Table of Contents generated with DocToc

• Overview
• Deprecation of Legacy Ratelimit Proto
  • Deprecation Schedule
• Building and Testing
  • Docker-compose setup
• Configuration
  • The configuration format
    • Definitions
    • Descriptor list definition
    • Rate limit definition
    • Examples
      • Example 1
      • Example 2
      • Example 3
      • Example 4
  • Loading Configuration
• Request Fields
• Statistics
• Debug Port
• Local Cache
• Redis
  • One Redis Instance
  • Two Redis Instances
• Contact

Overview

The rate limit service is a Go/gRPC service designed to enable generic rate limit scenarios from different types of applications. Applications request a rate limit decision based on a domain and a set of descriptors. The service reads the configuration from disk via runtime, composes a cache key, and talks to the Redis cache. A decision is then returned to the caller.

Deprecation of Legacy Ratelimit Proto

Envoy's data-plane-api defines a ratelimit service proto rls.proto. Logically the data-plane-api rls is equivalent to the ratelimit.proto defined in this repo. However, due to the namespace differences and how gRPC routing works it is not possible to transparently route the legacy ratelimit (ones based in the ratelimit.proto defined in this repo) requests to the data-plane-api definitions. Therefore, the ratelimit service will upgrade the requests, process them internally as it would process a data-plane-api ratelimit request, and then downgrade the response to send back to the client. This means that, for a slight performance hit for clients using the legacy proto, ratelimit is backwards compatible with the legacy proto.

Deprecation Schedule

1. v1.0.0 tagged on commit 0ded92a2af8261d43096eba4132e45b99a3b8b14. Ratelimit has been in production use at Lyft for over 2 years.
2. v1.1.0 introduces the data-plane-api proto and initiates the deprecation of the legacy ratelimit.proto.
3. v2.0.0 deletes support for the legacy ratelimit.proto. This version will be tagged by the end of 2018Q3 (~September 2018) to give time to community members running ratelimit off of master.

Building and Testing

• Install Redis-server.

• Make sure go is setup correctly and checkout rate limit service into your go path. More information about installing go here.

• In order to run the integration tests using a local Redis server please run two Redis-server instances: one on port 6379 and another on port 6380

  redis-server --port 6379 &
  redis-server --port 6380 &

• To setup for the first time (only done once):

  make bootstrap

• To compile:

  make compile

  Ensure you set the correct platform if running OSX host with a linux container e.g.

  GOOS=linux make compile

• To compile and run tests:

  make tests

• To run the server locally using some sensible default settings you can do this (this will setup the server to read the configuration files from the path you specify):

  USE_STATSD=false LOG_LEVEL=debug REDIS_SOCKET_TYPE=tcp REDIS_URL=localhost:6379 RUNTIME_ROOT=/home/user/src/runtime/data RUNTIME_SUBDIRECTORY=ratelimit

Docker-compose setup

The docker-compose setup has three containers: redis, ratelimit-build, and ratelimit. In order to run the docker-compose setup from the root of the repo, run

docker-compose up

The ratelimit-build container will build the ratelimit binary. Then via a shared volume the binary will be shared with the ratelimit container. This dual container setup is used in order to use a a minimal container to run the application, rather than the heftier container used to build it.

If you want to run with two redis instances, you will need to modify the docker-compose.yaml file to run a second redis container, and change the environment variables as explained in the two redis instances section.

Configuration

The configuration format

The rate limit configuration file format is YAML (mainly so that comments are supported).

Definitions

• Domain: A domain is a container for a set of rate limits. All domains known to the Ratelimit service must be globally unique. They serve as a way for different teams/projects to have rate limit configurations that don't conflict.
• Descriptor: A descriptor is a list of key/value pairs owned by a domain that the Ratelimit service uses to select the correct rate limit to use when limiting. Descriptors are case-sensitive. Examples of descriptors are:
  • ("database", "users")
  • ("message_type", "marketing"),("to_number","2061234567")
  • ("to_cluster", "service_a")
  • ("to_cluster", "service_a"),("from_cluster", "service_b")

Descriptor list definition

Each configuration contains a top level descriptor list and potentially multiple nested lists beneath that. The format is:

domain: <unique domain ID>
descriptors:
  - key: <rule key: required>
    value: <rule value: optional>
    rate_limit: (optional block)
      unit: <see below: required>
      requests_per_unit: <see below: required>
    descriptors: (optional block)
      - ... (nested repetition of above)

Each descriptor in a descriptor list must have a key. It can also optionally have a value to enable a more specific match. The "rate_limit" block is optional and if present sets up an actual rate limit rule. See below for how the rule is defined. If the rate limit is not present and there are no nested descriptors, then the descriptor is effectively whitelisted. Otherwise, nested descriptors allow more complex matching and rate limiting scenarios.

