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| (Empty) |
| 1 package db | |
| 2 | |
| 3 import ( | |
| 4 "errors" | |
| 5 "io" | |
| 6 "time" | |
| 7 | |
| 8 "github.com/skia-dev/glog" | |
| 9 ) | |
| 10 | |
| 11 const ( | |
| 12 // Maximum number of simultaneous GetModifiedTasks users. | |
| 13 MAX_MODIFIED_TASKS_USERS = 10 | |
| 14 | |
| 15 // Expiration for GetModifiedTasks users. | |
| 16 MODIFIED_TASKS_TIMEOUT = 10 * time.Minute | |
| 17 | |
| 18 // Retries attempted by UpdateWithRetries and UpdateTaskWithRetries. | |
| 19 NUM_RETRIES = 5 | |
| 20 ) | |
| 21 | |
| 22 var ( | |
| 23 ErrAlreadyExists = errors.New("Object already exists and modification
not allowed.") | |
| 24 ErrConcurrentUpdate = errors.New("Concurrent update") | |
| 25 ErrNotFound = errors.New("Task with given ID does not exist") | |
| 26 ErrTooManyUsers = errors.New("Too many users") | |
| 27 ErrUnknownId = errors.New("Unknown ID") | |
| 28 ) | |
| 29 | |
| 30 func IsAlreadyExists(e error) bool { | |
| 31 return e != nil && e.Error() == ErrAlreadyExists.Error() | |
| 32 } | |
| 33 | |
| 34 func IsConcurrentUpdate(e error) bool { | |
| 35 return e != nil && e.Error() == ErrConcurrentUpdate.Error() | |
| 36 } | |
| 37 | |
| 38 func IsNotFound(e error) bool { | |
| 39 return e != nil && e.Error() == ErrNotFound.Error() | |
| 40 } | |
| 41 | |
| 42 func IsTooManyUsers(e error) bool { | |
| 43 return e != nil && e.Error() == ErrTooManyUsers.Error() | |
| 44 } | |
| 45 | |
| 46 func IsUnknownId(e error) bool { | |
| 47 return e != nil && e.Error() == ErrUnknownId.Error() | |
| 48 } | |
| 49 | |
| 50 // TaskReader is a read-only view of a DB. | |
| 51 type TaskReader interface { | |
| 52 io.Closer | |
| 53 | |
| 54 // GetModifiedTasks returns all tasks modified since the last time | |
| 55 // GetModifiedTasks was run with the given id. | |
| 56 GetModifiedTasks(string) ([]*Task, error) | |
| 57 | |
| 58 // GetTaskById returns the task with the given Id field. Returns nil, ni
l if | |
| 59 // task is not found. | |
| 60 GetTaskById(string) (*Task, error) | |
| 61 | |
| 62 // GetTasksFromDateRange retrieves all tasks which started in the given
date range. | |
| 63 GetTasksFromDateRange(time.Time, time.Time) ([]*Task, error) | |
| 64 | |
| 65 // StartTrackingModifiedTasks initiates tracking of modified tasks for | |
| 66 // the current caller. Returns a unique ID which can be used by the call
er | |
| 67 // to retrieve tasks which have been modified since the last query. The
ID | |
| 68 // expires after a period of inactivity. | |
| 69 StartTrackingModifiedTasks() (string, error) | |
| 70 | |
| 71 // StopTrackingModifiedTasks cancels tracking of modified tasks for the | |
| 72 // provided ID. | |
| 73 StopTrackingModifiedTasks(string) | |
| 74 } | |
| 75 | |
| 76 // DB is used by the task scheduler to store Tasks. | |
| 77 type DB interface { | |
| 78 TaskReader | |
| 79 | |
| 80 // AssignId sets the given task's Id field. Does not insert the task int
o the | |
| 81 // database. | |
| 82 AssignId(*Task) error | |
| 83 | |
| 84 // PutTask inserts or updates the Task in the database. Task's Id field
must | |
| 85 // be empty or set with AssignId. PutTask will set Task.DbModified. | |
