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Using a9s Redis

This section describes how to use a9s Redis.

Use a9s Redis with an Application

To use a9s Redis with an application, create a service instance and bind the service instance to your app. For more information about managing service instances, see Managing Service Instances with the cf CLI.

View the a9s Redis Service

After the tile is installed, you can see the redis32 and its service plans appear in your CF marketplace. Run cf marketplace to see the service listing:

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$ cf marketplace
Getting services from marketplace in org test / space test as admin...
OK
service    plans                     description
redis32    redis-xs, redis-m    This is the anynines Redis 32 service.

Create a Service Instance

To provision a Redis database, run cf create-service. For example.

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cf create-service redis32 redis-xs my-redis-service

Depending on your infrastructure and service broker utilization, it might take several minutes to create the service instance.

Run the cf services command to view the creation status. This command displays a list of all your service instances. To view the status of a specific service instance, run cf service NAME-OF-YOUR-SERVICE.

Bind an Application to a Service Instance

After your database is created, run cf bind-service to bind the service to your application:

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cf bind-service redis-app my-redis-service

Restage or Restart Your Application

To enable your application to access the service instance, run cf restage or cf restart to restage or restart your application.

Obtain Service Instance Access Credentials

After a service instance is bound to an application, the credentials of your Redis database are stored in the environment variables of the application. Run cf env APP-NAME to display the environment variables.

You can find the credentials in the VCAP_SERVICES key.

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$ cf env redis-app
Getting env variables for app redis-app in org test / space test as admin...
OK

System-Provided:
{
 "VCAP_SERVICES": {
  "redis": [
   {
    "credentials": {
     "host": "EXAMPLE-HOST",
     "password": "EXAMPLE-PWD",
     "port": 6379
    },
    "label": "redis",
    "name": "my-redis-service",
    "plan": "redis-xs",
   }
  ]
 }
}
...

You can use the host and password values to connect to your database with a Redis client.

Delete an a9s Redis Service Instance

Warning

Before deleting a service instance, you must backup data stored in your database. This operation cannot be undone and all the data is lost when the service is deleted.

Before you can delete a service instance, you must unbind it from all apps.

List Available Services

Run cf services to list available services.

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$ cf services

Getting services in org test / space test as admin...
OK

name                 service       plan                   bound apps        last operation
my-redis-service     redis     redis-xs     redis-app     create succeeded

This example shows that my-redis-service is bound to the redis-app application.

Unbind a Service Instance

Run cf unbind-service to unbind the service from your app:

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cf unbind-service redis-app my-redis-service

Delete a Service Instance

After unbinding the service, it is no longer bound to an app. Run cf delete-service to delete the service:

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cf delete-service my-redis-service

It may take several minutes to delete the service. Deleting a service deprovisions the corresponding infrastructure resources. Run the cf services command to view the deletion status.

Upgrade the Service Instance to another Service Plan

Once created, you can upgrade your service instance to another, larger service plan. A larger service plan provides more CPU, RAM and storage. For more information, refer to Update a Service Instance.

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cf update-service my-redis-service -p a-bigger-plan

Here are the plans you can upgrade to depending on the one you are currently using:

  • If you are currently using the redis-xs plan, you can upgrade to redis-m plan.

Change RDB Persistence Settings

a9s Redis supports RDB persistence with point in time snapshots. This setting can be changed by the user.

Default Behavior

Setting Effect
save 900 1 Create a snapshot after 900 seconds if 1 write operations occurred.
save 300 10 Create a snapshot after 300 seconds if 10 write operations occurred.
save 60 10000 Create a snapshot after 300 seconds if 10 write operations occurred.

Configuring RDB

You can configure RDB according to the needs of your apps by providing customer settings. This setting must follow the original Redis configuration for RDB -c {"snapshot": "['save 900 1', 'save 300 10']"}.

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cf update-service my-redis-service -c {"snapshot": "['save 900 1', 'save 300 10']"}

In this example, it configures to snapshot the Redis database according to the following rules:

Setting Effect
save 900 1 Create a snapshot after 900 seconds if 1 write operations occurred.
save 300 10 Create a snapshot after 300 seconds if 10 write operations occurred.

Cache Only

You can disable snapshots and use Redis as cache only by creating the service with the following customer setting -c '{"snapshot": "[]"}'.

The command is:

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cf update-service my-redis-service -c {"snapshot": "[]"}

For more information, see the snapshot settings in the documentation of Redis Persistence.

Change Maxmemory Policy

With the maxmemory_policy, you can configure a9s Redis which key to remove when maxmemory is reached. Ther are several configurable behaviors. noeviction is the default.

Setting Effect
volatile-lru remove the key with an expire set using an LRU algorithm
allkeys-lru remove any key according to the LRU algorithm
volatile-random remove a random key with an expire set
allkeys-random remove a random key, any key
volatile-ttl remove the key with the nearest expire time (minor TTL)
noeviction don't expire at all, just return an error on write operations

You can use -c {"maxmemory_policy": "volatile-ttl"} to update the maxmemory-policy.

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cf update-service my-redis-service -c {"maxmemory_policy": "volatile-ttl"}

For more information, see the maxmemory-policy settings in the self documented redis.conf.

