✨ [RUM-3710] Update session ID handling to support cookie deletion (#…

…2673)

developer-extension/src/panel/components/tabs/infosTab.tsx

@@ -257,9 +257,12 @@ function formatSessionType(value: string, ...labels: string[]) {
 }
 
 function endSession() {
+  const fourHours = 1000 * 60 * 60 * 4
+  const expires = new Date(Date.now() + fourHours).toUTCString()
+
   evalInWindow(
     `
-      document.cookie = '_dd_s=; expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/'
+      document.cookie = '_dd_s=isExpired=1; expires=${expires}; path=/'
     `
   ).catch((error) => logger.error('Error while ending session:', error))
 }

packages/core/src/domain/session/README.md

@@ -0,0 +1,193 @@
+## possible states:
+
+| state                   | value                                                        |
+| ----------------------- | ------------------------------------------------------------ |
+| NotStarted<sup>\*</sup> | `{}`                                                         |
+| Expired                 | `{expired: '1'}` or `expire >  15 minutes` or `created > 4H` |
+| Tracked                 | `{id: 'xxxx-xx-xx}`                                          |
+| NotTracked              | `{rum: 0}` or `{logs: 0}`                                    |
+
+(<sup>\*</sup>) `NotStarted` is a state that can happen in a few different ways:
+
+- First load of the page if there is no cookie present already
+- After the cookie has been deleted by a 3rd party (user, ad blocker, ...)
+- After the cookie has expired (it is deleted by the browser)
+
+Other terminology:
+
+- A _started_ session is a session that is either `Expired`, `Tracked`, or `NotTracked`.
+- An _active_ session is a session that is either `Tracked` or `NotTracked`.
+
+## start session
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+state fork_state2 <<fork>>
+
+[*] --> fork_state
+
+fork_state --> NotStarted
+fork_state --> Expired
+fork_state --> Tracked
+fork_state --> NotTracked
+NotStarted --> Expired: startSession()
+
+Expired --> fork_state2
+Tracked --> fork_state2
+NotTracked --> fork_state2
+fork_state2 --> [*]: expandOrRenew()
+```
+
+## On User Activity
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+
+[*] --> fork_state
+
+fork_state --> [*]: expandOrRenew()
+```
+
+## On Visibility Change
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+state visibility <<choice>>
+
+[*] --> visibility: VisibilityChange
+
+visibility --> [*]: hidden
+visibility --> fork_state : visible
+
+fork_state --> [*]: extendOrExpire()
+```
+
+## On resume from frozen state
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+state fork_state2 <<fork>>
+
+[*] --> fork_state: Resume
+
+fork_state --> NotStarted
+fork_state --> Expired
+fork_state --> Tracked
+fork_state --> NotTracked
+
+NotStarted --> Expired: restartSession()
+Expired --> fork_state2
+Tracked --> fork_state2
+NotTracked --> fork_state2
+
+fork_state2 --> [*]: extendOrExpire()
+```
+
+## Watch (every second)
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+
+
+[*] --> fork_state
+fork_state --> [*]: extendOrExpire()
+```
+
+## 3rd party cookie clearing
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+state join_state <<join>>
+NotStarted2: NotStarted
+
+[*] --> fork_state
+
+fork_state --> NotStarted
+fork_state --> Expired
+fork_state --> Tracked
+fork_state --> NotTracked
+
+Expired --> join_state
+Tracked --> join_state
+NotTracked --> join_state
+NotStarted --> join_state
+
+join_state --> NotStarted2 : clearCookies()
+
+NotStarted2 --> [*]
+```
+
+## Expand Or Renew
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+state fork_state2 <<fork>>
+state fork_state3 <<fork>>
+
+
+state expandOrRenew() {
+  [*] --> fork_state: expandOrRenew()
+  Tracked2: Tracked
+  NotTracked2: NotTracked
+
+  fork_state --> NotStarted
+  fork_state --> Expired
+  fork_state --> Tracked
+  fork_state --> NotTracked
+
+  NotStarted --> [*]
+
+  Expired --> fork_state2: renew()
+  Tracked --> fork_state2: extend()
+  NotTracked --> fork_state2: extend()
+
+  fork_state2 --> fork_state3: computeTrackingType()
+
+  fork_state3 --> Tracked2
+  fork_state3 --> NotTracked2
+
+  Tracked2 --> [*]
+  NotTracked2 --> [*]
+}
+```
+
+> [!NOTE]  
+> Because `computeTrackingType()` happens at every `expandOrRenew()`, it is in theory possible to switch from `Tracked` to `NotTracked` and vice versa within an active session. However, this is not expected to happen in practice at this time.
+
+## Extend Or Expire
+
+```mermaid
+stateDiagram-v2
+state fork_state <<fork>>
+
+state extendOrExpire() {
+  [*] --> fork_state : extendOrExpire()
+  Tracked2: Tracked
+  NotTracked2: NotTracked
+  Expired2: Expired
+
+  fork_state --> NotStarted
+  fork_state --> Expired
+  fork_state --> Tracked
+  fork_state --> NotTracked
+
+  Tracked --> Tracked2: extend()
+  NotTracked --> NotTracked2: extend()
+  Expired --> Expired2: expire()
+
+  NotStarted --> [*]
+  Tracked2 --> [*]
+  NotTracked2 --> [*]
+  Expired2 --> [*]
+}
+```
+
+> [!NOTE]  
+> Because a session time out can result in an `Expired` state, `expire()` explicitly normalizes the state to `isExpired=1`

packages/core/src/domain/session/oldCookiesMigration.ts

@@ -2,7 +2,7 @@ import { getInitCookie } from '../../browser/cookie'
 import type { SessionStoreStrategy } from './storeStrategies/sessionStoreStrategy'
 import { SESSION_STORE_KEY } from './storeStrategies/sessionStoreStrategy'
 import type { SessionState } from './sessionState'
-import { expandSessionState, isSessionInExpiredState } from './sessionState'
+import { expandSessionState, isSessionStarted } from './sessionState'
 
 export const OLD_SESSION_COOKIE_NAME = '_dd'
 export const OLD_RUM_COOKIE_NAME = '_dd_r'
@@ -34,7 +34,7 @@ export function tryOldCookiesMigration(cookieStoreStrategy: SessionStoreStrategy
       session[RUM_SESSION_KEY] = oldRumType
     }
 
-    if (!isSessionInExpiredState(session)) {
+    if (isSessionStarted(session)) {
       expandSessionState(session)
       cookieStoreStrategy.persistSession(session)
     }