After picking a site in the coverage form, a new optional dropdown
lets the user attach the coverage to one of the devices at that site.
The dropdown reloads on every site change. If the site has no devices
yet, a hint replaces it.
Schema: nullable device_id FK on coverages (on_delete: nilify_all so
deleting a device leaves the coverage standing). Filtered by both
site_id and organization_id when loading the dropdown options.
Show page lists the attached device by name (or IP) when set.
Form simplification per user feedback. Form now shows only the
essentials (Name, Site, Antenna, Frequency, TX power, Range, Height,
Azimuth, Tilt, Foliage tuning) with imperial units throughout (ft, mi,
GHz). Defaults: TX power 18 dBm, height 100 ft, azimuth 0°, frequency
5.8 GHz, range 4 mi.
EIRP is calculated, not entered: shown as a live-updating badge in
the form header as `TX power + antenna.gain`.
Removed from the form (still on the schema with sensible defaults so
existing callers and the worker keep working): cell_size_m (auto-
computed from radius / 200, clamped 5–50 m), cable_loss_db, sm_gain_dbi,
tx_clearance_m, height_above_rooftop_m, receiver_height_m,
rx_threshold_dbm, latitude/longitude_override.
Schema:
- Six virtual imperial fields (height_agl_ft, height_above_rooftop_ft,
receiver_height_ft, tx_clearance_ft, radius_mi, frequency_ghz). The
changeset converts to SI before validation. Tests/workers/API keep
sending SI directly.
- ensure_cell_size_m/1: defaults the cell size when callers omit it.
Show + index pages now display GHz / ft / mi.
Propagation accuracy upgrade:
- Earth-curvature correction (4/3-Earth model, ITU-R P.453) applied
per profile sample. Important for paths over ~5 km.
- Replaced Bullington single-knife-edge with Deygout three-edge
multi-obstacle method (ITU-R P.526 §4.5): catches multi-ridge
terrain shadowing that a single dominant obstacle would miss.
Tests: 67 coverage tests pass (added Earth-curvature and Deygout
multi-obstacle reference checks). Full suite: 10817 tests.
The compute pipeline now actually runs: per-pixel path loss over LIDAR
terrain, antenna pattern lookup, real GeoTIFF + colored PNG output,
Leaflet imageOverlay rendering with opacity slider and dBm legend.
Propagation:
- Towerops.Coverages.Propagation: Friis FSPL + Bullington single-knife-edge
diffraction (ITU-R P.526). Pure Elixir, closed-form, no NIF dependency.
Clean signature so a future ITM/Longley-Rice backend can drop in.
- Towerops.Coverages.Profile: AAIGrid sampler with elevation_at, sample
along great circle, haversine distance.
- Towerops.Coverages.Raster: Float32 GeoTIFF via gdal_translate (with VRT
wrapper) and colored PNG via gdaldem color-relief. Outputs to
priv/static/coverage/<org>/<id>/, served by existing Plug.Static.
Worker:
- Towerops.Workers.CoverageWorker now does the full pipeline: bbox compute
-> Towerops.Lidar.get_elevation_grid -> per-pixel Task.async_stream
(parallel = schedulers) running antenna pattern lookup + propagation +
RSSI threshold check, write rasters. Configurable terrain source via
:coverage_terrain_module application env so tests can stub. Friendly
failure messages for :no_tile, :grid_too_large, :nodata,
:unknown_antenna, :missing_location.
Bundled antenna catalog (~95 entries):
- AntennaCatalog with compact specs for every antenna in the request list:
Cambium, ALPHA, Antel, ITELITE, KP Performance, L-com, MARS, MikroTik,
Mimosa, MTI, RADWIN, RF Elements, Ruckus, Tarana, Simulate, Ubiquiti.
- Antenna.from_spec/1 synthesizes 360+360 attenuation patterns from
gain+beamwidth (cosine-squared main lobe, smooth transition,
front-to-back floor with mild ripple). Real .ant files in priv/antennas/
override the catalog by slug. Test fixtures moved to test/support.
Schema (migration add_radio_fields_to_coverages):
- tx_power_dbm replaces eirp_dbm; EIRP is now derived as
tx_power + antenna.gain - cable_loss in Coverage.eirp_dbm/2 and shown
live in the form header.
- cable_loss_db, sm_gain_dbi, latitude_override, longitude_override,
height_above_rooftop_m, tx_clearance_m, foliage_tuning (0-100 slider).
