scs: add stub implementation of megarepo svc

Summary:
This diff adds megarepo service methods to SCS. Each of the methods just returns "not implemented" at the moment.

The main goal of this diff is to provide a reference against which a sample client can be built.

This diffs makes two decisions that came from the source control discussion presentation:
1. expensive calls are asynchronous. This means that they are separated into an initial "request placing" call, which returns a polling token; and a polling call, which takes said token and blocks until it either times out or until the request is satisfied
1. racy calls take target location and only advance target if this location does not change until the advancement time comes. This ensures that the clients are aware that changing sync config versions or re-merging sources should be done why `megarepo_sync_changeset` calls are paused

There are also some decisions that I made while writing this, which may be questionable:
1. The polling token types are just string aliases. This is fine atm, but may be a problem in the future if we want to implement `AddScubaResponse` or `AddScubaParams` for some but not others. Moreover, now I had to implement both traits for `String`, which I am also not too happy about. Maybe I should turn polling tokens into wrapper structs right now
1. all new methods start with `megarepo_` or `poll_megarepo`. Generally I dislike name-based namespacing, but in this case the alternative is to either keep the names like `sync_changeset` (not descriptive enough), or move these methods into a separate service definition (too much overhead, and probably not desirable from operational perspective anyways). So I went with prefixes.
1. **the most questionable decision IMO** is about a config design. ATM the `SyncTargetConfig` type contains the `Target` internally. At the same time, `MegarepoChangeTargetConfigParams` contains both the `Target` and the `SyncTargetConfig` and will error out if `SyncTargetConfig` refers to a different target. The API could be made simpler by just taking `SyncTargetConfig`, but it feels a bit wrong to not have the client give us the target they want to change the config for. I can be easily persuaded to remove `Target` from `MegarepoChangeTargetConfigParams`. It can also be done incrementally, until we have any real clients, so figuring this out now is not important.

Reviewed By: markbt

Differential Revision: D26549580

fbshipit-source-id: 2d38d6273fb5ec46b846a242f4f1abf61502cb1c

eden/mononoke/scs_server/src/errors.rs

@@ -127,6 +127,14 @@ impl_into_thrift_error!(service::FileContentChunkExn);
 impl_into_thrift_error!(service::FileDiffExn);
 impl_into_thrift_error!(service::CommitLookupXrepoExn);
 impl_into_thrift_error!(service::RepoListHgManifestExn);
+impl_into_thrift_error!(service::MegarepoAddSyncTargetConfigExn);
+impl_into_thrift_error!(service::MegarepoAddSyncTargetExn);
+impl_into_thrift_error!(service::MegarepoChangeTargetConfigExn);
+impl_into_thrift_error!(service::MegarepoChangeTargetConfigPollExn);
+impl_into_thrift_error!(service::MegarepoSyncChangesetExn);
+impl_into_thrift_error!(service::MegarepoSyncChangesetPollExn);
+impl_into_thrift_error!(service::MegarepoRemergeSourceExn);
+impl_into_thrift_error!(service::MegarepoRemergeSourcePollExn);
 
 pub(crate) fn invalid_request(reason: impl ToString) -> thrift::RequestError {
     thrift::RequestError {
@@ -209,3 +217,10 @@ pub(crate) fn not_available(reason: String) -> thrift::RequestError {
         reason,
     }
 }
+
+pub(crate) fn not_implemented(reason: impl ToString) -> thrift::RequestError {
+    thrift::RequestError {
+        kind: thrift::RequestErrorKind::NOT_IMPLEMENTED,
+        reason: reason.to_string(),
+    }
+}

eden/mononoke/scs_server/src/methods/megarepo.rs

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This software may be used and distributed according to the terms of the
+ * GNU General Public License version 2.
+ */
+
+use context::CoreContext;
+use source_control as thrift;
+
+use crate::errors;
+use crate::source_control_impl::SourceControlServiceImpl;
+
+impl SourceControlServiceImpl {
+    pub(crate) async fn megarepo_add_sync_target_config(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoAddConfigParams,
+    ) -> Result<thrift::MegarepoAddConfigResponse, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "megarepo_add_sync_target_config is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_add_sync_target(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoAddTargetParams,
+    ) -> Result<thrift::MegarepoAddTargetResponse, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "megarepo_add_sync_target is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_change_target_config(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoChangeTargetConfigParams,
+    ) -> Result<thrift::MegarepoChangeConfigToken, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "megarepo_change_target_config is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_change_target_config_poll(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoChangeConfigToken,
+    ) -> Result<thrift::MegarepoChangeTargetConfigResponse, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "poll_megarepo_change_config is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_sync_changeset(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoSyncChangesetParams,
+    ) -> Result<thrift::MegarepoSyncChangesetToken, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "megarepo_sync_changeset is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_sync_changeset_poll(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoSyncChangesetToken,
+    ) -> Result<thrift::MegarepoSyncChangesetResponse, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "poll_megarepo_sync_changeset is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_remerge_source(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoRemergeSourceParams,
+    ) -> Result<thrift::MegarepoRemergeSourceToken, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "megarepo_remerge_source is not yet implemented",
+        )))
+    }
+
+    pub(crate) async fn megarepo_remerge_source_poll(
+        &self,
+        _ctx: CoreContext,
+        _params: thrift::MegarepoRemergeSourceToken,
+    ) -> Result<thrift::MegarepoRemergeSourceResponse, errors::ServiceError> {
+        Err(errors::ServiceError::from(errors::not_implemented(
+            "poll_megarepo_remerge_source is not yet implemented",
+        )))
+    }
+}

