feat(deploy): sync schema to replication subscribers before migrating

Logical replication carries rows but not DDL, so a migration that adds a column stalls every subscriber with "missing replicated columns" until the column exists there too. _prisma_migrations is replicated, so migrate deploy on a subscriber reports nothing pending while its tables lag behind. sync-replica-schema.sh applies pending migrations to each subscriber first, tracking them locally in _replica_ddl_applied, then migrates the publisher. --check reports subscription state and columns missing on any replica. Co-authored-by: Cursor <cursoragent@cursor.com>
2026-08-11 21:34:02 +03:30
parent aec5e08a1e
commit 515e39d420
5 changed files with 206 additions and 1 deletions
@@ -0,0 +1,168 @@
+#!/usr/bin/env bash
+# Keep logical-replication subscribers in schema sync with the publisher.
+#
+# Logical replication ships rows, not DDL. When a migration adds a column on the
+# publisher, every subscriber keeps crashing with
+#   "logical replication target relation ... is missing replicated columns"
+# and the whole subscription stalls until the column exists there too.
+#
+# _prisma_migrations is itself replicated, so `prisma migrate deploy` on a
+# subscriber reports "No pending migrations" even when its tables lag behind.
+# Applied migrations are therefore tracked per subscriber in _replica_ddl_applied.
+#
+# Usage:
+#   bash deploy/sync-replica-schema.sh --init      # baseline: mark current migrations as applied
+#   bash deploy/sync-replica-schema.sh --dry-run   # list what would run
+#   bash deploy/sync-replica-schema.sh             # apply to replicas, then migrate publisher
+#   bash deploy/sync-replica-schema.sh --check     # replication + schema drift report
+set -euo pipefail
+
+API_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+MIGRATIONS_DIR="$API_DIR/prisma/migrations"
+CONFIG_FILE="${REPLICAS_ENV_FILE:-$API_DIR/deploy/replicas.env}"
+MODE="${1:-apply}"
+
+case "$MODE" in
+  apply|--init|--dry-run|--check) ;;
+  *)
+    echo "Usage: $0 [--init|--dry-run|--check]" >&2
+    exit 1
+    ;;
+esac
+
+command -v psql >/dev/null || { echo "psql not found" >&2; exit 1; }
+
+if [[ -f "$CONFIG_FILE" ]]; then
+  # shellcheck disable=SC1090
+  set -a && source "$CONFIG_FILE" && set +a
+fi
+
+if [[ -z "${REPLICA_DSNS:-}" ]]; then
+  echo "REPLICA_DSNS is empty. Create $CONFIG_FILE from deploy/replicas.env.example" >&2
+  exit 1
+fi
+
+if [[ -z "${DATABASE_URL:-}" && -f "$API_DIR/.env" ]]; then
+  # shellcheck disable=SC1091
+  set -a && source "$API_DIR/.env" && set +a
+fi
+
+read -r -a REPLICAS <<< "$(tr ',\n' '  ' <<< "$REPLICA_DSNS")"
+
+# psql would otherwise swallow the loop input it is called from
+run_psql() {
+  psql "$@" </dev/null
+}
+
+# host:port/db only — DSNs carry passwords
+label() {
+  sed -E 's#^[a-z]+://([^@]*@)?##; s#\?.*$##' <<< "$1"
+}
+
+# every list feeding comm is sorted with the same collation
+migration_names() {
+  find "$MIGRATIONS_DIR" -mindepth 1 -maxdepth 1 -type d -printf '%f\n' | LC_ALL=C sort
+}
+
+ensure_marker_table() {
+  run_psql "$1" -v ON_ERROR_STOP=1 -q -c "
+    CREATE TABLE IF NOT EXISTS _replica_ddl_applied (
+      migration_name text PRIMARY KEY,
+      applied_at timestamptz NOT NULL DEFAULT now()
+    );"
+}
+
+applied_names() {
+  run_psql "$1" -v ON_ERROR_STOP=1 -At -c \
+    "SELECT migration_name FROM _replica_ddl_applied" | LC_ALL=C sort
+}
+
+pending_names() {
+  comm -23 <(migration_names) <(applied_names "$1")
+}
+
+apply_migration() {
+  local dsn="$1" name="$2"
+  local sql_file="$MIGRATIONS_DIR/$name/migration.sql"
+  [[ -f "$sql_file" ]] || { echo "  ! missing $sql_file" >&2; return 1; }
+
+  local bundle
+  bundle="$(mktemp)"
+  cat "$sql_file" > "$bundle"
+  printf "\nINSERT INTO _replica_ddl_applied (migration_name) VALUES ('%s') ON CONFLICT DO NOTHING;\n" \
+    "$name" >> "$bundle"
+
+  run_psql "$dsn" -v ON_ERROR_STOP=1 -q --single-transaction -f "$bundle"
+  rm -f "$bundle"
+}
+
+column_fingerprint() {
+  run_psql "$1" -v ON_ERROR_STOP=1 -At -c "
+    SELECT table_name || '.' || column_name
+      FROM information_schema.columns
+     WHERE table_schema = 'public'
+       AND table_name NOT IN ('_replica_ddl_applied')" | LC_ALL=C sort
+}
+
+if [[ "$MODE" == "--check" ]]; then
+  for dsn in "${REPLICAS[@]}"; do
+    echo "== $(label "$dsn")"
+    run_psql "$dsn" -v ON_ERROR_STOP=1 -At -c "
+      SELECT subname || '  received=' || COALESCE(received_lsn::text, '-')
+             || '  latest=' || COALESCE(latest_end_lsn::text, '-')
+             || '  last_msg=' || COALESCE(last_msg_receipt_time::text, '-')
+        FROM pg_stat_subscription" || true
+
+    if [[ -n "${DATABASE_URL:-}" ]]; then
+      drift="$(comm -23 <(column_fingerprint "$DATABASE_URL") <(column_fingerprint "$dsn") || true)"
+      if [[ -n "$drift" ]]; then
+        echo "  ! columns present on publisher but missing here:"
+        sed 's/^/    /' <<< "$drift"
+      else
+        echo "  columns match publisher"
+      fi
+    fi
+  done
+  exit 0
+fi
+
+for dsn in "${REPLICAS[@]}"; do
+  echo "== $(label "$dsn")"
+  ensure_marker_table "$dsn"
+
+  if [[ "$MODE" == "--init" ]]; then
+    while read -r name; do
+      run_psql "$dsn" -v ON_ERROR_STOP=1 -q -c \
+        "INSERT INTO _replica_ddl_applied (migration_name) VALUES ('$name') ON CONFLICT DO NOTHING"
+    done < <(migration_names)
+    echo "  baseline recorded (no SQL executed)"
+    continue
+  fi
+
+  pending="$(pending_names "$dsn")"
+  if [[ -z "$pending" ]]; then
+    echo "  up to date"
+    continue
+  fi
+
+  while read -r name; do
+    if [[ "$MODE" == "--dry-run" ]]; then
+      echo "  would apply $name"
+    else
+      echo "  applying $name"
+      apply_migration "$dsn" "$name"
+    fi
+  done <<< "$pending"
+done
+
+if [[ "$MODE" == "--dry-run" || "$MODE" == "--init" ]]; then
+  exit 0
+fi
+
+echo "== publisher"
+cd "$API_DIR"
+npx prisma migrate deploy
+
+echo
+echo "Replicas apply DDL first, so the publisher can stream the new columns right away."
+echo "Verify with: bash deploy/sync-replica-schema.sh --check"