1905958 - Create a JSON schema to describe the graph that is serialized for session restore

Status: ASSIGNED

(Firefox :: Session Restore, task, P3)

Description

[Sam Foster [:sfoster] (he/him)]

In bug 1849393 we identified a need for a formal schema that defines what goes into a session file. These are an in-memory javascript graph that gets serialized to JSON and compressed and written to disk as a .jsonlz4 file, allowing a user to seamlessly resume a session after a restart or crash.

The basic structure looks something like this:

{
  "version": [
    "sessionrestore",
    1
  ],
  "windows": [
    {
      "tabs": [
        {
          "entries": [
            {
              "url": "https://example.com/",
              "title": "Page title",
              "hasUserInteraction": false,
              "triggeringPrincipal_base64": "{\"3\":{}}"
            },
            ....
          ],
          "lastAccessed": 1697149705740,
          "hidden": false,
          "searchMode": null,
          "userContextId": 0,
          "attributes": {},
          "index": 3,
          "requestedIndex": 0,
          "image": "data:image/x-icon;base64,etc.."
        },
        ...
      ],
      "_closedTabs": [
        {
          "state": {
            "entries": [
              {
                "url": "https://elsewhere.com/",
                "title": "Page title",
                "resultPrincipalURI": null,
                "principalToInherit_base64": "{\"0\":{\"0\":\"moz-nullprincipal:{b8140753-f226-4c5d-9749-fc3eea899d9f}\"}}",
                "hasUserInteraction": true,
                "triggeringPrincipal_base64": "{\"3\":{}}",
                "persist": true
              }
            ],
            "lastAccessed": 1697142677640,
            "hidden": false,
            "searchMode": null,
            "userContextId": 0,
            "attributes": {},
            "index": 1,
            "requestedIndex": 0,
            "image": "..."
          },
          "title": "Page title",
          "image": "...",
          "pos": 0,
          "closedAt": 1697147353955,
          "closedInGroup": false,
          "removeAfterRestore": true,
          "closedId": 3,
          "sourceWindowId": "window0"
        },
        ...
      ]
    },
    ...
  },
  "selectedWindow": 0,
  "_closedWindows": [
     ...
  ],

  "session": {
    "lastUpdate": 1697149716870,
    "startTime": 1697149627011,
    "recentCrashes": 1
  },
  "global": {},
  "cookies": [
     {
      "host": "example.com",
      "value": "af6e3...",
      "path": "/",
      "name": "someName",
      "secure": true,
      "httponly": true,
      "expiry": 1697142669447,
      "originAttributes": {
        "firstPartyDomain": "",
        "geckoViewSessionContextId": "",
        "inIsolatedMozBrowser": false,
        "partitionKey": "",
        "privateBrowsingId": 0,
        "userContextId": 3
      },
      "sameSite": 1,
      "schemeMap": 2
    },
    ...
 ]
}

...but there is quite a lot of detail down at the individual entries level for each tab.

Having a schema would be useful in tests and also a known quantity and jumping off point for any future optimization or re-architecting of how session (res)store works.

Comment 1

[Sam Foster [:sfoster] (he/him)]

I have a work-in-progress for the JSON schema at https://github.com/sfoster/moz-sessionrestore-tools, the draft schema itself its at session-schema.json. Once that is closer to done and we have figured out where in the tree this should live, I'll get a patch on here. PRs welcome in the meantime.