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Scheduled invocations are held in memory until they are written into a response, so an application that keeps scheduling ones that never reach the browser runs out of memory. Flow now warns about it. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
mcollovati
requested changes
Sep 21, 2026
| Where only the latest value matters -- a progress value, a clock, a live measurement -- avoid scheduling a new invocation for every update: | ||
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| - Keep the [classname]`PendingJavaScriptResult` that [methodname]`executeJs()` returns, and call [methodname]`cancelExecution()` on it before scheduling the next one. | ||
| - Set an element property with [methodname]`Element.setProperty()` instead. Only the last value of a property is sent. |
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It seems not clear to me how element properties are related to pending JavaScript invocation. Do we have documentation that suggests setting properties via JavaScript?
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Documents vaadin/flow#25252
memory leak · flow/component-internals, flow/production ·
applications that schedule
executeJs()from background threads or forcomponents that are not on screen
JavaScript scheduled on the server is held in memory until it's written
into a response for the browser, so an application that keeps
scheduling invocations which never reach the browser runs out of
memory. Flow now logs a warning once 1000 of them are waiting for one
UI. Nothing in the docs described the retention, the warning, or the
alternatives, and the symptom is hard to recognize from a heap dump.
Risks:
✅ Docs only. One new section and one troubleshooting entry, no
moved anchors.
Added an "Undelivered Invocations" section to Calling JavaScript from
the Server, with the anchor
undelivered-invocations.Listed the three cases where invocations pile up: a detached owner,
an invisible owner, and a UI with no open push connection.
Listed the alternatives for values where only the latest one matters:
cancelExecution()on the returnedPendingJavaScriptResult,Element.setProperty(), andUI.getLastUpdateSentTimestamp()tostop scheduling while the browser isn't receiving.
Added an entry to Common Issues on the production troubleshooting
page, pointing at the new section.
🤖 Generated with Claude Code