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tracing

distributed tracing

OpenTelemetry, Jaeger

SystemTechniques · 6Primitives · 29 tracing 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.›Critical path analysisgraphs · medium: Longest dependency chain in a DAG of timed spans or build actionsColumnar storagestorage · medium: Store each column contiguously so analytic scans read only the columns they need, compress well and run as tight SIMD loops.›Distributed tracingsystems · medium: Give each request a 128-bit id, record timed spans linked by parent ids, pass the ids in a header across every hop, and join the spans back into a tree afterwards.›Telemetry samplingsystems · medium: Head, tail and dynamic sampling of traces, events and logs to a budgetVectorized executionstorage · medium: Query operators pass batches of about 1-2K values per column instead of single tuples, amortizing interpretation overhead and enabling tight SIMD loops.›Protobuf wire formatnetworking · low: Protocol Buffers wire format: tags, varints, length-delimited fields and schema evolutionBloom filterdata-structures · low: Bit array answering "definitely not present" or "probably present" in about 10 bits per key for 1 % false positives; inserts are cheap, deletes impossible.›Quantile sketchesdata-structures · low: Mergeable quantile sketches: t-digest, DDSketch, HDR histogramsConsistent hashingdistributed · low: Hash nodes and keys onto a ring; each key belongs to the next node clockwise, so membership changes move only about 1/n of keys.›Segmented logdistributed · low: Split an append-only log into files named by their first offset, write only the newest, and find any record by binary search plus a sparse index.›Ebpfhardware-os · low: Verified in-kernel programs on hooks (kprobes, XDP, tc) with mapsGrpc protocolnetworking · low: GRPC framing over HTTP/2: unary and streaming RPCs, deadlines, statusPRNGs (PCG, xoshiro)numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.›Time partitioningstorage · low: Cut a table into fixed-interval time blocks so queries read only overlapping blocks and retention drops a whole block as one metadata change.›Backpressuresystems · low: Bound every queue and make a full queue push back on the producer by blocking, dropping, rejecting or withholding credit.›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.›BFS and DFSgraphs · low: The two basic graph traversals; BFS gives hop distances and levels, DFS gives discovery/finish order for cycles, components and topological order.›Topological sortgraphs · low: Order the vertices of a DAG so every edge points forward; the core of build systems, schedulers and dependency resolution, with cycle detection for free.›Bit packing and PFORcompression · low: Store blocks of integers with exactly b bits each and patch rare outliers separately (PFOR); the fastest integer codec family, billions of values per second.›+ 13 more primitives

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