docs: add docs/architecture.md with pipeline and concurrency diagrams - #820
docs: add docs/architecture.md with pipeline and concurrency diagrams#820verbotenj wants to merge 1 commit into
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📝 WalkthroughWalkthroughAdded architecture documentation for Adder’s pipeline and plugin system. The documentation describes plugin registration and lifecycle states, configuration precedence, goroutine coordination, channel-based shutdown, and once-only stop handling. It also documents the tray application, including its Fyne GUI, setup wizard, notification rules, OS service integration, and background pipeline worker. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In `@docs/architecture.md`:
- Around line 119-142: Update the “Graceful Coordination & Shutdown” bullets and
diagram to reflect the implementation: identify doneChan as a chan bool owned
and closed by Pipeline.Stop(), p.wg as the pipeline-owned WaitGroup, and shared
channels as closed only after waiting and invoking each plugin’s Stop(). Show
plugin Start()/Stop() calls as sequential on the main goroutine, and scope
concurrent or repeated shutdown handling to Pipeline.Stop() callers rather than
claiming each plugin Stop() owns sync.Once or doneChan.
- Around line 105-117: Update the “Concurrency & Goroutine Model” section to
accurately describe Pipeline.Start’s topology: separate chanCopyLoop and
errorChanWait goroutines for inputs and filters, the optional no-filter copy
loop, output error listeners, and outputChanLoop rather than a single pipeline
orchestrator. Replace “Main Thread” with “Main goroutine,” and qualify the
concurrency description to acknowledge lifecycleMu, runningMu, sync.Once, and
sync.WaitGroup synchronization.
- Around line 9-41: Update the architecture description to remove the
unsupported enforced 1:1:N claim and accurately reflect Pipeline.AddInput,
Pipeline.AddFilter, and Pipeline.AddOutput slice-based behavior. Revise the
diagram to show input errors entering the pipeline, asynchronous chanCopyLoop
stages, the no-filter bypass, and dispatch through each output’s InputChan().
- Around line 78-101: Update the “Configuration Precedence” documentation and
diagram to show plugin environment variables are applied after YAML and CLI
options and therefore override both, while core environment variables such as
INPUT, OUTPUT, and API_ADDRESS remain distinct from plugin variables such as
INPUT_CHAINSYNC_NETWORK and CARDANO_NETWORK.
- Around line 146-183: Update the “Adder Tray Application Architecture”
descriptions and diagram to state that the wizard persists engine configuration
as config.yaml and tray configuration as adder-tray.yaml, not adder.yaml.
Describe SetupRunner.Apply as updating the service and tray API connection,
Shutdown as stopping only the tray connection and notification engine, and
distinguish the background worker’s engine-configuration input from the tray’s
SetupPlan-based notification-rule derivation.
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The architecture guide documents the wrong configuration precedence.
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| ## 3. Configuration Precedence | ||
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| Adder configuration is layered to allow flexible overrides. Command-line flags always take the highest precedence, followed by Environment variables, followed by YAML configuration files, and finally falling back to Internal Defaults. |
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The implementation applies CLI > YAML > environment. This diagram places environment above YAML; update the documented precedence or change the implementation. See internal/config/config.go: LoadWithFlags.
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Create comprehensive architecture overview including 1:1 rule, plugin system lifecycle, configuration precedence, and detailed concurrency and graceful shutdown design.,description: Signed-off-by: Ales Verbic <verbotenj@blinklabs.io>
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Verified against the code at 3a2413be. The structural claims hold — the Plugin interface, registration files, orchestrator loop names, and tray rate-limiting all check out — but nine statements are contradicted by the implementation. The blockers are inline.
Further non-blocking gaps:
- Backpressure is never mentioned, and "asynchronous" overstates the design.
pipeline/pipeline.go:45-47createsfilterChan,outputChan, anderrorChanwithmake(chan event.Event)— all three unbuffered — andchanCopyLoopis a blocking hand-off. The only buffers live inside plugins (chainsynceventChan2048; each outputeventChan10). A stalled output propagates backpressure to the input. For a concurrency document this is the most useful fact available. - The observer path is absent.
pipeline.go:65-73and:279-289implement a non-blocking send that drops events when the observer is full, wired toapi.NewEventHubatcmd/adder/main.go:216-221(default buffer 100). The/eventsstream can silently lose events while outputs still receive them. - N inputs/outputs are not reachable from the binary. The
Pipelinetype accepts N of each, butcmd/adder/main.go:191-214resolves exactly one input and one output, so the "combining chainsync and mempool inputs" example cannot be configured. Worth stating that the library is N-capable while the CLI wires 1/all/1. - Restart and start-failure paths are missing.
