Refactor mc cp and make session optional.

Now `mc cp --recursive --continue` creates copy session on failure or
resumes if previous failed session is found.

Fixes #2893

cmd/cp-main.go

@@ -61,6 +61,10 @@ var (
  Name: "attr",
  Usage: "add custom metadata for the object",
  },
+ cli.BoolFlag{
+ Name: "continue, c",
+ Usage: "create or resume copy session.",
+ },
  }
 )
 
@@ -127,6 +131,9 @@ EXAMPLES:
 
  13. Copy a text file to an object storage and assign REDUCED_REDUNDANCY storage-class to the uploaded object.
  {{.Prompt}} {{.HelpName}} --storage-class REDUCED_REDUNDANCY myobject.txt play/mybucket
+
+ 14. Copy a text file to an object storage and create or resume copy session.
+ $ {{.HelpName}} --recursive --continue myobject.txt play/mybucket
  `,
 }
 
@@ -431,7 +438,7 @@ loop:
  // For critical errors we should exit. Session
  // can be resumed after the user figures out
  // the problem.
- session.CloseAndDie()
+ session.copyCloseAndDie(session.Header.CommandBoolFlags["session"])
  }
  }
  }
@@ -497,14 +504,21 @@ func mainCopy(ctx *cli.Context) error {
  }
  sse := ctx.String("encrypt")
 
- session := newSessionV8()
+ sessionID := getHash("cp", ctx.Args())
+ if ctx.Bool("continue") && isSessionExists(sessionID) {
+ resumeSession(sessionID)
+ return nil
+ }
+
+ session := newSessionV8(sessionID)
  session.Header.CommandType = "cp"
  session.Header.CommandBoolFlags["recursive"] = recursive
  session.Header.CommandStringFlags["older-than"] = olderThan
  session.Header.CommandStringFlags["newer-than"] = newerThan
  session.Header.CommandStringFlags["storage-class"] = storageClass
  session.Header.CommandStringFlags["encrypt-key"] = sseKeys
  session.Header.CommandStringFlags["encrypt"] = sse
+ session.Header.CommandBoolFlags["session"] = ctx.Bool("continue")
  session.Header.UserMetaData = userMetaMap
 
  var e error

cmd/session-v8.go

@@ -162,7 +162,7 @@ func loadSessionV8(sid string) (*sessionV8, *probe.Error) {
 }
 
 // newSessionV8 provides a new session.
-func newSessionV8() *sessionV8 {
+func newSessionV8(sessionID string) *sessionV8 {
  s := &sessionV8{}
  s.Header = &sessionV8Header{}
  s.Header.Version = globalSessionConfigVersion
@@ -177,7 +177,7 @@ func newSessionV8() *sessionV8 {
  s.Header.UserMetaData = make(map[string]string)
  s.Header.When = UTCNow()
  s.mutex = new(sync.Mutex)
- s.SessionID = newRandomID(8)
+ s.SessionID = sessionID
 
  sessionDataFile, err := getSessionDataFile(s.SessionID)
  fatalIf(err.Trace(s.SessionID), "Unable to create session data file \""+sessionDataFile+"\".")
@@ -375,6 +375,18 @@ func (s sessionV8) CloseAndDie() {
  console.Fatalln("Session safely terminated. To resume session `mc session resume " + s.SessionID + "`")
 }
 
+func (s sessionV8) copyCloseAndDie(sessionFlag bool) {
+ if sessionFlag {
+ s.Close()
+ console.Fatalln("Command terminated safely. Run this command to resume copy again.")
+ } else {
+ s.mutex.Lock()
+ defer s.mutex.Unlock()
+
+ s.DataFP.Close() // ignore error.
+ }
+}
+
 // Create a factory function to simplify checking if
 // object was last operated on.
 func isLastFactory(lastURL string) func(string) bool {

cmd/session.go

@@ -17,6 +17,8 @@
 package cmd
 
 import (
+ "crypto/sha256"
+ "encoding/hex"
  "os"
  "path/filepath"
  "strings"
@@ -136,3 +138,14 @@ func removeSessionDataFile(sid string) {
  }
  os.Remove(dataFile)
 }
+
+func getHash(prefix string, args []string) string {
+ hasher := sha256.New()
+ for _, arg := range args {
+ if _, err := hasher.Write([]byte(arg)); err != nil {
+ panic(err)
+ }
+ }
+
+ return prefix + "-" + hex.EncodeToString(hasher.Sum(nil))
+}