HA Cluster with Redis Sentinel

a9s Redis uses Redis Sentinel to provide a high available replication set. Redis Sentinel is monitoring the several nodes, takes care about the automatic failover and is able to send notifcation when something in the cluster is changing.

a9s Redis provides two settings to adjust the cluster behaviour. min_slaves_max_lag and down_after_milliseconds

Setting Effect
min_slaves_max_lag Time in seconds how long the master waits before he stops accepting writes when slaves are no more reachable. Default is 10 seconds. min-slaves-to-write can not be changed, it is fxed set to 1. See redis.conf
down_after_milliseconds Number of milliseconds the master should be unreachable in order to consider it in S_DOWN state. Default is 30000 ms. See sentinel.conf
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cf update-service my-redis-service -c {"min_slaves_max_lag": "10"}
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cf update-service my-redis-service -c {"down_after_milliseconds": "30000"}

Add a Graphite Endpoint

If you want to monitor your service with Graphite, you can set an endpoint to where to information will be sent with the cf update-service command. This command expects the -c flag and a JSON string containing the graphite and metrics_prefix keys. Depending on your graphite provider the metrics_prefix might require that each metrics must start with an API key in their name. You can also change the interval within the data is send to the endpoint. Do to this modify interval the default is 10s.

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cf update-service my-rabbitmq-service -c '{ "graphite": ["yourspace.your-graphite-endpoint.com:12345"], "metrics_prefix": "your-api-key.my-cluster-rabbitmq", "interval": "5"}'

Add a Syslog Endpoint

The cf update-service command used with the -c flag can let you stream your syslog to a third-party service. In this case, the command expects a JSON string containing the syslog key. You can also change the interval for the syslog with the same key than for the graphite endpoint interval.

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cf update-service my-rabbitmq-service -c '{ "syslog": ["logs4.your-syslog-endpoint.com:54321"], "interval": "5" }'

Cloud Foundry Application Security Groups

This section describes how to check whether a security group was created.

Each a9s Data Service will automatically create and update Cloud Foundry security groups in order to protected service instances to be accessed by applications not running in the same Cloud Foundry applications space. To get a better understanding about Security Groups, refer to Understanding Application Security Groups.

Get Service Instance GUID

Run cf service INSTANCE_NAME --guid to get the guid of the service instance.

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$ cf service my-rabbitmq --guid
ca16f111-5073-40b7-973a-156c75dd3028

Check available Security Groups

To see all available security groups use cf security-groups.

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$cf security-groups
Getting security groups as demo@anynines.com
OK

     Name                                         Organization     Space
#0   public_networks
#1   dns
#2   tcp_open
#3   guard_432fb752-876d-443b-a311-a075f4df2237   demonstrations   demo
#4   guard_ca16f111-5073-40b7-973a-156c75dd3028   demonstrations   demo

There we can see a security group with the named guard_ca16f111-5073-40b7-973a-156c75dd3028 was successfully created.

Note

If the connection between the application and the service instance cannot be established, check if a security group was created.

Backup and Restore Service Instances

a9s RabbitMQ provides an easy way to create backups and restore if needed.

Get Dashboard Address, Login and Authorize

  1. Get the dashboard URL with cf service SERVICE-NAME.

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    $cf service my-rabbitmq
    
    Service instance: my-rabbitmq
    Service: rabbitmq
    Bound apps:
    Tags:
    Plan: rabbitmq-xs
    Description: This is a service creating and managing dedicated RabbitMQ service instances and clusters, powered by the anynines Service Framework
    Documentation url:
    Dashboard: https://a9s-rabbitmq-dashboard.aws.ie.apps.eu1.mindsphere.io/service-instances/ca16f111-5073-40b7-973a-156c75dd3028
    
    Last Operation
    Status: update succeeded
    Message:
    Started: 2017-10-26T08:28:38Z
    Updated: 2017-10-26T08:28:38Z
    
  2. Browse to the dashboard URL and authenticate on the redirected page with the "Login with WebKey" method:
    authentication-page

  3. Click Authorize to approve the authorization request:
    authorization-page

Perform a Backup

On the dashboard as shown above you can trigger a backup by clicking Trigger backup

service-dashboard

After a short period of time the backup will be queued. The backup process will start soon.

service-dashboard

Note

Depending on the size of the data the backup will take some time.

Restore a Backup

Open the dashboard again and select the backup you would like to restore. Click the Restore button of the backup. After a short period of time the restore will be triggered.

service-dashboard

Note

As for the backup, depending on the size of the data, the restore will take some time.

service-dashboard

Make a Service Instance Locally Available

It is possible to access any of the a9s Data Services locally. That means you can connect with a local client to the service for any purpose such as debbuging. CF provides a smart way to create SSH forward tunnels via a pushed application. For more information about this feature see the Accessing Apps with SSH section of the CF documentation.

First of all you must have an application bound to the service. How to do this see Bind an Application to a Service Instance.

Note

cf ssh support must be enabled in the platform. Ask your administrator if you are not sure.

Get The Service Url and Credentials

When you follow this instructions Obtain Service Instance Access Credentials you will get the hostname of the service and the user credentials.

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$ cf env redis-app
Getting env variables for app redis-app in org test / space test as admin...
OK

System-Provided:
{
  "VCAP_SERVICES": {
   "redis": [
    {
      "credentials": {
       "host": [
        "d67901c.service.dc1.a9svs"
       ],
       "password": "brk-usr",
       "username": "password"
     },
     "label": "redis",
     "name": "my-redis-service",
     "plan": "redis-xs"
    }
   ]
  }
}
...

Notice the host d67901c.service.dc1.a9svs, the username brk-usr and the password password. You will need this in the next step.

Create a Tunnel to The Service

With the cf ssh as mentioned before you can create a ssh forward tunnel to the management dashboard. Use port 6379 to connect to the a9s Redis Instance.

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$ cf ssh redis-app -L 6379:d67901c.service.dc1.a9svs:6379
vcap@956aaf4e-6da9-4f69-4b1d-8e631a403312:~$

When the ssh tunnel is open you can access the instance over the address localhost:6379.

Note

Don't forget to close the session with exit.

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