- Coverage.location/1 returns {lat, lon} from override or parent site.
UI:
- form.html.heex: cnHeat-style grouped form (Identity / Location /
Mounting / RF / Coverage extent), foliage tuning range slider,
computed EIRP badge in the header.
- show.html.heex: Leaflet map area with L.imageOverlay heatmap,
opacity slider, dBm color legend, antenna marker with directional
wedge for azimuth.
- assets/js/app.ts: CoverageMap hook registered.
Tests: 24 new (propagation reference values, profile sampling,
worker end-to-end with stubbed terrain that writes real GeoTIFF + PNG,
org-mismatch job-cancel guard). Full suite: 10815 tests.
End-to-end CRUD scaffold for per-site, per-antenna RF coverage
prediction. Schema, context, antenna registry, Oban worker stub, and
three LiveViews are wired up; the actual ITM + LIDAR + buildings
compute pipeline lands in a follow-up.
- Migration + Coverage schema with full validation (RF params, pixel-
budget cap, antenna_slug existence). organization_id excluded from
cast (programmatic-only).
- Coverages context: org-scoped CRUD, validate_site_in_organization
rejects cross-tenant site_id refs at insert/update, queue_compute
with PubSub broadcast on per-coverage and per-org topics.
- MSI Planet .ant parser + persistent_term registry loaded at boot
from priv/antennas/. Two synthetic .ant fixtures (omni + 90deg
sector) bundled.
- CoverageWorker on new :coverage Oban queue (concurrency 2). Job
args carry organization_id; worker refuses to run on org mismatch.
Stub flips status to "failed" with "compute not yet implemented"
so the UI flow is exercisable.
- LiveViews: index (org-wide, live status updates), form (antenna
picker grouped by manufacturer), show (status banners, params
panel, map placeholder). Sidebar nav link added.
- Routes /coverage, /coverage/new, /coverage/:id, /coverage/:id/edit
under :require_authenticated_user_with_default_org.
- 41 new tests covering schema validation, .ant parsing, context
CRUD with cross-org guards, Oban job enqueue.
device_down alerts and active incidents represent the same outage.
Filter device_down alerts from the alerts section for devices already
shown as incidents, so a down device shows as 1 issue not 2.
unpkg.com fetches were intermittently failing in production, leaving
the /sites-map page without a working map. Vendoring Leaflet (JS, CSS,
marker/layer images) under priv/static/vendor/leaflet/ removes the
runtime CDN dependency, the matching CSP relaxation, and the SRI hash
churn on future updates.
Add 'vendor' to ToweropsWeb.static_paths/0 so Plug.Static serves the
new tree, and revert script-src/style-src to no longer list unpkg.com.
connect-src still allows *.tile.openstreetmap.org for tile fetches.
The /sites-map page loads leaflet from unpkg.com (CSS + JS) and fetches
tiles from *.tile.openstreetmap.org. Update Content-Security-Policy to
permit those origins so the map can render.
Adds:
- script-src https://unpkg.com (leaflet.js)
- style-src https://unpkg.com (leaflet.css)
- connect-src https://*.tile.openstreetmap.org (tile fetches)
Apply patterns from testingliveview.com — replace render_click/submit/change
event-name calls with element/form-targeted equivalents that validate the
actual DOM wiring, not just handler logic. Adds stable test selectors
(id="...") to interactive elements across 10 LiveView templates.
Surfaces (and fixes) several real issues that the bypass-style tests masked:
- Removes dead regenerate_token handler in agent_live/index.ex (no UI ever
triggered it) and its corresponding test.
- Removes dead refresh_topology test in network_map_live_test (event was
referenced only in the test — no handler, no button, no JS anywhere).
- Corrects "shows notification tab with add device modal" — modal lives on
the security tab; original test mounted ?tab=notifications and only
worked because direct event calls bypassed tab gating.
- Corrects form input shape mismatches in agent_live/index_test that the
handler's defensive case clauses had been masking.
- Expands setup data for org/settings_live_test (snmp_community,
default_agent_token_id, multi-org membership) so the gated buttons
actually render.
11 direct render_click/submit/change calls remain — all intentional,
documented server-side guard tests (tampered POSTs, race conditions,
defensive idempotent handlers).
Full LiveView test suite: 1300 tests, 0 failures.
