FCFS load balancer (central queue) with Erlang-C validation, proper Wq measurement, and metrics plumbing #29

GioeleB00 · 2025-09-18T15:09:21Z

What we changed

New FCFS implementation (central queue)

Rewrote LB FCFS to a token-based FIFO:
- LoadBalancerRuntime._free_edges: simpy.Store holding one token per free LB→server edge.
- On dispatch, LB get()s one token (blocking if none), then forwards the request to that edge.
- Servers call notify_server_free → lb.mark_free(edge_id) to return the token when they finish.
- Zero “thundering herd”: only one waiting request wakes up per free server.
Added LoadBalancerRuntime.on_edge_added(edge_id) so EventInjection can re-enable edges cleanly (push a token when a server comes back).

Accurate FCFS waiting-time metric

LB now records per-request waiting times for FCFS in _lb_waiting_time and exposes them via lb_waiting_times
Arrival time at the LB is taken from the request’s last hop timestamp (history) at LOAD_BALANCER entry.
Ensured link edges deliver on the next tick (yield env.timeout(0)) to preserve causal order of timestamps.

Results & analysis integration

SimulationRunner.run() now passes the LB runtime into ResultsAnalyzer (lb=self._lb_runtime).
ResultsAnalyzer exposes get_lb_waiting_times() and uses LB reference safely.
MMc analyzer:
- Detects FCFS and uses Erlang-C formulas for theory.
- For observed Wq under FCFS, it now uses LB waiting times (central queue), not per-server CPU wait.
- Compatibility checks cleaned up (LB must be FCFS for pooled queue; RANDOM/RR still treated as split model).

Event injection integration

EventInjectionRuntime re-adds edges (server up) and calls lb_on_edge_added(edge_id) (wired from the runner) so the token is immediately available again.
Removal of edges (server down) simply deletes from the LB’s OrderedDict; any stale tokens are discarded by the LB loop.

Unit tests

New FCFS tests covering the token FIFO:
- Immediate free edge ⇒ no wait recorded.
- Wait until edge is added ⇒ Wq ≈ Δt.
- Stale token discarded when edge removed, request waits for a valid edge.
- FIFO order preserved across multiple edges & requests.
Adjusted annotations (mypy) and lints (no blind except).

* setting up the generator * poisson-poisson requests sampling * Delete docker_fs/.env.dev * Delete docker_fs/.env.test * changes * refactor for event generator * added gaussian truncated generator and unit tests for helpers * imprved documentantion and simulation time handling * simulation start with the vent generator * small refactor + tests for the generation of events * minor changes * Update src/app/schemas/simulation_input.py Co-authored-by: Copilot <[email protected]> * Update tests/unit/sampler/test_sampler_helper.py Co-authored-by: Copilot <[email protected]> * Update scripts/quality-check.sh Co-authored-by: Copilot <[email protected]> * Update tests/integration/db_initialization/test_init_models.py Co-authored-by: Copilot <[email protected]> * minor changes after PR review --------- Co-authored-by: Copilot <[email protected]>

…evelop

* moving file to correct folder * Documentation added * Update requests_generator.md * test Added, introduced constants for the sampling window * Update tests/unit/sampler/test_poisson_posson.py Co-authored-by: Copilot <[email protected]> --------- Co-authored-by: Copilot <[email protected]>

* Introduction of the input structure for endpoints * Documentation + foundation of topology input * Improve Step validation, added unit test for the input * improved documentation for the input

* Improved input structure and pytest * Improved pytest structure accordingly to the new schema * definition of the metrics to be measured and update of the simulation input * improved documentations added rationale behind metrics * improved pytest logic and code coherence * Update src/app/core/helpers.py Co-authored-by: Copilot <[email protected]> --------- Co-authored-by: Copilot <[email protected]>

* definition of state and RqsGeneratorRuntime * defined edge runtime and more central logic for sampler * minor changes * minor changes * minor bug fixed * pytest adapted to the new structure, added pytest for rqs_state * Update src/app/core/runtime/rqs_generator.py Co-authored-by: Copilot <[email protected]> * Update src/app/core/runtime/rqs_generator.py Co-authored-by: Copilot <[email protected]> * Update src/app/core/runtime/edge.py Co-authored-by: Copilot <[email protected]> * Update src/app/core/runtime/edge.py Co-authored-by: Copilot <[email protected]> * Update tests/unit/runtime/test_requests_generator.py Co-authored-by: Copilot <[email protected]> * Update src/app/core/event_samplers/common_helpers.py Co-authored-by: Copilot <[email protected]> * Update src/app/core/event_samplers/common_helpers.py Co-authored-by: Copilot <[email protected]> * Update src/app/core/event_samplers/common_helpers.py Co-authored-by: Copilot <[email protected]> * minor changes --------- Co-authored-by: Copilot <[email protected]>

