Connecting to a Redis instance from an App Engine flexible environment application

App Engine applications must be on the same authorized network as the Redis instance in order to access it.

Setup

If you have already installed the Google Cloud CLI and have created a Redis instance, you can skip these steps.

Install the gcloud CLI and initialize:
```
 gcloud init 
```
Follow the Quickstart Guide to create a Redis instance. Take note of the zone, IP address, and port of the Redis instance.

Sample application

This sample HTTP server application establishes a connection to a Redis instance from an App Engine flexible environment instance.

Clone the repository for your desired programming language and navigate to the folder that contains the sample code:

Go

  git 
  
 clone 
  
 https 
 : 
 //github.com/GoogleCloudPlatform/golang-samples 
 cd 
  
 golang 
 - 
 samples 
 / 
 memorystore 
 / 
 redis

Java

  git 
  
 clone 
  
 https 
 : 
 //github.com/GoogleCloudPlatform/java-docs-samples 
 cd 
  
 java 
 - 
 docs 
 - 
 samples 
 / 
 memorystore 
 / 
 redis

Node.js

  git 
  
 clone 
  
 https 
 : 
 //github.com/GoogleCloudPlatform/nodejs-docs-samples 
 cd 
  
 nodejs 
 - 
 docs 
 - 
 samples 
 / 
 memorystore 
 / 
 redis

Python

  git 
 clone 
 https 
 : 
 // 
 github 
 . 
 com 
 / 
 GoogleCloudPlatform 
 / 
 python 
 - 
 docs 
 - 
 samples 
 cd 
 python 
 - 
 docs 
 - 
 samples 
 / 
 memorystore 
 / 
 redis

This sample application increments a Redis counter every time the / endpoint is accessed.

Go

This application uses the github.com/gomodule/redigo/redis client. Install it by running the following command:

  go 
  
 get 
  
 github 
 . 
 com 
 / 
 gomodule 
 / 
 redigo 
 / 
 redis

  // Command redis is a basic app that connects to a managed Redis instance. 
 package 
  
 main 
 import 
  
 ( 
  
 "fmt" 
  
 "log" 
  
 "net/http" 
  
 "os" 
  
 "github.com/gomodule/redigo/redis" 
 ) 
 var 
  
 redisPool 
  
 * 
 redis 
 . 
 Pool 
 func 
  
 incrementHandler 
 ( 
 w 
  
 http 
 . 
 ResponseWriter 
 , 
  
 r 
  
 * 
 http 
 . 
 Request 
 ) 
  
 { 
  
 conn 
  
 := 
  
 redisPool 
 . 
 Get 
 () 
  
 defer 
  
 conn 
 . 
 Close 
 () 
  
 counter 
 , 
  
 err 
  
 := 
  
 redis 
 . 
 Int 
 ( 
 conn 
 . 
 Do 
 ( 
 "INCR" 
 , 
  
 "visits" 
 )) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 http 
 . 
 Error 
 ( 
 w 
 , 
  
 "Error incrementing visitor counter" 
 , 
  
 http 
 . 
 StatusInternalServerError 
 ) 
  
 return 
  
 } 
  
 fmt 
 . 
 Fprintf 
 ( 
 w 
 , 
  
 "Visitor number: %d" 
 , 
  
 counter 
 ) 
 } 
 func 
  
 main 
 () 
  
 { 
  
 redisHost 
  
 := 
  
 os 
 . 
 Getenv 
 ( 
 "REDISHOST" 
 ) 
  
 redisPort 
  
 := 
  
 os 
 . 
 Getenv 
 ( 
 "REDISPORT" 
 ) 
  
 redisAddr 
  
 := 
  
 fmt 
 . 
 Sprintf 
 ( 
 "%s:%s" 
 , 
  
 redisHost 
 , 
  
 redisPort 
 ) 
  
 const 
  
 maxConnections 
  
 = 
  
 10 
  
 redisPool 
  
 = 
  
& redis 
 . 
 Pool 
 { 
  
 MaxIdle 
 : 
  
 maxConnections 
 , 
  
 Dial 
 : 
  
 func 
 () 
  
 ( 
 redis 
 . 
 Conn 
 , 
  
 error 
 ) 
  
 { 
  
 return 
  
 redis 
 . 
 Dial 
 ( 
 "tcp" 
 , 
  
 redisAddr 
 ) 
  
