Documentation: add a roadmap

Signed-off-by: Benjamin Wang <wachao@vmware.com>

Documentation/contributor-guide/roadmap.md

@@ -0,0 +1,54 @@
+# roadmap
+
+etcd uses GitHub milestones to track all tasks in each major or minor release. The roadmap.md file only records the most
+important tasks for each release.
+Please also refer to [here](https://docs.google.com/spreadsheets/d/1hFpIbkI0IDum0SPy8txj7bVHxQRrAB_82f1Yqz_Pa8M/edit#gid=0&fvid=1685003197)
+for more context. The list is based on current maintainers capacity that may shift over time. Proposed milestones is what we think we can
+deliver with people we have. If we have more support on the important stuff, we could pick up more items from backlog.
+Note that etcd will continue to mainly focus on technical debt over the next few major or minor releases.
+
+Each item has an assigned priority:
+- P0 - Critical for the current milestone, and blocks the release.
+- P1 - Important for the current milestone, and critical for the next milestone.
+- P2 - Nice to have, can be always skipped and should not block anything.
+
+## v3.6.0
+
+For a full list of tasks in v3.6.0, please see [milestone etcd-v3.6](https://github.com/etcd-io/etcd/milestone/38).
+
+| Title                                                              | Priority | Note                                                                                                         |
+|--------------------------------------------------------------------|----------|--------------------------------------------------------------------------------------------------------------|
+| Support downgrade                                                  | P0       | etcd will support downgrade starting from 3.6.0. But it will also support offline downgrade from 3.5 to 3.4. |
+| StoreV2 deprecation                                                | P0       | This task will be covered in both 3.6 and 3.7.                                                               |
+| Support /livez and /readyz endpoints                               | P1       | It provides clearer APIs, and can also workaround the stalled writes issue                                   |
+| Bump gRPC                                                          | P1       | It isn't guaranteed to be resolved in 3.6, and might be postponed to 3.7 depending on the effort and risk.   |
+| Deprecate grpc-gateway or bump it                                  | P1       | It isn't guaranteed to be resolved in 3.6, and might be postponed to 3.7 depending on the effort and risk.   |
+| Release raft 3.6.0                                                 | P1       | etcd 3.6.0 will depends on raft 3.6.0                                                                        |
+| bbolt: Add logger into bbolt                                       | P1       | It's important to diagnose bbolt issues                                                                      |
+| bbolt: Add surgery commands                                        | P1       | Surgery commands are important for fixing corrupted db files                                                 |
+| Release bbolt 1.3.8                                                | P1       | etcd 3.6.0 will depends on bbolt 1.3.8                                                                       |
+| Evaluate and (Gradulate or deprecate/remove) experimental features | P2       | This task will be covered in both 3.6 and 3.7.                                                               |
+
+## v3.7.0
+
+For a full list of tasks in v3.7.0, please see [milestone etcd-v3.7](https://github.com/etcd-io/etcd/milestone/39).
+
+| Title                                                             | Priority | Note                                                                              |
+|-------------------------------------------------------------------|----------|-----------------------------------------------------------------------------------|
+| StoreV2 deprecation                                               | P0       | Finish the remaining tasks 3.7.                                                   |
+| Refactor lease: Lease might be revoked by mistake by old leader   | P1       | to be investigated & discussed                                                    |
+| Integrate raft's new feature (async write) into etcd              | P1       | It should can improve the performance                                             |
+| bbolt: Support customizing the bbolt rebalance threshold          | P2       | It may get rid of etcd's defragmentation. Both bbolt and etcd need to be changed. |
+| Evaluate and (graduate or deprecate/remove) experimental features | P2       | Finish the remaining tasks 3.7.                                                   |
+
+## Backlog (future releases)
+
+| Title                                                     | Priority | Note |
+|-----------------------------------------------------------|----------|------|
+| Remove the dependency on grpc-go's experimental API       |          |      |
+| Protobuf: cleanup both golang/protobuf and gogo/protobuf  |          |      |
+| Proposals should include a merkle root                    |          |      |
+| Add Distributed Tracing using OpenTelemetry               |          |      |
+| Support CA rotation                                       |          |      |
+| bbolt: Migrate all commands to cobra style commands       |          |      |
+| raft: enhance the configuration change validation         |          |      |

README.md

@@ -161,6 +161,8 @@ See [CONTRIBUTING](CONTRIBUTING.md) for details on setting up your development e
 
 Please refer to [community-membership.md](Documentation/contributor-guide/community-membership.md#member) for information on becoming an etcd project member.  We welcome and look forward to your contributions to the project!
 
+Please also refer to [roadmap](Documentation/contributor-guide/roadmap.md) to get more details on the priorities for the next few major or minor releases.
+
 ## Reporting bugs
 
 See [reporting bugs](https://github.com/etcd-io/etcd/blob/main/Documentation/contributor-guide/reporting_bugs.md) for details about reporting any issues. Before opening an issue please check it is not covered in our [frequently asked questions].