Rate limit definition

rate_limit:
  unit: <second, minute, hour, day>
  requests_per_unit: <uint>

The rate limit block specifies the actual rate limit that will be used when there is a match. Currently the service supports per second, minute, hour, and day limits. More types of limits may be added in the future based on user demand.

Examples

Example 1

Let's start with a simple example:

domain: mongo_cps
descriptors:
  - key: database
    value: users
    rate_limit:
      unit: second
      requests_per_unit: 500

  - key: database
    value: default
    rate_limit:
      unit: second
      requests_per_unit: 500

In the configuration above the domain is "mongo_cps" and we setup 2 different rate limits in the top level descriptor list. Each of the limits have the same key ("database"). They have a different value ("users", and "default"), and each of them setup a 500 request per second rate limit.

Example 2

A slightly more complex example:

domain: messaging
descriptors:
  # Only allow 5 marketing messages a day
  - key: message_type
    value: marketing
    descriptors:
      - key: to_number
        rate_limit:
          unit: day
          requests_per_unit: 5

  # Only allow 100 messages a day to any unique phone number
  - key: to_number
    rate_limit:
      unit: day
      requests_per_unit: 100

In the preceding example, the domain is "messaging" and we setup two different scenarios that illustrate more complex functionality. First, we want to limit on marketing messages to a specific number. To enable this, we make use of nested descriptor lists. The top level descriptor is ("message_type", "marketing"). However this descriptor does not have a limit assigned so it's just a placeholder. Contained within this entry we have another descriptor list that includes an entry with key "to_number". However, notice that no value is provided. This means that the service will match against any value supplied for "to_number" and generate a unique limit. Thus, ("message_type", "marketing"), ("to_number", "2061111111") and ("message_type", "marketing"),("to_number", "2062222222") will each get 5 requests per day.

The configuration also sets up another rule without a value. This one creates an overall limit for messages sent to any particular number during a 1 day period. Thus, ("to_number", "2061111111") and ("to_number", "2062222222") both get 100 requests per day.

When calling the rate limit service, the client can specify multiple descriptors to limit on in a single call. This limits round trips and allows limiting on aggregate rule definitions. For example, using the preceding configuration, the client could send this complete request (in pseudo IDL):

RateLimitRequest:
  domain: messaging
  descriptor: ("message_type", "marketing"),("to_number", "2061111111")
  descriptor: ("to_number", "2061111111")

And the service will rate limit against all matching rules and return an aggregate result; a logical OR of all the individual rate limit decisions.

Example 3

An example to illustrate matching order.

domain: edge_proxy_per_ip
descriptors:
  - key: remote_address
    rate_limit:
      unit: second
      requests_per_unit: 10

  # Black list IP
  - key: remote_address
    value: 50.0.0.5
    rate_limit:
      unit: second
      requests_per_unit: 0

In the preceding example, we setup a generic rate limit for individual IP addresses. The architecture's edge proxy can be configured to make a rate limit service call with the descriptor ("remote_address", "50.0.0.1") for example. This IP would get 10 requests per second as would any other IP. However, the configuration also contains a second configuration that explicitly defines a value along with the same key. If the descriptor ("remote_address", "50.0.0.5") is received, the service will attempt the most specific match possible. This means the most specific descriptor at the same level as your request. Thus, key/value is always attempted as a match before just key.

Example 4

The Ratelimit service matches requests to configuration entries with the same level, i.e same number of tuples in the request's descriptor as nested levels of descriptors in the configuration file. For instance, the following request:

RateLimitRequest:
  domain: example4
  descriptor: ("key", "value"),("subkey", "subvalue")

Would not match the following configuration. Even though the first descriptor in the request matches the 1st level descriptor in the configuration, the request has two tuples in the descriptor.

domain: example4
descriptors:
  - key: key
    value: value
    rate_limit:
      requests_per_unit: 300
      unit: second

However, it would match the following configuration:

domain: example4
descriptors:
  - key: key
    value: value
    descriptors:
      - key: subkey
        rate_limit:
          requests_per_unit: 300
          unit: second

Loading Configuration

The Ratelimit service uses a library written by Lyft called goruntime to do configuration loading. Goruntime monitors a designated path, and watches for symlink swaps to files in the directory tree to reload configuration files.

