NIP-66: measure relays from the traffic a client already makes

A monitor normally probes — opens connections purely to measure, then
throws them away. A client that is already subscribing, fetching and
publishing has better data for free: measured under real load, against
the relays it actually uses, at the concurrency it actually runs.

RelayObserver is a RelayConnectionListener, so it sees every connection
whichever code path opened it and none of them has to report anything:

  rtt-open      onConnecting to onConnected
  rtt-read      first REQ to its EOSE
  rtt-write     first EVENT to its OK
  reachable     it opened, or served something
  auth-required it sent AUTH, or CLOSED saying so
  the error, verbatim, when it never opened

Everything is OBSERVED. Nothing is copied from a relay's NIP-11: that is
the relay's own claim, available to anyone who asks, and republishing it
under a monitor's signature adds nothing but a chance to go stale. Where
the two disagree — a relay advertising open reads that then challenges
us — the observation is the half worth having, and copying the claim
would erase it. It also keeps quartz free of an HTTP dependency.

RelayMonitor is the whole wiring: construct one and connections are
measured, signed as 30166s on an interval, and folded into a cheap
in-memory isKnownDead for picking relays. That read has to be cheap — an
outbox picker runs per event — so it answers from a snapshot refreshed on
an interval, never a store query.

The signer is required. Measuring relay quality and letting others check
it IS NIP-66, and an optional signer would just add the failure mode this
library keeps designing out: configured, silent, doing nothing. A client
that should not publish does not construct one.

RelayObserver also replaces the CLI's RelayDiagnostics, which was the
same listener minus the timings. Porting it surfaced a bug both shared:
substringBefore(':') returns the WHOLE string when there is no colon, so
a relay's free-form CLOSED prose became its own tally key and the map
grew with the number of distinct sentences relays wrote. The colon is
now required.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/Context.kt

@@ -65,6 +65,7 @@ import com.vitorpamplona.quartz.nip11RelayInfo.Nip11RelayInformation
 import com.vitorpamplona.quartz.nip17Dm.settings.ChatMessageRelayListEvent
 import com.vitorpamplona.quartz.nip46RemoteSigner.signer.NostrSignerRemote
 import com.vitorpamplona.quartz.nip65RelayList.AdvertisedRelayListEvent
+import com.vitorpamplona.quartz.nip66RelayMonitor.reachability.RelayObserver
 import com.vitorpamplona.quartz.nip66RelayMonitor.reachability.RelayReachabilityStore
 import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.Dispatchers
@@ -210,8 +211,12 @@ class Context(
      * (auth-required / rate-limited / restricted / …), and NIP-42 AUTH
      * challenges — so a failed REQ can be explained instead of guessed at.
      * Registered on [client] for the life of this run.
+     *
+     * Quartz's [RelayObserver], which also measures the connect/read/write
+     * round trips behind that feedback and is what a [RelayMonitor] publishes
+     * as NIP-66. One listener now answers both questions.
      */
-    val relayDiagnostics: RelayDiagnostics = RelayDiagnostics().also { client.addConnectionListener(it) }
+    val relayDiagnostics: RelayObserver = RelayObserver().also { client.addConnectionListener(it) }
 
