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perf(calendar): use async ICS parsing to avoid blocking event loop#4143

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KristjanESPERANTO:calendar-async
May 6, 2026
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perf(calendar): use async ICS parsing to avoid blocking event loop#4143
khassel merged 1 commit into
MagicMirrorOrg:developfrom
KristjanESPERANTO:calendar-async

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@KristjanESPERANTO KristjanESPERANTO commented May 6, 2026

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This switches the calendar fetcher from synchronous to asynchronous ICS parsing.

It does not necessarily make parsing faster overall, but it avoids long event-loop stalls with large calendar files (especially on slower devices and with multiple feeds).

So this does not fully solve #4103 on its own, but it clearly mitigates it.

It should also combine well with a future pre-filter approach discussed in the issue:

  • with pre-filter = less data to parse (future PR)
  • with async parsing = less blocking while parsing (this PR)

Together, that is likely the strongest path to fully address #4103.

@KristjanESPERANTO
perf(calendar): use async ICS parsing to avoid blocking event loop
6b9b0f8 
Replace synchronous ical.parseICS() with ical.async.parseICS(), which
processes data in batches via setImmediate(). Prevents the Node.js event
loop from freezing on large calendars (1000+ events) on low-end hardware.

Ref MagicMirrorOrg#4103
@khassel khassel merged commit 7da9e5a into MagicMirrorOrg:develop May 6, 2026
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@KristjanESPERANTO KristjanESPERANTO deleted the calendar-async branch May 6, 2026 19:34
@rejas rejas mentioned this pull request Jul 1, 2026
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rejas added a commit that referenced this pull request Jul 1, 2026
@rejas @KristjanESPERANTO
@bughaver @khassel @MagMar94 @plebcity @bugsounet @dathbe @dependabot @m-idler @sdetweil @Crazylegstoo @jboucly @jarnoml @JHWelch @Blackspirits @xsorifc28 @in-voker @angeldeejay @cgillinger @sonnyb9 @egeekial @claude @MikeBishop
Release 2.37.0 (#4194)
4b4a595 
## Release Notes
Thanks to: @angeldeejay, @egeekial, @khassel, @KristjanESPERANTO,
@MikeBishop, @rejas
> ⚠️ This release needs nodejs version >=22.21.1 <23 || >=24 (no change
to previous release)

[Compare to previous Release
v2.36.0](v2.36.0...develop)


### [core]
- Prepare Release 2.37.0 (#4193)
- fix(electron): map IPv6 :: wildcard to localhost (#4188)
- refactor(main): modernize DOM update flow with async/await (#4186)
- refactor(main): simplify _updateDom with async/await (#4185)
- fix(security): prevent unauthorized secret expansion in socket
payloads (#4184)
- refactor(main): simplify updateDomWithContent async flow (#4182)
- fix: modules losing data after HTTP 304 responses (#4180)
- chore: add missing core defaults (#4181)
- fix(server): enforce ipWhitelist for Socket.IO too (#4169)
- feat(systeminfo): include Git hash and branch in system information
log (#4167)
- feat(electron): support object-based electronSwitches (#4161)
- systeminformation thread not ending: move error handling from utils to
app (#4160)
- fix systeminformation thread not ending (#4155)
- refactor: use ES module imports in browser core (#4158)
- refactor(core): remove old Object.assign polyfill (#4157)
- refactor: rewrite Module as an ES6 class (#4151)
- refactor: rewrite NodeHelper as an ES6 class (#4147)
- update eletron to v42 (#4144)
- refactor(utils): drop ajv dependency (#4142)
- fix(systeminformation): output right 'used node' version (from parent
process) (#4141)
- fix: skip postinstall git clean when not in a git repository (#4139)
- Remove unnecessary conditionals and fix falsy property check in
imperial conversion (#4135)
- update version in package.json

### [dependencies]
- update dependencies (#4191)
- Bump actions/checkout from 6 to 7 (#4190)
- chore: update dependencies and adjust import path for SunCalc (#4189)
- update dependencies incl. electron and revert
yauzl-electron-install-fix (#4183)
- update dependencies, add electron fix in package.json (#4175)
- chore: update dependencies (#4162)
- Bump actions/dependency-review-action from 4 to 5 (#4152)
- Unify linting: replace Stylelint and markdownlint with ESLint (#4148)
- update dependencies and workflows to node v26 (#4140)

### [modules/alert]
- CodeQL cleanup for alerts #18, #19, #20 (#4153)
- fix: resolve CodeQL alerts #24 and #26 (#4145)
- fix(electron): resolve CodeQL alerts #22 and #25 in electron.js
(#4136)

### [modules/calendar]
- perf(calendar): pre-filter ICS data before parsing (#4168)
- perf(calendar): use async ICS parsing to avoid blocking event loop
(#4143)

### [modules/newsfeed]
- [newsfeed] add allowBasicHtmlTags option for basic emphasis (#4176)

### [modules/updatenotification]
- fix(updatenotification): don't spawn a child process when running
under PM2 (#4166)
- fix(updatenotification): use process.argv[0] as restart binary (#4163)
- fix(updatenotification): preserve start mode on restart (#4156)
- fix(updatenotification): fix ref diff parsing for fetch --dry-run
(#4138)
- refactor(updatenotification): replace pm2 usage with node logic
(#4134)

### [modules/weather]
- feat(weather): add Buienradar provider (#4164)

### [testing]
- remove warning in unit tests (for nodejs >= v25) (#4149)
- polish HTTP 304 docs/test/handling (#4129)

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: Kristjan ESPERANTO <35647502+KristjanESPERANTO@users.noreply.github.com>
Co-authored-by: BugHaver <43462320+bughaver@users.noreply.github.com>
Co-authored-by: BugHaver <43462320+lsaadeh@users.noreply.github.com>
Co-authored-by: Karsten Hassel <hassel@gmx.de>
Co-authored-by: Magnus <34011212+MagMar94@users.noreply.github.com>
Co-authored-by: Koen Konst <koenspero@gmail.com>
Co-authored-by: Koen Konst <c.h.konst@avisi.nl>
Co-authored-by: Bugsounet - Cédric <github@bugsounet.fr>
Co-authored-by: dathbe <github@beffa.us>
Co-authored-by: veeck <gitkraken@veeck.de>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Marcel <m-idler@users.noreply.github.com>
Co-authored-by: sam detweiler <sdetweil@gmail.com>
Co-authored-by: Kevin G. <crazylegstoo@gmail.com>
Co-authored-by: Jboucly <33218155+jboucly@users.noreply.github.com>
Co-authored-by: Jboucly <contact@jboucly.fr>
Co-authored-by: Jarno <54169345+jarnoml@users.noreply.github.com>
Co-authored-by: Jordan Welch <JordanHWelch@gmail.com>
Co-authored-by: Blackspirits <blackspirits@gmail.com>
Co-authored-by: Samed Ozdemir <samed@xsor.io>
Co-authored-by: in-voker <58696565+in-voker@users.noreply.github.com>
Co-authored-by: Andrés Vanegas Jiménez <142350+angeldeejay@users.noreply.github.com>
Co-authored-by: cgillinger <christian.gillinger@gmail.com>
Co-authored-by: Sonny B <43247590+sonnyb9@users.noreply.github.com>
Co-authored-by: sonnyb9 <sonnyb9@users.noreply.github.com>
Co-authored-by: Morgan McBee <egeekial@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Mike Bishop <mbishop@evequefou.be>
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