Performance:
- schedule_live: preload page once instead of get_schedule!/1 per row
- alert_live + alerts: DB-side status filter; Repo.aggregate counts replace length/Enum.count over 500-row fetches on every event
- dashboard_live: drop duplicate get_device_status_counts; cap active alerts to 20 + use count_active_alerts/1
- maintenance.active_windows_for_device: 3 round-trips collapsed into one query (per-site-id branch keeps Postgres parameter types unambiguous)
- sites.build_site_tree: O(N^2) -> O(N) via group_by(parent_site_id)
- accounts.sole_owner_organizations: single group_by + having instead of per-org Repo.aggregate loop
- agents + agent_live (org + admin): count_assigned_devices_batch/1 + count_agent_polling_targets/1 (no preloads)
- alert_digest_worker: list_alerts_by_ids/1 batches digest fetch
- gaiia: distinct: true at DB; limit 50 on bidirectional ilike
Indexes:
- maintenance_windows(organization_id, starts_at, ends_at) WHERE suppress_alerts = true
- alerts(check_id) WHERE resolved_at IS NULL
Antipatterns:
- agents.delete_agent_token: PubSub.broadcast moved outside Repo.transaction so a rollback no longer leaves subscribers acting on a non-existent deletion
- integrations_controller.to_atom_keys: replaced String.to_existing_atom on user-controlled JSON keys with explicit allowlist
- 9 Task.start callsites converted to Task.Supervisor.start_child(Towerops.TaskSupervisor, ...) so background DB writes survive shutdown (test-mode discovery shims left as-is for sandbox semantics)
Three deferred followups from the chunk-4 plan, all together:
A. Restrictions editor
- Resolver: time_of_week support (weekday set + time-of-day window),
in addition to the existing time_of_day.
- New OnCall.update_layer_restrictions/2 + clear_layer_restrictions/1.
- schedule_live/show: per-layer Restrict on-call shifts form
(Always on call / Time of day / Time of week with Mon-Sun checkboxes),
changes patched live and persisted via the resolver.
B. Drag-and-drop reorder
- New OnCall.reorder_layers/2 + reorder_escalation_rules/2 (atomic
transaction; validates id count + membership).
- assets/js/sortable_list.ts: minimal HTML5 drag-and-drop hook (no
external dep; mirrors the existing DeviceListReorder pattern),
registered as SortableList in app.ts.
- schedule_live/show + escalation_policy_live/show: layer/level cards
now carry data-id + draggable + a visible drag handle. Up/down arrow
buttons remain as a fallback for users on assistive tech.
C. Unified new-schedule UX
- schedule_live/show pre-opens the Add Layer form when the schedule
has zero layers, so the new-schedule -> add-layers flow lands ready
to act on. Two existing tests updated to seed a layer first; two
new tests verify the auto-open behaviour both ways.
Full suite 10,231 / 0 failures. Format/dialyzer clean.
ScheduleLive.Index
- Name search input above the date nav (phx-debounce 300ms).
- Standard <.pagination> footer (10 per page) under the gantt cards.
- Both reflected in URL params (?search= and ?page=) for shareable
links; defaults are stripped from the URL.
- Refactored: load_schedules_with_timeline/3 -> hydrate_schedules/3
so filter/paginate/hydrate are clearly separate steps.
Tests
- 2 new ExUnit integration tests (search filter narrows results +
search input renders).
- e2e/tests/schedules.spec.ts: switched from table-row selectors to
card-link selectors (schedules tab is now gantt cards, not a table),
added smoke tests for date nav controls + search input + REPEAT
footer + Services sidebar, renamed "Add Rule" -> "Add Level".
Full suite 10,216 / 0 failures. Format/dialyzer clean.
OnCall context
- move_layer/2: up/down position swap for schedule layers, mirror of
move_escalation_rule/2 (tested for both directions + boundary no-op).
ScheduleLive.Show
- New move_layer event handler.
- Up/down arrow buttons on each layer card; the top arrow is disabled on
the first layer, the bottom on the last (matches the escalation policy
level reorder UX shipped in chunk 1).
- Replaced two per-hour walks (build_layer_spans + build_final_spans -
~672 resolve calls per render at 14 days) with Resolver.resolve_range/3
+ a small segments_to_spans/3 mapper. Per-layer view wraps each layer
in a temporary single-layer %Schedule{} so the resolver code path is
shared and overrides don't bleed into the per-layer strip.
