upgrade: Container upgrades existing data on start

Postgres will not automatically upgrade existing data when moving
to a different major version. These changes detect existing data
and compare their major versions to see if an upgrade is required.
If the upgrade is required then the correct tooling for the existing
data is installed and `pg_upgrade` is run.

Also part of this PR is the restructure of the data volume so that a
versioned sub-directory is used instead of the root of the mount. This
means that as you upgrade major versions you will keep a version of your
data which can be used.

Signed-off-by: Rich Bayliss <[email protected]>
Change-type: minor

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}/${TARGET_VERSION}"
+
+# run the existing Postgres entrypoint script...
+. /docker-entrypoint.sh
+_main "$@"