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Extension causes periodic freeze in browser

When I have Checker for Calendar enabled, I experience random multi-second pauses in which the browser stops displaying input. If I'm typing that seems to get buffered and displayed after the pause ends, but it's still very distracting because I'll be typing along and suddenly characters stop appearing on the screen.

I've already reinstalled the extension a couple of times. It is very clearly associated with this extension - it happens when Checker is enabled, and never happens when it is disabled.

I love the extension and would be happy to support it, but this bug makes it unworkable. Help?



  • Has thisbeen an issue since you first started using the extension?

    Would you say you have many calendars or events?

    Is your system generally responsive to other software ?

    1. Yes.
    2. I have many calendars (for my coworkers) in my google Calendar view, but only my calendar is connected to Checker. I don't have that many meetings (maybe a dozen per week). So I think the answer is "no".
    3. Yes. I use gmail etc on Chrome all day. This freezing behavior is very distinctive, and unique to when I have Checker enabled.
  • After you reinstalled the extension, have you change many options in the extension? if so which ones?

    I'd like to verify that the resources are being taken by the extension, can you open the task manager and wait for that minute interval and see which resources spike:


  • I changed quite a few of the options.

    • rich notifications
    • changed the default alarm to 7 minutes in advance and snooze to 5 minutes
    • run in the background when the browser is closed.
    • show minutes/hours instead of time of event
    • show day of the week in icon, unless next event is minutes/hours away
    • 3 day custom view
    • dim past days
    • show snoozed events

    I will use the task manager to try to identify the exact source of the issue (thanks, I didn't know about this)

    I have so far seen the CPU usage of this extension spike as high as 131%, but I have not been able to connect it to a momentary freeze - it came and went too quickly. I'll keep monitoring.

  • After additional observation I was able to see the effect in task manager of a couple of freeze events. In each case, browser CPU usage was high during the freeze, but IMMEDIATELY after the CPU usage for Checker would spike over 100%.

    I tried to capture this with Snipping tool but was never fast enough.

    BTW I also turned off the right-click context menu because I didn't need it. Didn't seem to make any difference though.

  • Ok good obvservations, so to rule out any of the setting, could you reinstall the extension and not change any settings?

    Actually for starters let's not even grant access to your calendar account upon installing and see if it's runs ok every minute, then let's try granting access.

  • OK. I reinstalled the extension and then closed then window when it asked me to configure it. The icon appears in my browser's bar with an X in it.

    So far, I have not observed any freezing with it in this state. I haven't been using this machine as much over the weekend. If the freezing reappears I'll update you but I think at this point that it is not occuring.

  • I can confirm that, with the extension installed but not configured, I have not been experiencing the freezes. Hopefully that helps narrow it down.

  • ok thank you that's a good first step, now let's try granting access and no further configuration and see.

    fyi i'm thinking this might be related to the many coworker calendars you mentioned earlier. do you see them in the extension popup window?

  • Does it make any difference whether I use Chrome Signin or Google Signin?

    The relevant calendar is attached to my primary google login on this computer, which is also the login for Chrome itself. So I've been using Chrome sign-in for all my previous efforts. I'm wondering if I should try google sign-in? Or is that unlikely to make a difference?

  • Good question, but makes no difference as either way they'll load the same account's data.

  • OK, I granted access and have changed nothing else. I will update you whether the freezing re-appears.

    To your question: the pop-up calendar (currently set to the default full month view) shows only my own meetings. There are no references to any of my co-workers calendars visible within the extension.

    UPDATE: If I turn on any of my coworkers' calendars, so that their appointments appear on my calendar view, that calendar ALSO shows up in the pop-up. But by default I do not have anyone else's calendars showing. (It's possible that this is still the source of the issue, if the extension is checking the data even if it's not displaying. But I have no way to know.)

  • So we'll do more tests an a slow incremental fashion as to determine our shared hypothesis :)

    FYI there is a different option for show visible calendars and getting notifications for certain calendars ... https://jasonsavard.com/wiki/Visible_calendars_in_popup_window

  • OK, thanks for clarifying.

    By default, only my personal calendar is set up for notifications.

    By default, all of my coworker's calendars DO appear in the left-side sidebar, but they are all unchecked.

    Also, I can confirm that the freezing behavior came back as soon as I configured the extension, without changing any other settings. It continues to be associated with CPU>100 for the extension in the chrome task manager.

  • ok can go into the extension ... Options .. Notifications ... and below you'll see notifications for calendars, how many are checked? and how many do you have?

    can you uncheck all of them and see if that makes a difference.

  • I have many calendars listed in that window - though oddly not as many as appear in my sidebar in Google Calendar.

    Only the first one (my personal calendar) is checked:

    Hypothesis: The extension is checking all the calendars rather than just the one that I actually care about?

  • Well that hypothesis might be wrong now that you've shared the screenshot showing only your primary calendar is checked. Can you try unchecking thst calendar and see if that helps.

  • Good thought.

    I tried running the extension with no calendar's checked, and the freezing occurred as previously.

  • Ok interesting, can you tell me how many total calendar you have?

