upgrade: Container upgrades existing data on start

Dockerfile

@@ -4,3 +4,7 @@ ENV POSTGRES_USER docker
 ENV POSTGRES_PASSWORD docker
 
 COPY create-resin-db.sh /docker-entrypoint-initdb.d/
+COPY balena-entrypoint.sh /balena-entrypoint.sh
+
+CMD [ "postgres" ]
+ENTRYPOINT [ "/balena-entrypoint.sh" ]

balena-entrypoint.sh

@@ -0,0 +1,118 @@
+#!/bin/bash
+
+set -e
+
+# creates a backup archive of the dir $1...
+backup_data () {
+    gosu postgres tar --exclude backup.tar.gz -zcf /tmp/backup.tar.gz -C "$1" .
+    mv /tmp/backup.tar.gz "${1}/backup.tar.gz"
+}
+
+# copies all the data from $1 to $2...
+restore_volume () {
+    echo "=== Restoring data volume structure"
+    find "$1" -maxdepth 1 \
+        ! -path "$1" \
+        | xargs mv -t "$2"
+}
+
+# install the old version of Postgres, required when doing an upgrade...
+install_old_version () {
+    if [ ! -d "/usr/lib/postgresql/$1/bin" ]; then
+        sed -i 's/$/ '"$1"'/' /etc/apt/sources.list.d/pgdg.list
+
+        apt-get -qq update \
+        && apt-get install -qq -y --no-install-recommends \
+            "postgresql-$1" \
+        && rm -rf /var/lib/apt/lists/*
+    fi
+}
+
+# creates a dir at $1 which is valid for Postgres data to live in...
+create_postgres_data_dir () {
+    echo "=== Creating data dir $1"
+    mkdir -p "$1"
+    chmod 700 "$1"
+    chown -R postgres:postgres "$1"
+}
+
+# echo a message and die...
+die_with_message () {
+    echo "[FATAL] $1"
+    exit 2
+}
+
+# check that this is running from within a valid Postgres container environment...
+[ ! -z "$PG_MAJOR" ] || die_with_message "Not a compatible Postgres runtime environment"
+
+# set our target version...
+TARGET_VERSION="$PG_MAJOR"
+
+# ensure we have a versioned data directory...
+[ -d "${PGDATA}/${TARGET_VERSION}" ] || create_postgres_data_dir "${PGDATA}/${TARGET_VERSION}"
+
+# check for Postgres data in the root of the $PGDATA directory...
+if [ -f "${PGDATA}/PG_VERSION" ]; then
+    SOURCE_VERSION="$(cat ${PGDATA}/PG_VERSION)"
+
+    # does the data need upgrading...
+    if [ "$SOURCE_VERSION" -ne "$TARGET_VERSION" ]; then
+        echo "=== Upgrading data from v${SOURCE_VERSION} to v${TARGET_VERSION}"
+
+        # define our directories...
+        PGDATAOLD="${PGDATA}/${SOURCE_VERSION}"
+        PGDATANEW="${PGDATA}/${TARGET_VERSION}"
+        PGBINOLD="/usr/lib/postgresql/$SOURCE_VERSION/bin"
+        PGBINNEW="/usr/lib/postgresql/$TARGET_VERSION/bin"
+
+        echo "=== Installing tools for Postgres v${SOURCE_VERSION}"
+        install_old_version "$SOURCE_VERSION"
+
+        echo "=== Moving extisting data to ${PGDATAOLD}"
+        create_postgres_data_dir "${PGDATAOLD}"
+        find "$PGDATA" -maxdepth 1 \
+            ! -path "$PGDATA" \
+            ! -path "$PGDATAOLD*" \
+            | xargs mv -t "${PGDATAOLD}"
+
+        trap "restore_volume ${PGDATAOLD} ${PGDATA}" ERR
+
+        echo "=== Initialising new data directory ${PGDATANEW}"
+        rm -rf "${PGDATANEW}"
+        create_postgres_data_dir "${PGDATANEW}"
+        gosu postgres initdb -D "$PGDATANEW" -U "$POSTGRES_USER" $POSTGRES_INITDB_ARGS
+
+        echo "=== Beginning pg_upgrade"
+        cd /tmp
+        gosu postgres pg_upgrade \
+            -U "$POSTGRES_USER" \
+            --old-datadir="$PGDATAOLD" \
+            --new-datadir="$PGDATANEW" \
+            --old-bindir="$PGBINOLD" \
+            --new-bindir="$PGBINNEW" \
+            --check
+
+        gosu postgres pg_upgrade \
+            -U "$POSTGRES_USER" \
+            --old-datadir="$PGDATAOLD" \
+            --new-datadir="$PGDATANEW" \
+            --old-bindir="$PGBINOLD" \
+            --new-bindir="$PGBINNEW"
+
+        echo "=== Restoring configuration files"
+        cp "${PGDATAOLD}/pg_hba.conf" "${PGDATANEW}/pg_hba.conf"
+        cp "${PGDATAOLD}/pg_ident.conf" "${PGDATANEW}/pg_ident.conf"
+    else
+        echo "=== Moving extisting data to directory "${PGDATA}/${TARGET_VERSION}""
+        find "$PGDATA" -maxdepth 1 \
+            ! -path "$PGDATA" \
+            | xargs mv -t "${PGDATA}/${TARGET_VERSION}"
+    fi
+fi
+
+# set our runtime data directory to the versioned one...
+export PGDATA="${PGDATA}/${TARGET_VERSION}"
+
+# run the existing Postgres entrypoint script...
+. /docker-entrypoint.sh
+_main "$@"