     /**
      * Adaptive per-relay concurrent-subscription cap. Starts every relay

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/RelayDiagnostics.kt

@@ -1,96 +0,0 @@
-/*
- * Copyright (c) 2025 Vitor Pamplona
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy of
- * this software and associated documentation files (the "Software"), to deal in
- * the Software without restriction, including without limitation the rights to use,
- * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
- * Software, and to permit persons to whom the Software is furnished to do so,
- * subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
- * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
- * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
- * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-package com.vitorpamplona.amethyst.cli
-
-import com.vitorpamplona.quartz.nip01Core.relay.client.listeners.RelayConnectionListener
-import com.vitorpamplona.quartz.nip01Core.relay.client.single.IRelayClient
-import com.vitorpamplona.quartz.nip01Core.relay.commands.toClient.AuthMessage
-import com.vitorpamplona.quartz.nip01Core.relay.commands.toClient.ClosedMessage
-import com.vitorpamplona.quartz.nip01Core.relay.commands.toClient.Message
-import com.vitorpamplona.quartz.nip01Core.relay.commands.toClient.NoticeMessage
-import java.util.concurrent.ConcurrentHashMap
-import java.util.concurrent.atomic.AtomicLong
-
-/**
- * Client-wide tally of the relay feedback the crawl would otherwise never see:
- * `NOTICE` frames, `CLOSED` reasons (`auth-required` / `rate-limited` /
- * `restricted` / …), and NIP-42 `AUTH` challenges. Registered as a
- * [RelayConnectionListener] on the shared client, so every incoming message
- * during a run is counted and a REQ failure can be explained instead of
- * guessed at.
- *
- * Callbacks fire on the per-relay socket threads, so all state is concurrent.
- */
-class RelayDiagnostics : RelayConnectionListener {
-    private val closedByReason = ConcurrentHashMap<String, AtomicLong>()
-    private val noticeSamples = ConcurrentHashMap<String, AtomicLong>()
-    private val authChallenges = AtomicLong()
-
-    override fun onIncomingMessage(
-        relay: IRelayClient,
-        msgStr: String,
-        msg: Message,
-    ) {
-        when (msg) {
-            // CLOSED reasons follow the NIP-01 machine-readable "word: text"
-            // convention, so the prefix categorises the failure.
-            is ClosedMessage -> bump(closedByReason, prefix(msg.message))
-            // NOTICE is free-form; keep the (truncated) text so recurring
-            // relay complaints ("too many concurrent REQs", …) are visible.
-            is NoticeMessage -> if (noticeSamples.size < MAX_DISTINCT_NOTICES) bump(noticeSamples, msg.message.trim().take(80))
-            is AuthMessage -> authChallenges.incrementAndGet()
-            else -> Unit
-        }
-    }
-
-    private fun bump(
-        map: ConcurrentHashMap<String, AtomicLong>,
-        key: String,
-    ) {
-        map.getOrPut(key) { AtomicLong() }.incrementAndGet()
-    }
-
-    /** The NIP-01 machine-readable prefix (`word` before `:`), or `other`. */
-    private fun prefix(message: String): String {
-        val head = message.substringBefore(':').trim().lowercase()
-        return head.ifEmpty { "other" }.take(24)
-    }
-
-    fun hadFeedback(): Boolean = authChallenges.get() > 0 || closedByReason.isNotEmpty() || noticeSamples.isNotEmpty()
-
-    /** JSON-friendly summary for the command output. */
-    fun snapshot(): Map<String, Any?> =
-        mapOf(
-            "auth_challenges" to authChallenges.get(),
-            "closed_by_reason" to closedByReason.entries.associate { it.key to it.value.get() }.toSortedMap(),
-            "notices" to noticeSamples.values.sumOf { it.get() },
-            "notice_top" to
-                noticeSamples.entries
-                    .sortedByDescending { it.value.get() }
-                    .take(TOP_NOTICES)
-                    .map { "${it.key} (${it.value.get()})" },
-        )
-
-    companion object {
-        private const val MAX_DISTINCT_NOTICES = 500
-        private const val TOP_NOTICES = 8
-    }
-}

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/commands/graperank/GrapeRankCrawl.kt

@@ -129,7 +129,7 @@ object GrapeRankCrawl {
     /** Echo any relay NOTICE/CLOSED feedback + adaptive throttling the crawl saw. */
     internal fun reportRelayFeedback(ctx: Context) {
         if (ctx.relayDiagnostics.hadFeedback()) {
-            System.err.println("[graperank] relay feedback: ${ctx.relayDiagnostics.snapshot()}")
+            System.err.println("[graperank] relay feedback: ${ctx.relayDiagnostics.summary()}")
         }
         if (ctx.relayLimiter.hadThrottling()) {
             System.err.println("[graperank] relay throttling: ${ctx.relayLimiter.snapshot()}")
@@ -204,7 +204,7 @@ object GrapeRankCrawl {
                     "observer" to observer,
                     "crawl_rounds" to stats.rounds,
                     "relays_contacted" to stats.relaysContacted,
-                    "relay_feedback" to if (ctx.relayDiagnostics.hadFeedback()) ctx.relayDiagnostics.snapshot() else null,
+                    "relay_feedback" to if (ctx.relayDiagnostics.hadFeedback()) ctx.relayDiagnostics.summary() else null,
                     "relay_throttling" to if (ctx.relayLimiter.hadThrottling()) ctx.relayLimiter.snapshot() else null,
                     "max_hop_reached" to (stats.hopHistogram.keys.maxOrNull() ?: 0),
                     "users_by_hop" to stats.hopHistogram.mapKeys { it.key.toString() },

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/commands/graperank/GrapeRankScore.kt

@@ -191,7 +191,7 @@ object GrapeRankScore {
                     "observer" to observer,
                     "crawl_rounds" to (crawlStats?.rounds ?: 0),
                     "relays_contacted" to (crawlStats?.relaysContacted ?: 0),
-                    "relay_feedback" to if (ctx.relayDiagnostics.hadFeedback()) ctx.relayDiagnostics.snapshot() else null,
+                    "relay_feedback" to if (ctx.relayDiagnostics.hadFeedback()) ctx.relayDiagnostics.summary() else null,
                     "relay_throttling" to if (ctx.relayLimiter.hadThrottling()) ctx.relayLimiter.snapshot() else null,
                     "max_hop_reached" to (hopHistogram.keys.maxOrNull() ?: 0),
                     "users_by_hop" to hopHistogram.mapKeys { it.key.toString() },