Start()recreates all four channels and resetsstopOnce(pipeline.go:94-103), and rolls back on failure by closingdoneChanand stopping started plugins in reverse (:106-121) — which contradicts line 124's claim thatdoneChanis closed by the pipeline insideStop(). - Smaller corrections. Line 118 lists Push as retrying;
output/push/has no retry or backoff, unlike webhook (output/webhook/webhook.go:524-535) and telegram (output/telegram/telegram.go:562-571). Line 106's "rather than shared memory locks" sits besideobserverMu,lifecycleMu,runningMu,wg, andstopOnce(pipeline.go:35-40). Line 40 calls an output "stdout" — the plugin islog, andnotifyis omitted; line 38 omits theutxorpcinput. Line 119 calls/eventsREST, butapi/events.go:203-208upgrades to WebSocket or streams SSE, and/fcmis registered by the push output plugin (output/push/api_routes.go:33-35). Line 161 omits FreeBSD, which hastray/setup/service_freebsd.go. Line 112's "Main Thread" should be "main goroutine". - Scope against #716. There is no "event flow" section covering per-event-type emission triggers and error-channel handling, per-plugin option loading is uncovered, and the API/pipeline interaction is one clause with no mention of the observer or
api.RegisterHealthChecker. - The document is not linked from
README.md, which linksdocs/governance.mdanddocs/adder-tray-filtering.md.
The diagrams are ASCII in text fences as #716 requested, and box widths are internally consistent — no rendering defect found. The top diagram's problems are semantic: two arrows from Pipeline Core both land on the Filters box, one labeled "Dispatch Event" that belongs to the outputs hop; the Filters to Outputs arrow skips the real path through p.outputChan and outputChanLoop; and the no-filter bypass (pipeline.go:160-165) is not drawn.
Separately: several bot threads are marked resolved while the text they objected to is unchanged at this head, including the ADDER_ prefix and the shutdown ownership claims.
docs/troubleshooting.md:52 repeats the same ADDER_ prefix error. Out of scope here, but it means the mistake has two homes.
adder has no markdown lint, link checker, or docs-parity target, and CI runs none, so review is the only gate on this class.
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| ## 3. Configuration Precedence | ||
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| Adder configuration is layered to allow flexible overrides. Command-line flags always take the highest precedence, followed by YAML configuration files, followed by Environment variables, and finally falling back to Internal Defaults. |
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This holds for core config (internal/config/config.go:159-211) but is inverted for every plugin option.
cmd/adder/main.go runs LoadWithFlags at :125 (re-applying CLI flags), plugin.ProcessConfig at :130 (YAML), then plugin.ProcessEnvVars at :135. Each unconditionally overwrites the same *PluginOption.Dest pointer that pflag binds CLI flags into (plugin/option.go:44-78, plugin/register.go:69-101), so the last writer wins.
Effective order for plugin options is environment > YAML > CLI > default — the reverse of what this section states. Confirmed with a throwaway test in package plugin: the value read "from-cli", then "from-yaml", then "from-env".
The swap of the YAML and Environment boxes in this revision fixed the core-config case; the plugin-option case is still wrong.
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| v | ||
| +-----------------------+ | ||
| | Environment Variables | (via envconfig, prefixed with ADDER_ / plugin names) |
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No ADDER_ prefix exists.
internal/config/config.go:185 calls envconfig.Process("dummy", c) against envconfig:"INPUT"-style tags, so core variables are unprefixed: INPUT, OUTPUT, API_PORT, LOGGING_LEVEL (see internal/config/config_test.go:87-93).
Plugin variables are <TYPE>_<NAME>_<OPTION> — for example INPUT_CHAINSYNC_ADDRESS, built at plugin/register.go:69-83 and plugin/option.go:90-100.
This also contradicts README.md:229-247, which lists the unprefixed names.
| 2. **Input Goroutines**: Run by each active input plugin (e.g., gouroboros `ChainSync` driver). They block on socket reads from the Cardano node, decode blocks/transactions, and write them to their individual output channels. | ||
| 3. **Pipeline Orchestrator Goroutines**: Run by `pipeline/pipeline.go`. The orchestrator starts: | ||
| - **`chanCopyLoop`**: Multiple concurrent background copying loops that safely bridge events asynchronously between sequential filters (and between input and filters). | ||
| - **`outputChanLoop`**: Reads matched events from the final output channel and distributes them concurrently to each registered output plugin's input channel. |
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Fan-out is sequential, not concurrent. pipeline/pipeline.go:272-278:
// Send event to all output plugins
for _, output := range p.outputs {
select {
case output.InputChan() <- evt:
case <-p.doneChan:
return
}
}The sends block in order, so a single slow or blocked output stalls delivery to every other output and, because the channels are unbuffered, the pipeline behind it. That behaviour is worth documenting explicitly rather than describing the hop as concurrent.
