Using a9s Redis

This topic 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 a9s-redis and its service plans appear in your CF marketplace. Run cf marketplace to see the service listing:

$ cf marketplace
Getting services from marketplace in org test / space test as admin...
OK
service        plans                                                                           description
a9s-redis      redis-single, redis-cluster, redis-single-ssl redis-cluster-ssl                 This is the a9s Redis service.

note

SSL/TLS plans are available with a9s Redis 6 and above.

Create a Service Instance

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

cf create-service a9s-redis redis-single 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:

cf bind-service a9s-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.

cf env a9s-redis-app
Getting env variables for app a9s-redis-app in org test / space test as admin...

System-Provided:
{
  "VCAP_SERVICES": {
    "a9s-redis": [
      {
        (...)
        "credentials": {
          "host": "EXAMPLE-master.service.dc1.a9ssvc",
          "hosts": [
            "EXAMPLE-redis-0.node.dc1.a9ssvc",
            "EXAMPLE-redis-1.node.dc1.a9ssvc",
            "EXAMPLE-redis-2.node.dc1.a9ssvc"
          ],
          "load_balanced_host": "EXAMPLE.service.dc1.a9ssvc",
          "redis": {
            "password": "EXAMPLE-REDIS-PASSWORD",
            "port": 6379,
            "username": "EXAMPLE-REDIS-USERNAME"
          },
          "sentinel": {
            "master_name": "EXAMPLE-master",
            "password": "EXAMPLE-SENTINEL-PASSWORD",
            "port": 26379,
            "username": "EXAMPLE-SENTINEL-PASSWORD"
          }
        }
        (...)
      }
    ]
  }
}

...

Check credentials for a9s Redis 7 RC and below

$ cf env a9s-redis-app
Getting env variables for app a9s-redis-app in org test / space test as admin...

System-Provided:
{
  "VCAP_SERVICES": {
    "a9s-redis": [
      {
        (...)
        "credentials": {
          "host": "EXAMPLE-master.service.dc1.consul",
          "hosts": [
            "EXAMPLE-redis-0.node.dc1.consul",
            "EXAMPLE-redis-1.node.dc1.consul",
            "EXAMPLE-redis-2.node.dc1.consul"
          ],
          "load_balanced_host": "EXAMPLE.service.dc1.consul",
          "password": "EXAMPLE-PWD",
          "port": 6379,
          "sentinel_master_name": "EXAMPLE-master",
          "sentinel_port": 26379
        }
        (...)
      }
    ]
  }
}
...

You can use the host and password values to connect to your database with a Redis client, by using only the host variable, your application does not need to know anything about Redis Sentinel. However if you use the hosts variable or the load_balanced_host, your application needs to know about Redis Sentinel and being able to work with Redis Sentinel. This means, by using the host variable, the failover is handled by the logic within our service and if you use one of the other variables, the failover needs to be handled by your application.

note

The sentinel information and its subfields are only present for Service Instances with cluster plans.

Access Credentials

caution

Versions bellow a9s Redis 7 GA do not have support for multiple unique access credentials. These versions share the same credentials for different service bindings/keys with administrator permissions.

The user access control is based on Redis Access Control List (ACL). Each credential has some pre-configured permissions and does not have admin privileges.

Best Practices

There are some best practices for using service binding information in apps in a separate document.

Delete an a9s Redis Service Instance

caution

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.

$ cf services

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

name                 service       plan                   bound apps        last operation
my-redis-service     a9s-redis     redis-single           a9s-redis-app     create succeeded

This example shows that my-redis-service is bound to the a9s-redis-app application.

Unbind a Service Instance

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

cf unbind-service a9s-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:

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, see the Update a Service Instance of the Managing Service Instances with the cf CLI topic.

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

Plan Upgrade Restrictions

Upgrades from single to cluster plans via the CF CLI update-service command are not possible for a9s Redis 6 and above.

However, it is possible to migrate to a new (empty) instance matching the desired plan via the migration feature. This way the you are able to import your data from a single instance into a cluster instance. For more information please refer to our migration guide.

Change RDB Persistence Settings

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

Default Behavior

By default, persistency is disabled for a9s Redis Service Instances. However, if a backup snapshot is created and the instance is restarted by an update, the backup snapshot is restored, even if persistence is disabled. This affects both single instances and clusters. Data created between the backup and the update is not persistent and will be lost after the restart. Therefore, we recommend the following setup for cache-only instances with disabled persistency: Use the exclude_from_auto_backup option to avoid the creation of backups. More information is available here.

