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071 DISTRIBUTED COORDINATION FLOWS

Documentation for 071_DISTRIBUTED_COORDINATION_FLOWS from the Foundation repository.

Distributed Coordination Primitive Flows

Diagram 1: Consensus Protocol - Network Message Flows

sequenceDiagram participant N1 as Node1@host1 participant N2 as Node2@host2 participant N3 as Node3@host3 participant N4 as Node4@host4 participant Net as Network Fabric Note over N1,N4: Phase 1: Propose (T0-T50ms) N1->>+Net: broadcast_propose(value: scale_up, term: 1) par Network Propagation Net-->>N2: {propose, scale_up, term: 1, from: node1} Net-->>N3: {propose, scale_up, term: 1, from: node1} Net-->>N4: {propose, scale_up, term: 1, from: node1} and Proposer Waits N1->>N1: start_timer(consensus_timeout: 5000ms) N1->>N1: await_responses(expected: 3) end Note over N1,N4: Phase 2: Promise Phase (T10-T80ms) par Concurrent Promise Processing N2->>N2: evaluate_proposal(scale_up, term: 1) N2->>N2: check_higher_term_seen? -> false N2->>+Net: promise_accept(term: 1, to: node1) and N3->>N3: evaluate_proposal(scale_up, term: 1) N3->>N3: check_higher_term_seen? -> false N3->>+Net: promise_accept(term: 1, to: node1) and N4->>N4: evaluate_proposal(scale_up, term: 1) N4->>N4: check_higher_term_seen? -> false N4->>+Net: promise_accept(term: 1, to: node1) end par Promise Collection Net-->>N1: {promise, term: 1, from: node2} Net-->>N1: {promise, term: 1, from: node3} Net-->>N1: {promise, term: 1, from: node4} and Network Delays Note over Net: node2->node1: 15ms latency Note over Net: node3->node1: 32ms latency Note over Net: node4->node1: 28ms latency end N1->>N1: promises_received: 3/3 (majority achieved) N1->>N1: commit_decision(value: scale_up) Note over N1,N4: Phase 3: Commit Broadcast (T80-T150ms) N1->>+Net: broadcast_commit(value: scale_up, term: 1) par Commit Propagation Net-->>N2: {commit, scale_up, term: 1} Net-->>N3: {commit, scale_up, term: 1} Net-->>N4: {commit, scale_up, term: 1} and Concurrent Application N2->>N2: apply_consensus(scale_up) -> local_state_update N3->>N3: apply_consensus(scale_up) -> local_state_update N4->>N4: apply_consensus(scale_up) -> local_state_update end par Acknowledgment Fan-back N2->>Net: ack_commit(term: 1) N3->>Net: ack_commit(term: 1) N4->>Net: ack_commit(term: 1) and Net-->>N1: {ack, term: 1, from: node2} Net-->>N1: {ack, term: 1, from: node3} Net-->>N1: {ack, term: 1, from: node4} end N1->>N1: consensus_complete(value: scale_up, duration: 145ms) Note over N1,N4: Result: All nodes committed 'scale_up' in 145ms

Network Flow Characteristics:

  • Message Amplification: 1 propose → 3 promises → 1 commit → 3 acks = 8 total messages
  • Latency Variance: Network delays vary (15ms, 32ms, 28ms) but consensus waits for slowest
  • Concurrent Processing: All nodes evaluate proposals simultaneously
  • Failure Window: 50ms window between propose and promise where network failures critical

