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// Copyright 2017 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"
"go.chromium.org/luci/common/errors"
"go.chromium.org/luci/common/logging"
"go.chromium.org/luci/machine-db/api/config/v1"
"go.chromium.org/luci/machine-db/appengine/database"
)
// OS represents a row in the oses table.
type OS struct {
config.OS
Id int64
}
// OSesTable represents the table of operating systems in the database.
type OSesTable struct {
// current is the slice of operating systems in the database.
current []*OS
// additions is a slice of operating systems pending addition to the database.
additions []*OS
// removals is a slice of operating systems pending removal from the database.
removals []*OS
// updates is a slice of operating systems pending update in the database.
updates []*OS
}
// fetch fetches the operating systems from the database.
func (t *OSesTable) fetch(c context.Context) error {
db := database.Get(c)
rows, err := db.QueryContext(c, `
SELECT id, name, description
FROM oses
`)
if err != nil {
return errors.Annotate(err, "failed to select operating systems").Err()
}
defer rows.Close()
for rows.Next() {
os := &OS{}
if err := rows.Scan(&os.Id, &os.Name, &os.Description); err != nil {
return errors.Annotate(err, "failed to scan operating system").Err()
}
t.current = append(t.current, os)
}
return nil
}
// needsUpdate returns true if the given row needs to be updated to match the given config.
func (*OSesTable) needsUpdate(row, cfg *OS) bool {
return row.Description != cfg.Description
}
// computeChanges computes the changes that need to be made to the operating systems in the database.
func (t *OSesTable) computeChanges(c context.Context, oses []*config.OS) {
cfgs := make(map[string]*OS, len(oses))
for _, cfg := range oses {
cfgs[cfg.Name] = &OS{
OS: config.OS{
Name: cfg.Name,
Description: cfg.Description,
},
}
}
for _, os := range t.current {
if cfg, ok := cfgs[os.Name]; ok {
// Operating system found in the config.
if t.needsUpdate(os, cfg) {
// Operating system doesn't match the config.
cfg.Id = os.Id
t.updates = append(t.updates, cfg)
}
// Record that the operating system config has been seen.
delete(cfgs, cfg.Name)
} else {
// Operating system not found in the config.
t.removals = append(t.removals, os)
}
}
// Operating systems remaining in the map are present in the config but not the database.
// Iterate deterministically over the slice to determine which operating systems need to be added.
for _, cfg := range oses {
if os, ok := cfgs[cfg.Name]; ok {
t.additions = append(t.additions, os)
}
}
}
// add adds all operating systems pending addition to the database, clearing pending additions.
// No-op unless computeChanges was called first. Idempotent until computeChanges is called again.
func (t *OSesTable) add(c context.Context) error {
// Avoid using the database connection to prepare unnecessary statements.
if len(t.additions) == 0 {
return nil
}
db := database.Get(c)
stmt, err := db.PrepareContext(c, `
INSERT INTO oses (name, description)
VALUES (?, ?)
`)
if err != nil {
return errors.Annotate(err, "failed to prepare statement").Err()
}
defer stmt.Close()
// Add each operating system to the database, and update the slice of operating systems with each addition.
for len(t.additions) > 0 {
os := t.additions[0]
result, err := stmt.ExecContext(c, os.Name, os.Description)
if err != nil {
return errors.Annotate(err, "failed to add operating system %q", os.Name).Err()
}
t.current = append(t.current, os)
t.additions = t.additions[1:]
logging.Infof(c, "Added operating system %q", os.Name)
os.Id, err = result.LastInsertId()
if err != nil {
return errors.Annotate(err, "failed to get operating system ID %q", os.Name).Err()
}
}
return nil
}
// remove removes all operating systems pending removal from the database, clearing pending removals.
// No-op unless computeChanges was called first. Idempotent until computeChanges is called again.
func (t *OSesTable) remove(c context.Context) error {
// Avoid using the database connection to prepare unnecessary statements.
if len(t.removals) == 0 {
return nil
}
db := database.Get(c)
stmt, err := db.PrepareContext(c, `
DELETE FROM oses
WHERE id = ?
`)
if err != nil {
return errors.Annotate(err, "failed to prepare statement").Err()
}
defer stmt.Close()
// Remove each operating system from the table. It's more efficient to update the slice of
// operating systems once at the end rather than for each removal, so use a defer.
removed := make(map[int64]struct{}, len(t.removals))
defer func() {
var oses []*OS
for _, os := range t.current {
if _, ok := removed[os.Id]; !ok {
oses = append(oses, os)
}
}
t.current = oses
}()
for len(t.removals) > 0 {
os := t.removals[0]
if _, err := stmt.ExecContext(c, os.Id); err != nil {
// Defer ensures the slice of operating systems is updated even if we exit early.
return errors.Annotate(err, "failed to remove operating system %q", os.Name).Err()
}
removed[os.Id] = struct{}{}
t.removals = t.removals[1:]
logging.Infof(c, "Removed operating system %q", os.Name)
}
return nil
}
// update updates all operating systems pending update in the database, clearing pending updates.
// No-op unless computeChanges was called first. Idempotent until computeChanges is called again.
func (t *OSesTable) update(c context.Context) error {
// Avoid using the database connection to prepare unnecessary statements.
if len(t.updates) == 0 {
return nil
}
db := database.Get(c)
stmt, err := db.PrepareContext(c, `
UPDATE oses
SET description = ?
WHERE id = ?
`)
if err != nil {
return errors.Annotate(err, "failed to prepare statement").Err()
}
defer stmt.Close()
// Update each operating system in the table. It's more efficient to update the slice of
// operating systems once at the end rather than for each update, so use a defer.
updated := make(map[int64]*OS, len(t.updates))
defer func() {
for _, os := range t.current {
if u, ok := updated[os.Id]; ok {
os.Description = u.Description
}
}
}()
for len(t.updates) > 0 {
os := t.updates[0]
if _, err := stmt.ExecContext(c, os.Description, os.Id); err != nil {
return errors.Annotate(err, "failed to update operating system %q", os.Name).Err()
}
updated[os.Id] = os
t.updates = t.updates[1:]
logging.Infof(c, "Updated operating system %q", os.Name)
}
return nil
}
// ids returns a map of operating system names to IDs.
func (t *OSesTable) ids(c context.Context) map[string]int64 {
oses := make(map[string]int64, len(t.current))
for _, os := range t.current {
oses[os.Name] = os.Id
}
return oses
}
// EnsureOSes ensures the database contains exactly the given operating systems.
func EnsureOSes(c context.Context, cfgs []*config.OS) error {
t := &OSesTable{}
if err := t.fetch(c); err != nil {
return errors.Annotate(err, "failed to fetch operating systems").Err()
}
t.computeChanges(c, cfgs)
if err := t.add(c); err != nil {
return errors.Annotate(err, "failed to add operating systems").Err()
}
if err := t.remove(c); err != nil {
return errors.Annotate(err, "failed to remove operating systems").Err()
}
if err := t.update(c); err != nil {
return errors.Annotate(err, "failed to update operating systems").Err()
}
return nil
}