| 86 PutTask(*Task) error | |
| 87 | |
| 88 // PutTasks inserts or updates the Tasks in the database. Each Task's Id
field | |
| 89 // must be empty or set with AssignId. Each Task's DbModified field will
be | |
| 90 // set. | |
| 91 PutTasks([]*Task) error | |
| 92 } | |
| 93 | |
| 94 // UpdateWithRetries wraps a call to db.PutTasks with retries. It calls | |
| 95 // db.PutTasks(f()) repeatedly until one of the following happen: | |
| 96 // - f or db.PutTasks returns an error, which is then returned from | |
| 97 // UpdateWithRetries; | |
| 98 // - PutTasks succeeds, in which case UpdateWithRetries returns the updated | |
| 99 // Tasks returned by f; | |
| 100 // - retries are exhausted, in which case UpdateWithRetries returns | |
| 101 // ErrConcurrentUpdate. | |
| 102 // | |
| 103 // Within f, tasks should be refreshed from the DB, e.g. with | |
| 104 // db.GetModifiedTasks or db.GetTaskById. | |
| 105 func UpdateWithRetries(db DB, f func() ([]*Task, error)) ([]*Task, error) { | |
| 106 var lastErr error | |
| 107 for i := 0; i < NUM_RETRIES; i++ { | |
| 108 t, err := f() | |
| 109 if err != nil { | |
| 110 return nil, err | |
| 111 } | |
| 112 lastErr = db.PutTasks(t) | |
| 113 if lastErr == nil { | |
| 114 return t, nil | |
| 115 } else if !IsConcurrentUpdate(lastErr) { | |
| 116 return nil, lastErr | |
| 117 } | |
| 118 } | |
| 119 glog.Warningf("UpdateWithRetries: %d consecutive ErrConcurrentUpdate.",
NUM_RETRIES) | |
| 120 return nil, lastErr | |
| 121 } | |
| 122 | |
| 123 // UpdateTaskWithRetries reads, updates, and writes a single Task in the DB. It: | |
| 124 // 1. reads the task with the given id, | |
| 125 // 2. calls f on that task, and | |
| 126 // 3. calls db.PutTask() on the updated task | |
| 127 // 4. repeats from step 1 as long as PutTasks returns ErrConcurrentUpdate and | |
| 128 // retries have not been exhausted. | |
| 129 // Returns the updated task if it was successfully updated in the DB. | |
| 130 // Immediately returns ErrNotFound if db.GetTaskById(id) returns nil. | |
| 131 // Immediately returns any error returned from f or from PutTasks (except | |
| 132 // ErrConcurrentUpdate). Returns ErrConcurrentUpdate if retries are exhausted. | |
| 133 func UpdateTaskWithRetries(db DB, id string, f func(*Task) error) (*Task, error)
{ | |
| 134 tasks, err := UpdateWithRetries(db, func() ([]*Task, error) { | |
| 135 t, err := db.GetTaskById(id) | |
| 136 if err != nil { | |
| 137 return nil, err | |
| 138 } | |
| 139 if t == nil { | |
| 140 return nil, ErrNotFound | |
| 141 } | |
| 142 err = f(t) | |
| 143 if err != nil { | |
| 144 return nil, err | |
| 145 } | |
| 146 return []*Task{t}, nil | |
| 147 }) | |
| 148 if err != nil { | |
| 149 return nil, err | |
| 150 } else { | |
| 151 return tasks[0], nil | |
| 152 } | |
| 153 } | |
| 154 | |
| 155 // RemoteDB allows retrieving tasks and full access to comments. | |
| 156 type RemoteDB interface { | |
| 157 TaskReader | |
| 158 CommentDB | |
| 159 } | |
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Chromium Code Reviews
Issue 2296763008:
[task scheduler] Move files from build_scheduler/ to task_scheduler/ (Closed)
Base URL: https://skia.googlesource.com/buildbot@master