test(archive): pin the insert counter to what really got written

Each test writes once through a driver that refuses everything and once
through a working one: the first half keeps the counter tied to successful
writes -- it is what fails if the increment ever moves above the error check
and turns into an attempt counter -- and the second half is what fails if the
increment is dropped. The counters are process-global, so both compare against
a baseline read inside the test rather than an absolute value.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/waku_archive/archive_utils.nim

@@ -24,6 +24,20 @@ proc newSqliteArchiveDriver*(): ArchiveDriver =
 proc newWakuArchive*(driver: ArchiveDriver): WakuArchive =
   WakuArchive.new(driver).get()
 
+type FailingArchiveDriver* = ref object of ArchiveDriver
+  ## Refuses every write, which is what a node with a broken database does.
+
+method put*(
+    driver: FailingArchiveDriver,
+    messageHash: WakuMessageHash,
+    pubsubTopic: PubsubTopic,
+    message: WakuMessage,
+): Future[ArchiveDriverResult[void]] {.async.} =
+  return err("failing archive driver stub")
+
+proc newFailingArchiveDriver*(): ArchiveDriver =
+  return FailingArchiveDriver()
+
 proc put*(
     driver: ArchiveDriver, pubsubTopic: PubSubTopic, msgList: seq[WakuMessage]
 ): ArchiveDriver =

tests/waku_archive/test_waku_archive.nim

@@ -1,6 +1,7 @@
 {.used.}
 
-import results, std/sequtils, testutils/unittests, chronos, libp2p/crypto/crypto
+import
+  results, std/sequtils, testutils/unittests, chronos, metrics, libp2p/crypto/crypto
 
 import
   logos_delivery/waku/[
@@ -9,10 +10,22 @@ import
     waku_core,
     waku_core/message/digest,
     waku_archive,
+    waku_archive/archive_metrics,
   ],
   ../waku_archive/archive_utils,
   ../testlib/wakucore
 
+proc insertCount(source: string): float64 =
+  ## `value(labelValues = ...)` ignores the label selector in metrics 0.2.1 and
+  ## answers with whichever child was created first, so the series has to be
+  ## read by name. Counters are registered with the '_total' suffix.
+  try:
+    return logos_delivery_archive_inserts.valueByName(
+      "logos_delivery_archive_inserts_total", [source]
+    )
+  except ValueError:
+    return 0.0
+
 suite "Waku Archive - message handling":
   test "it should archive a valid and non-ephemeral message":
     ## Setup
@@ -539,3 +552,34 @@ procSuite "Waku Archive - find messages":
     let response = res.tryGet()
     check:
       response.messages.len == 0
+
+suite "Waku Archive - insert metrics":
+  ## The collectors are process-global and shared with every other test in this
+  ## binary, hence the baseline taken inside each test.
+  test "the insert counter only moves when the relay ingress wrote":
+    let baseline = insertCount(relayIngress)
+
+    let failing = newWakuArchive(newFailingArchiveDriver())
+    waitFor failing.handleMessage(DefaultPubSubTopic, fakeWakuMessage())
+
+    check insertCount(relayIngress) == baseline
+
+    let stored = newWakuArchive(newSqliteArchiveDriver())
+    waitFor stored.handleMessage(DefaultPubSubTopic, fakeWakuMessage())
+
+    check insertCount(relayIngress) == baseline + 1
+
+  test "the insert counter only moves when the sync ingress wrote":
+    let baseline = insertCount(syncIngress)
+    let message = fakeWakuMessage()
+    let messageHash = computeMessageHash(DefaultPubSubTopic, message)
+
+    let failing = newWakuArchive(newFailingArchiveDriver())
+    check (waitFor failing.syncMessageIngress(messageHash, DefaultPubSubTopic, message)).isErr()
+
+    check insertCount(syncIngress) == baseline
+
+    let stored = newWakuArchive(newSqliteArchiveDriver())
+    check (waitFor stored.syncMessageIngress(messageHash, DefaultPubSubTopic, message)).isOk()
+
+    check insertCount(syncIngress) == baseline + 1