From a0c1f69ae2e17bc6a938c1a1044cdb33276b7a65 Mon Sep 17 00:00:00 2001
From: Jeff Mitchell <jeffrey.mitchell@gmail.com>
Date: Thu, 20 May 2021 20:07:22 -0500
Subject: [PATCH] Already-canceled sessions return 200 (#1243)

If a session is already canceled or terminated, attempting to cancel it
will return the current session state and a 200, instead of an error.
---
 CHANGELOG.md                                      | 12 ++++++++++++
 .../handlers/sessions/session_service.go          | 15 ++++++++-------
 .../handlers/sessions/session_service_test.go     |  3 +--
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6b77d9fe1..5331de557 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,18 @@ Canonical reference for changes, improvements, and bugfixes for Boundary.
 
 ## Next
 
+### Deprecations/Changes
+
+* If a `cancel` operation is run on a session already in a canceling or
+  terminated state, a `200` and the session information will be returned instead
+  of an error.
+
+### New and Improved
+
+* sessions: Return a `200` and session information when canceling an
+  already-canceled or terminated session
+  ([PR](https://github.com/hashicorp/boundary/pull/1243))
+
 ## 0.2.2 (2021/05/17)
 
 ### New and Improved
diff --git a/internal/servers/controller/handlers/sessions/session_service.go b/internal/servers/controller/handlers/sessions/session_service.go
index ecd242393..42c60f6e2 100644
--- a/internal/servers/controller/handlers/sessions/session_service.go
+++ b/internal/servers/controller/handlers/sessions/session_service.go
@@ -237,18 +237,19 @@ func (s Service) CancelSession(ctx context.Context, req *pbs.CancelSessionReques
 		}
 	}
 
+	var skipCancel bool
 	for _, state := range ses.States {
 		switch state.Status {
-		case session.StatusCanceling:
-			return nil, errors.New(errors.InvalidSessionState, op, "session already in canceling state")
-		case session.StatusTerminated:
-			return nil, errors.New(errors.InvalidSessionState, op, "session already terminated")
+		case session.StatusCanceling, session.StatusTerminated:
+			skipCancel = true
 		}
 	}
 
-	ses, err = s.cancelInRepo(ctx, req.GetId(), req.GetVersion())
-	if err != nil {
-		return nil, err
+	if !skipCancel {
+		ses, err = s.cancelInRepo(ctx, req.GetId(), req.GetVersion())
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	outputOpts := make([]handlers.Option, 0, 3)
diff --git a/internal/servers/controller/handlers/sessions/session_service_test.go b/internal/servers/controller/handlers/sessions/session_service_test.go
index ad13af01f..d12a26dca 100644
--- a/internal/servers/controller/handlers/sessions/session_service_test.go
+++ b/internal/servers/controller/handlers/sessions/session_service_test.go
@@ -521,8 +521,7 @@ func TestCancel(t *testing.T) {
 			name:    "Already canceled",
 			scopeId: sess.ScopeId,
 			req:     &pbs.CancelSessionRequest{Id: sess.GetPublicId()},
-			res:     nil,
-			err:     errors.New(errors.InvalidSessionState, "sessions.(Service).CancelSession", "session already in canceling state"),
+			res:     &pbs.CancelSessionResponse{Item: wireSess},
 		},
 		{
 			name: "Cancel a non existing Session",