transactions - run event emitters outside context of _setTxStatus #4131
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kumavis
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Apr 30, 2018
| this.updateTx(txMeta, `txStateManager: setting status to ${status}`) | ||
| this.emit(`${txMeta.id}:${status}`, txId) | ||
| this.emit(`tx:status-update`, txId, status) | ||
| if (['submitted', 'rejected', 'failed'].includes(status)) { |
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we should break this utility out
kumavis
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Apr 30, 2018
Gudahtt
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May 9, 2020
All transaction status updates were moved into a `setTimeout` callback and wrapped in a `try...catch` block in #4131, apparently in an attempt to prevent failures in event subscribers from interrupting the transaction logic. The `try...catch` block did accomplish that, but by putting the status update in a `setTimeout` callback the operation was made asynchronous. Transaction status updates now happen unpredictably, in some future event loop from when they're triggered. This creates a race condition, where the transaction status update may occur before or after subsequent state changes. This also introduces a risk of accidentally undoing a change to the transaction state, as the update made to the transaction inside the `setTimeout` callback uses a reference to `txMeta` obtained synchronously before the `setTimeout` call. Any replacement of the `txMeta` between the `setTxStatus` call and the execution of the timeout would be erased. Luckily the `txMeta` object is more often than not mutated rather than replaced, which may explain why we haven't seen this happen yet. Everything seems to work correctly with the `setTimeout` call removed, and now the transaction logic is easier to understand.
Gudahtt
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May 9, 2020
All transaction status updates were moved into a `setTimeout` callback and wrapped in a `try...catch` block in #4131, apparently in an attempt to prevent failures in event subscribers from interrupting the transaction logic. The `try...catch` block did accomplish that, but by putting the status update in a `setTimeout` callback the operation was made asynchronous. Transaction status updates now happen unpredictably, in some future event loop from when they're triggered. This creates a race condition, where the transaction status update may occur before or after subsequent state changes. This also introduces a risk of accidentally undoing a change to the transaction state, as the update made to the transaction inside the `setTimeout` callback uses a reference to `txMeta` obtained synchronously before the `setTimeout` call. Any replacement of the `txMeta` between the `setTxStatus` call and the execution of the timeout would be erased. Luckily the `txMeta` object is more often than not mutated rather than replaced, which may explain why we haven't seen this happen yet. Everything seems to work correctly with the `setTimeout` call removed, and now the transaction logic is easier to understand.
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this wraps emitters so they excute safely