 }, 
  
 } 
  
 http 
 . 
 HandleFunc 
 ( 
 "/" 
 , 
  
 incrementHandler 
 ) 
  
 port 
  
 := 
  
 os 
 . 
 Getenv 
 ( 
 "PORT" 
 ) 
  
 if 
  
 port 
  
 == 
  
 "" 
  
 { 
  
 port 
  
 = 
  
 "8080" 
  
 } 
  
 log 
 . 
 Printf 
 ( 
 "Listening on port %s" 
 , 
  
 port 
 ) 
  
 if 
  
 err 
  
 := 
  
 http 
 . 
 ListenAndServe 
 ( 
 ":" 
 + 
 port 
 , 
  
 nil 
 ); 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 log 
 . 
 Fatal 
 ( 
 err 
 ) 
  
 } 
 }

Java

This application is Jetty 3.1 servlet-based.

It uses the Jedis library:

 <dependency>  
<groupId>redis.clients</groupId>  
<artifactId>jedis</artifactId>  
<version>5.1.0</version>
</dependency>

The AppServletContextListener class is used to create a long-lived Redis connection pool:

  package 
  
 com.example.redis 
 ; 
 import 
  
 java.io.IOException 
 ; 
 import 
  
 java.util.Properties 
 ; 
 import 
  
 javax.servlet.ServletContextEvent 
 ; 
 import 
  
 javax.servlet.ServletContextListener 
 ; 
 import 
  
 javax.servlet.annotation.WebListener 
 ; 
 import 
  
 redis.clients.jedis.JedisPool 
 ; 
 import 
  
 redis.clients.jedis.JedisPoolConfig 
 ; 
 @WebListener 
 public 
  
 class 
 AppServletContextListener 
  
 implements 
  
 ServletContextListener 
  
 { 
  
 private 
  
 Properties 
  
 config 
  
 = 
  
 new 
  
 Properties 
 (); 
  
 private 
  
 JedisPool 
  
 createJedisPool 
 () 
  
 throws 
  
 IOException 
  
 { 
  
 String 
  
 host 
 ; 
  
 Integer 
  
 port 
 ; 
  
 config 
 . 
 load 
 ( 
  
 Thread 
 . 
 currentThread 
 () 
  
 . 
 getContextClassLoader 
 () 
  
 . 
 getResourceAsStream 
 ( 
 "application.properties" 
 )); 
  
 host 
  
 = 
  
 config 
 . 
 getProperty 
 ( 
 "redis.host" 
 ); 
  
 port 
  
 = 
  
 Integer 
 . 
 valueOf 
 ( 
 config 
 . 
 getProperty 
 ( 
 "redis.port" 
 , 
  
 "6379" 
 )); 
  
 JedisPoolConfig 
  
 poolConfig 
  
 = 
  
 new 
  
 JedisPoolConfig 
 (); 
  
 // Default : 8, consider how many concurrent connections into Redis you will need under load 
  
 poolConfig 
 . 
 setMaxTotal 
 ( 
 128 
 ); 
  
 return 
  
 new 
  
 JedisPool 
 ( 
 poolConfig 
 , 
  
 host 
 , 
  
 port 
 ); 
  
 } 
  
 @Override 
  
 public 
  
 void 
  
 contextDestroyed 
 ( 
 ServletContextEvent 
  
 event 
 ) 
  
 { 
  
 JedisPool 
  
 jedisPool 
  
 = 
  
 ( 
 JedisPool 
 ) 
  
 event 
 . 
 getServletContext 
 (). 
 getAttribute 
 ( 
 "jedisPool" 
 ); 
  
 if 
  
 ( 
 jedisPool 
  
 != 
  
 null 
 ) 
  
 { 
  
 jedisPool 
 . 
 destroy 
 (); 
  
 event 
 . 
 getServletContext 
 (). 
 setAttribute 
 ( 
 "jedisPool" 
 , 
  
 null 
 ); 
  
 } 
  
 } 
  
 // Run this before web application is started 
  
 @Override 
  
 public 
  
 void 
  
 contextInitialized 
 ( 
 ServletContextEvent 
  
 event 
 ) 
  
 { 
  
 JedisPool 
  
 jedisPool 
  
 = 
  
 ( 
 JedisPool 
 ) 
  
 event 
 . 
 getServletContext 
 (). 
 getAttribute 
 ( 
 "jedisPool" 
 ); 
  
 if 
  
 ( 
 jedisPool 
  
 == 
  
 null 
 ) 
  
