fix: clickhouse entrypoint - backup download is best-effort (server must start regardless)

The previous entrypoint treated clickhouse-backup as required: a download failure
(rate-limit or transient network) caused install_clickhouse_backup to return 1 which
with set -e exited the entrypoint before /entrypoint.sh ran. ClickHouse never started,
the swarm restarted it, the download was retried, amplifying the throttle -> crash-loop
-> deploy timeout (cc-ci Q4.7b).

Fix: install_clickhouse_backup || true — the server starts even if the backup tool
cannot be fetched. Backup/restore degrades until a later restart fetches it.

Also: fix stray trailing quote in backupbot.restore.post-hook; bump
CLICKHOUSE_ENTRYPOINT_VERSION v3->v4 (config content changed).

abra.sh

@@ -1,3 +1,3 @@
 export CLICKHOUSE_CONF_VERSION=v2
 export CLICKHOUSE_USER_CONF_VERSION=v2
-export CLICKHOUSE_ENTRYPOINT_VERSION=v3
+export CLICKHOUSE_ENTRYPOINT_VERSION=v4

compose.yml

@@ -82,7 +82,7 @@ services:
         backupbot.backup.path: "/var/lib/clickhouse/backup/events"
         backupbot.backup.post-hook: "rm -rf /var/lib/clickhouse/backup/events"
         backupbot.restore: "true"
-        backupbot.restore.post-hook: clickhouse-backup restore --rm events && rm -rf /var/lib/clickhouse/backup/events"
+        backupbot.restore.post-hook: clickhouse-backup restore --rm events && rm -rf /var/lib/clickhouse/backup/events
 
 volumes:
   db-data:

entrypoint.clickhouse.sh

@@ -1,12 +1,17 @@
 #!/bin/bash
-
-# clickhouse-backup is a backup tool (backupbot pre/post-hooks: `clickhouse-backup create/restore`).
-# It is a 22 MB GitHub download (rate-limit / network), which can fail to download, and lead to crash loop and download throttling. 
+# clickhouse-backup is the BACKUP tool (backupbot pre/post-hooks: `clickhouse-backup create/restore`).
+# It is NOT required for clickhouse-SERVER (`/entrypoint.sh`) to run. The published recipe fetched it
+# with `set -ex` + a single silenced no-retry wget to ephemeral /tmp, so ANY transient failure of the
+# 22 MB GitHub download (rate-limit / network) exited the container BEFORE the server started -> swarm
+# restarted it -> re-downloaded -> amplified the throttle -> crash-loop -> deploy timeout (cc-ci Q4.7).
 #
-# to make the download smoother:
-#   - cache the binary on the persistent clickhouse data volume (/var/lib/clickhouse) so it is fetched
+# Hardening (no behaviour change when the download succeeds first try):
+#   - cache the binary on the PERSISTENT clickhouse data volume (/var/lib/clickhouse) so it is fetched
 #     at most once and reused on every container restart (no re-download amplification);
-#   - retry with backoff to ride out transient GitHub failures
+#   - retry with backoff;
+#   - NEVER let a download failure block the server start (best-effort: the server comes up, backup/
+#     restore degrade until the next successful fetch);
+#   - un-silenced so a failure is diagnosable in `docker service logs`.
 
 set -e
 
@@ -47,11 +52,11 @@ install_clickhouse_backup() {
     echo "clickhouse-backup: fetch attempt ${attempt} failed; backing off $((attempt * 10))s" >&2
     sleep $((attempt * 10))
   done
-  echo "clickhouse-backup: fetch FAILED after all retries — aborting; clickhouse-server will NOT start (backup tool is required)" >&2
+  echo "clickhouse-backup: fetch FAILED after retries — starting clickhouse-server WITHOUT the backup tool (backup/restore unavailable until a later restart fetches it)" >&2
   return 1
 }
 
-#if the backup tool cannot be installed after retries, it aborts (set -e) so the deploy fails
-install_clickhouse_backup
+# Best-effort: the server MUST start even if the backup-tool fetch fails (it is not a server dependency).
+install_clickhouse_backup || true
 
 exec /entrypoint.sh