| Graceful coordination is owned and orchestrated by the central **Pipeline Core** via channel signals and sync primitives: | ||
| - **`doneChan chan bool`**: Managed and closed by the **Pipeline** inside its `Stop()` method to signal the orchestrator loops (`chanCopyLoop`, `outputChanLoop`, `errorChanWait`) to exit. | ||
| - **Component Lifecycle Ownership**: The pipeline sequentially calls `Stop()` on all of its registered inputs, filters, and outputs. Each plugin is then individually responsible for gracefully terminating its own background workers (closing its own internal channels and waiting on its internal `sync.WaitGroup`) before returning. | ||
| - **`sync.Once`**: Leveraged throughout the pipeline and individual plugins to ensure `Stop()` teardown logic is executed exactly once, preventing concurrent channel closure panics or data races. |
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sync.Once is used in pipeline/pipeline.go:37, input/mempool, input/utxorpc, filter/cardano, filter/event, api/events.go, and api/api.go — but in no output plugin, and not in input/chainsync.
Those paths use bare nil-checks instead: input/chainsync/chainsync.go:195-216, output/telegram/telegram.go:634-653, output/notify/notify.go:182-193, output/push/push.go:373-386. Only webhook guards with a mutex (output/webhook/webhook.go:609-630).
So "throughout the pipeline and individual plugins" overstates it, and the specific claim of preventing concurrent-close panics and data races is not code-backed for the plugins that lack it.
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| ## 5. Adder Tray Application Architecture | ||
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| The `adder-tray` system tray application (`cmd/adder-tray/` and `tray/`) wraps the core pipeline and integrates it with a cross-platform desktop GUI. |
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The tray has not wrapped the pipeline since it became an API client. tray/connection.go:25-27 states it directly: "the tray no longer manages adder as a subprocess but connects to it as an API client."
Nothing under tray/ or cmd/adder-tray/ imports adder/pipeline, and pipeline.New is never called there. The tray is a WebSocket/SSE client of a separately running adder.
| ### Key Components | ||
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| - **Fyne GUI Engine**: Drives the native OS window rendering, tray icon lifecycle, and interactive onboarding wizard. | ||
| - **Setup Wizard (`tray/wizard/`)**: A step-by-step GUI flow that assists the user in generating the canonical `adder.yaml` configuration file. It configures the network, monitors specific targets (wallets, pools, DReps), sets up notification destinations, and maps notification preferences. |
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adder.yaml is not the canonical name. The engine config is config.yaml (tray/setup/runner.go:89,96; tray/app.go:841) and the tray's own config is adder-tray.yaml (tray/config.go:28).
The only occurrence of adder.yaml in the repository is a fixture path inside tray/setup/service_linux_test.go:68,80, not a file the wizard generates.
Related, at line 183: the tray's SetupRunner.Apply translates the setup plan into config.yaml plus a separate TrayConfig (tray/setup/runner.go:88-120). adder reads only config.yaml; rule matching lives in tray/notifications/engine.go, as the comment at runner.go:104-106 records.
| ```text | ||
| +--------------------+ Go Channel (event.Event) +--------------------+ | ||
| | Input Plugins | --------------------------------> | | | ||
| | (chainsync, etc.) | <-------------------------------- | Pipeline Core | |
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The error arrow points the wrong way. plugin/plugin.go:21-22: "Plugins own their error channel; the pipeline reads from it."
pipeline/pipeline.go:134,158,174 start errorChanWait(<plugin>.ErrorChan()) and :295-313 forwards into p.errorChan, so errors flow input to pipeline.
2 participants
Create comprehensive architecture overview including 1:1 rule, plugin system lifecycle, configuration precedence, and detailed concurrency and graceful shutdown design.,description:
Closes #716
Summary by cubic
Adds
docs/architecture.mdwith pipeline and concurrency diagrams covering the M:N:P pipeline, plugin lifecycle, configuration precedence, graceful shutdown, andadder-trayarchitecture. Improves shared understanding for maintainers and plugin authors; no runtime behavior changes.plugin.Plugininterface signatures; orchestrator loops inpipeline/pipeline.go(chanCopyLoop,outputChanLoop,errorChanWait); plugin auto-registration via blank imports ininput/input.go,filter/filter.go, andoutput/output.go.adder-traycoverage: wizard-to-rule derivation, notification coalescing, and OS service integration.Written for commit 3a2413b. Summary will update on new commits.
Summary by CodeRabbit