Function Compute:Access a Tair (Redis OSS-compatible) database example

Step 1: Initialize the project

Run the following command to initialize a project:

sudo s init

In the CLI prompts:

1. Select Alibaba Cloud as the vendor.

2. Choose the quick start mode.

3. Select a built-in Python runtime.

4. Specify the project name and region. This guide uses the start-fc-redis-python project in the China (Hangzhou) region.

Navigate to the project directory:

cd start-fc-redis-python

Step 2: Configure the project files

edition: 1.0.0
name: fcDeployApp
access: "default"

services:
 fc-db-redis-python:
  component: devsapp/fc
  props:
   region: cn-hangzhou
   service:
    name: fc-db-demo
    description: 'demo for fc visit db'
    internetAccess: true
    vpcConfig:
     vpcId: vpc-bp1oeg1fwxzuxcliq****       # VPC ID where the Tair instance resides
     securityGroupId: sg-bp164seaxj7wc4d0**** # Security group ID
     vswitchIds:
      - vsw-bp1192npo1ziqzw4****             # vSwitch ID (add its CIDR block to the Tair whitelist)
   function:
    name: redis
    description: visit redis
    runtime: python3
    codeUri: ./code
    handler: index.handler
    memorySize: 256
    timeout: 30
    initializationTimeout: 60
    initializer: index.initializer
    environmentVariables:
     REDIS_HOST: r-bp1h2g53l3thqg****.redis.rds.aliyuncs.com # Private endpoint of the Tair instance
     REDIS_PASSWORD: ****                                      # Tair instance password
     REDIS_PORT: 63**                                          # Private port of the Tair instance

# -*- coding: utf-8 -*-
import os
import redis

# Global connection pool, reused across function invocations to reduce latency
conn_pool = None


def initializer(context):
    """Initialize a Redis connection pool using environment variables."""
    global conn_pool
    conn_pool = redis.ConnectionPool(
        host=os.environ['REDIS_HOST'],
        password=os.environ['REDIS_PASSWORD'],
        port=os.environ['REDIS_PORT'],
        db=1,
        decode_responses=True
    )


def handler(event, context):
    """Read, increment, and write back a counter value in Tair."""
    global conn_pool
    r = redis.Redis(connection_pool=conn_pool)

    counter = r.get('counter')

    if counter is None:
        counter = 0
    else:
        counter = int(counter)

    print('counter: ' + str(counter))

    r.set('counter', str(counter + 1))
    return counter

Step 3: Build and deploy

Build the project:

sudo s build --use-docker

Deploy the project:

sudo s deploy -y

Step 4: Invoke and verify the function

sudo s invoke -e "{}"

Expected output:

[2021-09-14T17:08:50.875] [INFO ] [S-CLI] - Start ...
========= FC invoke Logs begin =========
FC Initialize Start RequestId: ccd73383-048d-4c8d-834e-93da59b86a21
FC Initialize End RequestId: ccd73383-048d-4c8d-834e-93da59b86a21
FC Invoke Start RequestId: eccafc0a-493e-4f3e-9afa-45c0b84a2c0f
counter: 0
FC Invoke End RequestId: eccafc0a-493e-4f3e-9afa-45c0b84a2c0f

Duration: 27.51 ms, Billed Duration: 28 ms, Memory Size: 256 MB, Max Memory Used: 34.05 MB
========= FC invoke Logs end =========

FC Invoke Result:
0


End of method: invoke

The returned value starts at 0 and increments with each invocation, confirming that the function reads and writes the counter key in the Tair instance. Run the invoke command multiple times to verify that the counter increments correctly: 0, 1, 2, and so on.

Connection timeout

Symptom: The function times out without returning a result.

Causes and solutions:

1. VPC misconfiguration: Verify that the vpcId, securityGroupId, and vswitchIds in s.yaml are correct and belong to the same VPC as the Tair instance.

2. Whitelist not configured: Confirm that the vSwitch CIDR block is added to the Tair instance whitelist. See Configure an IP address whitelist.

3. vSwitch in an unsupported zone: Create a vSwitch in a zone that Function Compute supports. See How can I resolve the "vSwitch is in unsupported zone" error?

Authentication failure

Symptom: The function returns a NOAUTH Authentication required, ERR invalid password, or WRONGPASS invalid username-password pair error.

Causes and solutions:

1. Incorrect password: Check the REDIS_PASSWORD environment variable in s.yaml.

2. Incorrect host or port: Verify that REDIS_HOST and REDIS_PORT match the private endpoint and port shown in the Tair console.

Dependency errors

Symptom: The function returns a ModuleNotFoundError: No module named 'redis' error.

Solution: Build the project with Docker before deploying:

sudo s build --use-docker
sudo s deploy -y

For more troubleshooting guidance, see Common errors and troubleshooting and How to troubleshoot database access failures?