fix: configuration example for selector (GreptimeTeam#4532)

* fix: configuration example for selector

* docs: update config docs

* test: update unit tests for configuration in meta

config/config.md

@@ -254,7 +254,7 @@
 | `bind_addr` | String | `127.0.0.1:3002` | The bind address of metasrv. |
 | `server_addr` | String | `127.0.0.1:3002` | The communication server address for frontend and datanode to connect to metasrv,  "127.0.0.1:3002" by default for localhost. |
 | `store_addr` | String | `127.0.0.1:2379` | Etcd server address. |
-| `selector` | String | `lease_based` | Datanode selector type.<br/>- `lease_based` (default value).<br/>- `load_based`<br/>For details, please see "https://docs.greptime.com/developer-guide/metasrv/selector". |
+| `selector` | String | `round_robin` | Datanode selector type.<br/>- `round_robin` (default value)<br/>- `lease_based`<br/>- `load_based`<br/>For details, please see "https://docs.greptime.com/developer-guide/metasrv/selector". |
 | `use_memory_store` | Bool | `false` | Store data in memory. |
 | `enable_telemetry` | Bool | `true` | Whether to enable greptimedb telemetry. |
 | `store_key_prefix` | String | `""` | If it's not empty, the metasrv will store all data with this key prefix. |

config/metasrv.example.toml

@@ -11,10 +11,11 @@ server_addr = "127.0.0.1:3002"
 store_addr = "127.0.0.1:2379"
 
 ## Datanode selector type.
-## - `lease_based` (default value).
+## - `round_robin` (default value)
+## - `lease_based`
 ## - `load_based`
 ## For details, please see "https://docs.greptime.com/developer-guide/metasrv/selector".
-selector = "lease_based"
+selector = "round_robin"
 
 ## Store data in memory.
 use_memory_store = false

src/cmd/tests/load_config_test.rs

@@ -169,7 +169,7 @@ fn test_load_metasrv_example_config() {
             compact_rt_size: 4,
         },
         component: MetasrvOptions {
-            selector: SelectorType::LeaseBased,
+            selector: SelectorType::default(),
             data_home: "/tmp/metasrv/".to_string(),
             logging: LoggingOptions {
                 dir: "/tmp/greptimedb/logs".to_string(),