Tests: 3 new context tests for move_layer, 1 new integration test for
the layer reorder UI. Full suite 10,214 / 0 failures. Format/dialyzer
clean.
Resolver
- Resolver.resolve_range/3: returns the contiguous on-call segments for a
schedule across [start_at, end_at). Walks layer handoffs + override
boundaries, drops gap segments, and merges adjacent same-user segments.
UserColor module
- New Towerops.OnCall.UserColor with deterministic id -> color mapping
(Tailwind class + matching #RRGGBB hex). Refactored ScheduleLive.Show
to use it instead of its own per-page index palette so the same person
gets the same color across the schedules list and detail pages.
ScheduleLive.Index
- Date navigation: Today / prev / next + 1/2/4-week range selector.
- URL-driven: ?start=YYYY-MM-DD&range=N for shareable views; falls back
to defaults on malformed values.
- Per-row card: schedule name link, on-call-now avatar swatch, day-of-week
header strip, gantt strip rendered as a CSS grid with one column per day,
Today marker overlay.
Tests: 5 new resolver tests, 9 new UserColor tests, 5 new ScheduleLive
integration tests. Full suite: 10,210 / 0 failures. Format/dialyzer clean.
Also: cleaned up two stale inline comments in k8s/deployment.yaml that
disagreed with the values they sat next to (replicas/maxSurge).
Chunk 1 of the on-call/escalation redesign plan
(docs/plans/2026-04-28-on-call-pagerduty-style-redesign.md):
Schema
- on_call.ex: list_devices_using_policy/2 (direct + org-default inheritance)
- on_call.ex: move_escalation_rule/2 for up/down level reordering
- list_escalation_policies/1 now preloads :rules
Show page
- Levels rendered as numbered cards with up/down/delete controls
- "Notify the following users immediately and escalate after N minutes."
- REPEAT footer surfaces repeat_count inline (no longer a standalone column)
- Right-side Services sidebar lists devices using the policy
- Header line shows the handoff notifications mode (when in use by a service /
always / never)
Edit form
- Removed standalone Repeat Count input
- Added handoff notifications mode select
- Added inline "If no one acknowledges, repeat this policy N time(s)" block
Index views (policies tab + standalone)
- Replaced Repeat Count column with a Levels (rule count) column
Other
- rate_limit.ex: bind unmatched :ets.new/2 + schedule_clean/1 returns to fix
dialyzer :unmatched_returns warning under the project's strict flags.
All 10,191 tests pass; mix format clean; mix compile --warnings-as-errors clean;
mix dialyzer passes.
Promoted pure presentation and utility helpers from `defp` to `def @doc false`
across ~20 LiveViews, Oban workers, and sync modules so they're reachable from
unit tests. Refactored several `cond` blocks into idiomatic function heads with
guards. Added ~250 new test cases in new files under test/towerops and
test/towerops_web, including DB-backed tests for CnMaestro.Sync and
AlertNotificationWorker, and removed dead LiveView tab components and
CapacityLive (no callers anywhere in lib/test).
Configured mix.exs test_coverage.ignore_modules to exclude vendored third-party
code (SnmpKit, protobuf-generated Towerops.Agent.*, Absinthe GraphQL types,
Phoenix HTML modules, Inspect protocol impls) from coverage calculations —
these are not our project code.
Coverage: 66.93% → 70.09%. Full suite: 10,127 tests, 0 failures.
Changes to eliminate @dialyzer suppressions by fixing underlying causes:
NIF stubs (towerops_native.ex, mib_translator.ex):
- Change stubs to :erlang.nif_error(:nif_not_loaded) (no_return type).
Real NIF replaces stubs at load time; calls to unloaded stubs now fail
loudly instead of returning fake data. Lets dialyzer trust @spec.
- Remove @dialyzer :nowarn_function on three NIFs and on translate/1.
Discovery sync_* functions (snmp/discovery.ex, channels/agent_channel.ex):
- agent_channel passes %{device_id: _, interfaces: _} and %{id: _} maps
into Discovery.sync_ip_addresses/sync_processors/sync_storage, which
@spec'd only %Device{}. Add narrow map-type unions (ip_sync_device,
snmp_device_ref) reflecting what the functions actually access.
