Configuring Redis with ElastiCache and ElasticBeanstalk on AWS

Question

I have a Tomcat + Redis app running on Elastic Beanstalk. In my code, I create a Redis client using

pool = new JedisPool(new JedisPoolConfig(), "localhost");

Of course, in production, I can't use "localhost" I've read through Customizing the Beanstalk Environment and about getting autodiscovery to work with your code, but that seems to only apply to Memcached.

Has anyone gotten a Redis ElastiCache cluster configured with Beanstalk. Where do you get the DNS address to use instead of "localhost"?

Answer 1

I'm afraid that you can't get the AWS ElastiCache endpoint easily (e.g: environment variable).

From AWS documentation on Deploying an Express Application with Clustering to Elastic Beanstalk, we can follow the NodeJS + ElastiCache Memcache solution. Create the two following .ebextensions (read more here) scripts in your root project:

.ebextenstions/elasticache-iam-with-script.config

## 
# This sample adds an ElastiCache cluster to the environment.
#  It creates an IAM user with the permisisons required to discover the elasticache nodes.  
#  It provides a cfn-hup responder if the cache changes to rewrite the file
#  It writes a file out to:  /var/www/html/nodelist
#   containing the cache nodes on startup and when the cache changes (through a cfn/eb update)
#
# Customers would generally not edit this file.
# Instead, they would have another file sitting in the same directory (or anywhere) with 
#  an option-settings section such as the following (all of these are showing the default value)
#
# option-settings:
#  "aws:elasticbeanstalk:customoption" :
#     CacheNodeType : cache.m1.small
#     NumCacheNodes : 1
#     Engine : memcached
#     NodeListPath : /var/www/html/nodelist
#
# Issues:
#   Requires ElastiCache CLI latest URL to point to version 1.7
##


Resources:
  MyElastiCache:
    Type: AWS::ElastiCache::CacheCluster
    Properties:
      CacheNodeType: 
         Fn::GetOptionSetting:
             OptionName : CacheNodeType
             DefaultValue: cache.m1.small
      NumCacheNodes: 
           Fn::GetOptionSetting:
             OptionName : NumCacheNodes
             DefaultValue: 1
      Engine: 
           Fn::GetOptionSetting:
             OptionName : Engine
             DefaultValue: memcached
      CacheSecurityGroupNames:
        - Ref: MyCacheSecurityGroup
  MyCacheSecurityGroup:
    Type: AWS::ElastiCache::SecurityGroup
    Properties:
      Description: "Lock cache down to webserver access only"
  MyCacheSecurityGroupIngress:
    Type: AWS::ElastiCache::SecurityGroupIngress
    Properties:
      CacheSecurityGroupName: 
        Ref: MyCacheSecurityGroup
      EC2SecurityGroupName:
        Ref: AWSEBSecurityGroup
  AWSEBAutoScalingGroup :
    Metadata :
      ElastiCacheConfig :
        CacheName :
          Ref : MyElastiCache
        CacheSize :
           Fn::GetOptionSetting:
             OptionName : NumCacheNodes
             DefaultValue: 1
  WebServerUser : 
    Type : AWS::IAM::User
    Properties :
      Path : "/"
      Policies:
        -
          PolicyName: root
          PolicyDocument :
            Statement :
              -
                Effect : Allow
                Action : 
                  - cloudformation:DescribeStackResource
                  - cloudformation:ListStackResources
                  - elasticache:DescribeCacheClusters
                Resource : "*"
  WebServerKeys :
    Type : AWS::IAM::AccessKey
    Properties :
      UserName :
        Ref: WebServerUser

Outputs:
  WebsiteURL:
    Description: sample output only here to show inline string function parsing
    Value: |
      http://`{ "Fn::GetAtt" : [ "AWSEBLoadBalancer", "DNSName" ] }`
  MyElastiCacheName:
    Description: Name of the elasticache
    Value:
      Ref : MyElastiCache
  NumCacheNodes:
    Description: Number of cache nodes in MyElastiCache
    Value:
      Fn::GetOptionSetting:
        OptionName : NumCacheNodes
        DefaultValue: 1

files:
  "/etc/cfn/cfn-credentials" :
    content : |
      AWSAccessKeyId=`{ "Ref" : "WebServerKeys" }`
      AWSSecretKey=`{ "Fn::GetAtt" : ["WebServerKeys", "SecretAccessKey"] }`
    mode : "000400"
    owner : root
    group : root

  "/etc/cfn/get-cache-nodes" :
    content : |
      # Define environment variables for command line tools
      export AWS_ELASTICACHE_HOME="/home/ec2-user/elasticache/$(ls /home/ec2-user/elasticache/)"
      export AWS_CLOUDFORMATION_HOME=/opt/aws/apitools/cfn
      export PATH=$AWS_CLOUDFORMATION_HOME/bin:$AWS_ELASTICACHE_HOME/bin:$PATH
      export AWS_CREDENTIAL_FILE=/etc/cfn/cfn-credentials
      export JAVA_HOME=/usr/lib/jvm/jre

      # Grab the Cache node names and configure the PHP page
      cfn-list-stack-resources `{ "Ref" : "AWS::StackName" }` --region `{ "Ref" : "AWS::Region" }` | grep MyElastiCache | awk '{print $3}' | xargs -I {} elasticache-describe-cache-clusters {} --region `{ "Ref" : "AWS::Region" }` --show-cache-node-info | grep CACHENODE | awk '{print $4 ":" $5}' > `{ "Fn::GetOptionSetting" : { "OptionName" : "NodeListPath", "DefaultValue" : "/var/www/html/nodelist" } }`
    mode : "000500"
    owner : root
    group : root

  "/etc/cfn/hooks.d/cfn-cache-change.conf" :
    "content": |
      [cfn-cache-size-change]
      triggers=post.update
      path=Resources.AWSEBAutoScalingGroup.Metadata.ElastiCacheConfig
      action=/etc/cfn/get-cache-nodes
      runas=root

sources :
  "/home/ec2-user/elasticache" : "https://s3.amazonaws.com/elasticache-downloads/AmazonElastiCacheCli-latest.zip"

commands: 
  make-elasticache-executable:
    command: chmod -R ugo+x /home/ec2-user/elasticache/*/bin/*

packages : 
  "yum" :
    "aws-apitools-cfn"  : []

container_commands:
  initial_cache_nodes:
    command: /etc/cfn/get-cache-nodes

.ebextensions/elasticache-settings.config

option_settings:
  "aws:elasticbeanstalk:customoption" :
    CacheNodeType : cache.t2.micro
    NumCacheNodes : 1
    Engine : redis
    NodeListPath : /var/nodelist

The first script (elasticache-iam-with-script.config) is used to create an ElastiCache resource which is attached to your Elastic Beanstalk environment.

The second script (elasticache-settings.config) is the custom configuration file for the first script. You may change the configuration as your need.

The first script will generate a file in /var/nodelist. The content of file looks like:

aws-my-xxxxxxxxxxxxx.xxxxxx.0001.use1.cache.amazonaws.com:us-east-1b

It's an endpoint and AZ pair which is separated by an colon (<endpoint>:<AZ>). Your Java may parse /var/nodelist and take the endpoint into the JedisPool.