The path to watch can be configured via the settings package with the following environment variables:

RUNTIME_ROOT default:"/srv/runtime_data/current"
RUNTIME_SUBDIRECTORY
RUNTIME_IGNOREDOTFILES default:"false"

Configuration files are loaded from RUNTIME_ROOT/RUNTIME_SUBDIRECTORY/config/*.yaml

For more information on how runtime works you can read its README.

Request Fields

For information on the fields of a Ratelimit gRPC request please read the information on the RateLimitRequest message type in the Ratelimit proto file.

Statistics

The rate limit service generates various statistics for each configured rate limit rule that will be useful for end users both for visibility and for setting alarms. Ratelimit uses gostats as its statistics library. Please refer to gostats' documentation for more information on the library.

Rate Limit Statistic Path:

ratelimit.service.rate_limit.DOMAIN.KEY_VALUE.STAT

DOMAIN:

• As specified in the domain value in the YAML runtime file

KEY_VALUE:

• A combination of the key value
• Nested descriptors would be suffixed in the stats path

STAT:

• near_limit: Number of rule hits over the NearLimit ratio threshold (currently 80%) but under the threshold rate.
• over_limit: Number of rule hits exceeding the threshold rate
• total_hits: Number of rule hits in total

These are examples of generated stats for some configured rate limit rules from the above examples:

ratelimit.service.rate_limit.mongo_cps.database_default.over_limit: 0
ratelimit.service.rate_limit.mongo_cps.database_default.total_hits: 2846
ratelimit.service.rate_limit.mongo_cps.database_users.over_limit: 0
ratelimit.service.rate_limit.mongo_cps.database_users.total_hits: 2939
ratelimit.service.rate_limit.messaging.message_type_marketing.to_number.over_limit: 0
ratelimit.service.rate_limit.messaging.message_type_marketing.to_number.total_hits: 0

Debug Port

The debug port can be used to interact with the running process.

$ curl 0:6070/
/debug/pprof/: root of various pprof endpoints. hit for help.
/rlconfig: print out the currently loaded configuration for debugging
/stats: print out stats

You can specify the debug port with the DEBUG_PORT environment variable. It defaults to 6070.

Local Cache

Ratelimit optionally uses freecache as its local caching layer, which stores the over-the-limit cache keys, and thus avoids reading the redis cache again for the already over-the-limit keys. The local cache size can be configured via LocalCacheSizeInBytes in the settings. If LocalCacheSizeInBytes is 0, local cache is disabled.

Redis

Ratelimit uses Redis as its caching layer. Ratelimit supports two operation modes:

1. One Redis server for all limits.
2. Two Redis instances: one for per second limits and another one for all other limits.

As well Ratelimit supports TLS connections and authentication. These can be configured using the following environment variables:

1. REDIS_TLS & REDIS_PERSECOND_TLS: set to "true" to enable a TLS connection for the specific connection type.
2. REDIS_AUTH & REDIS_PERSECOND_AUTH: set to "password" to enable authentication to the redis host.

One Redis Instance

To configure one Redis instance use the following environment variables:

1. REDIS_SOCKET_TYPE
2. REDIS_URL
3. REDIS_POOL_SIZE

This setup will use the same Redis server for all limits.

Two Redis Instances

To configure two Redis instances use the following environment variables:

1. REDIS_SOCKET_TYPE
2. REDIS_URL
3. REDIS_POOL_SIZE
4. REDIS_PERSECOND: set this to "true".
5. REDIS_PERSECOND_SOCKET_TYPE
6. REDIS_PERSECOND_URL
7. REDIS_PERSECOND_POOL_SIZE

This setup will use the Redis server configured with the _PERSECOND_ vars for per second limits, and the other Redis server for all other limits.

Contact

• envoy-announce: Low frequency mailing list where we will email announcements only.
• envoy-users: General user discussion. Please add [ratelimit] to the email subject.
• envoy-dev: Envoy developer discussion (APIs, feature design, etc.). Please add [ratelimit] to the email subject.
• Slack: Slack, to get invited go here. We have the IRC/XMPP gateways enabled if you prefer either of those. Once an account is created, connection instructions for IRC/XMPP can be found here. The #ratelimit-users channel is used for discussions about the ratelimit service.