/
vlans.go
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/
vlans.go
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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"
)
// VLAN represents a row in the vlans table.
type VLAN struct {
config.VLAN
}
// VLANsTable represents the table of VLANs in the database.
type VLANsTable struct {
// current is the slice of VLANs in the database.
current []*VLAN
// additions is a slice of VLANs pending addition to the database.
additions []*VLAN
// removals is a slice of VLANs pending removal from the database.
removals []*VLAN
// updates is a slice of VLANs pending update in the database.
updates []*VLAN
}
// fetch fetches the VLANs from the database.
func (t *VLANsTable) fetch(c context.Context) error {
db := database.Get(c)
rows, err := db.QueryContext(c, `
SELECT id, alias, state, cidr_block
FROM vlans
`)
if err != nil {
return errors.Annotate(err, "failed to select VLANs").Err()
}
defer rows.Close()
for rows.Next() {
vlan := &VLAN{}
if err := rows.Scan(&vlan.Id, &vlan.Alias, &vlan.State, &vlan.CidrBlock); err != nil {
return errors.Annotate(err, "failed to scan VLAN").Err()
}
t.current = append(t.current, vlan)
}
return nil
}
// needsUpdate returns true if the given row needs to be updated to match the given config.
func (*VLANsTable) needsUpdate(row, cfg *VLAN) bool {
return row.Alias != cfg.Alias || row.State != cfg.State || row.CidrBlock != cfg.CidrBlock
}
// computeChanges computes the changes that need to be made to the VLANs in the database.
func (t *VLANsTable) computeChanges(c context.Context, vlans []*config.VLAN) {
cfgs := make(map[int64]*VLAN, len(vlans))
for _, cfg := range vlans {
cfgs[cfg.Id] = &VLAN{
VLAN: config.VLAN{
Id: cfg.Id,
Alias: cfg.Alias,
State: cfg.State,
CidrBlock: cfg.CidrBlock,
},
}
}
for _, vlan := range t.current {
if cfg, ok := cfgs[vlan.Id]; ok {
// VLAN found in the config.
if t.needsUpdate(vlan, cfg) {
// VLAN doesn't match the config.
t.updates = append(t.updates, cfg)
}
// Record that the VLAN config has been seen.
delete(cfgs, cfg.Id)
} else {
// VLAN not found in the config.
t.removals = append(t.removals, vlan)
}
}
// VLANs remaining in the map are present in the config but not the database.
// Iterate deterministically over the slice to determine which VLANs need to be added.
for _, cfg := range vlans {
if p, ok := cfgs[cfg.Id]; ok {
t.additions = append(t.additions, p)
}
}
}
// add adds all VLANs pending addition to the database, clearing pending additions.
// No-op unless computeChanges was called first. Idempotent until computeChanges is called again.
func (t *VLANsTable) 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 vlans (id, alias, state, cidr_block)
VALUES (?, ?, ?, ?)
`)
if err != nil {
return errors.Annotate(err, "failed to prepare statement").Err()
}
defer stmt.Close()
// Add each VLAN to the database, and update the slice of VLANs with each addition.
for len(t.additions) > 0 {
vlan := t.additions[0]
_, err := stmt.ExecContext(c, vlan.Id, vlan.Alias, vlan.State, vlan.CidrBlock)
if err != nil {
return errors.Annotate(err, "failed to add VLAN %d", vlan.Id).Err()
}
t.current = append(t.current, vlan)
t.additions = t.additions[1:]
logging.Infof(c, "Added VLAN %d", vlan.Id)
}
return nil
}
// remove removes all VLANs pending removal from the database, clearing pending removals.
// No-op unless computeChanges was called first. Idempotent until computeChanges is called again.
func (t *VLANsTable) 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 vlans
WHERE id = ?
`)
if err != nil {
return errors.Annotate(err, "failed to prepare statement").Err()
}
defer stmt.Close()
// Remove each VLAN from the table. It's more efficient to update the slice of
// VLANs once at the end rather than for each removal, so use a defer.
removed := make(map[int64]struct{}, len(t.removals))
defer func() {
var vlans []*VLAN
for _, vlan := range t.current {
if _, ok := removed[vlan.Id]; !ok {
vlans = append(vlans, vlan)
}
}
t.current = vlans
}()
for len(t.removals) > 0 {
vlan := t.removals[0]
if _, err := stmt.ExecContext(c, vlan.Id); err != nil {
// Defer ensures the slice of VLANs is updated even if we exit early.
return errors.Annotate(err, "failed to remove VLAN %d", vlan.Id).Err()
}
removed[vlan.Id] = struct{}{}
t.removals = t.removals[1:]
logging.Infof(c, "Removed VLAN %d", vlan.Id)
}
return nil
}
// update updates all VLANs pending update in the database, clearing pending updates.
// No-op unless computeChanges was called first. Idempotent until computeChanges is called again.
func (t *VLANsTable) 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 vlans
SET alias = ?, state = ?, cidr_block = ?
WHERE id = ?
`)
if err != nil {
return errors.Annotate(err, "failed to prepare statement").Err()
}
defer stmt.Close()
// Update each VLAN in the table. It's more efficient to update the slice of
// VLANs once at the end rather than for each update, so use a defer.
updated := make(map[int64]*VLAN, len(t.updates))
defer func() {
for _, vlan := range t.current {
if u, ok := updated[vlan.Id]; ok {
vlan.Alias = u.Alias
vlan.State = u.State
vlan.CidrBlock = u.CidrBlock
}
}
}()
for len(t.updates) > 0 {
vlan := t.updates[0]
if _, err := stmt.ExecContext(c, vlan.Alias, vlan.State, vlan.CidrBlock, vlan.Id); err != nil {
return errors.Annotate(err, "failed to update VLAN %d", vlan.Id).Err()
}
updated[vlan.Id] = vlan
t.updates = t.updates[1:]
logging.Infof(c, "Updated VLAN %d", vlan.Id)
}
return nil
}
// EnsureVLANs ensures the database contains exactly the given VLANs.
func EnsureVLANs(c context.Context, cfgs []*config.VLAN) error {
t := &VLANsTable{}
if err := t.fetch(c); err != nil {
return errors.Annotate(err, "failed to fetch VLANs").Err()
}
t.computeChanges(c, cfgs)
if err := t.add(c); err != nil {
return errors.Annotate(err, "failed to add VLANs").Err()
}
if err := t.remove(c); err != nil {
return errors.Annotate(err, "failed to remove VLANs").Err()
}
if err := t.update(c); err != nil {
return errors.Annotate(err, "failed to update VLANs").Err()
}
return nil
}