feat(health): KPI history + sustained-backlog badge for LocalDb replication (row 33)
LocalDbOplogBacklog was reported and Prometheus-exported with nothing consuming it: not sampled into KPI history, so a purge-burst spike could not be reviewed after the fact, and no threshold treatment anywhere. Both halves shipped. KPI SAMPLING. SiteHealthKpiSampleSource now emits localDbOplogBacklog and localDbReplicationConnected (0/1), and the backlog is charted on the Health dashboard's per-site trend panel. Charting is the point: a point-in-time tile can never answer 'did that spike drain?', which is the only thing separating an expected purge burst from a stalled peer. Both are CONDITIONALLY emitted rather than coerced with ?? 0 like the auditBacklogPending metric beside them. Both health-report fields are nullable and null means 'no reading' — replication not configured (rig site-b/site-c) or a failed poll — never zero. A fabricated 0 would render a pair that cannot read its own oplog, or one deliberately unreplicated, as perfectly healthy once a minute forever, burying the real series. So a site emits 12 metrics when unreplicated and 14 when replicated, and a GAP in these two series truthfully means 'not replicated / not reporting'. Note false and null differ for the connected flag: a configured link that is DOWN samples as 0; no link samples as nothing. Both fold as Gauge (summing an oplog depth, or a 0/1 flag, per hour is meaningless). THRESHOLD SEMANTICS — sustained, not instantaneous. This is the design, not a refinement. The site_events retention purge is CDC-captured like any other write, so the backlog jumps by the deleted batch and drains as the peer acks it; a bare 'backlog > threshold' badge would fire on every replicated site every day and be ignored within a week. Healthy is defined by the backlog RETURNING to ~0, which only a dwell can express. CentralHealthAggregator holds LocalDbBacklogAboveSince — the instant the backlog first rose above LocalDbBacklogThreshold (default 1000) — and the badge appears only after LocalDbBacklogSustainedFor (default 15 min). A report at or below the threshold clears the anchor; one above leaves the ORIGINAL instant intact, so the window is sustained rather than sliding. The null case is deliberately a third branch: a null backlog leaves the anchor UNCHANGED rather than clearing it. Null is evidence neither of a drain nor of a backlog, so a node going blind mid-climb must not silently reset its own dwell, and an unreplicated site (null forever) never accumulates an anchor and can never be badged. Validation rejects a non-positive threshold (0 would badge every replicated site permanently, since an idle backlog already sits at it) and a dwell shorter than one ReportInterval (satisfiable by a single sample, which collapses the check back into the bare threshold it replaces). DOC CORRECTION worth flagging: this row's premise was 'mirror the SiteAuditBacklog configurable threshold badge'. That badge does not exist — Component-HealthMonitoring.md described it in two places but no option, no comparison and no markup were ever implemented. The two stale claims are corrected here rather than left to send the next reader looking for it; the LocalDb badge is built fresh on the Metrics-stale badge's pattern, which is a real configurable-threshold badge. Tests: HealthMonitoring 115 (9 new aggregator tests incl. purge-burst-drains, unreplicated-never-anchors, null-mid-climb, exact-threshold, stale-report; 5 new validator tests; 4 new sampler tests incl. the null-semantics and false-vs-null cases); CentralUI 1042 (5 new badge/chart tests incl. the purge-burst negative control); Commons Kpi 93; KpiHistory 54.
This commit is contained in:
Joseph Doherty
+85
-1
@@ -99,11 +99,95 @@ public class SiteHealthKpiSampleSourceTests
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Assert.Equal(9, byMetric["auditBacklogPending"]);
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Assert.Equal(11, byMetric["eventLogWriteFailures"]);
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// All 12 metrics emitted, exactly once each, for the one populated site.
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// 12 metrics for an UNREPLICATED site — this fixture leaves both LocalDb replication
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// fields null, and register row 33 emits those two conditionally rather than coercing
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// null to 0. A replicated site emits 14; see the LocalDb tests below.
