Empty syncer config item cause DM-master panic

[GMHDBJD]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do? If possible, provide a recipe for reproducing the error.
   task config

---
name: test
task-mode: all

target-database:
  host: "127.0.0.1"
  port: 4000
  user: "test"
  password: "/Q7B9DizNLLTTfiZHv9WoEAKamfpIUs="

mysql-instances:
  - source-id: "mysql-replica-01"
    syncer-config-name: "global"

syncers:
  global:

start-task ./task.toml

2. What did you expect to see?
   task runs normal or report a config error
3. What did you see instead?
   master panic

dm-master startup 2021-08-21 16:28:34.106341359 +0800 CST m=+0.239573077
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x3627087]

goroutine 487 [running]:
github.com/pingcap/dm/dm/config.(*TaskConfig).adjust(0xc000f6a360, 0x0, 0x0)
        /nvme1n1/gmhdbjd/code/dm/dm/config/task.go:592 +0x73c7
github.com/pingcap/dm/dm/config.(*TaskConfig).Decode(0xc000f6a360, 0xc000f90500, 0x49c, 0x0, 0x0)
        /nvme1n1/gmhdbjd/code/dm/dm/config/task.go:393 +0x3a5
github.com/pingcap/dm/dm/master.(*Server).generateSubTask(0xc000450240, 0x52c1138, 0xc0006bdda0, 0xc000f90500, 0x49c, 0xa, 0xa, 0x0, 0x0, 0x0, ...)
        /nvme1n1/gmhdbjd/code/dm/dm/master/server.go:1341 +0x10a
github.com/pingcap/dm/dm/master.(*Server).StartTask(0xc000450240, 0x52c1138, 0xc0006bdda0, 0xc0006bddd0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/code/dm/dm/master/server.go:419 +0x546
github.com/pingcap/dm/dm/pb._Master_StartTask_Handler.func1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/code/dm/dm/pb/dmmaster.pb.go:3666 +0x19c
github.com/grpc-ecosystem/go-grpc-prometheus.(*ServerMetrics).UnaryServerInterceptor.func1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0xc000a467e0, 0xc000410bb8, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-prometheus@v1.2.0/server_metrics.go:107 +0x1b5
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.1.0/chain.go:25 +0x13c
go.etcd.io/etcd/etcdserver/api/v3rpc.newUnaryInterceptor.func1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0xc000a467e0, 0xc000a46800, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20200824191128-ae9734ed278b/etcdserver/api/v3rpc/interceptor.go:70 +0x80a
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.1.0/chain.go:25 +0x13c
go.etcd.io/etcd/etcdserver/api/v3rpc.newLogUnaryInterceptor.func1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0xc000a467e0, 0xc000a46820, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20200824191128-ae9734ed278b/etcdserver/api/v3rpc/interceptor.go:77 +0x143
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.1.0/chain.go:25 +0x13c
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1(0x52c1138, 0xc0006bdda0, 0x42cffe0, 0xc0006bddd0, 0xc000a467e0, 0xc000410bb8, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.1.0/chain.go:34 +0x290
github.com/pingcap/dm/dm/pb._Master_StartTask_Handler(0x43b25c0, 0xc000450240, 0x52c1138, 0xc0006bdda0, 0xc0007abb60, 0xc0007389f0, 0x0, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/code/dm/dm/pb/dmmaster.pb.go:3668 +0x4a7
google.golang.org/grpc.(*Server).processUnaryRPC(0xc0003ac480, 0x52d5658, 0xc0010dd500, 0xc0007ae500, 0xc000bc28a0, 0x681e160, 0x0, 0x0, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/google.golang.org/grpc@v1.27.1/server.go:1024 +0x1a5c
google.golang.org/grpc.(*Server).handleStream(0xc0003ac480, 0x52d5658, 0xc0010dd500, 0xc0007ae500, 0x0)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/google.golang.org/grpc@v1.27.1/server.go:1313 +0xf11
google.golang.org/grpc.(*Server).serveStreams.func1.1(0xc00073b0f0, 0xc0003ac480, 0x52d5658, 0xc0010dd500, 0xc0007ae500)
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/google.golang.org/grpc@v1.27.1/server.go:722 +0x199
created by google.golang.org/grpc.(*Server).serveStreams.func1
        /nvme1n1/gmhdbjd/environment/go/pkg/mod/google.golang.org/grpc@v1.27.1/server.go:720 +0x131

[lance6716]

not sure if our linter doesn't work

[lance6716]

even if we fix the panic in adjust, the behaviour is not expected

loaders:
  global:

this will add a config that has 0 pool-size, and "" dir. Maybe user is expecting two default values?

PTAL @sunzhaoyang

[sunzhaoyang]

even if we fix the panic in adjust, the behaviour is not expected

loaders:
  global:

this will add a config that has 0 pool-size, and "" dir. Maybe user is expecting two default values?

PTAL @sunzhaoyang

If a configuration item is filled in, press the filled value; if not filled in, press the default value, there should be no 0 or “”.

[lance6716]

/assign @docsir

[ti-chi-bot]

@lance6716: GitHub didn't allow me to assign the following users: docsir.

Note that only pingcap members, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time.
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In response to this:

/assign @docsir

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[sylzd]

encountered at version 5.4