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discourse/pg_backup.sh
2026-06-22 18:37:15 +00:00

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#!/bin/bash
# Postgres backup/restore hook for the discourse `db` service (discourse/postgres image).
set -e
# constants
BACKUP_FILE='/var/lib/postgresql/backup.sql'
DATADIR="${PGDATA:-/var/lib/postgresql/18/docker}"
DB_NAME="${POSTGRES_DB:-discourse}"
# The bootstrap superuser (install user, oid 10) differs between deployments
# (`postgres` on bitnami-origin clusters, `discourse` on others). Detect it at
# runtime over the local trust socket rather than hard-coding a name.
detect_superuser() {
local u name
for u in discourse postgres; do
name="$(psql -U "$u" -d "$DB_NAME" -tAc 'select rolname from pg_roles where oid = 10' 2>/dev/null | tr -d '[:space:]')"
if [ -n "$name" ]; then echo "$name"; return 0; fi
done
echo postgres
}
SU="$(detect_superuser)"
function backup {
pg_dump -U "$SU" "$DB_NAME" | gzip > "$BACKUP_FILE"
}
function restore {
cd "$DATADIR"
# Block all non-local connections so the running discourse app + sidekiq cannot reconnect and
# interfere with the drop/recreate/reimport. Restored on exit.
restore_hba() {
cat pg_hba.conf.bak > pg_hba.conf
rm -f pg_hba.conf.bak
su postgres -c "pg_ctl -D '$DATADIR' reload"
}
cp pg_hba.conf pg_hba.conf.bak
echo 'local all all trust' > pg_hba.conf
su postgres -c "pg_ctl -D '$DATADIR' reload"
trap restore_hba EXIT INT TERM
# terminate any lingering local sessions before recreate
# see https://stackoverflow.com/questions/5108876/kill-a-postgresql-session-connection
psql -U "$SU" -d postgres -c \
"SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname='${DB_NAME}' AND pid<>pg_backend_pid();"
# drop database and then recreate it
psql -U "$SU" -d postgres -c "DROP DATABASE ${DB_NAME} WITH (FORCE);"
createdb -U "$SU" "$DB_NAME"
# reimport data
gunzip -c "$BACKUP_FILE" | psql -U "$SU" -d "$DB_NAME" -1 -v ON_ERROR_STOP=1 -f -
}
$@