feat(Dgraph): Online restores allows to restore a specific backup.

[martinmr]

Currently online restores will restore the entire backup series. This PR allows to
restore the backup series up to a specific backup.

Fixes DGRAPH-1648

---

This change is 

Docs Preview:

[martinmr]

Disregard the changes to the docker-compose files and the makefiles. They are a workaround to an issue I'm having (my workstation has a different version of glibc than the docker image). I will revert these changes before I merge this PR.

[parasssh]

Took a stab. Lets do synchronous review so I can understand better.

[martinmr]

Reviewable status: 0 of 13 files reviewed, 2 unresolved discussions (waiting on @manishrjain, @MichaelJCompton, @pawanrawal, and @vvbalaji-dgraph)

---

systest/online-restore/online_restore_test.go, line 178 at r3 (raw file):

t.Logf(string(resp.GetJson()))
			t.Logf(string(bodies[1]))

revert this

---

worker/backup_handler.go, line 63 at r3 (raw file):

 GetManfiest

typo

[parasssh]

minor comments. Feel free to resolve.

Reviewable status: 0 of 13 files reviewed, 5 unresolved discussions (waiting on @manishrjain, @martinmr, @MichaelJCompton, @pawanrawal, and @vvbalaji-dgraph)

---

dgraph/Makefile, line 46 at r3 (raw file):

lastCommitTime  = github.com/dgraph-io/dgraph/x.lastCommitTime

BUILD_FLAGS   ?= -ldflags '-X ${lastCommitSHA}=${BUILD} -X "${lastCommitTime}=${BUILD_DATE}" -X "${dgraphVersion}=${BUILD_VERSION}" -X "${dgraphCodename}=${BUILD_CODENAME}${MODIFIED}" -X ${gitBranch}=${BUILD_BRANCH}' -tags netgo

what is netgo tag for?

---

worker/backup_handler.go, line 66 at r3 (raw file):

	// and backup number at the specified location. If backupNum is set to zero,
	// all the manifests for the backup series will be returned.
	GetManifests(*url.URL, string, uint64) ([]*Manifest, error)

Maybe clarify comment that given a backupNum, it returns manifests from 0 to thru the backupNum. Not clear as it is.

---

worker/backup_handler.go, line 318 at r3 (raw file):

	if backupNum > 0 {
		if len(manifests) < int(backupNum) {

are we off by 1? e.g. if backupNum = 1, i expect 2 manifests at 0 and 1, no?

[martinmr]

Reviewable status: 0 of 11 files reviewed, 3 unresolved discussions (waiting on @manishrjain, @MichaelJCompton, @parasssh, @pawanrawal, and @vvbalaji-dgraph)

---

dgraph/Makefile, line 46 at r3 (raw file):

Previously, parasssh wrote…

what is netgo tag for?

Ignore that. It's just because I couldn't build Dgraph on my machine. I'll revert that.

But the tag is to build the net library without using the c standard library.

---

systest/online-restore/online_restore_test.go, line 178 at r3 (raw file):

Previously, martinmr (Martin Martinez Rivera) wrote…

t.Logf(string(resp.GetJson()))
			t.Logf(string(bodies[1]))

revert this

Done.

---

worker/backup_handler.go, line 63 at r3 (raw file):

Previously, martinmr (Martin Martinez Rivera) wrote…

 GetManfiest

typo

Done.

---

worker/backup_handler.go, line 66 at r3 (raw file):

Previously, parasssh wrote…

Maybe clarify comment that given a backupNum, it returns manifests from 0 to thru the backupNum. Not clear as it is.

Done.

---

worker/backup_handler.go, line 318 at r3 (raw file):

Previously, parasssh wrote…

are we off by 1? e.g. if backupNum = 1, i expect 2 manifests at 0 and 1, no?

There's no backup with backupNum 0. We start the count at 1.