improve snapshots and add some tests

[pengweisong]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Description:

Fix Bug:

1. check running job may mutate data before create snapshot.
2. when create snapshot failed in some storage host, unlock the writing before return.

Add tests for Create/Drop/ListSnapshots

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:

ex. Fixed the bug .....

[critical27]

Good job.

BTW, I recall one detail: you'd better check the snapshot related timeout in AdminClient, there is an issue that

• create snapshot with a big dataset, AdminClient will report timeout,
• and AdminClient has retry default with 3 times, which will create 3 snapshot in storage
• and user will get a failed (I don't remember precisely), but storage will create 3 snapshot

You could mock it in storage by adding a sleep

[critical27]

Good job

[czpmango]

timeout is a uint.

[pengweisong]

It is supposed to, I'll remove the condition then.

[czpmango]

Please check this warning:

[  0%] Building CXX object src/clients/meta/CMakeFiles/meta_client_obj.dir/MetaClient.cpp.o
In file included from /home/kyle.cao/workspace/fork/nebula/src/common/thrift/ThriftClientManager.h:46,
                 from /home/kyle.cao/workspace/fork/nebula/src/clients/meta/MetaClient.h:27,
                 from /home/kyle.cao/workspace/fork/nebula/src/clients/meta/MetaClient.cpp:6:
/home/kyle.cao/workspace/fork/nebula/src/common/thrift/ThriftClientManager-inl.h: In instantiation of ‘std::shared_ptr<_Tp> nebula::thrift::ThriftClientManager<ClientType>::client(const nebula::HostAddr&, folly::EventBase*, bool, uint32_t) [with ClientType = nebula::meta::cpp2::MetaServiceAsyncClient; uint32_t = unsigned int]’:
/home/kyle.cao/workspace/fork/nebula/src/clients/meta/MetaClient.cpp:715:49:   required from ‘void nebula::meta::MetaClient::getResponse(Request, RemoteFunc, RespGenerator, folly::Promise<nebula::StatusOr<Response> >, bool, int32_t, int32_t) [with Request = nebula::meta::cpp2::AdminJobReq; RemoteFunc = nebula::meta::MetaClient::submitJob(nebula::GraphSpaceID, nebula::meta::cpp2::JobOp, nebula::meta::cpp2::JobType, std::vector<std::__cxx11::basic_string<char> >)::<lambda(auto:157, auto:158)>; RespGenerator = nebula::meta::MetaClient::submitJob(nebula::GraphSpaceID, nebula::meta::cpp2::JobOp, nebula::meta::cpp2::JobType, std::vector<std::__cxx11::basic_string<char> >)::<lambda(nebula::meta::cpp2::AdminJobResp&&)>; RpcResponse = nebula::meta::cpp2::AdminJobResp; Response = nebula::meta::cpp2::AdminJobResult; int32_t = int]’
/home/kyle.cao/workspace/fork/nebula/src/clients/meta/MetaClient.cpp:1216:14:   required from here
/home/kyle.cao/workspace/fork/nebula/src/common/thrift/ThriftClientManager-inl.h:87:15: error: comparison of unsigned expression in ‘>= 0’ is always true [-Werror=type-limits]
   87 |   if (timeout >= 0) {
      |       ~~~~~~~~^~~~
cc1plus: all warnings being treated as errors