# Configuring Rate Limits

Swipechain Core is mainly used in the context of public services, providing desktop wallets with the necessary endpoints to function. Since they serve anonymous users and to protect against DDoS attacks, Swipechain Core nodes have strict rate limits. Enterprise users (such as exchanges) might encounter a problem creating large batches of transactions and broadcasting them. The rate limit can be configured in multiple ways to solve these problems.

# Exceeding the Rate Limit

By default, rate limits are enabled on Swipechain Core nodes. When the rate limit is exceeded; a 429 HTTP status is returned.

# Configuring the Rate Limit

The default way to configure the node's rate limit is by editing the .env file found at ~/.config/swipechain-core/{network}/.env. Two keys interest us here:

# file: ~/.config/swipechain-core/{network}/.env

CORE_API_RATE_LIMIT=true
CORE_API_RATE_LIMIT_USER_LIMIT=300

Setting CORE_API_RATE_LIMIT to false will globally disable all rate limits. For internal use this is secure. More fine-grained control may be exerted by using CORE_API_RATE_LIMIT_USER_LIMIT, which uses IP addresses to assign rate limits. The unit is requests/minute.

# Configuration Through a Plugin

Lower access to the rate limiting can be obtained by writing a plugin at ~/.config/swipechain-core/{network}/plugin.js. We can define custom behavior and monkey patch the Swipechain Core rate limiter.

"@swipechain/core-api": {
    enabled: !process.env.CORE_API_DISABLED,
    host: process.env.CORE_API_HOST || "0.0.0.0",
    port: process.env.CORE_API_PORT || 4003,
    whitelist: ["*"],
}

The whitelist option may be used to allow specific IP addresses to access the RPC service, which by default is only accessible by requests originating from localhost.

Cache timeouts can be disabled, which is especially useful on resource-strained machines running heavy queries, such as walking the chain block by block.

# Further Reference

Swipechain Core uses the hapi framework for its API internals and more specifically hapi-rate-limit. This ratelimiter can be configured by setting/altering core-api.

rateLimit: {
    enabled: !process.env.CORE_API_RATE_LIMIT,
    pathLimit: false,
    userLimit: process.env.CORE_API_RATE_LIMIT_USER_LIMIT || 300,
    userCache: {
        expiresIn: process.env.CORE_API_RATE_LIMIT_USER_EXPIRES || 60000,
    },
    ipWhitelist: ["127.0.0.1", "::ffff:127.0.0.1"],
},

Here, pathLimit can be used to limit the total requests per path per given period, or set it to false to disable it. By default pathLimits are disabled.