A wedged explorer produced 83 Signal messages in six hours. Nothing about that
was a monitoring success: the checks were right, the cadence was wrong.
monerod-box is a Monero node in the middle of a multi-week initial sync on a
rotating disk. A 5-minute poll tells you nothing a daily one does not, and when
something breaks it turns one fault into a message every five minutes until
somebody silences the phone - which is the failure mode that makes people stop
reading alerts entirely.
So both Monero probes move to OnCalendar:
monerod *-*-* 05:00:00 RandomizedDelaySec=900
xmrblocks *-*-* 05:30:00 RandomizedDelaySec=900
systemd units (infra/401 per-host timer) *-*-* 05:15:00
30 minutes apart on purpose: both read the same LMDB, and the explorer's check
renders a full page out of it - a cold one measured 68 seconds. Running them
together would have each paying the other's cache misses.
OnCalendar rather than OnUnitActiveSec: an interval timer re-bases on every
restart, so "daily" silently becomes "a day after whenever it last came up".
── The window and the cadence are ONE decision ─────────────────────────────
The Gatus heartbeat moves with them, to 26h. Not 24h: the window must EXCEED
the push interval, or a check reporting exactly on schedule races its own
deadline and alerts on jitter alone. With a 900s randomized delay the true
worst case is ~24h15m, so 26h leaves real headroom.
The same logic drops the pulled public-site checks to a 24h interval - and
their failure-threshold from 3 to 1 with it. Three failures at 5m is 15 minutes
of tolerance; three at 24h would be THREE DAYS before anyone heard. A daily
check has no room for a blip, so it alerts on the first.
── Scoping ────────────────────────────────────────────────────────────────
infra/401's timer is ONE PER HOST and iterates every unit in
monitored_services, so slowing it slows all of them. That is safe here only
because monerod-box runs nothing but Monero units; the knobs are therefore in
its host_vars rather than the role, and both 401 and 403 now take a per-host
(resp. per-probe) override with the old 11m as the default. Every other host
is untouched.
Host liveness and disk are deliberately NOT slowed. They answer "is the box
alive", which is still wanted within minutes.
The role-level OnCalendar defaults are prefixed (monero_healthcheck_on_calendar,
xmrblocks_healthcheck_on_calendar) because the generic `healthcheck` role owns
the unprefixed name, and an unprefixed default here would shadow it for any
play that includes both.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The Onion Monero Blockchain Explorer on monerod-box, published at
exmrplore.contrapeso.xyz. Ten Gatus endpoints green across the node and the
explorer.
── It needs a compiled monero source tree, not a running monerod ───────────
xmrblocks is not an RPC client. cmake/FindMonero.cmake imports 21 STATIC
libraries out of a monero build tree and includes its headers, because it opens
the LMDB directly. The release tarball we install for the daemon ships only
executables - no .a files, no headers - so there is nothing on the box to link
against, and building it means compiling monero first.
Measured on Debian 13, building only the libraries it links:
peak RSS, one cc1plus ~3.2 GB
peak RSS at -j4 ~5.5 GB
wall time at -j4 167 s
source + build tree 195 MB
toolchain 1.6 GB
That rules the box out at ANY parallelism: 768 MiB and 1800 MiB were both
OOM-killed at -j1 and -j2, because a single translation unit over 3 GB is not
something lower -j works around. My first estimate of "~10 GB of disk" was
wrong by two orders of magnitude - that figure describes upstream's full `make`,
which also builds monerod, both wallets and the test suite, none of it linked
here. Disk was never the constraint.
So scripts/build-xmrblocks.sh does the build in a debian:13 container. An
artefact only one machine can produce is one nobody can audit; this way any host
with Docker and ~6 GB reproduces it. It verifies the monero source against
binaryFate's signature exactly as roles/monero does for the daemon, and the role
asserts the resulting sha256 ON THE CONTROL NODE before copying a single byte.
── Three upstream problems, none documented anywhere ───────────────────────
Found by building, not by reading:
1. libasio-dev is absent from upstream's dependency list. That list is
Ubuntu-based; Crow wants standalone asio.hpp, not boost/asio.hpp, and on
Debian 13 the build dies outright.