 { 
  
 try 
  
 { 
  
 jedisPool 
  
 = 
  
 createJedisPool 
 (); 
  
 event 
 . 
 getServletContext 
 (). 
 setAttribute 
 ( 
 "jedisPool" 
 , 
  
 jedisPool 
 ); 
  
 } 
  
 catch 
  
 ( 
 IOException 
  
 e 
 ) 
  
 { 
  
 // handle exception 
  
 } 
  
 } 
  
 } 
 }

The VisitCounterServlet class is a web servlet that increments a Redis counter:

  package 
  
 com.example.redis 
 ; 
 import 
  
 java.io.IOException 
 ; 
 import 
  
 java.net.SocketException 
 ; 
 import 
  
 javax.servlet.annotation.WebServlet 
 ; 
 import 
  
 javax.servlet.http.HttpServlet 
 ; 
 import 
  
 javax.servlet.http.HttpServletRequest 
 ; 
 import 
  
 javax.servlet.http.HttpServletResponse 
 ; 
 import 
  
 redis.clients.jedis.Jedis 
 ; 
 import 
  
 redis.clients.jedis.JedisPool 
 ; 
 @WebServlet 
 ( 
 name 
  
 = 
  
 "Track visits" 
 , 
  
 value 
  
 = 
  
 "" 
 ) 
 public 
  
 class 
 VisitCounterServlet 
  
 extends 
  
 HttpServlet 
  
 { 
  
 @Override 
  
 public 
  
 void 
  
 doGet 
 ( 
 HttpServletRequest 
  
 req 
 , 
  
 HttpServletResponse 
  
 resp 
 ) 
  
 throws 
  
 IOException 
  
 { 
  
 try 
  
 { 
  
 JedisPool 
  
 jedisPool 
  
 = 
  
 ( 
 JedisPool 
 ) 
  
 req 
 . 
 getServletContext 
 (). 
 getAttribute 
 ( 
 "jedisPool" 
 ); 
  
 if 
  
 ( 
 jedisPool 
  
 == 
  
 null 
 ) 
  
 { 
  
 throw 
  
 new 
  
 SocketException 
 ( 
 "Error connecting to Jedis pool" 
 ); 
  
 } 
  
 Long 
  
 visits 
 ; 
  
 try 
  
 ( 
 Jedis 
  
 jedis 
  
 = 
  
 jedisPool 
 . 
 getResource 
 ()) 
  
 { 
  
 visits 
  
 = 
  
 jedis 
 . 
 incr 
 ( 
 "visits" 
 ); 
  
 } 
  
 resp 
 . 
 setStatus 
 ( 
 HttpServletResponse 
 . 
 SC_OK 
 ); 
  
 resp 
 . 
 getWriter 
 (). 
 println 
 ( 
 "Visitor counter: " 
  
 + 
  
 String 
 . 
 valueOf 
 ( 
 visits 
 )); 
  
 } 
  
 catch 
  
 ( 
 Exception 
  
 e 
 ) 
  
 { 
  
 resp 
 . 
 sendError 
 ( 
 HttpServletResponse 
 . 
 SC_INTERNAL_SERVER_ERROR 
 , 
  
 e 
 . 
 getMessage 
 ()); 
  
 } 
  
 } 
 }

Node.js

This application uses the redis module.

  { 
  
 "name" 
 : 
  
 "memorystore-redis" 
 , 
  
 "description" 
 : 
  
 "An example of using Memorystore(Redis) with Node.js" 
 , 
  
 "version" 
 : 
  
 "0.0.1" 
 , 
  
 "private" 
 : 
  
 true 
 , 
  
 "license" 
 : 
  
 "Apache Version 2.0" 
 , 
  
 "author" 
 : 
  
 "Google Inc." 
 , 
  
 "engines" 
 : 
  
 { 
  
 "node" 
 : 
  
 ">=16.0.0" 
  
 }, 
  
 "dependencies" 
 : 
  
 { 
  
 "redis" 
 : 
  
 "^4.0.0" 
  
