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load-testing

load testing harness

k6, Gatling

SystemTechniques · 13Primitives · 52 load-testing Clock synchronizationdistributed · medium: Estimate a clock's offset from four timestamps, filter out queueing noise, and steer the clock smoothly; NTP gets about a millisecond, PTP with hardware timestamps under a microsecond.›Deterministic simulation testingdistributed · medium: Run the whole system in one thread under a seeded scheduler with simulated network, disk and clock, so every failure replays from its seed.›Open-loop load generationdistributed · medium: Send requests on a fixed or random schedule regardless of replies, and time each from its intended send time, so stalls show up in the tail.›Primary-backup replicationdistributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.›Coverage-guided fuzzingsecurity · medium: Mutate inputs, run an instrumented target, and keep any input that reaches a new code edge; feedback turns blind guessing into incremental search.›TLS 1.3security · medium: The standard encrypted, authenticated transport; one round trip, only forward-secret AEAD suites, and little left to misconfigure.›Hypothesis testingstatistics · medium: Pick a test statistic, compare it to its distribution under "no effect", read off a p-value, and control error rates across one test or many.›Cooperative schedulingconcurrency · low: Green threads/coroutines yielding at await points on a user-space schedulerPRNGs (PCG, xoshiro)numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.›Hdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesHierarchical timing wheelsystems · low: Timers bucketed by expiry into wheels of slots, coarser wheels for far deadlines: O(1) insert and cancel for millions of timeouts.›Quantile sketchesdata-structures · low: Mergeable quantile sketches: t-digest, DDSketch, HDR histogramsProcess supervisionhardware-os · low: A parent process starts services, reaps their exits and restarts them under a delay and burst-limit policy, then stops them with SIGTERM before SIGKILL.›epoll event loopnetworking · low: One thread waits on thousands of non-blocking sockets with epoll_wait and handles only ready ones; the core of nginx, Redis and tokio.›HTTP/2networking · low: Binary multiplexed framing for HTTP over one TCP connection: streams, per-stream and per-connection credit windows, HPACK header compression and the limits that contain abuse.›io_uringnetworking · low: Linux async I/O through two shared-memory rings (submissions in, completions out), batching or eliminating syscalls for sockets and files alike.›WebSocketsnetworking · low: Full-duplex message framing over one upgraded HTTP connection; the standard way to push real-time data to browsers.›Mutual TLSsecurity · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.›Graceful drainingsystems · low: On a termination signal, stop taking new work, finish in-flight work until a deadline, tell clients to reconnect elsewhere, then exit; clients resume from a token.›Token bucketsystems · low: A bucket of up to b tokens refilled at rate r; requests spend tokens, enforcing an average rate while allowing bursts of b.›PID controllerrobotics · low: Drive a measured value to a setpoint with three terms on the error: proportional, integral, derivative. The default feedback loop for motors, heaters, drones and gimbals.›Phase-locked loop (digital)signal-processing · low: Feedback loop that locks a local oscillator to the phase and frequency of an input tone; the core of carrier recovery, clock recovery and GNSS tracking.›Robust statisticsstatistics · low: Location and scale estimates (median, MAD, trimmed mean, Huber M-estimator) that stay correct when a minority of the data is garbage.›+ 6 more techniques+ 36 more primitives

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