Edge Stack and Redis

The Ambassador Edge Stack make use of Redis for several purposes. By default, all components of the Ambassador Edge Stack share a Redis connection pool.

Rate Limit Service

The rate limiting service, can be configured to use different connection pools for handling per-second rate limits or connecting to Redis clusters.

AES_RATELIMIT_PREVIEW

Set AES_RATELIMIT_PREVIEW to true to access support for redis clustering, local caching, and an upgraded redis client with improved scalability in preview mode.

REDIS_PERSECOND

If REDIS_PERSECOND is true, a second Redis connection pool is created (to a potentially different Redis instance) that is only used for per-second RateLimits; this second connection pool is configured by the REDIS_PERSECOND_* variables rather than the usual REDIS_* variables.

Redis layer 4 connectivity (L4)

SOCKET_TYPE

The Go network to use to talk to Redis. see Go net.Dial

Most users will leave this as the default of tcp.

URL

The URL to dial to talk to Redis

This will be either a hostname:port pair or a comma separated list of hostname:port pairs depending on the TYPE you are using.

For REDIS_URL (but not REDIS_PERSECOND_URL), not setting a value disables Ambassador Edge Stack features that require Redis.

TLS_ENABLED

Specifies whether to use TLS when talking to Redis.

TLS_INSECURE

Specifies whether to skip certificate verification when using TLS to talk to Redis.

Consider installing the self-signed certificate for your Redis in to the Ambassador Edge Stack container in order to leave certificate verification on.

Redis authentication (auth)

Default

Configure authentication to a redis pool using the default implementation.

PASSWORD

If set, it is used to AUTH to Redis immediately after the connection is established.

USERNAME

If set, then that username is used with the password to log in as that user in the Redis 6 ACL. It is invalid to set a username without setting a password. It is invalid to set a username with Redis 5 or lower.

The following YAML snippet is an example of configuring Redis authentication in the Ambassador deployment's environment variables.

Rate Limit Preview

Configure authentication to a redis pool using the preview rate limiting implementation

AUTH

Required for authentication with Rate Limit Preview. You must also configure REDIS_USERNAME and REDIS_PASSWORD for the rest of Ambassador's Redis usage.

If you configure REDIS_AUTH, then REDIS_USERNAME cannot be changed from the value default, and REDIS_PASSWORD should contain the same value as REDIS_AUTH.

REDIS_USERNAME and REDIS_PASSWORD handle all Redis authentication that is separate from Rate Limit Preview so failing to set them when using REDIS_AUTH will result in Ambassador not being able to authenticate with Redis for all of its other functionality.

Adding AUTH to the example above for rate limit preview would look like the following snippet.

Redis performance tuning (tune)

POOL_SIZE

The number of connections to keep around when idle.

The total number of connections may go lower than this if there are errors.

The total number of connections may go higher than this during a load surge.

PING_INTERVAL

The rate at which Ambassador will ping the idle connections in the normal pool (not extra connections created for a load surge).

Ambassador will PING one of them every PING_INTERVAL÷POOL_SIZE so that each connection will on average be PINGed every PING_INTERVAL.

TIMEOUT

Sets 4 different timeouts:

1. (*net.Dialer).Timeout for establishing connections
2. (*redis.Client).ReadTimeout for reading a single complete response
3. (*redis.Client).WriteTimeout for writing a single complete request
4. The timeout when waiting for a connection to become available from the pool (not including the dial time, which is timed out separately)

A value of "0" means "no timeout".

SURGE_LIMIT_INTERVAL

During a load surge, if the pool is depleted, then Ambassador may create new connections to Redis in order to fulfill demand, at a maximum rate of one new connection per SURGE_LIMIT_INTERVAL.

A value of "0" (the default) means "allow new connections to be created as fast as necessary.

The total number of connections that Ambassador can surge to is unbounded.

SURGE_LIMIT_AFTER

The number of connections that can be created after the normal pool is depleted before SURGE_LIMIT_INTERVAL kicks in.

The first POOL_SIZE+SURGE_LIMIT_AFTER connections are allowed to be created as fast as necessary.

This setting has no effect if SURGE_LIMIT_INTERVAL is 0.

SURGE_POOL_SIZE

Normally during a surge, excess connections beyond POOL_SIZE are closed immediately after they are done being used, instead of being returned to a pool.

SURGE_POOL_SIZE configures a "reserve" pool for excess connections created during a surge.

Excess connections beyond POOL_SIZE+SURGE_POOL_SIZE will still be closed immediately after use.

SURGE_POOL_DRAIN_INTERVAL

How quickly to drain connections from the surge pool after a surge is over.

Connections are closed at a rate of one connection per SURGE_POOL_DRAIN_INTERVAL.

This setting has no effect if SURGE_POOL_SIZE is 0.

Redis type

Redis currently support three different deployment methods. Ambassador Edge Stack can now support using a Redis deployed in any of these ways for rate limiting when AES_RATELIMIT_PREVIEW=true.

TYPE

• SINGLE: Talk to a single instance of redis, or a redis proxy.

  Requires the redis REDIS_URL or REDIS_PERSECOND_URL to be either a single hostname:port pair or a unix domain socket reference.

• SENTINEL: Talk to a redis deployment with sentinel instances (see https://redis.io/topics/sentinel).

  Requires the redis REDIS_URL or REDIS_PERSECOND_URL to be a comma separated list with the first string as the master name of the sentinel cluster followed by hostname:port pairs. The list size should be >= 2. The first item is the name of the master and the rest are the sentinels.

• CLUSTER: Talk to a redis in cluster mode (see https://redis.io/topics/cluster-spec)

  Requires the redis REDIS_URL or REDIS_PERSECOND_URL to be either a single hostname:port pair of the read/write endpoint or a comma separated list of hostname:port pairs with all the nodes in the cluster.

  PIPELINE_WINDOW must be set when TYPE: CLUSTER.

PIPELINE_WINDOW

The duration after which internal pipelines will be flushed.

If window is zero then implicit pipelining will be disabled.

150us is recommended when using implicit pipelining in production.

PIPELINE_LIMIT

The maximum number of commands that can be pipelined before flushing.

If limit is zero then no limit will be used and pipelines will only be limited by the specified time window.