* defined client runtime + tests * initiated the server runtime plus correction of tghe structure * code refactor + test added for runtime + documentation * Update tests/conftest.py Co-authored-by: Copilot <[email protected]> --------- Co-authored-by: Copilot <[email protected]>

* defined architecture for the central collector + documentation * server modification to collect metrics and updated docs * Completed metric collector for server plus test * remove web app dependencies and added metrics for rqs latency * improved docs and improved metric collection * changes to make the code compatible with new changes * improved ci against toml changes * update lock file * minor change

* introduction to the analyzer class + tests * refactor of the analyzer

* Added LB structure in the input for the simulation + tests * introduced LB runtime + documentation * Added test for LB and small refactor to define the SimRunner

* added the first method to the simulation runner * added methods to handle nodes * completed simulation runtime + integration test

* new integration test + bug fixing * added integration and unit test * first tests working * minor change * first working example, upgrade docs, upgrade docstrings * improvements * path bug fixed

* Changed name from fastsim to asyncflow app folder renamed in asyncflow * improved docs

* Reafctor for the folder schemas + defined import for public api * Defined public api, improved docs

* Readme final, docs improved * Docs improvement, refactor analyzer, example added * Added scripts for setup, added pytest, improved readme * Example LB improvements * CI for main + system tests

# Conflicts: # pyproject.toml

* Structure defined for the pydantic model representing Event to be injected * Pydantic validation in the payload for events part 1 * Definition of the input for the events injection part 2 * minor fixes ruff and mypy compliant * full tests and docs added for input event injection * fixed minor bugs

* Events injection for edges part 1 * Logic + docs for the event injection to simulate a server down * Added pydantic validation + unit + int tests for eventinjection * added exaple for event inj yaml + builder added int tests * improved server model + system tests for eventinjection * ruff small fix

* new readme, ci to have pycov badge, comment on server runtime * small changes

# Conflicts: # .github/workflows/ci-main.yml # README.md # tests/system/test_sys_ev_inj_lb_two_servers.py

…tion (#23)

* added metric for server, added logic to collect them + tests * add kpi to collect in settings default * added metric plot for server and tests * Sweep introduction + MM1 heory vs observation + tests * analysis for sweep results + tests * mm1 notebook complete + server latency

… and end-to-end comparison reports (#26) * mmc split + notebook mmc split + random lb algo * tests for mmc

* changing api per ArrivalsGenerator and implementing distrib for ArrivalRuntime * Reafctoring API Arrival generator, tests integrations now working * Api Arrival generator migration complete with tests

codecov · 2025-09-18T15:13:16Z

Codecov Report

❌ Patch coverage is 90.43611% with 125 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/asyncflow/queue_theory_analysis/mmc.py	82.31%	52 Missing ⚠️
src/asyncflow/metrics/simulation_analyzer.py	86.50%	17 Missing ⚠️
src/asyncflow/metrics/sweep_analyzer.py	93.19%	16 Missing ⚠️
src/asyncflow/schemas/topology/endpoint.py	72.97%	10 Missing ⚠️
src/asyncflow/builder/asyncflow_builder.py	88.00%	6 Missing ⚠️
src/asyncflow/runner/simulation.py	64.70%	6 Missing ⚠️
src/asyncflow/runtime/actors/edge.py	68.75%	5 Missing ⚠️
src/asyncflow/runtime/actors/load_balancer.py	89.47%	4 Missing ⚠️
src/asyncflow/runtime/actors/server.py	95.83%	3 Missing ⚠️
src/asyncflow/samplers/arrivals.py	96.96%	3 Missing ⚠️
... and 3 more

📢 Thoughts on this report? Let us know!