- Remove @dialyzer :nowarn_function on three agent_channel helpers.
remote_ip.ex — real bug caught and fixed:
- `:ranch.get_addr(socket.transport_pid)` was always raising since
Bandit uses ThousandIsland, not Ranch; the rescue _ -> nil silently
returned nil every time. Switched to Phoenix's documented
:peer_data connect_info (already enabled in endpoint.ex) via
socket.assigns; remote IP now actually works.
- Remove remote_ip.ex entry from .dialyzer_ignore.exs.
Accounts / Organizations (Ecto.Multi opacity):
- Add @specs to Multi-building helpers, refactor into pipe chains.
- 6 @dialyzer :nowarn_function → 0, but 7 :no_opaque remain. Root
cause is upstream: Ecto.Multi.new/0 returns a struct with a literal
%MapSet{} whose @opaque internal representation trips dialyzer on
every subsequent Multi.* call. Unfixable without an Ecto patch or
bypassing Multi entirely. Comments document the specific upstream
issue rather than a vague "Ecto.Multi opacity" claim.
Devices.ex:
- Adding @specs made it worse (call_without_opaque → contract_with_
opaque); inlining the Multi didn't help either — same MapSet root
cause. Suppression kept with a sharper comment.
Categories addressed:
- pattern_match / pattern_match_cov (32): remove dead case/with clauses
that dialyzer proved unreachable from the caller types.
- contract_supertype / extra_range / invalid_contract /
contract_with_opaque (25): narrow @spec declarations to match actual
success typings.
- call / call_without_opaque (18): fix bad calls, narrow User.t to
allow nil for in-memory changeset structs, suppress Ecto.Multi
opaque-type false positives with targeted @dialyzer directives.
- guard_fail / no_return / unused_fun / unknown_function (13): remove
dead || fallbacks, simplify always-true params, cascade-resolve
no_returns via the underlying pattern_match and call fixes.
Real production bug fixed: StormDetector.handle_cast/2 had swapped
`:queue.in` args (`queue |> :queue.in(ts)` which desugars to
`:queue.in(queue, ts)` — wrong argument order). Alert timestamps
were never being enqueued, so storm detection would fail at runtime.
Corrected to `ts |> :queue.in(queue)`.
.dialyzer_ignore.exs: suppress two genuine dep-PLT gaps
(:ranch.get_addr/1 false positive from Bandit's transitive ranch,
and the Cloak.Vault GenServer callback_info on the CI build path).
`mix dialyzer` now: Total errors: 114, Skipped: 114 — passes clean.
Warnings: 88 → 0.
Prefix fire-and-forget calls (PubSub.broadcast, Oban enqueue, Logger,
update_*, etc.) with `_ =` so dialyzer knows the return value is
intentionally discarded. Wrap a few if/case expressions whose
branches produce mixed types the same way.
No behavior changes — only explicit acknowledgement of discarded
returns.
Warnings: 242 → 88.
- Add @type t :: %__MODULE__{} to schemas referenced by callers:
ApiToken, Monitoring.Check, OnCall.Schedule, SiteOutage,
NotificationDigest, Snmp.WirelessClient, Topology.DeviceLink,
Agent.AgentJob, Agent.MikrotikResult.
- Proto.Types: qualify forward references to nested modules with
Types. prefix, and fix Metric typo (should be union type metric()).
- data_loaders.ex / chart_builders.ex: Snmp.SNMPDevice.t was a ghost
spec — module is Snmp.Device.
Warnings: 328 → 242.
Ignore file was silencing every warning under lib/towerops/**. Root
cause was plt_add_deps: :apps_direct missing Plug/Phoenix/Oban/Decimal
/Redix/ssl/public_key — hundreds of false `unknown_function` warnings
were being papered over.
Expand plt_add_apps to cover the common deps, narrow the ignore file
to real dep-PLT gaps only, and fix two concrete bugs uncovered by the
change:
- ScopedResource.fetch_preload/4: spec was atom() | [atom()] but
callers pass keyword lists (e.g. [rules: :targets]).
- ToweropsNative: tag NIF stubs with @dialyzer :nowarn_function so
dialyzer trusts the @spec instead of the fallback body.
Remaining 328 real warnings surface for follow-up.
Intercepts requests with Accept: text/markdown at endpoint level (before
the router's :accepts plug rejects them) and returns hardcoded markdown
representations for /, /privacy, and /terms.
