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ci-runner-fleet

autoscaling ephemeral CI runners

actions-runner-controller

SystemTechniques · 20Primitives · 62 ci-runner-fleet Desired-state reconciliationdistributed · medium: Declare the target in a store; controllers repeatedly diff actual against desired from full state and apply idempotent fixes, so missed events only delay convergence.›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.›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.›Vm snapshot restorehardware-os · medium: Snapshot an initialised VM/isolate heap and restore it for fast cold startsCoverage-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.›Workload identity (SPIFFE-style)security · medium: A local agent works out which workload is calling, then hands it a short-lived signed identity that it renews automatically; no secret is shipped in advance.›Point-in-time recoverystorage · medium: Periodic base backups plus a continuously archived change log let you rebuild the state as of any instant, then branch from there.›Leasesdistributed · low: A lock that expires on its own: bounded-time ownership that survives crashes and partitions, given bounded clock drift and fencing tokens on writes.›Hardware virtualization kvmhardware-os · low: VT-x/AMD-V via KVM: vCPU run loop, VM exits, MMIO emulationMutual TLSsecurity · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.›Bin packingoptimization · low: Pack items of given sizes into the fewest fixed-capacity bins; sort descending, then first-fit, gives at most 11/9 of optimal and runs in O(n log n).›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.›Hdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesCgroups and namespaceshardware-os · low: Linux namespaces limit what a process can see; cgroup v2 limits and accounts what it may use. Containers, sandboxes and job schedulers are built from the two.›Process 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.›Long pollingnetworking · low: The client asks "anything after cursor X?"; the server holds the request until there is news or a timeout, and the client immediately asks again.›Content-addressed storagestorage · low: Store each blob under the hash of its bytes: immutable, deduplicated by construction, self-verifying on every read, and composable into Merkle trees.›Conditional writesdistributed · low: Put-if-absent / if-match compare-and-swap on objects or keys as a commit primitiveExponential backoff with jittersystems · low: Retry after delays that grow geometrically and are randomized, so failed clients spread out instead of hammering a recovering service in synchronized waves.›Cooperative schedulingconcurrency · low: Green threads/coroutines yielding at await points on a user-space schedulerRecord replaydistributed · low: Record every nondeterministic input (time, randomness, I/O, model and tool outputs, per-tick player input) and re-execute deterministically for debugging, replays and state rebuildPRNGs (PCG, xoshiro)numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.›Write-ahead logstorage · low: Append each change to a checksummed sequential log and fsync it before touching data pages; the basis of crash durability in nearly every database.›+ 13 more techniques+ 46 more primitives

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