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Assert.Equal(12, byMetric.Count);
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Assert.Equal(12, samples.Count);
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}
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// ------------------------------------------------------------------
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// LocalDb replication metrics (register row 33)
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// ------------------------------------------------------------------
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[Fact]
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public async Task CollectAsync_NullLocalDbFields_EmitsNeitherLocalDbMetric()
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{
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// THE null-semantics case, and the reason these two are not `?? 0` like the audit
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// backlog above. Null means "no reading" — an unreplicated site (rig site-b/site-c) or
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// a failed poll. A fabricated 0 backlog would render a pair that cannot read its own
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// oplog, or one deliberately not replicated, as perfectly healthy once a minute forever.
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var report = MinimalReport("site-a") with
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{
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LocalDbOplogBacklog = null,
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LocalDbReplicationConnected = null,
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};
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var aggregator = new StubAggregator
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{
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States = { ["site-a"] = new SiteHealthState { SiteId = "site-a", LatestReport = report } },
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};
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var samples = await new SiteHealthKpiSampleSource(aggregator).CollectAsync(CapturedAt);
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Assert.DoesNotContain(samples, s => s.Metric == "localDbOplogBacklog");
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Assert.DoesNotContain(samples, s => s.Metric == "localDbReplicationConnected");
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Assert.Equal(12, samples.Count);
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}
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[Fact]
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public async Task CollectAsync_ReplicatedSite_EmitsBothLocalDbMetrics()
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{
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var report = MinimalReport("site-a") with
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{
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LocalDbOplogBacklog = 4242,
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LocalDbReplicationConnected = true,
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};
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var aggregator = new StubAggregator
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{
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States = { ["site-a"] = new SiteHealthState { SiteId = "site-a", LatestReport = report } },
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};
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var samples = await new SiteHealthKpiSampleSource(aggregator).CollectAsync(CapturedAt);
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Assert.Equal(4242, samples.Single(s => s.Metric == "localDbOplogBacklog").Value);
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Assert.Equal(1, samples.Single(s => s.Metric == "localDbReplicationConnected").Value);
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Assert.Equal(14, samples.Count);
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}
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[Fact]
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public async Task CollectAsync_ZeroBacklog_IsStillEmitted()
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{
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// A real, measured 0 is genuinely different from "no reading" and must be recorded —
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// otherwise a healthy replicated site would be indistinguishable from an unreplicated
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// one, and the drain half of a purge burst would never appear in the series.
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var report = MinimalReport("site-a") with { LocalDbOplogBacklog = 0 };
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var aggregator = new StubAggregator
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{
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States = { ["site-a"] = new SiteHealthState { SiteId = "site-a", LatestReport = report } },
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};
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var samples = await new SiteHealthKpiSampleSource(aggregator).CollectAsync(CapturedAt);
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Assert.Equal(0, samples.Single(s => s.Metric == "localDbOplogBacklog").Value);
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}
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[Fact]
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public async Task CollectAsync_DisconnectedReplication_EmitsZeroNotAbsent()
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{
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// false and null are different states: a configured link that is DOWN versus no link
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// at all. Only the former is a fault, and it must show up as a 0 sample rather than a
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// gap, or a broken link would look exactly like an unreplicated site.
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var report = MinimalReport("site-a") with { LocalDbReplicationConnected = false };
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var aggregator = new StubAggregator
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{
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States = { ["site-a"] = new SiteHealthState { SiteId = "site-a", LatestReport = report } },
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};
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var samples = await new SiteHealthKpiSampleSource(aggregator).CollectAsync(CapturedAt);
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Assert.Equal(0, samples.Single(s => s.Metric == "localDbReplicationConnected").Value);
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}
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[Fact]
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public async Task CollectAsync_NullAuditBacklog_EmitsZeroAuditBacklogPending()
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{
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