Cannot run multiple bench-cases together

[ssmails]

Configured below bench case file-

bench_cases:
- name: "insert-person"
concurrency: 2
- name: "insert-friend"
concurrency: 2

Seeing errors from dgraph [ dgraph/dgraph:v1.0.12-rc1]
2019/01/06 23:10:05 Failed to call mutate: rpc error: code = Unknown desc = Uid: [3073121] cannot be greater than lease: [10000]
2019/01/06 23:10:05 Failed to call mutate: rpc error: code = Unknown desc = Uid: [972337] cannot be greater than lease: [10000]

When the bench file is changed as below to run only single bench-case, it works fine.

bench_cases:
- name: "insert-person"
concurrency: 2

[MichelDiz]

You need to allocate UIDs /assign?what=uids&num=100000000000
https://docs.dgraph.io/deploy/#more-about-dgraph-alpha