Should check whether the dirs under "storage" configuration is valid string array

[JaySon-Huang]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

If the user set the config file with

[storage]
[storage.main]
dir = "/data0/db"
# Should be: dir = ["/data0/db"]
[storage.raft]
dir = "/data0/db"
# Should be: dir = ["/data0/db"]

If storage.main.dir,storage.latest.dir,storage.raft.dir is a string instead of string-array, TiFlash now consider it is an empty array without any warning/exception.
https://github.com/pingcap/tics/blob/fb00fbba50d802164a975daa3107478888ae0e25/dbms/src/Server/StorageConfigParser.cpp#L124-L135

We should check whether the dirs under "storage" configuration is a string array or not. If not, make TiFlash quit and tell the users to correct their configuration file.

---

In one scenario, users set ...

path="/data0/db"
raft.kvstore_path="/data0/kvstore"

in their cluster, after upgrading to v5.4.0, they replace those configurations with ...

[storage]
[storage.main]
dir = ["/data0/db"]
[storage.raft]
dir = "/data0/kvstore" # Should be: dir = ["/data0/kvstore"]

with the later configuration, TiFlash consider "storage.raft.dir" as an empty array and set it to "/data0/db/kvstore", which is not the same as upgrade before.

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiFlash version? (Required)

[fuzhe1989]

treat a single string as an array with one item?

[JaySon-Huang]

@fuzhe1989 I think explicit require an array would be better.

In the old configuration, we use this for the multi-disks feature ...

path="/data0/tiflash,/data1/tiflash"

while in the new configuration, we use this for multi-disks feature ...

[storage.main]
dir = [ "/data0/tiflash", "/data1/tiflash"]

I don't want to see users mistakenly set sth like this in the future.... It is terrible...

[storage.main]
dir = "/data0/tiflash,/data1/tiflash"