Phase 1: Foundation Types (100% complete)
- query_helpers: SQL LIKE sanitization with pipe operators
- numeric: Integer parsing with pattern matching guards
- result: Pure Elixir Result monad (map, and_then, unwrap_or)
Phase 2: Ecto Domain Types (100% complete)
- ip_address: IPv4/IPv6 validation using :inet directly
- mac_address: Multi-format MAC parsing (colon/hyphen/dot/compact)
- snmp_oid: OID parsing/manipulation with recursive pattern matching
All 198 tests passing across converted modules.
API changed from Gleam-style {:some/:none to idiomatic {:ok/:error.
Refactored parse_numeric_oid to use with statement, reducing nesting depth.
Reviewed-on: graham/towerops-web#196
Fixes FunctionClauseError when DashboardLive receives {:alert_changed, org_id}
message broadcast by user_auth hooks.
The user_auth module subscribes all LiveViews to the
"organization:#{org_id}:alerts" topic and broadcasts {:alert_changed, org_id}
messages when alerts are created or resolved. DashboardLive was missing a
handle_info/2 clause to handle this message format, causing crashes in
production.
Solution:
- Added handle_info/2 clause for {:alert_changed, _org_id} message
- Uses existing debounced reload pattern to update dashboard
- Added test to verify message is handled without crashing
- Updated both technical and user-facing changelogs
All tests pass. The fix follows the same pattern used in AlertLive.Index
and DeviceLive.Show.
Reviewed-on: graham/towerops-web#189
- Check device.snmp_enabled before creating discovery/polling jobs
- Also check snmp_enabled for MikroTik jobs
- Prevents agent from attempting SNMP operations on ping-only devices
- Fixes "Agent collected 0 OIDs" errors for devices without SNMP
Reviewed-on: graham/towerops-web#180
Commented out weathermap navigation in sidebar and mobile menu.
Feature not ready for production use yet.
Files: lib/towerops_web/components/layouts.ex
Changelog: CHANGELOG.txt
Reviewed-on: graham/towerops-web#174
- Create WeathermapLive module at /weathermap with 60s auto-refresh
- Extend Topology.get_topology_for_weathermap with bandwidth utilization data
- Add WeathermapViewer JavaScript hook with color-coded edges:
* Green (0-30%) → Yellow (30-60%) → Orange (60-80%) → Red (80%+)
- Display throughput/capacity labels on edges (e.g., '847 Mbps / 1 Gbps')
- Add utilization stats dashboard with link count by usage level
- Support full-screen mode for NOC displays
- Integrate with existing dark mode and responsive design
- Add navigation links in sidebar and mobile menu
Technical implementation:
- Leverages existing Capacity module for interface utilization calculations
- Extends topology edges with utilization_level, utilization_pct, throughput_bps
- Builds on NetworkMapLive foundation with enhanced edge styling
- Auto-refresh via Phoenix PubSub and 60s timer
- Filter support for high/critical utilization links
Reviewed-on: graham/towerops-web#172
Devices configured as SNMPv1 were being force-upgraded to v2c for agent
polling, which breaks devices that don't support v2c (returning empty
OID responses and no throughput/capacity data).
Reviewed-on: graham/towerops-web#166
The wrap detection only applied the 2^32 correction when the previous
counter was in the upper half of the 32-bit range (> 2^31). On fast
links, counters wrap regardless of where in the range they sit. Three
graph rendering paths had no wrap detection at all, just max(0).
Consolidated all bps calculations into a single public
Capacity.calculate_bps/3 that always tries the 2^32 correction for
negative deltas. 64-bit HC counter resets remain clamped to zero since
the corrected delta stays negative.
Reviewed-on: graham/towerops-web#163
Standard ifInOctets/ifOutOctets are 32-bit counters that wrap around
4,294,967,296 bytes (~4.3 GB). At 1 Gbps this wraps every ~34 seconds,
causing brief drops to 0 bps in traffic charts and capacity reports.
When prev > 2^31 and delta is negative, add 2^32 to recover the correct
rate. If the result is still negative (HC 64-bit counter after reboot),
clamp to 0. Small-value decreases (prev < 2^31) continue to clamp to 0
since they cannot be real 32-bit wraps.
Fixes both capacity.ex (utilization reports) and device_live/show.ex
(per-device traffic chart).
Reviewed-on: graham/towerops-web#161
