[pr]rule 文件存储路径以及tsdb 文件的持久化存储

[MrYueQ]

建议在 rule-engine 模块中设置 rule 文件存储路径以及 tsdb 数据的持久化存储。

https://github.com/Qihoo360/doraemon/blob/931e0651b950866379e2ce834c62a283a94dd3ea/cmd/rule-engine/modules/storage.go#L28

https://github.com/Qihoo360/doraemon/blob/931e0651b950866379e2ce834c62a283a94dd3ea/cmd/rule-engine/modules/manager.go#L80

[MrYueQ]

1. wal 是否开启压缩。
2. tsdb 文件生成频次较高，建议优化

    db, err := tsdb.Open(dir, logger, nil, &tsdb.Options{
        WALSegmentSize:         DefaultSegmentSize,
        RetentionDuration:      model.Duration(15 * 24 * time.Hour / time.Millisecond),
        MinBlockDuration:       model.Duration(DefaultBlockDuration),
        MaxBlockDuration:       model.Duration(DefaultBlockDuration),
        NoLockfile:             false,
        AllowOverlappingBlocks: false,
        WALCompression:         true,
    })

https://github.com/Qihoo360/doraemon/blob/931e0651b950866379e2ce834c62a283a94dd3ea/cmd/rule-engine/modules/storage.go#L28

[MrYueQ]

建议使用 switch 替换 if else

https://github.com/Qihoo360/doraemon/blob/931e0651b950866379e2ce834c62a283a94dd3ea/cmd/alert-gateway/initial/send.go#L74