 } 
 }

  'use strict' 
 ; 
 const 
  
 http 
  
 = 
  
 require 
 ( 
 'http' 
 ); 
 const 
  
 redis 
  
 = 
  
 require 
 ( 
 'redis' 
 ); 
 const 
  
 REDISHOST 
  
 = 
  
 process 
 . 
 env 
 . 
 REDISHOST 
  
 || 
  
 'localhost' 
 ; 
 const 
  
 REDISPORT 
  
 = 
  
 process 
 . 
 env 
 . 
 REDISPORT 
  
 || 
  
 6379 
 ; 
 const 
  
 client 
  
 = 
  
 redis 
 . 
 createClient 
 ( 
 REDISPORT 
 , 
  
 REDISHOST 
 ); 
 client 
 . 
 on 
 ( 
 'error' 
 , 
  
 err 
  
 = 
>  
 console 
 . 
 error 
 ( 
 'ERR:REDIS:' 
 , 
  
 err 
 )); 
 // create a server 
 http 
  
 . 
 createServer 
 (( 
 req 
 , 
  
 res 
 ) 
  
 = 
>  
 { 
  
 // increment the visit counter 
  
 client 
 . 
 incr 
 ( 
 'visits' 
 , 
  
 ( 
 err 
 , 
  
 reply 
 ) 
  
 = 
>  
 { 
  
 if 
  
 ( 
 err 
 ) 
  
 { 
  
 console 
 . 
 log 
 ( 
 err 
 ); 
  
 res 
 . 
 status 
 ( 
 500 
 ). 
 send 
 ( 
 err 
 . 
 message 
 ); 
  
 return 
 ; 
  
 } 
  
 res 
 . 
 writeHead 
 ( 
 200 
 , 
  
 { 
 'Content-Type' 
 : 
  
 'text/plain' 
 }); 
  
 res 
 . 
 end 
 ( 
 `Visitor number: 
 ${ 
 reply 
 } 
 \n` 
 ); 
  
 }); 
  
 }) 
  
 . 
 listen 
 ( 
 8080 
 );

Python

This application uses Flask for web serving and the redis-py package to communicate with the Redis instance.

  Flask 
 == 
 3.0.3 
 gunicorn 
 == 
 23.0.0 
 redis 
 == 
 6.0.0 
 Werkzeug 
 == 
 3.0.3

  import 
  
 logging 
 import 
  
 os 
 from 
  
 flask 
  
 import 
 Flask 
 import 
  
 redis 
 app 
 = 
 Flask 
 ( 
 __name__ 
 ) 
 redis_host 
 = 
 os 
 . 
 environ 
 . 
 get 
 ( 
 "REDISHOST" 
 , 
 "localhost" 
 ) 
 redis_port 
 = 
 int 
 ( 
 os 
 . 
 environ 
 . 
 get 
 ( 
 "REDISPORT" 
 , 
 6379 
 )) 
 redis_client 
 = 
 redis 
 . 
 StrictRedis 
 ( 
 host 
 = 
 redis_host 
 , 
 port 
 = 
 redis_port 
 ) 
 @app 
 . 
 route 
 ( 
 "/" 
 ) 
 def 
  
 index 
 (): 
 value 
 = 
 redis_client 
 . 
 incr 
 ( 
 "counter" 
 , 
 1 
 ) 
 return 
 f 
 "Visitor number: 
 { 
 value 
 } 
 " 
 @app 
 . 
 errorhandler 
 ( 
 500 
 ) 
 def 
  
 server_error 
 ( 
 e 
 ): 
 logging 
 . 
 exception 
 ( 
 "An error occurred during a request." 
 ) 
 return 
 ( 
  
 """ 
 An internal error occurred: <pre>{}</pre> 
 See logs for full stacktrace. 
 """ 
 . 
 format 
 ( 
 e 
 ), 
 500 
 , 
 ) 
 if 
 __name__ 
 == 
 "__main__" 
 : 
 # This is used when running locally. Gunicorn is used to run the 
 # application on Google App Engine and Cloud Run. 
 # See entrypoint in app.yaml or Dockerfile. 
 app 
 . 
 run 
 ( 
 host 
 = 
 "127.0.0.1" 
 , 
 port 
 = 
 8080 
 , 
 debug 
 = 
 True 
 )

Preparing the application for deployment

To access the Redis instance, the App Engine instance must be deployed on the same authorized network as the Redis instance, and you must provide your Redis instance's connection details. You can find your Redis instance's authorized network, IP address, and port by running the following command:

   
 gcloud 
  
 redis 
  
 instances 
  
 describe 
  
 [ 
 INSTANCE_ID 
 ] 
  
 --region [REGION]

Create an App Engine application .