GioeleB00 and others added 30 commits July 3, 2025 15:20

setting up the branch

2b26ea2

minor correction

9e48446

minor changes

7a0f860

improved script for linux

1ab21d5

minor change

2a4675f

Delete docker_fs/.env.dev

91c0a7e

Delete docker_fs/.env.test

ab6c48a

minor changes

86501f9

Merge branch 'develop' of github.com:GioeleB00/FastSim-backend into d…

4a7081e

…evelop

README update

d43c915

Improved constants management

02b4756

Clean and refactor

6f06bb7

Features/request handler endpoint input (#3)

ee5d202

* Introduction of the input structure for endpoints * Documentation + foundation of topology input * Improve Step validation, added unit test for the input * improved documentation for the input

Features/metrics elaboration (#8)

7f1f7de

* introduction to the analyzer class + tests * refactor of the analyzer

Features/load balancer node (#9)

84f9897

* Added LB structure in the input for the simulation + tests * introduced LB runtime + documentation * Added test for LB and small refactor to define the SimRunner

Features/simulation runner (#10)

7649866

* added the first method to the simulation runner * added methods to handle nodes * completed simulation runtime + integration test

Features/integration tests unit tests (#11)

d6ff9f6

* new integration test + bug fixing * added integration and unit test * first tests working * minor change * first working example, upgrade docs, upgrade docstrings * improvements * path bug fixed

new readme and guide to build yaml

90df33d

Update README.md

43eb8c5

Added pybuilder and unit tests (#12)

2a306ac

Refactor/change project name plus docs improvement (#13)

0098453

* Changed name from fastsim to asyncflow app folder renamed in asyncflow * improved docs

minor changes

c900708

Refactor/pypi preparation (#14)

adcb9eb

* Reafctor for the folder schemas + defined import for public api * Defined public api, improved docs

minor changes

111cf7b

GioeleB00 and others added 26 commits August 17, 2025 17:43

Ci for main (#16)

de52d04

* Readme final, docs improved * Docs improvement, refactor analyzer, example added * Added scripts for setup, added pytest, improved readme * Example LB improvements * CI for main + system tests

fixing a bug

fb08027

bug fixed

09d99dc

Merge branch 'main' into develop

bc5e329

version bump

1c47441

Merge branch 'main' into develop

dfea747

# Conflicts: # pyproject.toml

Merge branch 'main' into develop

c0684f0

Merge branch 'main' into develop

7d641e9

Merge branch 'main' into develop

623cd6a

# Conflicts: # pyproject.toml

version bump

f57059b

Refactor/fixing readme small fixes (#21)

75a025f

* new readme, ci to have pycov badge, comment on server runtime * small changes

Merge branch 'main' into develop

d4f57aa

# Conflicts: # .github/workflows/ci-main.yml # README.md # tests/system/test_sys_ev_inj_lb_two_servers.py

bump version

6e4355b

Structure input for multiprocessing, improved tests, improved descrip…

87d30ea

…tion (#23)

better test coverage, edges deterministic, step server random (#24)

a5936ab

new sim value

ce37e7c

Add M/M/c (split) queue-theory analyzer, RANDOM load-balancer policy,…

d38d927

… and end-to-end comparison reports (#26) * mmc split + notebook mmc split + random lb algo * tests for mmc

New Api RqsGenerator ---> ArrivalsGenerator (#27)

b22f1e2

* changing api per ArrivalsGenerator and implementing distrib for ArrivalRuntime * Reafctoring API Arrival generator, tests integrations now working * Api Arrival generator migration complete with tests

Updated plots

6ea44ff

Added edges without network latency plus tests (#28)

c66eeb9

Implemented fcfs with tests

07c7f7e

Implemented fcfs algo and validation of mmc models Erlang C

8f30a98

small changes

c4c9309

GioeleB00 merged commit a726a2a into main Sep 18, 2025
1 of 2 checks passed

GioeleB00 mentioned this pull request Sep 18, 2025

Revert "FCFS load balancer (central queue) with Erlang-C validation, proper Wq measurement, and metrics plumbing" #30

Merged

GioeleB00 deleted the feature/FCFS-lb-algo branch September 18, 2025 15:29

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FCFS load balancer (central queue) with Erlang-C validation, proper Wq measurement, and metrics plumbing #29

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FCFS load balancer (central queue) with Erlang-C validation, proper Wq measurement, and metrics plumbing #29

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GioeleB00 commented Sep 18, 2025

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