Configuring RDB

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

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 custom parameter: -c "{\"snapshot\": \"[]\"}".

The command is:

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. There are several configurable behaviors.

Setting	Effect
volatile-lru	Remove the key with an expire set using an LRU algorithm This is the default value.
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
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.

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 several nodes, takes care of the automatic failover and is able to send notifications when something in the cluster is changing.

a9s Redis provides some settings to adjust the cluster behavior. min-slaves-max-lag, down-after-milliseconds, and failover-timeout.

Setting	Effect
min-slaves-max-lag	Redis < 6: Time in seconds how long the master waits before he stops accepting write operations, when slaves are no more reachable. Default is 10 seconds. min-slaves-to-write can not be changed, it is fixed set to 1. See redis.conf
min_replicas_max_lag	Redis >= 6: Time in seconds how long the master waits before he stops accepting write operations, when replicas are no more reachable. Default is 10 seconds. min-replicas-to-write can not be changed, it is fixed set to 1. See redis.conf
down-after-milliseconds	Number of milliseconds the master is unreachable in order to mark it a S_DOWN state. Default is 10000 ms. See sentinel.conf
failover-timeout	The failover timeout value in milliseconds. Default is 30000 ms. See sentinel.conf

# a9s Redis < 6
cf update-service my-redis-service -c {"min-slaves-max-lag": "10"}

# a9s Redis >= 6
cf update-service my-redis-service -c {"min_replicas_max_lag": "10"}

cf update-service my-redis-service -c '{"down-after-milliseconds": "10000"}'

cf update-service my-redis-service -c '{"failover-timeout": "30000"}'

Add a Graphite Endpoint

Important: Streaming of logs and metrics might not be availabale for your plan! If unsure, please check your plan description.

If you want to monitor your service with Graphite, you can set the custom parameter graphite. It expects the host and port where the Graphite metrics should be sent to.

For example, in order to send Graphite metrics to an endpoint yourspace.your-graphite-endpoint.com:12345, you can use the following command:

cf update-service my-instance -c '{ "graphite": "yourspace.your-graphite-endpoint.com:12345" }'

The endpoint would then receive metrics in the format:

<service_guid>.<service_type>.<host>.<metric> <metric value> <metric timestamp>

Metrics Frequency

By default, metrics will be emitted every 10 seconds. You can change the interval via the custom parameter metrics_frequency.

For example, in order to send Graphite metrics to an endpoint every minute, you would set the custom parameter metrics_frequency to 60 using the following command:

cf update-service my-instance -c '{  "metrics_frequency": 60 }'

Metrics Prefix

Depending on your graphite provider, you might need to prefix the metrics with a certain value, like an API key for example. In this case you can leverage the custom parameter metrics_prefix.

cf update-service my-instance -c '{  "metrics_prefix": "my-api-key-for-a-certain-provider" }'

The resulting metric path would have the format:

<metrics_prefix>.<service_guid>.<service_type>.<host>.<metric>

Metrics

These are all metrics provided by a9s Redis.

Metric Id	Type	Description
blocked_clients	Integer	Number of clients pending on a blocking call (BLPOP, BRPOP, BRPOPLPUSH, BLMOVE, BZPOPMIN, BZPOPMAX). documentation
connected_clients	Integer	Number of client connections (excluding connections from replicas). documentation
evicted_keys	Integer	Number of evicted keys due to maxmemory limit. documentation
expired_keys	Integer	Total number of key expiration events. documentation
instantaneous_ops_per_sec	Integer	Number of commands processed per second. documentation
keyspace_hits	Integer	Number of successful lookup of keys in the main dictionary. documentation
keyspace_misses	Integer	Number of failed lookup of keys in the main dictionary. documentation
mem_fragmentation_ratio	Float	Ratio between usedmemory_rss and used_memory. Note that this doesn't only includes fragmentation, but also other process overheads (see the allocator* metrics), and also overheads like code, shared libraries, stack, etc. documentation
rejected_connections	Integer	Number of connections rejected because of maxclients limit. documentation
total_commands_processed	Integer	Total number of commands processed by the server. documentation
total_connections_received	Integer	Total number of connections accepted by the server. documentation
used_memory	Integer	Total number of bytes allocated by Redis using its allocator (either standard libc, jemalloc, or an alternative allocator such as tcmalloc) documentation
used_memory_lua	Integer	Number of bytes used by the Lua engine. documentation
used_memory_peak	Integer	Peak memory consumed by Redis (in bytes). documentation
used_memory_rss	Integer	Number of bytes that Redis allocated as seen by the operating system (a.k.a resident set size). documentation

