machine-db/appengine/model/hosts.go

// Copyright 2018 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package model

import (
	"context"
	"strings"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	"github.com/VividCortex/mysqlerr"
	"github.com/go-sql-driver/mysql"

	"go.chromium.org/luci/common/errors"

	"go.chromium.org/luci/machine-db/appengine/database"
	"go.chromium.org/luci/machine-db/common"
)

// AssignHostnameAndIP assigns the given hostname and IP address using the given transaction.
// The caller must commit or roll back the transaction appropriately.
func AssignHostnameAndIP(c context.Context, tx database.ExecerContext, hostname string, ipv4 common.IPv4) (int64, error) {
	// By setting hostnames.vlan_id as both FOREIGN KEY and NOT NULL when setting up the database,
	// we can avoid checking if the given VLAN is valid. MySQL will ensure the given VLAN exists.
	res, err := tx.ExecContext(c, `
		INSERT INTO hostnames (name, vlan_id)
		VALUES (?, (SELECT vlan_id FROM ips WHERE ipv4 = ? AND hostname_id IS NULL))
	`, hostname, ipv4)
	if err != nil {
		switch e, ok := err.(*mysql.MySQLError); {
		case !ok:
			// Type assertion failed.
		case e.Number == mysqlerr.ER_DUP_ENTRY && strings.Contains(e.Message, "'name'"):
			// e.g. "Error 1062: Duplicate entry 'hostname-vlanId' for key 'name'".
			return 0, status.Errorf(codes.AlreadyExists, "duplicate hostname %q", hostname)
		case e.Number == mysqlerr.ER_BAD_NULL_ERROR && strings.Contains(e.Message, "'vlan_id'"):
			// e.g. "Error 1048: Column 'vlan_id' cannot be null".
			return 0, status.Errorf(codes.NotFound, "ensure IPv4 address %q exists and is free first", ipv4)
		}
		return 0, errors.Annotate(err, "failed to create hostname").Err()
	}
	hostnameID, err := res.LastInsertId()
	if err != nil {
		return 0, errors.Annotate(err, "failed to fetch hostname").Err()
	}

	res, err = tx.ExecContext(c, `
		UPDATE ips
		SET hostname_id = ?
		WHERE ipv4 = ?
			AND hostname_id IS NULL
	`, hostnameID, ipv4)
	if err != nil {
		return 0, errors.Annotate(err, "failed to assign IP address").Err()
	}
	switch rows, err := res.RowsAffected(); {
	case err != nil:
		return 0, errors.Annotate(err, "failed to fetch affected rows").Err()
	case rows == 1:
		return hostnameID, nil
	default:
		// Shouldn't happen because IP address is unique per VLAN in the database.
		return 0, errors.Reason("unexpected number of affected rows %d", rows).Err()
	}
}