Mitra availability: read paths respect require_mitra_ping=false

When the operator sets require_mitra_ping=false, the auto-offline sweep
early-returns (by design — "don't gate online status on heartbeat
freshness"). The three Valkey read paths still gated on heartbeat
freshness anyway, which trapped the system: sweep won't remove the
mitra from mitras:online, but readers reject them as stale. The customer
CTA stayed permanently disabled with no recovery.

Fix all three to skip the heartbeat-freshness check when require_ping
is off, matching the sweep's contract:
- computeAvailabilityFromValkey (customer beacon)
- isMitraReachable (extension service)
- findAvailableMitrasFromValkey (pairing candidate finder)

The Postgres fallbacks already did the right thing (is_online only,
no heartbeat compare); this aligns the Valkey hot path.

Also: PATCH /internal/config/mitra-ping now publishes config:invalidate
for require_mitra_ping and mitra_stale_after_seconds, and the subscriber
in mitra-status.service was widened to listen for both. Flipping the
toggle in CC now busts the 10s availability snapshot immediately instead
of waiting out the TTL.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/src/routes/internal/config.routes.js

@@ -190,6 +190,14 @@ export const internalConfigRoutes = async (app) => {
       }
     }
     const config = await setMitraPingConfig({ require_ping, stale_after_seconds })
+    // Bust the customer availability cache on any instance — subscribers in
+    // mitra-status.service.js listen for these keys and call invalidate.
+    if (require_ping !== undefined) {
+      await publishConfigInvalidate('require_mitra_ping')
+    }
+    if (stale_after_seconds !== undefined) {
+      await publishConfigInvalidate('mitra_stale_after_seconds')
+    }
     return reply.send({ success: true, data: config })
   })
 

backend/src/services/mitra-status.service.js

@@ -74,14 +74,23 @@ export const invalidateAvailabilityCache = async () => {
   }
 }
 
-// Bust the shared cache when CC changes max_customers_per_mitra (any instance).
+// Bust the shared cache when CC changes any config that the beacon snapshots
+// over: max_customers_per_mitra (capacity gate), require_mitra_ping (whether
+// stale heartbeats exclude candidates), mitra_stale_after_seconds (the gate's
+// threshold itself).
+const AVAILABILITY_CACHE_INVALIDATING_KEYS = new Set([
+  'max_customers_per_mitra',
+  'require_mitra_ping',
+  'mitra_stale_after_seconds',
+])
+
 let _subscribed = false
 const ensureSubscribed = () => {
   if (_subscribed) return
   _subscribed = true
   try {
     subscribe('config:invalidate', (msg) => {
-      if (msg?.key === 'max_customers_per_mitra') {
+      if (msg?.key && AVAILABILITY_CACHE_INVALIDATING_KEYS.has(msg.key)) {
         invalidateAvailabilityCache()
       }
     })
@@ -349,7 +358,7 @@ export const mirrorHeartbeatsToPostgres = async () => {
  */
 const computeAvailabilityFromValkey = async () => {
   const { max_customers_per_mitra } = await getMaxCustomersPerMitra()
-  const { stale_after_seconds } = await getMitraPingConfig()
+  const { require_ping, stale_after_seconds } = await getMitraPingConfig()
 
   const candidates = await valkey.sdiff(VK_MITRAS_ONLINE, VK_MITRAS_DEACTIVATED)
   if (!candidates.length) return { available: false, count: 0 }
@@ -357,17 +366,26 @@ const computeAvailabilityFromValkey = async () => {
   const pipe = valkey.pipeline()
   for (const id of candidates) {
     pipe.get(vkCapacityKey(id))
-    pipe.get(vkHeartbeatKey(id))
+    if (require_ping) pipe.get(vkHeartbeatKey(id))
   }
   const results = await pipe.exec()
+  const stride = require_ping ? 2 : 1
 
   const cutoff = Date.now() - stale_after_seconds * 1000
   let count = 0
   for (let i = 0; i < candidates.length; i++) {
-    const capacity = Number(results[i * 2][1] ?? 0)
-    const heartbeat = results[i * 2 + 1][1]
+    const capacity = Number(results[i * stride][1] ?? 0)
     if (capacity >= max_customers_per_mitra) continue
-    if (!heartbeat || Date.parse(heartbeat) < cutoff) continue
+    // When the operator has turned `require_mitra_ping` off, the auto-offline
+    // sweep is also a no-op (see autoOfflineStaleMitras early-return). Mitras
+    // stay in `mitras:online` until they explicitly toggle offline, so reading
+    // a stale heartbeat here doesn't mean "unreachable" — it means "we aren't
+    // tracking liveness." Skip the freshness gate to stay consistent with the
+    // sweep, and to match what the Postgres fallback returns (is_online only).
+    if (require_ping) {
+      const heartbeat = results[i * stride + 1][1]
+      if (!heartbeat || Date.parse(heartbeat) < cutoff) continue
+    }
     count++
   }
   return { available: count > 0, count }
@@ -409,14 +427,19 @@ export const countAvailableMitrasFromCache = async () => {
  * Falls back to a Postgres `is_online` read if Valkey is unreachable; the
  * fallback skips the heartbeat-freshness check (sweep takes care of stale rows
  * within `stale_after_seconds + sweep_cadence`).
+ *
+ * When `require_mitra_ping=false`, both the auto-offline sweep AND this check
+ * skip the heartbeat gate so the read path matches the sweep's contract: a
+ * mitra stays "reachable" until they explicitly toggle offline.
  */
 export const isMitraReachable = async (mitraId) => {
   try {
     const inSet = await valkey.sismember(VK_MITRAS_ONLINE, mitraId)
     if (!inSet) return false
+    const { require_ping, stale_after_seconds } = await getMitraPingConfig()
+    if (!require_ping) return true
     const heartbeat = await valkey.get(vkHeartbeatKey(mitraId))
     if (!heartbeat) return false
-    const { stale_after_seconds } = await getMitraPingConfig()
     return Date.parse(heartbeat) >= Date.now() - stale_after_seconds * 1000
   } catch (err) {
     console.warn('[isMitraReachable] valkey unavailable, falling back to DB:', err.message)

