fix scatter range receive npe when get store info of non-eixst store

[nanne007]

What problem does this PR solve?

Fix a npe when get store info of a non-exist stores in scatter range

What is changed and how it works?

We got a stack error in our online env.

2019/02/22 15:28:53.887 log.go:274: [fatal] panic: runtime error: invalid memory address or nil pointer dereference, stack: goroutine 6
2180022 [running]:
runtime/debug.Stack(0xc42caa76d8, 0xfe4e40, 0x18cf570)
        /data/program/tistack/tistack-release/local/go/src/runtime/debug/stack.go:24 +0xa7
github.com/pingcap/pd/pkg/logutil.LogPanic()
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/pkg/logutil/log.go:274 +0x5a
panic(0xfe4e40, 0x18cf570)
        /data/program/tistack/tistack-release/local/go/src/runtime/panic.go:505 +0x229
github.com/pingcap/pd/server/schedule.(*RangeCluster).updateStoreInfo(0xc421d0bb20, 0x0)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/schedule/range_cluster.go:62 +0x26
github.com/pingcap/pd/server/schedule.(*RangeCluster).GetStore(0xc421d0bb20, 0x11f4b5, 0xc4277ca010)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/schedule/range_cluster.go:81 +0x5d
github.com/pingcap/pd/server/schedulers.(*balanceLeaderScheduler).transferLeaderIn(0xc42619b060, 0xc4282f7030, 0x12af300, 0xc421d0bb20,
 0xc4282facc0, 0xc4282facf0, 0x0, 0x0, 0x0)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/schedulers/balance_leader.go:139 +0x10b
github.com/pingcap/pd/server/schedulers.(*balanceLeaderScheduler).Schedule(0xc42619b060, 0x12af300, 0xc421d0bb20, 0xc4282facc0, 0xc4282
facf0, 0xc4282facc0, 0xc4282facf0, 0x20)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/schedulers/balance_leader.go:101 +0x5e0
github.com/pingcap/pd/server/schedulers.(*scatterRangeScheduler).Schedule(0xc42a29c850, 0x12af180, 0xc42a3ce700, 0xc42ec8e6f0, 0xc42ec8
e720, 0xa, 0xc42a3ce700, 0x0)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/schedulers/scatter_range.go:101 +0x205
github.com/pingcap/pd/server.scheduleByNamespace(0x12af000, 0xc424294960, 0x12a4380, 0xc421adf040, 0x12a62a0, 0xc42a29c850, 0xc42ec8e6f
0, 0xc42ec8e720, 0xc42ec8e720, 0x11f1b3, ...)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/namespace_cluster.go:142 +0x13e
github.com/pingcap/pd/server.(*scheduleController).Schedule(0xc42ad3ed20, 0x12af000, 0xc424294960, 0xc42ec8e6f0, 0xc42ec8e720, 0xc42ec8
e6f0, 0xc42ec8e720, 0x0)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/coordinator.go:689 +0xa3
github.com/pingcap/pd/server.(*coordinator).runScheduler(0xc42002f680, 0xc42ad3ed20)
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/coordinator.go:433 +0x2be
created by github.com/pingcap/pd/server.(*coordinator).addScheduler
        /data/program/tistack/tistack-release/go/src/github.com/pingcap/pd/server/coordinator.go:394 +0x16a

Check List

Tests

• No code

Related changes

• Need to cherry-pick to the release branch

[sre-bot]

Hi contributor, thanks for your PR.

This patch needs to be approved by someone of admins. They should reply with "/ok-to-test" to accept this PR for running test automatically.

[sre-bot]

Hi contributor, thanks for your PR.

This patch needs to be approved by someone of admins. They should reply with "/ok-to-test" to accept this PR for running test automatically.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@c996046). Click here to learn what that means.
The diff coverage is 50%.

@@            Coverage Diff            @@
##             master    #1439   +/-   ##
=========================================
  Coverage          ?   67.73%           
=========================================
  Files             ?      158           
  Lines             ?    15182           
  Branches          ?        0           
=========================================
  Hits              ?    10283           
  Misses            ?     3978           
  Partials          ?      921

Impacted Files	Coverage Δ
server/schedule/range_cluster.go	90.24% <50%> (ø)

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[siddontang]

Thank you @lerencao

[siddontang]

@nolouch

how can we meet this? seem we need to add a test.

[nanne007]

after pd server restarts, not all region infos are updated, and region info's default store id is 0.
So NPE can appear when the code get store info of id 0.

[nolouch]

@lerencao can you add this situation in the test?

[nanne007]

@nolouch Yes, will work on it.

[nanne007]

@nolouch PTAL

Test cases and another nil check are added

[nolouch]

@lerencao ci failed, may related to gofmt.

[nanne007]

@nolouch updated.

[rleungx]

It seems we don't need it?

[nanne007]

Maybe the store info is not used in the underlining implementations, but it should be here to make things straight.

[nolouch]

LGTM