databricks-cli/libs/sync/snapshot.go

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package sync
import (
"context"
"encoding/json"
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"fmt"
"os"
"path/filepath"
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"strings"
"time"
"crypto/md5"
"encoding/hex"
"github.com/databricks/bricks/libs/fileset"
"github.com/databricks/bricks/libs/log"
"github.com/databricks/bricks/libs/notebook"
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)
// Bump it up every time a potentially breaking change is made to the snapshot schema
const LatestSnapshotVersion = "v1"
// A snapshot is a persistant store of knowledge bricks cli has about state of files
// in the remote repo. We use the last modified times (mtime) of files to determine
// whether a files need to be updated in the remote repo.
//
// 1. Any stale files in the remote repo are updated. That is if the last modified
// time recorded in the snapshot is less than the actual last modified time of the file
//
// 2. Any files present in snapshot but absent locally are deleted from remote path
//
// Changing either the databricks workspace (ie Host) or the remote path (ie RemotePath)
// local files are being synced to will make bricks cli switch to a different
// snapshot for persisting/loading sync state
type Snapshot struct {
// Path where this snapshot was loaded from and will be saved to.
// Intentionally not part of the snapshot state because it may be moved by the user.
SnapshotPath string `json:"-"`
// New indicates if this is a fresh snapshot or if it was loaded from disk.
New bool `json:"-"`
// version for snapshot schema. Only snapshots matching the latest snapshot
// schema version are used and older ones are invalidated (by deleting them)
Version string `json:"version"`
// hostname of the workspace this snapshot is for
Host string `json:"host"`
// Path in workspace for project repo
RemotePath string `json:"remote_path"`
// Map of all files present in the remote repo with the:
// key: relative file path from project root
// value: last time the remote instance of this file was updated
LastUpdatedTimes map[string]time.Time `json:"last_modified_times"`
// This map maps local file names to their remote names
// eg. notebook named "foo.py" locally would be stored as "foo", thus this
// map will contain an entry "foo.py" -> "foo"
LocalToRemoteNames map[string]string `json:"local_to_remote_names"`
// Inverse of localToRemoteNames. Together the form a bijective mapping (ie
// there is a 1:1 unique mapping between local and remote name)
RemoteToLocalNames map[string]string `json:"remote_to_local_names"`
}
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const syncSnapshotDirName = "sync-snapshots"
func GetFileName(host, remotePath string) string {
hash := md5.Sum([]byte(host + remotePath))
hashString := hex.EncodeToString(hash[:])
return hashString[:16] + ".json"
}
// Compute path of the snapshot file on the local machine
// The file name for unique for a tuple of (host, remotePath)
// precisely it's the first 16 characters of md5(concat(host, remotePath))
func SnapshotPath(opts *SyncOptions) (string, error) {
snapshotDir := filepath.Join(opts.SnapshotBasePath, syncSnapshotDirName)
if _, err := os.Stat(snapshotDir); os.IsNotExist(err) {
err = os.MkdirAll(snapshotDir, 0755)
if err != nil {
return "", fmt.Errorf("failed to create config directory: %s", err)
}
}
fileName := GetFileName(opts.Host, opts.RemotePath)
return filepath.Join(snapshotDir, fileName), nil
}
func newSnapshot(ctx context.Context, opts *SyncOptions) (*Snapshot, error) {
path, err := SnapshotPath(opts)
if err != nil {
return nil, err
}
return &Snapshot{
SnapshotPath: path,
New: true,
Version: LatestSnapshotVersion,
Host: opts.Host,
RemotePath: opts.RemotePath,
LastUpdatedTimes: make(map[string]time.Time),
LocalToRemoteNames: make(map[string]string),
RemoteToLocalNames: make(map[string]string),
}, nil
}
func (s *Snapshot) Save(ctx context.Context) error {
f, err := os.OpenFile(s.SnapshotPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
if err != nil {
return fmt.Errorf("failed to create/open persisted sync snapshot file: %s", err)
}
defer f.Close()
// persist snapshot to disk
bytes, err := json.MarshalIndent(s, "", " ")
if err != nil {
return fmt.Errorf("failed to json marshal in-memory snapshot: %s", err)
}
_, err = f.Write(bytes)
if err != nil {
return fmt.Errorf("failed to write sync snapshot to disk: %s", err)
}
return nil
}
func (s *Snapshot) Destroy(ctx context.Context) error {
err := os.Remove(s.SnapshotPath)
if err != nil {
return fmt.Errorf("failed to destroy sync snapshot file: %s", err)
}
return nil
}
func loadOrNewSnapshot(ctx context.Context, opts *SyncOptions) (*Snapshot, error) {
snapshot, err := newSnapshot(ctx, opts)
if err != nil {
return nil, err
}
// Snapshot file not found. We return the new copy.
