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add some documentation for our idb investigations
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Bruno Windels
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doc/INDEXEDDB.md
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doc/INDEXEDDB.md
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## Promises, async/await and indexedDB
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Doesn't indexedDB close your transaction if you don't queue more requests from an idb event handler?
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So wouldn't that mean that you can't use promises and async/await when using idb?
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It used to be like this, and for IE11 on Win7 (not on Windows 10 strangely enough), it still is like this.
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Here we manually flush the promise queue synchronously at the end of an idb event handler.
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In modern browsers, indexedDB transactions should only be closed after flushing the microtask queue of the event loop,
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which is where promises run.
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Keep in mind that indexedDB events, just like any other DOM event, are fired as macro tasks.
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Promises queue micro tasks, of which the queue is drained before proceeding to the next macro task.
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This also means that if a transaction is completed, you will only receive the event once you are ready to process the next macro tasks.
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That doesn't prevent any placed request from throwing TransactionInactiveError though.
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## TransactionInactiveError in Safari
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Safari doesn't fully follow the rules above, in that if you open a transaction,
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you need to "use" (not sure if this means getting a store or actually placing a request) it straight away,
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without waiting for any *micro*tasks. See comments about Safari at https://github.com/dfahlander/Dexie.js/issues/317#issue-178349994.
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Another failure mode perceived in Hydrogen on Safari is that when the (readonly) prepareTxn in sync wasn't awaited to be completed before opening and using the syncTxn.
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I haven't found any documentation online about this at all. Awaiting prepareTxn.complete() fixed the issue below. It's strange though the put does not fail.
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What is happening below is:
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- in the sync loop:
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- we first open a readonly txn on inboundGroupSessions, which we don't use in the example below
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- we then open a readwrite txn on session, ... (does not overlap with first txn)
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- first the first incremental sync on a room (!YxKeAxtNcDZDrGgaMF:matrix.org) it seems to work well
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- on a second incremental sync for that same room, the first get throws TransactionInactiveError for some reason.
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- the put in the second incremental sync somehow did not throw.
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So it looks like safari doesn't like (some) transactions still being active while a second one is being openened, even with non-overlapping stores.
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For now I haven't awaited every read txn in the app, as this was the only place it fails, but if this pops up again in safari, we might have to do that.
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Keep in mind that the `txn ... inactive` logs are only logged when the "complete" or "abort" events are processed,
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which happens in a macro task, as opposed to all of our promises, which run in a micro task.
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So the transaction is likely to have closed before it appears in the logs.
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```
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[Log] txn 4504181722375185 active on inboundGroupSessions
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[Log] txn 861052256474256 active on session, roomSummary, roomState, roomMembers, timelineEvents, timelineFragments, pendingEvents, userIdentities, groupSessionDecryptions, deviceIdentities, outboundGroupSessions, operations, accountData
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[Info] hydrogen_session_5286139994689036.session.put({"key":"sync","value":{"token":"s1572540047_757284957_7660701_602588550_435736037_1567300_101589125_347651623_132704","filterId":"2"}})
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[Info] hydrogen_session_5286139994689036.userIdentities.get("@bwindels:matrix.org")
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[Log] txn 4504181722375185 inactive
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[Log] * applying sync response to room !YxKeAxtNcDZDrGgaMF:matrix.org ...
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[Info] hydrogen_session_5286139994689036.roomMembers.put({"roomId":"!YxKeAxtNcDZDrGgaMF:matrix.org","userId":"@bwindels:matrix.org","membership":"join","avatarUrl":"mxc://matrix.org/aerWVfICBMcyFcEyREcivLuI","displayName":"Bruno","key":"!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org"})
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[Info] hydrogen_session_5286139994689036.roomMembers.get("!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org")
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[Info] hydrogen_session_5286139994689036.timelineEvents.add({"fragmentId":0,"eventIndex":2147483658,"roomId":"!YxKeAxtNcDZDrGgaMF:matrix.org","event":{"content":{"body":"haha","msgtype":"m.text"},"origin_server_ts":1601457573756,"sender":"@bwindels:matrix.org","type":"m.room.message","unsigned":{"age":8360},"event_id":"$eD9z73-lCpXBVby5_fKqzRZzMVHiPzKbE_RSZzqRKx0"},"displayName":"Bruno","avatarUrl":"mxc://matrix.org/aerWVfICBMcyFcEyREcivLuI","key":"!YxKeAxtNcDZDrGgaMF:matrix.org|00000000|8000000a","eventIdKey":"!YxKeAxtNcDZDrGgaMF:matrix.org|$eD9z73-lCpXBVby5_fKqzRZzMVHiPzKbE_RSZzqRKx0"})
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[Info] hydrogen_session_5286139994689036.roomSummary.put({"roomId":"!YxKeAxtNcDZDrGgaMF:matrix.org","name":"!!!test8!!!!!!","lastMessageBody":"haha","lastMessageTimestamp":1601457573756,"isUnread":true,"encryption":null,"lastDecryptedEventKey":null,"isDirectMessage":false,"membership":"join","inviteCount":0,"joinCount":2,"heroes":null,"hasFetchedMembers":false,"isTrackingMembers":false,"avatarUrl":null,"notificationCount":5,"highlightCount":0,"tags":{"m.lowpriority":{}}})
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[Log] txn 861052256474256 inactive
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[Info] syncTxn committed!!
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... two more unrelated sync responses ...
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[Log] starting sync request with since s1572540191_757284957_7660742_602588567_435736063_1567300_101589126_347651632_132704 ...
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[Log] txn 8104296957004707 active on inboundGroupSessions
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[Log] txn 2233038992157489 active on session, roomSummary, roomState, roomMembers, timelineEvents, timelineFragments, pendingEvents, userIdentities, groupSessionDecryptions, deviceIdentities, outboundGroupSessions, operations, accountData
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[Info] hydrogen_session_5286139994689036.session.put({"key":"sync","value":{"token":"s1572540223_757284957_7660782_602588579_435736078_1567300_101589130_347651633_132704","filterId":"2"}})
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[Log] * applying sync response to room !YxKeAxtNcDZDrGgaMF:matrix.org ...
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[Info] hydrogen_session_5286139994689036.roomMembers.get("!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org")
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[Warning] stopping sync because of error
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[Error] StorageError: get("!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org") failed on txn with stores accountData, deviceIdentities, groupSessionDecryptions, operations, outboundGroupSessions, pendingEvents, roomMembers, roomState, roomSummary, session, timelineEvents, timelineFragments, userIdentities on hydrogen_session_5286139994689036.roomMembers: (name: TransactionInactiveError) (code: 0) Failed to execute 'get' on 'IDBObjectStore': The transaction is inactive or finished.
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(anonymous function)
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asyncFunctionResume
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(anonymous function)
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promiseReactionJobWithoutPromise
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promiseReactionJob
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[Log] newStatus – "SyncError"
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[Log] txn 8104296957004707 inactive
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[Log] txn 2233038992157489 inactive
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```
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@ -235,6 +235,7 @@ export class Sync {
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await Promise.all(roomStates.map(async rs => {
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rs.preparation = await rs.room.prepareSync(rs.roomResponse, rs.membership, prepareTxn);
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}));
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// This is needed for safari to not throw TransactionInactiveErrors on the syncTxn. See docs/INDEXEDDB.md
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await prepareTxn.complete();
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await Promise.all(roomStates.map(rs => rs.room.afterPrepareSync(rs.preparation)));
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}
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