Health checks configuration in GCP - Step-by-Step Execution

Process Flow - Health checks configuration

Start

↓

Define Health Check Parameters

↓

Create Health Check Resource

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Attach Health Check to Backend Service

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Health Check Runs Periodically

↓

Check Response Status

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Healthy?

Yes→Keep Backend Serving

No↓

Mark Backend as Unhealthy

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Stop Sending Traffic to Unhealthy Backend

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End

This flow shows how a health check is configured, attached, and used to monitor backend health, deciding traffic routing.

Execution Sample

GCP

gcloud compute health-checks create http my-health-check \
  --port 80 \
  --request-path /healthz \
  --check-interval 10s \
  --timeout 5s \
  --unhealthy-threshold 3 \
  --healthy-threshold 1

This command creates an HTTP health check that probes port 80 at path /healthz every 10 seconds, timing out after 5 seconds, marking unhealthy after 3 failures.

Process Table

Step	Action	Parameter/Value	Result/State
1	Define health check type	HTTP	Health check type set to HTTP
2	Set port	80	Health check will probe port 80
3	Set request path	/healthz	Health check requests /healthz path
4	Set check interval	10s	Health check runs every 10 seconds
5	Set timeout	5s	Health check waits 5 seconds for response
6	Set unhealthy threshold	3	Backend marked unhealthy after 3 failed checks
7	Create health check resource	my-health-check	Health check resource created
8	Attach to backend service	backend-service-1	Backend service linked to health check
9	Health check runs	First probe	Backend responds 200 OK, marked healthy
10	Health check runs	Second probe	Backend times out, failure count 1
11	Health check runs	Third probe	Backend times out, failure count 2
12	Health check runs	Fourth probe	Backend times out, failure count 3, marked unhealthy
13	Traffic routing	Backend unhealthy	Traffic stops routing to this backend
14	Health check runs	Backend recovers, responds 200 OK	Backend marked healthy again, traffic resumes

💡 Health check continuously runs; backend marked unhealthy after 3 failures and healthy after successful response.

Status Tracker

Variable	Start	After Step 9	After Step 12	After Step 14
failure_count	0	0	3	0
backend_health	unknown	healthy	unhealthy	healthy
traffic_routing	not set	routes to backend	stops routing	routes to backend

Key Moments - 3 Insights

Why does the backend only get marked unhealthy after 3 failed checks?

Because the unhealthy threshold is set to 3 (see execution_table step 6 and step 12), the system waits for 3 consecutive failures before marking unhealthy to avoid false positives.

What happens if the backend responds successfully after being unhealthy?

As shown in step 14, a successful response resets failure count and marks backend healthy again, resuming traffic routing.

Why is the timeout important in health checks?

Timeout (step 5) defines how long the check waits for a response; if exceeded, it counts as a failure, helping detect unresponsive backends.

Visual Quiz - 3 Questions

Look at the execution_table at which step does the backend become unhealthy?

A Step 12

B Step 10

C Step 9

D Step 14

💡 Hint

Check the 'Result/State' column in execution_table rows for failure count reaching 3.

According to variable_tracker, what is the failure_count after step 14?

A 3

B 0

C 1

D Unknown

💡 Hint

Look at the failure_count row in variable_tracker under 'After Step 14'.

If the check interval was changed from 10s to 5s, how would the execution_table change?

A Unhealthy threshold would change to 5

B Timeout would increase to 10s

C Health checks would run twice as often, steps 9-14 would happen faster

D Backend would never be marked unhealthy

💡 Hint

Check step 4 in execution_table about check interval and its effect on health check frequency.

Concept Snapshot

Health checks monitor backend health by sending requests at intervals.
Configure type, port, path, interval, timeout, and thresholds.
Failures count until unhealthy threshold marks backend unhealthy.
Healthy backends receive traffic; unhealthy ones do not.
Recovery happens when backend responds successfully again.

Full Transcript

Health checks configuration in GCP involves defining parameters like type (HTTP), port, request path, check interval, timeout, and unhealthy threshold. The health check resource is created and attached to a backend service. The health check runs periodically, sending requests to the backend. If the backend responds successfully, it is marked healthy and receives traffic. If it fails consecutively as per the unhealthy threshold, it is marked unhealthy and traffic stops routing to it. When the backend recovers and responds successfully, it is marked healthy again and traffic resumes. This process ensures only healthy backends serve traffic, improving reliability.