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