backend/src/services/pairing.service.js

@@ -83,7 +83,7 @@ const notifyCustomer = async (customerId, data) => {
 // Postgres fallback runs if any Valkey op throws (full JOIN as before).
 const findAvailableMitrasFromValkey = async () => {
   const { max_customers_per_mitra } = await getMaxCustomersPerMitra()
-  const { stale_after_seconds } = await getMitraPingConfig()
+  const { require_ping, stale_after_seconds } = await getMitraPingConfig()
 
   const candidates = await valkey.sdiff(VK_MITRAS_ONLINE, VK_MITRAS_DEACTIVATED)
   if (!candidates.length) return []
@@ -91,17 +91,23 @@ const findAvailableMitrasFromValkey = async () => {
   const pipe = valkey.pipeline()
   for (const id of candidates) {
     pipe.get(vkCapacityKey(id))
-    pipe.get(vkHeartbeatKey(id))
+    if (require_ping) pipe.get(vkHeartbeatKey(id))
   }
   const results = await pipe.exec()
+  const stride = require_ping ? 2 : 1
 
   const cutoff = Date.now() - stale_after_seconds * 1000
   const eligible = []
   for (let i = 0; i < candidates.length; i++) {
-    const capacity = Number(results[i * 2][1] ?? 0)
-    const heartbeat = results[i * 2 + 1][1]
+    const capacity = Number(results[i * stride][1] ?? 0)
     if (capacity >= max_customers_per_mitra) continue
-    if (!heartbeat || Date.parse(heartbeat) < cutoff) continue
+    // See computeAvailabilityFromValkey in mitra-status.service.js: when the
+    // ping requirement is off, the sweep is off too, so we don't gate
+    // candidate selection on heartbeat freshness here either.
+    if (require_ping) {
+      const heartbeat = results[i * stride + 1][1]
+      if (!heartbeat || Date.parse(heartbeat) < cutoff) continue
+    }
     eligible.push({ id: candidates[i], active_session_count: capacity })
   }
   return eligible

backend/test/services/mitra-status.valkey-mirror.test.js

@@ -224,6 +224,27 @@ describe('mitra-status valkey mirror', () => {
 
       expect(await isMitraReachable(m.id)).toBe(false)
     })
+
+    // Mirrors the autoOfflineStaleMitras "no-op when require_ping=false"
+    // contract: read paths must not gate on heartbeat when sweep doesn't.
+    it('returns true with stale heartbeat when require_ping=false', async () => {
+      const sql = db()
+      try {
+        await sql`
+          UPDATE app_config SET value=${sql.json({ value: false })}
+          WHERE key='require_mitra_ping'
+        `
+        const m = await createMitra({ callName: 'NoPing', isOnline: true })
+        await v().set(vkHeartbeatKey(m.id), new Date(Date.now() - 3_600_000).toISOString())
+
+        expect(await isMitraReachable(m.id)).toBe(true)
+      } finally {
+        await sql`
+          UPDATE app_config SET value=${sql.json({ value: true })}
+          WHERE key='require_mitra_ping'
+        `
+      }
+    })
   })
 
   // ---------- recomputeCapacity ----------
@@ -331,6 +352,35 @@ describe('mitra-status valkey mirror', () => {
       await invalidateAvailabilityCache()
       expect(await v().get('availability:snapshot')).toBeNull()
     })
+
+    // Regression: when an operator turns off the ping requirement, the
+    // auto-offline sweep is also disabled, so heartbeats may legitimately
+    // become arbitrarily old. The beacon must NOT filter those out — that
+    // would put the CTA in a permanently-disabled state with no recovery
+    // path (sweep won't remove the mitra; cache always re-computes false).
+    it('includes mitras with stale heartbeats when require_ping=false', async () => {
+      const sql = db()
+      try {
+        await sql`
+          UPDATE app_config SET value=${sql.json({ value: false })}
+          WHERE key='require_mitra_ping'
+        `
+        const m = await createMitra({ callName: 'NoPingRequired', isOnline: true })
+        // Heartbeat 1 hour old — well past any reasonable stale_after_seconds.
+        await v().set(vkHeartbeatKey(m.id), new Date(Date.now() - 3_600_000).toISOString())
+        await v().del('availability:snapshot')
+
+        const result = await countAvailableMitrasFromCache()
+        expect(result.available).toBe(true)
+        expect(result.count).toBe(1)
+      } finally {
+        await sql`
+          UPDATE app_config SET value=${sql.json({ value: true })}
+          WHERE key='require_mitra_ping'
+        `
+        await v().del('availability:snapshot')
+      }
+    })
   })
 
   // ---------- autoOfflineStaleMitras ----------