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directory-service

enterprise directory with Kerberos, LDAP and group policy

Active Directory, FreeIPA, OpenLDAP

SystemTechniques · 21Primitives · 62 directory-service Anti-entropy repairdistributed · medium: Replicas compare hash trees of a key range, descend only into differing subtrees and stream just those ranges, healing silent divergence in the background.›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.›Config distributiondistributed · medium: A control plane pushes versioned resource changes over long-lived streams; each node validates, ACKs or NACKs and keeps its last good copy, so a bad change stops at a canary.›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.›Incremental sync cursorsdistributed · medium: The client keeps one opaque token; each pull returns only the changes after it plus the next token, so sync cost scales with what changed, not with the dataset.›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.›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.›X509 certificatessecurity · low: Certificate chains, path validation, SANs, revocation and short-lived issuanceB+ treestorage · low: Balanced high-fanout search tree with all values in linked leaves; the default on-disk index for point lookups and range scans.›Hdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesVector clocksdistributed · low: One counter per node; comparing two vectors tells whether events are ordered or concurrent, which is exactly what conflict detection needs.›Minimum spanning treegraphs · low: Cheapest set of edges connecting all vertices; Kruskal sorts edges and joins components with union-find, Prim grows one tree, Boruvka merges in parallel rounds.›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.›Asn1 encodingnetworking · low: ASN.1 schemas with BER/DER/PER encodings used in X.509 and 3GPP signallingDNS message format and client looku…networking · low: Binary query/response format of DNS (RFC 1035) and how a stub client uses it: record types, name compression, UDP/TCP/EDNS sizes, TTL caching.›Authorization models (RBAC, ABAC, R…security · low: How to decide who may do what to which object; roles for coarse rules, relationships for sharing, and checks on every object.›Ldap directorysecurity · low: LDAP directory model, bind, search filters and group membership queries for enterprise identityMessage authentication codes (HMAC,…security · low: A keyed short tag proving a message is unmodified and came from a key holder; pick HMAC, CMAC, KMAC or a one-time polynomial MAC by what primitive you already have.›Mutual TLSsecurity · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.›Scram authenticationsecurity · low: SCRAM-SHA-256 challenge-response login without sending the passwordGraceful 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.›Merkle treedata-structures · low: Hash tree for verifying and diffing large datasets with logarithmic proofs+ 14 more techniques+ 46 more primitives

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