    And then for some techy debugging stuff :) can you do this to let me know how many events the extension is trying to process...

    1. Click the Chrome menu icon > More tools > Extensions
    2. Select Developer mode at the top right
    3. Find the extension and click the background link
    4. Select the Console tab
    5. Then paste this command in the console and hit enter and let me know the resulting number... (await getEvents()).length

  • I have four calendars under "My Calendars":

    • my personal calendar
    • Reminders and Tasks, which I do not use (but can't get rid of as far as I know)
    • a calendar for my team

    Under "Other Calendars" I have about 50 entries. In general, none of those are checked/active.

  • For the debugging, if I typed exactly what you showed including the leading open paran, I get this (all red error text):


    Uncaught (in promise) ReferenceError: getEvents is not defined ReferenceError: getEvents is not defined

    at <anonymous>:1:15

    at <anonymous>:2:3



    Uncaught (in promise) ReferenceError: getEvents is not defined

    at <anonymous>:1:15

    at <anonymous>:2:3


    I'm not sure if the leading paren is a typo or not. If I enter it WITHOUT the leading paren ("await getEvents()).length") then I get this:

    (first line is in red error text; other lines are black text)

    VM39:1 Uncaught SyntaxError: await is only valid in async function

    common.js:1178 initWindowVars

    common.js:1190 initWindowBGVars

    checkerPlusForCalendar.js:2577 allDayVStimeSpecific: 0.466064453125ms

    checkerPlusForCalendar.js:3336 sortevents: 17.89599609375ms

    common.js:1208 mergeevents: 74.152099609375ms

    common.js:1209 feeds: 74.370849609375ms

    common.js:1211 initMisc: 2546.331787109375ms

    background.js:2389 vars: 1.35302734375ms

    common.js:1211 initMisc: 0.0068359375ms

    background.js:2389 vars: 3.466064453125ms

    Does this help?

  • ok thanks for the details, you might be on an older version, can you try this command instead...


    note that I suspect the issue is probably caused by 50 calendars you mentioned under the "Other calendars" can you send me a screenshot of that, or let me know what these are for.

  • When I enter "events.length" it responds with "7816".

    The other calendars are my colleagues' calendars and conference room calendars. As I said, they are generally turned off - occasionally I'll turn one or two of them on for a few minutes, to check someone else's schedule.

    If that's what's causing the issue I'm surprised you haven't seen this before. I don't think my arrangement is that unusual. We use Google's conferencing system, for example, which necessitates at least some of these calendars.

    To be clear, I don't need ANY of these calendars in Checker. I just want it to look at my personal calendar - so if there is anyway to force that behavior, that would be a perfectly fine workaround (assuming the cause is as you suspect).

  • Interesting. As I was writing this, with the console still open and Checker enabled, it spontaneously generated a bunch of error messages related to calendar stuff. I'm not sure if this is related to Checker, but I thought I'd pass it along.

    The error text looks like this.

    As you can see, each error message is the same EXCEPT for the "ID" string. That value is the same for typically 1-4 consecutive messages, then it changes. All the other values are unchanging as far as I can see.

    There are a few dozen of these messages in my console right now.

    To anticipate your question: I did not perceive a freeze when these messages were generated. But I am not sure I was typing at that exact moment - it's possible there was a freeze and I didn't notice.

  • Great investigations, so most likely the issue is with that high number of events (7000+)

    I know you haven't "enabled" these associated calendars in my extension, however the current logic does iterate through them then it decides if it's associated calendars has been enabled or not by you. I will have to refactor the code to avoid this scenario, however, I would be curious if there'a another colleague with the same issue and if it's possible to remove these "other calendars" from a test user - to confirm this is the source of the issue. Or maybe you're aware of one of those particular calendars having several events (or recurring events) that could be removed for testing purposes.

    As for those specific errors in the console, we can pursue that latter, but they could be normal given more context.

  • I don't really have a good way to test what you are asking. I can't unsubscribe from those calendars - I need access to that information.

    As far as I know, I'm the only person in the office who uses Checker - although if we can figure this out, I will definitely recommend it as it meets a need that I think other people have as well.

    All of these calendars have large numbers of events on them, since they are people's individual work calendars. So I don't think there is any one calendar I could unsubscribe from to prove your hypothesis. I'd have to unsub from all of them.

    That said, if your code first iterates through all subscribed calendars and only then decides which calendars are relevant, then I believe you've found the smoking gun. That has to be it.

    Do you foresee being able to make that update?


  • edited December 2019

    so there's already an unrelated update being pushed, but i'll be concentrating my efforts on this issue.

    can you send me a screenshot of your google calendar, showing your calendars and these "other calendars" just to get some context.

  • There's about 50% more calendars on the list if you were to scroll down all the way.

  • edited December 2019

    ok thanks, I noticed you have a "my calendar" with the title _000_BIG

    is that calendar big? ie. in terms of many events or it's unrelated?

  • No. BIG is my team name/acronym. That's the "I am out of office" calendar for my team. It has few events and they change infrequently.

    (I hadn't mentioned it before because it's a new thing my boss just set up. the issues I described occurred before it existed.)

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