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watch.go
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/
watch.go
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package main
import (
"os"
"path/filepath"
"time"
log "github.com/sirupsen/logrus"
mbtiles "github.com/brendan-ward/mbtiles-go"
"github.com/consbio/mbtileserver/handlers"
"github.com/fsnotify/fsnotify"
)
// debounce debounces requests to a callback function to occur no more
// frequently than interval; once this is reached, the callback is called.
//
// Unique values sent to the channel are stored in an internal map and all
// are processed once the the interval is up.
func debounce(interval time.Duration, input chan string, firstCallback func(arg string), callback func(arg string)) {
// keep a log of unique paths
var items = make(map[string]bool)
var item string
timer := time.NewTimer(interval)
for {
select {
case item = <-input:
if _, ok := items[item]; !ok {
// first time we see a given path, we need to call lockHandler
// to lock it (unlocked by callback)
firstCallback(item)
}
items[item] = true
timer.Reset(interval)
case <-timer.C:
for path := range items {
callback(path)
delete(items, path)
}
}
}
}
// FSWatcher provides a filesystem watcher to detect when mbtiles files are
// created, updated, or removed on the filesystem.
type FSWatcher struct {
watcher *fsnotify.Watcher
svcSet *handlers.ServiceSet
generateID handlers.IDGenerator
}
// NewFSWatcher creates a new FSWatcher to watch the filesystem for changes to
// mbtiles files and updates the ServiceSet accordingly.
//
// The generateID function needs to be of the same type used when the tilesets
// were originally added to the ServiceSet.
func NewFSWatcher(svcSet *handlers.ServiceSet, generateID handlers.IDGenerator) (*FSWatcher, error) {
watcher, err := fsnotify.NewWatcher()
if err != nil {
return nil, err
}
return &FSWatcher{
watcher: watcher,
svcSet: svcSet,
generateID: generateID,
}, nil
}
// Close closes the FSWatcher and stops watching the filesystem.
func (w *FSWatcher) Close() {
if w.watcher != nil {
w.watcher.Close()
}
}
// WatchDir sets up the filesystem watcher for baseDir and all existing subdirectories
func (w *FSWatcher) WatchDir(baseDir string) error {
c := make(chan string)
// debounced call to create / update tileset
go debounce(500*time.Millisecond, c, func(path string) {
// callback for first time path is debounced
id, err := w.generateID(path, baseDir)
if err != nil {
log.Errorf("Could not create ID for tileset %q\n%v", path, err)
return
}
// lock tileset for writing, if it exists
w.svcSet.LockTileset(id)
}, func(path string) {
// callback after debouncing incoming requests
// Verify that file can be opened with mbtiles-go, which runs
// validation on open.
// If file cannot be opened, assume it is still being written / copied.
db, err := mbtiles.Open(path)
if err != nil {
return
}
db.Close()
// determine file ID for tileset
id, err := w.generateID(path, baseDir)
if err != nil {
log.Errorf("Could not create ID for tileset %q\n%v", path, err)
return
}
// update existing tileset
if w.svcSet.HasTileset(id) {
err = w.svcSet.UpdateTileset(id)
if err != nil {
log.Errorf("Could not update tileset %q with ID %q\n%v", path, id, err)
} else {
// only unlock if successfully updated
w.svcSet.UnlockTileset(id)
log.Infof("Updated tileset %q with ID %q\n", path, id)
}
return
}
// create new tileset
err = w.svcSet.AddTileset(path, id)
if err != nil {
log.Errorf("Could not add tileset for %q with ID %q\n%v", path, id, err)
} else {
log.Infof("Updated tileset %q with ID %q\n", path, id)
}
return
})
go func() {
for {
select {
case event, ok := <-w.watcher.Events:
if !ok {
log.Errorf("error in filewatcher for %q, exiting filewatcher", event.Name)
return
}
if !((event.Op&fsnotify.Create == fsnotify.Create) ||
(event.Op&fsnotify.Write == fsnotify.Write) ||
(event.Op&fsnotify.Remove == fsnotify.Remove) ||
(event.Op&fsnotify.Rename == fsnotify.Rename)) {
continue
}
path := event.Name
if ext := filepath.Ext(path); ext != ".mbtiles" {
continue
}
if _, err := os.Stat(path + "-journal"); err == nil {
// Don't try to load .mbtiles files that are being written
log.Debugf("Tileset %q is currently being created or is incomplete\n", path)
continue
}
if (event.Op&fsnotify.Create == fsnotify.Create) ||
(event.Op&fsnotify.Write == fsnotify.Write) {
// This event may get called multiple times while a file is being copied into a watched directory,
// so we debounce this instead.
c <- path
continue
}
if (event.Op&fsnotify.Remove == fsnotify.Remove) || (event.Op&fsnotify.Rename == fsnotify.Rename) {
// some file move events trigger remove / rename, so if the file still exists, assume it is
// one of these
_, err := os.Stat(path)
if err == nil {
// debounce to give it a little more time to update, if needed
c <- path
continue
}
// remove tileset immediately so that there are not other errors in request handlers
id, err := w.generateID(path, baseDir)
if err != nil {
log.Errorf("Could not create ID for tileset %q\n%v", path, err)
}
err = w.svcSet.RemoveTileset(id)
if err != nil {
log.Errorf("Could not remove tileset %q with ID %q\n%v", path, id, err)
} else {
log.Infof("Removed tileset %q with ID %q\n", path, id)
}
}
case err, ok := <-w.watcher.Errors:
if !ok {
log.Errorf("error in filewatcher, exiting filewatcher")
return
}
log.Error(err)
}
}
}()
err := filepath.Walk(baseDir,
func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if info.Mode().IsDir() {
return w.watcher.Add(path)
}
return nil
})
if err != nil {
return err
}
return nil
}
func exists(path string) bool {
_, err := os.Stat(path)
if err != nil {
return false
}
return true
}