Access a Lindorm database - Function Management| Alibaba Cloud Documentation Center

In Function Compute, you can use a function to call the Lindorm API to perform operations such as insert and query on a Lindorm instance. In normal cases, states cannot be shared among different execution environments in Function Compute. You can persist structured data in a database so that states can be shared. This topic describes how to use Funcraft to deploy a function to access a Lindorm database.

Prerequisites

You have created a virtual private cloud (VPC) and a VSwitch.
The VSwitch must belong to a zone supported by Function Compute. For more information about the zones supported by Function Compute, see VPC access.
A Lindorm instance that meets your business needs has been created.
You have created a database instance in same VPC as Function Compute. You do not need to create the VSwitch in the same zone as Function Compute. VSwitches under the same VPC can communicate with each other even when they are in different zones.
Configure a whitelist for an ApsaraDB RDS for PostgreSQL instance.
If you need to control access to databases by using an IP address whitelist, ensure that you have entered the internal Classless Inter-Domain Routing (CIDR) blocks of the target VPCs in the IP field. To find the CIDR block of a VPC, log on to the VPC console and view the VPC Details page.
Create a security group
You have configured the security group to allow outbound traffic from the internal CIDR block and port of the database.

Write a function

The following section describes how to use Funcraft to write a function that accesses a database. The sample code is written in Python 3.

On the local machine, create a directory to store code and dependent modules. In the directory, create the template.yml file. In this example, the /tmp/code/template.yml file is created and contains the following content:
```
ROSTemplateFormatVersion: '2015-09-01'
Transform: 'Aliyun::Serverless-2018-04-03'
Resources:
  service:
    Type: 'Aliyun::Serverless::Service'
    Properties:
      Description: This is Lindorm service
      Policies:
        - AliyunECSNetworkInterfaceManagementAccess
      VpcConfig:
        VpcId: vpc-XXXX
        VSwitchIds:
          - vsw-XXX
        SecurityGroupId: sg-XXXX
      InternetAccess: true
    function:
      Type: 'Aliyun::Serverless::Function'
      Properties:
        Handler: 'index.handler'
        Runtime: python3
        Timeout: 100
        MemorySize: 1024
        CodeUri: '. /'
```
The following list describes the main parameters:
- A service named service is declared.
  - Policies: grants Function Compute permission to manage elastic network interfaces (ENIs) attached to Elastic Compute Service (ECS) instances. Function Compute can then access resources in the VPC.
  - VpcConfig: binds the VPC to the service. You must replace the following values with the information for your VPC.
    - VpcId: the ID of the VPC.
    - VSwitchId: the ID of the VSwitch.
    - SecurityGroupId: the ID of the security group.
- A function named function is declared.
  - Initializer: the initializer function. For more information, see Initializer function.
  - Handler: the function handler. For more information, see Function entry point.
  - Runtime: the runtime environment of the function.
  - CodeUri: the directory where the code package is located.
    During function deployment, Funcraft packages and uploads the items in the directory specified by the CodeUri parameter.
In the directory that contains the template.yml file, create the Funfile file. In this example, the new file contains the following sample content:
```
RUNTIME python3
RUN fun-install pip install cassandra-driver
```
Run the fun install command to install dependencies.
```
fun install
```
When the code editor shows the following content, the dependencies have been installed.
```
Install Success
```

In the directory that contains the template.yml file, create a Python file. In this example, the /tmp/code/index.py file is created and contains the following sample content:

Note You can log on to the Lindorm console, find the destination instance, and obtain the endpoint, username, and password on the Wide Table Engine tab of the Database Connection page.

# -*- coding: utf-8 -*-
import logging
import sys
from cassandra.cluster import Cluster
from cassandra.auth import PlainTextAuthProvider

logger = logging.getLogger()

def handler(event, context):
    logger.info("start to test Lindorm ")
    cluster = Cluster(
        # Configure the endpoint.
        contact_points=["ld-bp10ljb1mxae5****-proxy-lindorm.lindorm.rds.aliyuncs.com"],
        # Configure the username and password.
        auth_provider=PlainTextAuthProvider("XXX", "XXX"))
    session = cluster.connect()
    session.execute("CREATE KEYSPACE IF NOT EXISTS testKeyspace WITH replication = {'class':'SimpleStrategy', 'replication_factor':1};");
    session.execute("CREATE TABLE IF NOT EXISTS testKeyspace.testTable (id int PRIMARY KEY, name text,age int,address text);");
    session.execute("INSERT INTO testKeyspace.testTable (id, name, age, address) VALUES ( 1, 'testname', 11, 'hangzhou');");
    rows = session.execute( "SELECT * FROM testKeyspace.testTable ;");
    for row in rows:
        logger.info("# row: {}".format(row))

    session.shutdown()
    cluster.shutdown()

Run the following command to deploy the function to Function Compute by using Funcraft:
```
fun deploy 
```
When the code editor shows the following content, the function has been deployed.
```
        function <function-name> deploy success
service <service-name> deploy success
```
After the deployment is complete, log on to the and click Service/Function. On the page that appears, you can see the newly deployed service and function.

Debug a function

After the function is deployed, you can debug it in the Function Compute console.

Log on to the Function Compute console.
In the top navigation bar, select a region.
In the left-side navigation pane, click Service/Function.
Find the required function in the required service and click the name of the function.
On the Code tab, click Invoke.
After the execution is complete, you can view the execution results and logs.