2. The explorer does not compile against monero v0.18.5.1. v0.18.5.0 changed
get_pruned_transaction_hash from returning the hash to returning bool with
an out-param, and src/page.h still calls the old form. Upstream's
Dockerfile pins v0.18.4.0, which is why nobody has hit it. Patched from an
exact-line anchor, so if upstream fixes it the build STOPS rather than
quietly doing something else. We patch instead of building against 0.18.4.0
because the signed hashes.txt only covers the current release - using the
older source would mean dropping the provenance chain. LMDB is VERSION 5 in
both, so either reads the other's database.
3. FindMonero.cmake hunts for miniupnpc inside the monero build tree with
NO_DEFAULT_PATH, but monero stopped vendoring miniupnp as a submodule.
Fixed with a cache override rather than patching their cmake.
USE_DEVICE_TREZOR=OFF as well - an explorer has no use for hardware wallets and
it drops the generated protobuf units. Verified that xmrblocks still links.
── Two things in the unit that look wrong and are not ──────────────────────
WorkingDirectory is load-bearing: page.h hardcodes TMPL_DIR as "./templates",
resolved relative to cwd at REQUEST time. Get it wrong and the service starts,
binds 8081, and 500s every page. That is also why the health check fetches a
real page and greps it instead of probing the port.
ReadWritePaths must include the blockchain directory even though the database is
opened read-only: monero sets mdb_flags = MDB_RDONLY WITHOUT MDB_NOLOCK, so
LMDB still registers this reader in lock.mdb. With ProtectSystem=strict and
nothing writable the open fails. "It only reads, so grant it nothing" is wrong.
── Timeouts are measured, not guessed ──────────────────────────────────────
proxmox-tank-1 is a spinning-disk mirror and xmrblocks says so on startup.
First start took 98s to open the LMDB before binding (wait_for now allows 300s),
and a COLD index page took 68 SECONDS where the next two took 0.87s and 0.012s
(the check now allows 90s, its unit 180s). The first pass used 90s and 25s and
produced exactly the false failures you would expect.
A stat() bug was caught the same way: `stat` computes a sha1 by default, so
checking that data.mdb exists was hashing the entire 40 GB blockchain. --check
found it before a real run did.
── Exposure ────────────────────────────────────────────────────────────────
Caddy on vipy terminates TLS; the upstream is reached over the tailnet, which
needed a headscale ACL entry for tag:monerod-box:8081 - without it the node is
invisible, not merely unreachable, and the symptom is a 502 "no such host".
No authentication, deliberately: it is a block explorer over public chain data.
That includes --enable-pusher, so a visitor can relay a raw transaction through
our node. A choice, not an oversight; flip xmrblocks_enable_pusher to close it.
── Also ────────────────────────────────────────────────────────────────────
monerod-box raised 2048 -> 6144 MiB. Not for the explorer: monerod alone had
outgrown 2 GB past ~39% of the chain and was OOM-killed twice in a morning at
1.74 GB anon-rss. Recorded in vms.auto.tfvars because ignore_changes = all means
tofu will not reconcile it. The box now idles at ~1.2 GB of 5.9 GB with both
services up.
No backups, deliberately - binary, templates and chain are all reproducible.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
monerod v0.18.5.1 on monerod-box (VMID 2400), Debian 13, systemd, no Docker.
Syncing at 24% as of this commit, 0 restarts, 0 OOM kills.
── The build-from-source requirement could not be met ──────────────────────
The intent was to build it ourselves and check the result against the published
checksums. That is not achievable for this release, and the role's README says
so at length so nobody re-derives it:
contrib/guix - the reproducible build that yields a byte-identical tarball -
exists ONLY on monero master. At tag v0.18.5.1 contrib/ contains `gitian`,
whose README wants an Ubuntu 18.04 host (EOL 2023) and python-cheetah.
A plain `make release-static` is not reproducible at all, so it produces a
binary whose hash matches nothing - failing both halves of the ask.
So we install the published binary and prove its provenance instead:
1. binaryFate's key is VENDORED at files/binaryfate.asc. A trust root fetched
over the network at the moment you need it is not a trust root. Its
fingerprint is asserted after import regardless.
2. hashes.txt is verified, and the assertion is on gpg's `VALIDSIG <fpr>`
status line - NOT on the string "Good signature", which is what
bitcoin_knots greps for and which passes for any key in the keyring.
