README

A very light php framework. Will probably not help you much.

Rate limiting

Neuron\RateLimit\RateLimiter is a fixed-window counter with weighted attempts. The cap check happens inside one conditional UPDATE, so bursts serialise on the row lock and a refused attempt never consumes budget.

use Neuron\RateLimit\DatabaseStore;
use Neuron\RateLimit\RateLimiter;

$limiter = new RateLimiter (new DatabaseStore ());          // table neuron_rate_limits
if (!$limiter->attempt ('user:export:' . $userId, 100, 3600, $itemCount)) {
    header ('Retry-After: ' . $limiter->retryAfter (3600));
    // 429
}
$limiter->cleanup ();  // from a daily cron: drops windows older than a day

The application owns the table. Default name neuron_rate_limits (pass another name to DatabaseStore; it must match /^[A-Za-z0-9_]+$/ and is quoted with backticks in every statement):

CREATE TABLE neuron_rate_limits (
  id int unsigned NOT NULL AUTO_INCREMENT,
  rl_key varchar(128) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL,
  window_start int unsigned NOT NULL,
  hits int unsigned NOT NULL DEFAULT 0,
  PRIMARY KEY (id),
  UNIQUE KEY neuron_rate_limits_key_window (rl_key, window_start),
  KEY neuron_rate_limits_window (window_start)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

rl_key uses a binary (case-sensitive) collation so keys match exactly; a case-insensitive collation would merge keys that differ only by case into the same bucket. neuron_rate_limits_window keeps the cleanup DELETE (which scans by window_start) indexed. A table with PRIMARY KEY (rl_key, window_start) and no id works too.

A few contract details worth knowing:

Key length. rl_key is varchar(128). INSERT IGNORE silently truncates a longer key to fit instead of erroring, so two distinct keys that only differ past the 128th character would share a bucket. Keep keys short, or hash the long/variable part before using it as a key.
max < 1 refuses every attempt. There's no special-casing: a cap below 1 can never be satisfied. If 0 should mean "disabled" (skip rate limiting entirely) in your application, guard for that case before calling attempt().
remaining() is a non-atomic read. It issues a plain SELECT with no lock, so its result can be stale relative to a concurrent attempt() against the same key and window.
Don't call attempt() inside a long-running explicit transaction. A rollback refunds the budget the INSERT/UPDATE charged, and holding that row's locks open for the rest of a long transaction can deadlock against other writers hitting the same key.
window_start is an unsigned 32-bit epoch bucket (seconds since the epoch, rounded down to a window boundary), matching the column's int unsigned type above.

Sessions

Routes with the session filter start a session through the application's session handler (Neuron\SessionHandlers\SessionHandler, which wraps PHP's own save handler, or DbSessionHandler, which stores sessions in a sessions table).

Session ids are validated. A request may only bring an id in the format PHP generates (22 to 256 characters out of A-Za-z0-9,-) that has a stored session. Any other id is ignored and the request gets a new session. The handlers switch on session.use_strict_mode when a session starts. SessionHandler can only check for a stored session when PHP's save handler is files.
The PSID query parameter is opt-in. A session id in the query string is only read after \Neuron\SessionHandlers\SessionHandler::setQueryParameterEnabled (true); and only when the request has no (valid) session cookie.
Sessions expire after session.gc_maxlifetime seconds without a request (DbSessionHandler). An older row is treated as absent and removed when it is read; garbage collection uses the same lifetime. Set session.gc_maxlifetime before the session starts.
$request->getSession ()->regenerate () gives the session a new id and keeps its data. Call it when a user logs in.

catlabinteractive / neuron

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Rate limiting

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