[task scheduler] Move files from build_scheduler/ to task_scheduler/

build_scheduler/go/db/db.go

Index: build_scheduler/go/db/db.go
diff --git a/build_scheduler/go/db/db.go b/build_scheduler/go/db/db.go
deleted file mode 100644
index d4401d22733538b341d76562d496837c94d93150..0000000000000000000000000000000000000000
--- a/build_scheduler/go/db/db.go
+++ /dev/null
@@ -1,159 +0,0 @@
-package db
-
-import (
-	"errors"
-	"io"
-	"time"
-
-	"github.com/skia-dev/glog"
-)
-
-const (
-	// Maximum number of simultaneous GetModifiedTasks users.
-	MAX_MODIFIED_TASKS_USERS = 10
-
-	// Expiration for GetModifiedTasks users.
-	MODIFIED_TASKS_TIMEOUT = 10 * time.Minute
-
-	// Retries attempted by UpdateWithRetries and UpdateTaskWithRetries.
-	NUM_RETRIES = 5
-)
-
-var (
-	ErrAlreadyExists    = errors.New("Object already exists and modification not allowed.")
-	ErrConcurrentUpdate = errors.New("Concurrent update")
-	ErrNotFound         = errors.New("Task with given ID does not exist")
-	ErrTooManyUsers     = errors.New("Too many users")
-	ErrUnknownId        = errors.New("Unknown ID")
-)
-
-func IsAlreadyExists(e error) bool {
-	return e != nil && e.Error() == ErrAlreadyExists.Error()
-}
-
-func IsConcurrentUpdate(e error) bool {
-	return e != nil && e.Error() == ErrConcurrentUpdate.Error()
-}
-
-func IsNotFound(e error) bool {
-	return e != nil && e.Error() == ErrNotFound.Error()
-}
-
-func IsTooManyUsers(e error) bool {
-	return e != nil && e.Error() == ErrTooManyUsers.Error()
-}
-
-func IsUnknownId(e error) bool {
-	return e != nil && e.Error() == ErrUnknownId.Error()
-}
-
-// TaskReader is a read-only view of a DB.
-type TaskReader interface {
-	io.Closer
-
-	// GetModifiedTasks returns all tasks modified since the last time
-	// GetModifiedTasks was run with the given id.
-	GetModifiedTasks(string) ([]*Task, error)
-
-	// GetTaskById returns the task with the given Id field. Returns nil, nil if
-	// task is not found.
-	GetTaskById(string) (*Task, error)
-
-	// GetTasksFromDateRange retrieves all tasks which started in the given date range.
-	GetTasksFromDateRange(time.Time, time.Time) ([]*Task, error)
-
-	// StartTrackingModifiedTasks initiates tracking of modified tasks for
-	// the current caller. Returns a unique ID which can be used by the caller
-	// to retrieve tasks which have been modified since the last query. The ID
-	// expires after a period of inactivity.
-	StartTrackingModifiedTasks() (string, error)
-
-	// StopTrackingModifiedTasks cancels tracking of modified tasks for the
-	// provided ID.
-	StopTrackingModifiedTasks(string)
-}
-
-// DB is used by the task scheduler to store Tasks.
-type DB interface {
-	TaskReader
-
-	// AssignId sets the given task's Id field. Does not insert the task into the
-	// database.
-	AssignId(*Task) error
-
-	// PutTask inserts or updates the Task in the database. Task's Id field must
-	// be empty or set with AssignId. PutTask will set Task.DbModified.
-	PutTask(*Task) error
-
-	// PutTasks inserts or updates the Tasks in the database. Each Task's Id field
-	// must be empty or set with AssignId. Each Task's DbModified field will be
-	// set.
-	PutTasks([]*Task) error
-}
-
-// UpdateWithRetries wraps a call to db.PutTasks with retries. It calls
-// db.PutTasks(f()) repeatedly until one of the following happen:
-//  - f or db.PutTasks returns an error, which is then returned from
-//    UpdateWithRetries;
-//  - PutTasks succeeds, in which case UpdateWithRetries returns the updated
-//    Tasks returned by f;
-//  - retries are exhausted, in which case UpdateWithRetries returns
-//    ErrConcurrentUpdate.
-//
-// Within f, tasks should be refreshed from the DB, e.g. with
-// db.GetModifiedTasks or db.GetTaskById.
-func UpdateWithRetries(db DB, f func() ([]*Task, error)) ([]*Task, error) {
-	var lastErr error
-	for i := 0; i < NUM_RETRIES; i++ {
-		t, err := f()
-		if err != nil {
-			return nil, err
-		}
-		lastErr = db.PutTasks(t)
-		if lastErr == nil {
-			return t, nil
-		} else if !IsConcurrentUpdate(lastErr) {
-			return nil, lastErr
-		}
-	}
-	glog.Warningf("UpdateWithRetries: %d consecutive ErrConcurrentUpdate.", NUM_RETRIES)
-	return nil, lastErr
-}
-
-// UpdateTaskWithRetries reads, updates, and writes a single Task in the DB. It:
-//  1. reads the task with the given id,
-//  2. calls f on that task, and
-//  3. calls db.PutTask() on the updated task
-//  4. repeats from step 1 as long as PutTasks returns ErrConcurrentUpdate and
-//     retries have not been exhausted.
-// Returns the updated task if it was successfully updated in the DB.
-// Immediately returns ErrNotFound if db.GetTaskById(id) returns nil.
-// Immediately returns any error returned from f or from PutTasks (except
-// ErrConcurrentUpdate). Returns ErrConcurrentUpdate if retries are exhausted.
-func UpdateTaskWithRetries(db DB, id string, f func(*Task) error) (*Task, error) {
-	tasks, err := UpdateWithRetries(db, func() ([]*Task, error) {
-		t, err := db.GetTaskById(id)
-		if err != nil {
-			return nil, err
-		}
-		if t == nil {
-			return nil, ErrNotFound
-		}
-		err = f(t)
-		if err != nil {
-			return nil, err
-		}
-		return []*Task{t}, nil
-	})
-	if err != nil {
-		return nil, err
-	} else {
-		return tasks[0], nil
-	}
-}
-
-// RemoteDB allows retrieving tasks and full access to comments.
-type RemoteDB interface {
-	TaskReader
-	CommentDB
-}