errors by stopping, and tracking retries to prevent infinite loops.