Fix URLs and queries in prober and alerts

alertserver/alerts.cfg

 # This file defines alerts to be triggered by the server.
 
 #
 # SkiaPerf and SkiaGold
 #
 
 [[rule]]
 name = "Perf Alerts"
 message = "At least one perf alert has been found. Please visit https://perf.skia.org/alerts/ to triage."
 query = "select value from /skiaperf.skia-perf.alerting.new.value/ limit 1"
 category = "Perf"
 condition = "x > 0"
 actions = ["Email(alerts@skia.org)"]
 auto-dismiss = true
 nag = "24h"
 
 [[rule]]
 name = "Gold Alert (GM)"
 message = "At least one untriaged GM has been found. Please visit https://gold.skia.org/ to triage."
-query = "select value from /skiacorrectness.skia-gold-prod.status.untriaged.by_corpus.gm.value/ limit 1"
+query = "select value from /^skiacorrectness.skia-gold-prod.status.untriaged.by_corpus.gm.value$/ limit 1"
 category = "Gold"
 condition = "x > 0"
 actions = ["Email(alerts@skia.org)"]
 auto-dismiss = true
 nag = "24h"
 
 [[rule]]
 name = "Expired Ingores (Gold)"
-message = "At least one expired ignore rule has been found. Please visit https://gold.skia.org/2/ignores to delete or extend."
-query = "select value from /skiacorrectness.skia-gold-prod.num-expired-ignore-rules.value/ limit 1"
+message = "At least one expired ignore rule has been found. Please visit https://gold.skia.org/ignores to delete or extend."
+query = "select value from /^skiacorrectness.skia-gold-prod.num-expired-ignore-rules.value$/ limit 1"
 category = "Gold"
 condition = "x > 0"
 actions = ["Email(alerts@skia.org)"]
 auto-dismiss = true
 nag = "24h"
 
 [[rule]]
 name = "Ingestion Failure (Perf)"
 message = "At least two rounds of perf ingestion have failed back to back."
 query = "select mean(value) from /ingest.skia-perf.ingester.nano-ingest.gauge.time-since-last-successful-update.value/ where time > now() - 10m"
@@ skipping 19 matching lines @@
 query = "select mean(value) from /ingest.skia-gold-prod.ingester.gold-ingest.gauge.time-since-last-successful-update.value/ where time > now() - 10m"
 category = "infra"
 condition = "x >= 750"
 actions = ["Email(infra-alerts@skia.org)"]
 auto-dismiss = true
 nag = "1h"
 
 [[rule]]
 name = "Ingore Monitoring Failure (Gold)"
 message = "At least two rounds of monitoring for expired ignore rules have failed back to back."
-query = "select mean(value) from /skiacorrectness.skia-gold-prod.expired-ignore-rules-monitoring.time-since-last-successful-update.value/ where time > now() - 10m"
+query = "select mean(value) from /^skiacorrectness.skia-gold-prod.expired-ignore-rules-monitoring.time-since-last-successful-update.value$/ where time > now() - 10m"
 category = "infra"
 condition = "x >= 200"
 actions = ["Email(infra-alerts@skia.org)"]
 auto-dismiss = true
 nag = "1h"
 
+[[rule]]
+name = "Gold Hash Prober"
+message = "The list of currently considered image digests is not accessible at https://gold.skia.org/_/hashes"
+query = "select mean(value) from /^prober.skiagold_hashes.failure.value$/ where time > now() - 10m;"
+category = "infra"
+condition = "x >= 1"
+actions = ["Email(infra-alerts@skia.org)"]
+auto-dismiss = false
+nag = "1h"
+
 #
 # SkFiddle
 #
 
 [[rule]]
 name = "Skia Fiddle Prober (main page)"
 message = "The main page at http://skfiddle.com has failed."
 query = "select mean(value) from /prober.skfiddle.failure.value/ where time > now() - 10m;"
 category = "infra"
 condition = "x >= 1"
@@ skipping 284 matching lines @@
 
 [[rule]]
 name = "Probe Failure (issue-tracker)"
 message = "Ingesting issue tracker issued has failed to run in at least 30 minutes."
 query = "select mean(value) from /probeserver.skia-monitoring.issue-tracker.time-since-last-successful-update.value/ where time > now() - 10m"
 category = "infra"
 condition = "x >= 1800"
 actions = ["Email(infra-alerts@skia.org)"]
 auto-dismiss = true
 nag = "1h"