*.redis.*.*.*.blocked_clients
*.redis.*.*.*.connected_clients
*.redis.*.*.*.evicted_keys
*.redis.*.*.*.expired_keys
*.redis.*.*.*.instantaneous_ops_per_sec
*.redis.*.*.*.keyspace_hits
*.redis.*.*.*.keyspace_misses
*.redis.*.*.*.mem_fragmentation_ratio 4
*.redis.*.*.*.rejected_connections
*.redis.*.*.*.total_commands_processed
*.redis.*.*.*.total_connections_received
*.redis.*.*.*.used_memory
*.redis.*.*.*.used_memory_lua
*.redis.*.*.*.used_memory_peak
*.redis.*.*.*.used_memory_rss

Cloud Foundry Org and Space Guid

The platform operators can enable support on a global level to prefix the Graphite metrics with the CloudFoundry organization and space. This means that all metrics of all Service Instances (not only yours!) contain that information.

In this case the Graphite metric paths have the following format:

<organization_guid>.<space_guid>.<service_guid>.<service_type>.<host>.<metric>

When you enable in addition the metrics_prefix for your instance, you will end up with the metric path format:

<metrics_prefix>.<organization_guid>.<space_guid>.<service_guid>.<service_type>.<host>.<metric>

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.

cf update-service my-redis-service \
  -c '{ "syslog": ["logs4.your-syslog-endpoint.com:54321"]}'

Cloud Foundry Application Security Groups

This topic 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 you can have a look on the Understanding Application Security Groups topic.

Get Service Instance GUID

Run cf service INSTANCE_NAME --guid to get the guid of the Service Instance.

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

Check available Security Groups

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

$ 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

In some circumstances the connection between the application and the Service Instance is not possible, in this case check if a security group was created.

Redis Custom Parameters

As an end user you have the opportunity to customize your Service Instance by using custom parameters. Custom parameters are passed on to a Service Instance by using the -c switch of the cf CLI commands cf create-service and cf update-service. For example

cf update-service myredis -c '{"maxclients": 1000}'

would set the maxclients limit to the value 1000 for the Service Instance myredis.

You don't have to utilize those settings. There are sane defaults in place that fit your service plan well.

Every parameter corresponds to a property in the configuration file for the respective Redis version.

lazyfree-lazy-eviction

The default value is no. The allowed values are yes and no.

lazyfree-lazy-expire

The default value is no. The allowed values are yes and no.

lua-time-limit

The default value is 5000. The value must be an integer.

maxclients

The default value is 10000. The value must be an integer > 0.

maxmemory-policy

The default value is volatile-lru The allowed string values are:

• volatile-lru
• volatile-lfu
• volatile-random
• volatile-ttl
• allkeys-lru
• allkeys-lfu
• allkeys-random
• noeviction

For an explanation, see here.

maxmemory-samples

The default value is 5. The value must be an integer >= 0.

notify-keyspace-events

This parameter allows to configure the Redis Keyspace Notifications.

The default value is '' which means by default keyspace events are disabled. The allowed value must include the following characters only:

• K
• E
• g
• $
• l
• s
• h
• z
• x
• e
• A
• t

failover-timeout

It is a Redis sentinel property that specifies the failover timeout in milliseconds. The default is 30 seconds.

The default value is 30000. The value must be an integer >= 0.

down-after-milliseconds

It is a Redis sentinel property that specifies the milliseconds a node is unreacheable in order to consider it subjectively down. The default is 10 seconds.

The default value is 10000. The value must be an integer >= 0.

tls-protocols

note

Only available with SSL/TLS plans that are available with a9s Redis 6 and above.

You can explicitly specify TLS versions to support. Allowed values are "TLSv1.2" and "TLSv1.3" or any combination.

caution

• Improper changes to this value can easily break existing instances.
• When using TLSv1.3 only, Redis specific metrics will not be provided.

The default value is null. In this case Redis uses TLSv1.2 and TLSv1.3.

tls-ciphers

note

Only available with SSL/TLS plans that are available with a9s Redis 6 and above. This configuration only applies when using TLSv1.2.

Configure allowed ciphers. See the ciphers(1ssl) manpage for more information about the syntax of this string.

caution

There is no validation enabled for the user provided values and therefore existing instances can break when applying this parameter.

The default value is null which comments out the Redis config tls-ciphers in the Redis and Sentinel configuration files.

tls-ciphersuites

note

Only available with SSL/TLS plans that are available with a9s Redis 6 and above. This configuration only applies when using TLSv1.3.