Note: You can also use an existing App Engine application.

Update the app's configuration to specify the IP address, port, and network of your Redis instance:

Go

Update the gae_flex_deployment/app.yaml file:

  runtime 
 : 
  
 go 
 env 
 : 
  
 flex 
 # Update with Redis instance details 
 env_variables 
 : 
  
 REDISHOST 
 : 
  
 '<REDIS_IP>' 
  
 REDISPORT 
 : 
  
 '6379' 
 # Update with Redis instance network name 
 network 
 : 
  
 name 
 : 
  
 default

See Configuring your App with app.yaml for more details.

Java

Update the gae_flex_deployment/app.yaml file to specify your Redis instance's network:

  runtime 
 : 
  
 java 
 env 
 : 
  
 flex 
 # Update with Redis instance network name 
 network 
 : 
  
 name 
 : 
  
 default

And update the src/main/resources/application.properties file with your Redis instance's IP address and port:

  redis 
 . 
 host 
 = 
 REDIS_HOST_IP 
 redis 
 . 
 port 
 = 
 6379

For more information about configuring your app, see Configuring your App with app.yaml .

Node.js

Update the gae_flex_deployment/app.yaml file:

  runtime 
 : 
  
 nodejs 
 env 
 : 
  
 flex 
 # Update with Redis instance details 
 env_variables 
 : 
  
 REDISHOST 
 : 
  
 '<REDIS_IP>' 
  
 REDISPORT 
 : 
  
 '6379' 
 # Update with Redis instance network name 
 network 
 : 
  
 name 
 : 
  
 default

See Configuring your App with app.yaml for more details.

Python

Update the gae_flex_deployment/app.yaml file:

  runtime 
 : 
  
 python 
 env 
 : 
  
 flex 
 entrypoint 
 : 
  
 gunicorn -b :$PORT main:app 
 runtime_config 
 : 
  
 python_version 
 : 
  
 3 
 # Update with Redis instance IP and port 
 env_variables 
 : 
  
 REDISHOST 
 : 
  
 '<REDIS_IP>' 
  
 REDISPORT 
 : 
  
 '6379' 
 # Update with Redis instance network name 
 network 
 : 
  
 name 
 : 
  
 default

See Configuring your App with app.yaml for more details.

Deploying the application to the App Engine flexible environment

To deploy the application:

Copy necessary configuration files into the source directory:

Go

Copy the app.yaml file into the source directory:

  cp 
  
 gae_flex_deployment 
 / 
 app 
 . 
 yaml 
  
 .

Java

Copy the app.yaml file into the source directory:

  mkdir 
  
 - 
 p 
  
 src 
 / 
 main 
 / 
 appengine 
 cp 
  
 gae_flex_deployment 
 / 
 app 
 . 
 yaml 
  
 src 
 / 
 main 
 / 
 appengine 
 /

Node.js

Copy the app.yaml file into the source directory:

  cp 
  
 gae_flex_deployment 
 / 
 app 
 . 
 yaml 
  
 .

Python

Copy the app.yaml file into the source directory:

  cp 
 gae_flex_deployment 
 / 
 app 
 . 
 yaml 
 .

Run the deploy command:

Go

  gcloud 
  
 app 
  
 deploy

This might take a few minutes.

Java

  mvn 
  
 appengine 
 : 
 deploy

This might take a few minutes.

Node.js

  gcloud 
  
 app 
  
 deploy

This might take a few minutes.

Python

  gcloud 
 app 
 deploy

This might take a few minutes.

After the deployment is complete, visit your app at the following URL, replacing [PROJECT_ID] with your Google Cloud project ID:

https://[PROJECT_ID].appspot.com

The count on your Redis instance increases each time the app is visited.

Connecting to a Redis instance from an App Engine flexible environment application Stay organized with collections Save and categorize content based on your preferences.

Setup

Sample application

Go

Java

Node.js

Python

Go

Java

Node.js

Python

Preparing the application for deployment

Go

Java

Node.js

Python

Deploying the application to the App Engine flexible environment

Go

Java

Node.js

Python

Go

Java

Node.js

Python

Connecting to a Redis instance from an App Engine flexible environment application