rate-limiting-advanced

The Rate Limiting Advanced plugin for Konnect Enterprise is a re-engineered version of the Kong Gateway (OSS) Rate Limiting plugin.

As compared to the standard Rate Limiting plugin, Rate Limiting Advanced provides:

• Enhanced capabilities to tune the rate limiter, provided by the parameters limit and window_size. Learn more in Multiple Limits and Window Sizes
• Support for Redis Sentinel, Redis cluster, and Redis SSL
• Increased performance: Rate Limiting Advanced has better throughput performance with better accuracy. The plugin allows you to tune performance and accuracy via a configurable synchronization of counter data with the backend storage. This can be controlled by setting the desired value on the sync_rate parameter.
• More limiting algorithms to choose from: These algorithms are more accurate and they enable configuration with more specificity. Learn more about our algorithms in How to Design a Scalable Rate Limiting Algorithm.
• Consumer groups support: Apply different rate limiting configurations to select groups of consumers. Learn more in Rate limiting for consumer groups

Notes:

• The plugin does not support the cluster strategy in hybrid mode. The redis strategy must be used instead.

• Redis configuration values are ignored if the cluster strategy is used.

• PostgreSQL 9.5+ is required when using the cluster strategy with postgres as the backing Kong cluster data store.

• The dictionary_name directive was added to prevent the usage of the kong shared dictionary, which could lead to no memory errors.

Headers sent to the client

When this plugin is enabled, Kong sends some additional headers back to the client indicating the allowed limits, how many requests are available, and how long it will take until the quota will be restored.

For example:

RateLimit-Limit: 6
RateLimit-Remaining: 4
RateLimit-Reset: 47

The plugin also sends headers indicating the limits in the time frame and the number of remaining minutes:

X-RateLimit-Limit-Minute: 10
X-RateLimit-Remaining-Minute: 9

You can optionally hide the limit and remaining headers with the hide_client_headers option.

If more than one limit is being set, the plugin returns a combination of more time limits:

X-RateLimit-Limit-Second: 5
X-RateLimit-Remaining-Second: 4
X-RateLimit-Limit-Minute: 10
X-RateLimit-Remaining-Minute: 9

If any of the limits configured has been reached, the plugin returns an HTTP/1.1 429 status code to the client with the following JSON body:

{ "message": "API rate limit exceeded" }

The Retry-After header will be present on 429 errors to indicate how long the service is expected to be unavailable to the client. When using window_type=sliding and RateLimit-Reset, Retry-After may increase due to the rate calculation for the sliding window.

The headers RateLimit-Limit, RateLimit-Remaining, and RateLimit-Reset are based on the Internet-Draft RateLimit Header Fields for HTTP and may change in the future to respect specification updates.

Multiple Limits and Window Sizes

An arbitrary number of limits/window sizes can be applied per plugin instance. This allows you to create multiple rate limiting windows (e.g., rate limit per minute and per hour, and per any arbitrary window size). Because of limitations with Kong’s plugin configuration interface, each nth limit will apply to each nth window size. For example:

curl -X POST http://
{LOCALHOST}
:8001/services/
{SERVICE}
/plugins \
  --data "name=rate-limiting-advanced" \
  --data "config.limit=10" \
  --data "config.limit=100" \
  --data "config.window_size=60" \
  --data "config.window_size=3600"

This example applies rate limiting policies, one of which will trip when 10 hits have been counted in 60 seconds, or the other when 100 hits have been counted in 3600 seconds. For more information, see the Enterprise Rate Limiting Library.

The number of configured window sizes and limits parameters must be equal (as shown above); otherwise, an error occurs:

You must provide the same number of windows and limits

Fallback to IP

When the selected strategy cannot be retrieved, the rate-limiting-advanced plugin will fall back to limit using IP as the identifier. This can happen for several reasons, such as the selected header was not sent by the client or the configured service was not found.

Fallback from Redis

When the redis strategy is used and a Kong Gateway node is disconnected from Redis, the rate-limiting-advanced plugin will fall back to local. This can happen when the Redis server is down or the connection to Redis broken. Kong Gateway keeps the local counters for rate limiting and syncs with Redis once the connection is re-established. Kong Gateway will still rate limit, but the Kong Gateway nodes can’t sync the counters. As a result, users will be able to perform more requests than the limit, but there will still be a limit per node.

Changelog

Kong Gateway 3.1.x

• Added the ability to customize the error code and message with the configuration parameters error_code and error_message.

Kong Gateway 3.0.x

• Kong Gateway now disallows enabling the plugin if the cluster strategy is set with DB-less or hybrid mode.

Kong Gateway 2.8.x

• Added the redis.username and redis.sentinel_username configuration parameters.

• The redis.username, redis.password, redis.sentinel_username, and redis.sentinel_password configuration fields are now marked as referenceable, which means they can be securely stored as secrets in a vault. References must follow a specific format.

Kong Gateway 2.7.x

• Added the enforce_consumer_groups and consumer_groups configuration parameters.

Kong Gateway 2.5.x

• Deprecated the timeout field and replaces it with three precise options: connect_timeout, read_timeout, and send_timeout.
• Added redis.keepalive_pool, redis.keepalive_pool_size, and redis.keepalive_backlog configuration options.
• ssl_verify and server_name configuration options now support Redis Sentinel-based connections.

Kong Gateway 2.2.x

• Added the redis.ssl, redis.ssl_verify, and redis.server_name parameters for configuring TLS connections.