Configure allowed ciphersuites. See the ciphers(1ssl) manpage for more information about the syntax of this string, and specifically for TLSv1.3 ciphersuites.

caution

There is no validation enabled for the user provided values and therefore existing instances can break when applying this parameter.

The default value is null which comments out the Redis config tls-ciphersuites in the Redis and Sentinel configuration files.

hostname-resolution

note

• This feature is exclusive to a9s Redis versions 7 and above.
• This feature specifically applies to a9s Redis Cluster instances.

caution

• When enabling or disabling the feature in an existing a9s Service Instance, there might be an increased downtime during the first cluster update due to a temporary divergence in Sentinel's settings when switching between IP address and hostname.
• When enabled, unexpected delays in address resolution may have a negative impact on Sentinel. For more information, refer to the Redis documentation.

The feature provides the option to enable and disable DNS/hostname support in Redis and Sentinel. When enabled, it will utilize the hostname for internal cluster communication and announce Redis and Sentinel node information using the hostname instead of the typical IP address.

Using this feature is useful when Redis clients use TLS to connect to Service Instances and require a hostname rather than an IP address in order to perform certificate ASN matching.

Using it

To enable or disable hostname-resolution, it is important to follow a series of steps to ensure safety and prevent significant downtime or data loss. Depending on its current state, the process may require adjusting a custom parameter in two steps. See the cases below:

• To enable it in an existing Service Instance, follow these steps: disabled → resolve-only → enabled.
• To disable it in an existing Service Instance, follow these steps: enabled → resolve-only → disabled.
• When you create a new Service Instance, you can set any value directly. We suggest using either enabled or disabled.

note

Please note that transitioning directly from disabled to enabled, and vice versa, is not possible in an existing Service Instance.

States/Values	Description
disabled	Hostname resolution and announcement are fully disabled.
resolve-only	Hostname resolution is enabled but announcement is disabled.
enabled	Hostname resolution and announcement are fully enabled.

The default value is disabled.

Backup and Restore Service Instances

a9s Redis provides an easy way to create backups and restore if needed. For a more detailed description, please see the a9s Service Dashboard documentation.

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 debugging. 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.

$ cf env a9s-redis-app
Getting env variables for app a9s-redis-app in org test / space test as admin...
OK

System-Provided:
{
  "VCAP_SERVICES": {
    "a9s-redis7": [
      {
        (...)
        "credentials": {
          "cacrt": "-----BEGIN CERTIFICATE-----\nMIIDGzCCAgOgAwIBAgIUJaCrwZnds7aY8+Jr+mvE....CMYZPYrlJ7jsTRt4NMrIp+jr+8tUd8J\n9eb7012/YK0d025ik2Qt\n-----END CERTIFICATE-----\n",
          "host": "EXAMPLE-master.service.dc1.a9ssvc",
          "redis": {
            "password": "EXAMPLE-REDIS-PASSWORD",
            "port": 6379,
            "username": "EXAMPLE-REDIS-USERNAME"
          },
          "sentinel": {
            "master_name": "EXAMPLE-master",
            "password": "EXAMPLE-SENTINEL-PASSWORD",
            "port": 26379,
            "username": "EXAMPLE-SENTINEL-PASSWORD"
          }
        }
        (...)
      }
    ]
  }
}
...

Notice the host EXAMPLE.service.dc1.a9svs, the username EXAMPLE-REDIS-USERNAME and the password EXAMPLE-REDIS-PASSWORD. You will need this in the next step.

note

a9s Redis 7 RC and below have a different structure for the credentials field. Please see Obtain Service Instance Access Credentials for more information.

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.

$ cf ssh a9s-redis-app -L 6379:EXAMPLE.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.

If the instance you have created is based on an SSL-plan, then you would need to provide a CA certificate when connecting to it using the tunnel approach. To do so you can rely on the certificate shown when executing cf env, as shown above.

You should save the certificate from the credentials.cacrt value of the VCAP_SERVICES object into some local file.

Then, while the tunnel is open you can use the redis-cli to interact with your Redis instance from your local machine:

redis-cli -h 127.0.0.1 -p 6379 --user <user> --pass <password> --tls --cacert "$LOCAL_CA_CERT_FILE"

note

Don't forget to close the session with exit.

Setup Disk Usage Alerts

Each service comes with the a9s Parachute. This component monitors ephemeral and persistent disk usage. See the a9s Parachute documentation how to configure the component.