eden/mononoke/scs_server/src/methods/mod.rs

@@ -14,6 +14,7 @@ use crate::source_control_impl::SourceControlServiceImpl;
 pub(crate) mod commit;
 pub(crate) mod commit_path;
 pub(crate) mod file;
+pub(crate) mod megarepo;
 pub(crate) mod repo;
 pub(crate) mod tree;
 

eden/mononoke/scs_server/src/scuba_params.rs

@@ -303,3 +303,16 @@ impl AddScubaParams for thrift::RepoListHgManifestParams {
         );
     }
 }
+
+// Various Megarepo polling tokens are just aliases for String
+impl AddScubaParams for String {}
+
+impl AddScubaParams for thrift::MegarepoSyncChangesetParams {}
+
+impl AddScubaParams for thrift::MegarepoRemergeSourceParams {}
+
+impl AddScubaParams for thrift::MegarepoChangeTargetConfigParams {}
+
+impl AddScubaParams for thrift::MegarepoAddTargetParams {}
+
+impl AddScubaParams for thrift::MegarepoAddConfigParams {}

eden/mononoke/scs_server/src/scuba_response.rs

@@ -74,3 +74,18 @@ impl AddScubaResponse for thrift::FileDiffResponse {}
 impl AddScubaResponse for thrift::TreeListResponse {}
 
 impl AddScubaResponse for thrift::RepoListHgManifestResponse {}
+
+// MegarepoRemergeSourceToken, MegarepoChangeConfigToken
+// MegarepoSyncChangesetToken are all just aliases for String
+impl AddScubaResponse for String {}
+
+// TODO: report cs_ids where possible
+impl AddScubaResponse for thrift::MegarepoRemergeSourceResponse {}
+
+impl AddScubaResponse for thrift::MegarepoSyncChangesetResponse {}
+
+impl AddScubaResponse for thrift::MegarepoChangeTargetConfigResponse {}
+
+impl AddScubaResponse for thrift::MegarepoAddTargetResponse {}
+
+impl AddScubaResponse for thrift::MegarepoAddConfigResponse {}

eden/mononoke/scs_server/src/source_control_impl.rs

@@ -574,6 +574,38 @@ impl SourceControlService for SourceControlServiceThriftImpl {
             params: thrift::RepoLandStackParams,
         ) -> Result<thrift::RepoLandStackResponse, service::RepoLandStackExn>;
 
+        async fn megarepo_add_sync_target_config(
+            params: thrift::MegarepoAddConfigParams,
+        ) -> Result<thrift::MegarepoAddConfigResponse, service::MegarepoAddSyncTargetConfigExn>;
+
+        async fn megarepo_add_sync_target(
+            params: thrift::MegarepoAddTargetParams,
+        ) -> Result<thrift::MegarepoAddTargetResponse, service::MegarepoAddSyncTargetExn>;
+
+        async fn megarepo_change_target_config(
+            params: thrift::MegarepoChangeTargetConfigParams,
+        ) -> Result<thrift::MegarepoChangeConfigToken, service::MegarepoChangeTargetConfigExn>;
+
+        async fn megarepo_change_target_config_poll(
+            token: thrift::MegarepoChangeConfigToken,
+        ) -> Result<thrift::MegarepoChangeTargetConfigResponse, service::MegarepoChangeTargetConfigPollExn>;
+
+        async fn megarepo_sync_changeset(
+            params: thrift::MegarepoSyncChangesetParams,
+        ) -> Result<thrift::MegarepoSyncChangesetToken, service::MegarepoSyncChangesetExn>;
+
+        async fn megarepo_sync_changeset_poll(
+            token: thrift::MegarepoSyncChangesetToken,
+        ) -> Result<thrift::MegarepoSyncChangesetResponse, service::MegarepoSyncChangesetPollExn>;
+
+        async fn megarepo_remerge_source(
+            params: thrift::MegarepoRemergeSourceParams,
+        ) -> Result<thrift::MegarepoRemergeSourceToken, service::MegarepoRemergeSourceExn>;
+
+        async fn megarepo_remerge_source_poll(
+            token: thrift::MegarepoRemergeSourceToken,
+        ) -> Result<thrift::MegarepoRemergeSourceResponse, service::MegarepoRemergeSourcePollExn>;
+
         async fn repo_list_hg_manifest(
             repo: thrift::RepoSpecifier,
             params: thrift::RepoListHgManifestParams,