Diagram 2: Leader Election During Network Partition

graph TB subgraph "Network Topology: T0" N1((Node1
candidate)) N2((Node2
follower)) N3((Node3
follower)) N4((Node4
follower)) N5((Node5
follower)) N1 -.->|heartbeat| N2 N1 -.->|heartbeat| N3 N1 -.->|heartbeat| N4 N1 -.->|heartbeat| N5 N2 -.->|ack| N1 N3 -.->|ack| N1 N4 -.->|ack| N1 N5 -.->|ack| N1 end subgraph "Network Partition Event: T100ms" direction TB subgraph "Partition A: Majority" N1_A((Node1
🔴 leader_timeout)) N2_A((Node2
🟡 follower)) N3_A((Node3
🟡 follower)) N2_A -.->|vote_request| N1_A N3_A -.->|vote_request| N1_A N1_A -.->|vote_grant| N2_A N1_A -.->|vote_grant| N3_A end subgraph "Partition B: Minority" N4_B((Node4
🔴 leader_timeout)) N5_B((Node5
🔴 leader_timeout)) N4_B -.->|vote_request| N5_B N5_B -.->|vote_request| N4_B N4_B -.->|vote_deny
tie| N5_B N5_B -.->|vote_deny
tie| N4_B end N1_A -.->X N4_B N1_A -.->X N5_B N4_B -.->X N1_A N5_B -.->X N1_A end subgraph "Election Resolution: T200-T400ms" direction TB subgraph "Partition A: Successful Election" N1_WIN((Node1
🟢 NEW LEADER
term: 2)) N2_WIN((Node2
🟢 follower)) N3_WIN((Node3
🟢 follower)) N1_WIN -.->|leader_announce
term: 2| N2_WIN N1_WIN -.->|leader_announce
term: 2| N3_WIN N2_WIN -.->|leader_ack| N1_WIN N3_WIN -.->|leader_ack| N1_WIN end subgraph "Partition B: Election Failure" N4_FAIL((Node4
🔴 candidate
no majority)) N5_FAIL((Node5
🔴 candidate
no majority)) N4_FAIL -.->|timeout_retry| N4_FAIL N5_FAIL -.->|timeout_retry| N5_FAIL end end subgraph "Partition Healing: T500ms" direction TB N1_FINAL((Node1
🟢 LEADER
term: 2)) N2_FINAL((Node2
🟢 follower)) N3_FINAL((Node3
🟢 follower)) N4_FINAL((Node4
🟡 sync_recovery)) N5_FINAL((Node5
🟡 sync_recovery)) N1_FINAL -.->|leader_announce
term: 2| N4_FINAL N1_FINAL -.->|leader_announce
term: 2| N5_FINAL N4_FINAL -.->|accept_leader
step_down| N1_FINAL N5_FINAL -.->|accept_leader
step_down| N1_FINAL N1_FINAL -.->|state_sync| N4_FINAL N1_FINAL -.->|state_sync| N5_FINAL end classDef leader fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px classDef follower fill:#e3f2fd,stroke:#1565c0 classDef candidate fill:#fff3e0,stroke:#ef6c00 classDef failed fill:#ffebee,stroke:#c62828 classDef recovering fill:#f3e5f5,stroke:#7b1fa2 class N1_WIN,N1_FINAL leader class N2_WIN,N3_WIN,N2_FINAL,N3_FINAL follower class N1_A,N4_B,N5_B,N4_FAIL,N5_FAIL candidate class N4_FINAL,N5_FINAL recovering

Partition Behavior Analysis:

  • Split Brain Prevention: Only partition with majority (3/5) can elect leader
  • Minority Starvation: Nodes 4&5 cannot progress, remain in candidate state
  • Recovery Synchronization: Healing requires state sync, not just leader acceptance
  • Time Delays: Election ~300ms, partition healing +200ms = 500ms total unavailability

Diagram 3: Distributed Mutex Contention (Lamport Algorithm)

gantt title Distributed Mutex Access - Concurrent Request Timeline dateFormat X axisFormat %L section Node1_Request Request Timestamp :milestone, n1_req, 0, 0ms Broadcast Request :n1_bc, after n1_req, 15ms Collect Responses :n1_wait, after n1_bc, 45ms Enter Critical Section :milestone, n1_enter, after n1_wait, 0ms Critical Work :n1_work, after n1_enter, 100ms Release Broadcast :n1_rel, after n1_work, 10ms section Node2_Request Request Timestamp :milestone, n2_req, 10, 0ms Broadcast Request :n2_bc, after n2_req, 12ms Collect Responses :n2_wait, after n2_bc, 135ms Enter Critical Section :milestone, n2_enter, after n2_wait, 0ms Critical Work :n2_work, after n2_enter, 80ms Release Broadcast :n2_rel, after n2_work, 8ms section Node3_Request Request Timestamp :milestone, n3_req, 25, 0ms Broadcast Request :n3_bc, after n3_req, 18ms Collect Responses :n3_wait, after n3_bc, 195ms Enter Critical Section :milestone, n3_enter, after n3_wait, 0ms Critical Work :n3_work, after n3_enter, 60ms Release Broadcast :n3_rel, after n3_work, 12ms section Node4_Observer Receive N1 Request :n4_r1, 20, 2ms Receive N2 Request :n4_r2, 25, 2ms Receive N3 Request :n4_r3, 50, 2ms Send Responses :n4_resp, after n4_r3, 5ms section Node5_Observer Receive N1 Request :n5_r1, 18, 3ms Receive N2 Request :n5_r2, 28, 3ms Receive N3 Request :n5_r3, 48, 3ms Send Responses :n5_resp, after n5_r3, 5ms

Mutex Flow Analysis:

  • Timestamp Ordering: Node1 (T=0) < Node2 (T=10) < Node3 (T=25) determines execution order
  • Broadcast Overlap: All nodes broadcast requests before any complete, creating contention
  • Wait Queue Formation: Node2 waits for Node1 completion, Node3 waits for both
  • Observer Load: Nodes 4&5 handle 3 concurrent requests each, respond to all
  • Total System Throughput: 240ms for 3 sequential critical sections vs potential parallelism

Diagram 4: Barrier Synchronization with Stragglers

flowchart TD subgraph "Phase 1: Barrier Setup (T0)" Coord[Barrier Coordinator
barrier_id: #ref123] Coord -.->|register| N1_P1[Node1: registered] Coord -.->|register| N2_P1[Node2: registered] Coord -.->|register| N3_P1[Node3: registered] Coord -.->|register| N4_P1[Node4: registered] Coord -.->|register| N5_P1[Node5: registered] end subgraph "Phase 2: Work Execution (T0-T200ms)" N1_P1 -.->|async work| W1[Work1: ML Training
⚡ Fast: 50ms] N2_P1 -.->|async work| W2[Work2: Data Processing
⚡ Fast: 75ms] N3_P1 -.->|async work| W3[Work3: Model Evaluation
🐌 Slow: 180ms] N4_P1 -.->|async work| W4[Work4: Result Aggregation
⚡ Fast: 60ms] N5_P1 -.->|async work| W5[Work5: Statistics Collection
🐌 Very Slow: 200ms] end subgraph "Phase 3: Barrier Arrival (T50-T200ms)" W1 -.->|T=50ms| Arr1[Node1 Arrives
✅ WAITING] W2 -.->|T=75ms| Arr2[Node2 Arrives
✅ WAITING] W4 -.->|T=60ms| Arr3[Node4 Arrives
✅ WAITING] W3 -.->|T=180ms| Arr4[Node3 Arrives
✅ WAITING] W5 -.->|T=200ms| Arr5[Node5 Arrives
🚀 TRIGGER!] Arr1 -.->|barrier_wait| BarrierQ{Barrier Queue
Count: 1/5} Arr2 -.->|barrier_wait| BarrierQ Arr3 -.->|barrier_wait| BarrierQ Arr4 -.->|barrier_wait| BarrierQ Arr5 -.->|barrier_wait| BarrierQ BarrierQ -.->|count check| CountCheck{Count == 5?} CountCheck -.->|YES| Release[🚀 RELEASE ALL] end subgraph "Phase 4: Synchronized Release (T200ms)" Release -.->|broadcast_release| N1_R[Node1 Released
Continue Phase 2] Release -.->|broadcast_release| N2_R[Node2 Released
Continue Phase 2] Release -.->|broadcast_release| N3_R[Node3 Released
Continue Phase 2] Release -.->|broadcast_release| N4_R[Node4 Released
Continue Phase 2] Release -.->|broadcast_release| N5_R[Node5 Released
Continue Phase 2] end subgraph "Timeline Analysis" Timeline[Barrier Efficiency
Total Wait Time: 150ms + 125ms + 140ms + 20ms + 0ms = 435ms
Slowest Task Determines All: 200ms
System Utilization During Wait: 0%
🔴 STRAGGLER PROBLEM] end classDef fast fill:#c8e6c9,stroke:#2e7d32 classDef slow fill:#ffecb3,stroke:#f57c00 classDef veryslow fill:#ffcdd2,stroke:#d32f2f classDef waiting fill:#e1f5fe,stroke:#0277bd classDef release fill:#e8f5e8,stroke:#388e3c,stroke-width:3px class W1,W2,W4 fast class W3 slow class W5 veryslow class Arr1,Arr2,Arr3,Arr4,BarrierQ waiting class Release,N1_R,N2_R,N3_R,N4_R,N5_R release

Barrier Synchronization Insights:

  • Straggler Dominance: Slowest task (200ms) determines barrier release for all
  • Wasted Resources: Fast tasks (50-75ms) wait 125-150ms doing nothing
  • Utilization Drop: System drops to 0% utilization during barrier wait
  • Cascade Effect: All subsequent phases delayed by slowest component
  • Optimization Opportunity: Timeout-based barriers could improve throughput at cost of consistency

Novel Concurrent Visualization Elements:

  • Gantt Timeline: Shows true temporal overlap and waiting periods
  • Straggler Highlighting: Color coding shows performance differences
  • Queue State Visualization: Shows barrier counter progression
  • Resource Utilization: Explicit wait time calculations
  • Network Partition Recovery: Shows both failure and healing flows
  • Message Amplification Tracking: Counts total messages in distributed protocols

This approach reveals distributed system behavior patterns like message amplification, partition tolerance, straggler effects, and resource utilization that are invisible in static code diagrams.