3. The hash is looked up in the output of `gpg --decrypt`, not in the raw
clearsigned file, so nothing unsigned is ever searched.
4. The lookup requires hash AND filename on one line.
Tested with a positive and a negative control before deploying: the real
tarball matches, a corrupted hash correctly fails. monero_sha256 in defaults/
is a second in-git assertion so a version bump cannot happen without the
checksum moving in the same diff.
When v0.19 ships with guix on the release branch this gets easier, and the
README records why: the published monero-linux-x64 tarball unpacks to
monero-x86_64-linux-gnu-v0.18.5.1/, i.e. it IS the guix DISTNAME renamed, so
sha256(guix output) will equal the hashes.txt entry exactly.
── The 500 GB disk is provisioned in code ──────────────────────────────────
knots-box mounts /mnt/knots_data (~875 GB of chain) entirely by hand; that
mount appears nowhere in Ansible and a rebuild of that host would come up with
the blockchain silently missing. tasks/storage.yml does not repeat it.
Whole device, no partition table. Everything after mkfs goes by UUID, because
/dev/sdX is assigned by the kernel at boot and this estate has been bitten
eight times by an identifier written down once whose thing then moved.
monero_data_device is used ONLY to create the filesystem. Guards refuse to
touch the root disk or to overwrite an unrecognised filesystem, and a final
assert confirms the data directory is not still on /.
fstab gets `nofail` so a missing disk cannot drop a headless VM into an
emergency shell - and the unit gets `RequiresMountsFor=`, without which monerod
would then start, find an empty directory, and write a 300 GB chain onto a
10 GB root disk. With it the unit refuses to start and infra/401 says so within
five minutes.
The mount-point task and the ownership task deliberately share owner and mode.
Writing the obvious root:root 0755 on the first made them disagree and every
run flipped the directory back and forth; caught by re-running --check.
── Exposure: one HTTPS vhost, zero new open ports ──────────────────────────
Two RPC servers, not one: unrestricted on 127.0.0.1:18081 for administration
and the health check, restricted on :18089 for everything else. That is
`rpc-restricted-bind-port` and deliberately NOT `restricted-rpc=1`, which would
restrict the loopback server too. Verified live: the restricted port reports
restricted=true and blanks version and start_time.
--rpc-login is HTTP Digest (contrib/epee/src/http_auth.cpp) and
core_rpc_server::init hands the same login to both servers. Caddy on vipy does
TLS and routing only - no caddy_site_basic_auth, because a Basic challenge
would collide with the Digest challenge Feather answers. Verified end to end
from the WAN: 401 unauthenticated, get_block_count over /json_rpc when
authenticated, 401 again with a wrong password.
No UFW rule, and that is correct: tailnet traffic bypasses UFW entirely because
`-A INPUT -j ts-input` sits ahead of every ufw-* chain. Confirmed on mempool-box
before relying on it here.
P2P is outbound only. Nothing forwards 18080, so the node dials out, syncs and
serves us without relaying for strangers; no-igd follows from that.
── Monitoring: infra, systemd, public. No backups ──────────────────────────
Six Gatus endpoints, all green: liveness, disk, services/monerod-box-local/
monerod, probe/monerod, dns/monero.contrapeso.xyz, public/monero.
The probe does NOT assert `synchronized`. A full sync takes days and a check
requiring it would report DOWN for every one of them - an alarm with the
batteries taken out. Height and sync state go in the message instead.
The timer carries no `Requires=monerod.service`. Fulcrum's did, and sat
active+enabled for seven months without firing once. public/monero asserts 401,
not 200, so it goes red if rpc-login ever stops being enforced.
No backups, deliberately, following the phoenixd precedent: the chain is
re-syncable public data and there is no wallet on this node.
── Known constraint ────────────────────────────────────────────────────────
The VM has 2 GB and no swap; monerod's RSS is ~1.3 GB mid-sync. It is holding
(0 OOM kills, ~1 GB available, kernel reclaiming cache) but 8 GB is the
recommendation once the initial sync is done. out-peers/in-peers are held at
16/8 partly for this reason. Bumping it is a Proxmox resize plus memory_mb
here, since the vm resource sets ignore_changes = all.
The 500 GB data disk is likewise invisible to tofu - it was attached in the UI
and the vm resource ignores it - so vms.auto.tfvars now carries a comment
saying where it is and what mounts it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
