HTTP triggered functions in GCP - Step-by-Step Execution

Process Flow - HTTP triggered functions

Client sends HTTP request

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Cloud Function receives request

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Function executes code

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Function sends HTTP response

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Client receives response

This flow shows how an HTTP request from a client triggers a cloud function, which runs code and sends back a response.

Execution Sample

GCP

def hello_http(request):
    name = request.args.get('name', 'World')
    return f'Hello, {name}!'

A simple HTTP function that greets the user by name or says 'Hello, World!' if no name is given.

Process Table

Step	Action	Input	Processing	Output
1	Receive HTTP request	GET /?name=Alice	Parse query parameters	name = 'Alice'
2	Execute function	name = 'Alice'	Create greeting string	'Hello, Alice!'
3	Send HTTP response	'Hello, Alice!'	Return response body	HTTP 200 OK with body 'Hello, Alice!'
4	Client receives response	HTTP 200 OK	Display response	Shows 'Hello, Alice!' on client
5	Receive HTTP request	GET /	Parse query parameters	name = 'World' (default)
6	Execute function	name = 'World'	Create greeting string	'Hello, World!'
7	Send HTTP response	'Hello, World!'	Return response body	HTTP 200 OK with body 'Hello, World!'
8	Client receives response	HTTP 200 OK	Display response	Shows 'Hello, World!' on client

💡 Execution stops after sending HTTP response and client receives it.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 6	Final
name	undefined	'Alice'	'Alice'	'World'	'World'
response	undefined	undefined	'Hello, Alice!'	'Hello, World!'	'Hello, World!'

Key Moments - 2 Insights

Why does the function use a default value 'World' for the name?

If the HTTP request has no 'name' parameter (see step 5), the function uses 'World' so it can still return a friendly greeting (see steps 6-8).

How does the function know what the client sent in the HTTP request?

The function reads the query parameters from the request object (step 1), extracting 'name' if present.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'name' after step 1 when the client sends GET /?name=Alice?

A 'Alice'

B 'World'

C undefined

D 'Hello, Alice!'

💡 Hint

Check the 'Input' and 'Processing' columns in row 1 of the execution table.

At which step does the function send the HTTP response back to the client?

A Step 2

B Step 3

C Step 4

D Step 1

💡 Hint

Look for the step where 'Send HTTP response' is the action in the execution table.

If the client sends GET / without a name parameter, what will the function output be?

A 'Hello, Alice!'

B An error message

C 'Hello, World!'

D Empty response

💡 Hint

Check steps 5 to 8 in the execution table and the variable_tracker for 'name' default.

Concept Snapshot

HTTP triggered functions run code when they get an HTTP request.
They read data from the request (like query parameters).
They process the data and send back an HTTP response.
If data is missing, they can use default values.
Clients see the response as a web page or message.

Full Transcript

An HTTP triggered function waits for a client to send an HTTP request. When the request arrives, the function reads any data sent, like a 'name' parameter. It then runs its code to create a response message. For example, it might say 'Hello, Alice!' if the name is Alice, or 'Hello, World!' if no name is given. The function sends this message back as an HTTP response. The client then shows this message. This process repeats for each request.