if _, err := os.Stat(snapshot.SnapshotPath); os.IsNotExist(err) {
return snapshot, nil
}
bytes, err := os.ReadFile(snapshot.SnapshotPath)
if err != nil {
return nil, fmt.Errorf("failed to read sync snapshot from disk: %s", err)
}
var fromDisk Snapshot
err = json.Unmarshal(bytes, &fromDisk)
if err != nil {
return nil, fmt.Errorf("failed to json unmarshal persisted snapshot: %s", err)
}
// invalidate old snapshot with schema versions
if fromDisk.Version != LatestSnapshotVersion {
log.Warnf(ctx, "Did not load existing snapshot because its version is %s while the latest version is %s", snapshot.Version, LatestSnapshotVersion)
return newSnapshot(ctx, opts)
}
// unmarshal again over the existing snapshot instance
err = json.Unmarshal(bytes, &snapshot)
if err != nil {
return nil, fmt.Errorf("failed to json unmarshal persisted snapshot: %s", err)
}
snapshot.New = false
return snapshot, nil
}
func (s *Snapshot) diff(all []fileset.File) (change diff, err error) {
lastModifiedTimes := s.LastUpdatedTimes
remoteToLocalNames := s.RemoteToLocalNames
localToRemoteNames := s.LocalToRemoteNames
// set of files currently present in the local file system and tracked by git
localFileSet := map[string]struct{}{}
for _, f := range all {
localFileSet[f.Relative] = struct{}{}
}
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for _, f := range all {
// get current modified timestamp
modified := f.Modified()
lastSeenModified, seen := lastModifiedTimes[f.Relative]
if !seen || modified.After(lastSeenModified) {
lastModifiedTimes[f.Relative] = modified
// change separators to '/' for file paths in remote store
unixFileName := filepath.ToSlash(f.Relative)
// put file in databricks workspace
change.put = append(change.put, unixFileName)
// get file metadata about whether it's a notebook
isNotebook, _, err := notebook.Detect(f.Absolute)
if err != nil {
return change, err
}
// Strip extension for notebooks.
remoteName := unixFileName
if isNotebook {
ext := filepath.Ext(remoteName)
remoteName = strings.TrimSuffix(remoteName, ext)
}
// If the remote handle of a file changes, we want to delete the old
// remote version of that file to avoid duplicates.
// This can happen if a python notebook is converted to a python
// script or vice versa
oldRemoteName, ok := localToRemoteNames[f.Relative]
if ok && oldRemoteName != remoteName {
change.delete = append(change.delete, oldRemoteName)
delete(remoteToLocalNames, oldRemoteName)
}
// We cannot allow two local files in the project to point to the same
// remote path
prevLocalName, ok := remoteToLocalNames[remoteName]
_, prevLocalFileExists := localFileSet[prevLocalName]
if ok && prevLocalName != f.Relative && prevLocalFileExists {
return change, fmt.Errorf("both %s and %s point to the same remote file location %s. Please remove one of them from your local project", prevLocalName, f.Relative, remoteName)
}
localToRemoteNames[f.Relative] = remoteName
remoteToLocalNames[remoteName] = f.Relative
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}
}
// figure out files in the snapshot.lastModifiedTimes, but not on local
// filesystem. These will be deleted
for localName := range lastModifiedTimes {
_, exists := localFileSet[localName]
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if exists {
continue
}
// TODO: https://databricks.atlassian.net/browse/DECO-429
// Add error wrapper giving instructions like this for all errors here :)
remoteName, ok := localToRemoteNames[localName]
if !ok {
return change, fmt.Errorf("missing remote path for local path: %s. Please try syncing again after deleting .databricks/sync-snapshots dir from your project root", localName)
}
// add them to a delete batch
change.delete = append(change.delete, remoteName)
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}
// and remove them from the snapshot
for _, remoteName := range change.delete {
// we do note assert that remoteName exists in remoteToLocalNames since it
// will be missing for files with remote name changed
localName := remoteToLocalNames[remoteName]
delete(lastModifiedTimes, localName)
delete(remoteToLocalNames, remoteName)
delete(localToRemoteNames, localName)
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}
return
}