#!/bin/bash
# This script is run by failover_command.

set -o xtrace

# Special values:
# 1)  %d = failed node id
# 2)  %h = failed node hostname
# 3)  %p = failed node port number
# 4)  %D = failed node database cluster path
# 5)  %m = new main node id
# 6)  %H = new main node hostname
# 7)  %M = old main node id
# 8)  %P = old primary node id
# 9)  %r = new main port number
# 10) %R = new main database cluster path
# 11) %N = old primary node hostname
# 12) %S = old primary node port number
# 13) %% = '%' character

FAILED_NODE_ID="$1"
FAILED_NODE_HOST="$2"
FAILED_NODE_PORT="$3"
FAILED_NODE_PGDATA="$4"
NEW_MAIN_NODE_ID="$5"
NEW_MAIN_NODE_HOST="$6"
OLD_MAIN_NODE_ID="$7"
OLD_PRIMARY_NODE_ID="$8"
NEW_MAIN_NODE_PORT="$9"
NEW_MAIN_NODE_PGDATA="${10}"
OLD_PRIMARY_NODE_HOST="${11}"
OLD_PRIMARY_NODE_PORT="${12}"

PGHOME=/usr/pgsql-13
REPL_SLOT_NAME=$(echo ${FAILED_NODE_HOST,,} | tr -- -. _)
POSTGRESQL_STARTUP_USER=postgres
SSH_KEY_FILE=id_rsa_pgpool
SSH_OPTIONS="-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ~/.ssh/${SSH_KEY_FILE}"


echo failover.sh: start: failed_node_id=$FAILED_NODE_ID failed_host=$FAILED_NODE_HOST \
    old_primary_node_id=$OLD_PRIMARY_NODE_ID new_main_node_id=$NEW_MAIN_NODE_ID new_main_host=$NEW_MAIN_NODE_HOST

## If there's no main node anymore, skip failover.
if [ $NEW_MAIN_NODE_ID -lt 0 ]; then
    echo failover.sh: All nodes are down. Skipping failover.
    exit 0
fi

## Test passwordless SSH
ssh -T ${SSH_OPTIONS} ${POSTGRESQL_STARTUP_USER}@${NEW_MAIN_NODE_HOST} ls /tmp > /dev/null

if [ $? -ne 0 ]; then
    echo failover.sh: passwordless SSH to ${POSTGRESQL_STARTUP_USER}@${NEW_MAIN_NODE_HOST} failed. Please setup passwordless SSH.
    exit 1
fi

## If Standby node is down, skip failover.
if [ $OLD_PRIMARY_NODE_ID != "-1" -a $FAILED_NODE_ID != $OLD_PRIMARY_NODE_ID ]; then

    # If Standby node is down, drop replication slot.
    ${PGHOME}/bin/psql -h ${OLD_PRIMARY_NODE_HOST} -p ${OLD_PRIMARY_NODE_PORT} postgres \
        -c "SELECT pg_drop_replication_slot('${REPL_SLOT_NAME}');"  >/dev/null 2>&1

    if [ $? -ne 0 ]; then
        echo ERROR: failover.sh: drop replication slot \"${REPL_SLOT_NAME}\" failed. You may need to drop replication slot manually.
    fi

    echo failover.sh: end: standby node is down. Skipping failover.
    exit 0
fi

## Promote Standby node.
echo failover.sh: primary node is down, promote new_main_node_id=$NEW_MAIN_NODE_ID on ${NEW_MAIN_NODE_HOST}.

ssh -T ${SSH_OPTIONS} ${POSTGRESQL_STARTUP_USER}@${NEW_MAIN_NODE_HOST} ${PGHOME}/bin/pg_ctl -D ${NEW_MAIN_NODE_PGDATA} -w promote

if [ $? -ne 0 ]; then
    echo ERROR: failover.sh: promote failed
    exit 1
fi

echo failover.sh: end: new_main_node_id=$NEW_MAIN_NODE_ID on ${NEW_MAIN_NODE_HOST} was successfully promoted to primary
exit 0