Enable user to avoid update on certain node.

disable-enable-update-on-node.sh

# 1. Create compute-host-to-exclude.txt

# one ip of compute nodes to be excluded from the update by line For
# instance this give the list of all compute node minus one.  those
# will be disable, letting only one computed being updated.

# openstack server list -f json | \
#    jq -r 'map(select(.Name |contains("compute")))[0:-1] | .[].Networks' \
#    | awk -F= '{print $2}' > compute-host-to-exclude.txt

# Please adjust to your own need, this is just an example.

# 2. Run the following on the undercloud.
cat > disable-update-on-node.sh <<'EOF'
fake_agents_dir=/root/fake-agents-dir
mkdir -p $fake_agents_dir
for agent in script puppet hiera apply-config; do
  cat > ${fake_agents_dir}/$agent <<EOS
#!/bin/bash
echo "Fake $agent being called" >> /tmp/fake.log
cat <<'EOJSON'
{
        "deploy_stdout": "Fake $agent run to skip update",
        "deploy_stderr": "",
        "deploy_status_code": 0
}
EOJSON
exit 0
EOS
  chmod +x ${fake_agents_dir}/$agent
done
mkdir -p /etc/systemd/system/os-collect-config.service.d/
cat > /etc/systemd/system/os-collect-config.service.d/90-disable-heat-agents.conf <<EOD
[Service]
Environment=HEAT_CONFIG_HOOKS=$fake_agents_dir
EOD
systemctl daemon-reload
systemctl restart os-collect-config
EOF

cat > enable-update-on-node.sh <<'EOF'
rm /etc/systemd/system/os-collect-config.service.d/90-disable-heat-agents.conf
systemctl daemon-reload
systemctl restart os-collect-config
EOF

# This will create two scripts:
# - disable-update-on-node.sh
# - enable-update-on-node.sh


# 3. Disable the needed nodes
for host in $(cat compute-host-to-exclude.txt); do
    scp disable-update-on-node.sh enable-update-on-node.sh heat-admin@${host}:
    ssh heat-admin@$host sudo bash ./disable-update-on-node.sh
done

# 4. Run the update as usual and do your testing on the canari node.

# 5. Re-enable the non-updated nodes.
for host in $(cat compute-host-to-exclude.txt); do
    ssh heat-admin@$host sudo bash ./enable-update-on-node.sh
done

# 6. Re-Run the update.