Javascript acting multitheaded in Firefox
Everything relevant on the internet I've read indicates that Javascript is single-threaded (aside from Web Workers, which run in a different global context and shouldn't be able to directly affect the state in the main thread). However, while debugging some code, I noticed that even while I was paused on such-and-such a line, variables kept changing, even when I didn't step over lines of code. Investigating further, I noticed that, again, even while paused in the debugger (and I wasn't touching anything), logs were logged and errors were thrown every second according to a timeout that had been set.
I am using OS: Windows 10 Enterprise, version 1803, OS build 17134.407.
I experienced the issue in Firefox 63.0.1 (64-bit).
When I tried it in Chrome 70.0.3538.102 (Official Build) (64-bit), however, the issue did not occur - pausing in the debugger appeared to pause all computation, as expected.
I can't provide any useful code, because 1. it's company code, and 2. it's a multithreading style problem, which makes it very difficult to narrow down to any given section of code. Things that might be relevant, aside from aforementioned browser differences: it's an AngularJS application, served to the browser from NodeJS. We're using $interval(), timeout(), $http, and Stomp websocket connections.
According to my understanding, this apparently multithreaded behavior should be impossible. How could this happen?
javascript multithreading
google-chrome firefox asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
add a comment |
Everything relevant on the internet I've read indicates that Javascript is single-threaded (aside from Web Workers, which run in a different global context and shouldn't be able to directly affect the state in the main thread). However, while debugging some code, I noticed that even while I was paused on such-and-such a line, variables kept changing, even when I didn't step over lines of code. Investigating further, I noticed that, again, even while paused in the debugger (and I wasn't touching anything), logs were logged and errors were thrown every second according to a timeout that had been set.
I am using OS: Windows 10 Enterprise, version 1803, OS build 17134.407.
I experienced the issue in Firefox 63.0.1 (64-bit).
When I tried it in Chrome 70.0.3538.102 (Official Build) (64-bit), however, the issue did not occur - pausing in the debugger appeared to pause all computation, as expected.
I can't provide any useful code, because 1. it's company code, and 2. it's a multithreading style problem, which makes it very difficult to narrow down to any given section of code. Things that might be relevant, aside from aforementioned browser differences: it's an AngularJS application, served to the browser from NodeJS. We're using $interval(), timeout(), $http, and Stomp websocket connections.
According to my understanding, this apparently multithreaded behavior should be impossible. How could this happen?
javascript multithreading
google-chrome firefox asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
If there is any multiprocessing going on, it is likely the browser's internal operations that are multithreaded for this anomaly and not the JS runtime. So this seems simply like Mozilla's debugger works differently than Chrome's.
– Randy Casburn
Nov 24 '18 at 2:24
@RandyCasburn Perhaps, depending on what you mean. If the debugger is to be believed, there is more than one thread of execution. I can step through code in one place, all the while code continues to be executed somewhere else. It seems like this would be an actual bug in Firefox's debugger, rather than a simple difference of operation - if invoking the debugger invisibly and significantly breaks one of the fundamental principles of programming in Javascript, that seems like a bug to me.
– Erhannis
Nov 24 '18 at 2:44
Then report it after you read the third essential quality here: developer.mozilla.org/en-US/docs/Tools/Debugger-API
– Randy Casburn
Nov 24 '18 at 2:51
add a comment |
Everything relevant on the internet I've read indicates that Javascript is single-threaded (aside from Web Workers, which run in a different global context and shouldn't be able to directly affect the state in the main thread). However, while debugging some code, I noticed that even while I was paused on such-and-such a line, variables kept changing, even when I didn't step over lines of code. Investigating further, I noticed that, again, even while paused in the debugger (and I wasn't touching anything), logs were logged and errors were thrown every second according to a timeout that had been set.
I am using OS: Windows 10 Enterprise, version 1803, OS build 17134.407.
I experienced the issue in Firefox 63.0.1 (64-bit).
When I tried it in Chrome 70.0.3538.102 (Official Build) (64-bit), however, the issue did not occur - pausing in the debugger appeared to pause all computation, as expected.
I can't provide any useful code, because 1. it's company code, and 2. it's a multithreading style problem, which makes it very difficult to narrow down to any given section of code. Things that might be relevant, aside from aforementioned browser differences: it's an AngularJS application, served to the browser from NodeJS. We're using $interval(), timeout(), $http, and Stomp websocket connections.
According to my understanding, this apparently multithreaded behavior should be impossible. How could this happen?
javascript multithreading
google-chrome firefox asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
Everything relevant on the internet I've read indicates that Javascript is single-threaded (aside from Web Workers, which run in a different global context and shouldn't be able to directly affect the state in the main thread). However, while debugging some code, I noticed that even while I was paused on such-and-such a line, variables kept changing, even when I didn't step over lines of code. Investigating further, I noticed that, again, even while paused in the debugger (and I wasn't touching anything), logs were logged and errors were thrown every second according to a timeout that had been set.
I am using OS: Windows 10 Enterprise, version 1803, OS build 17134.407.
I experienced the issue in Firefox 63.0.1 (64-bit).
When I tried it in Chrome 70.0.3538.102 (Official Build) (64-bit), however, the issue did not occur - pausing in the debugger appeared to pause all computation, as expected.
I can't provide any useful code, because 1. it's company code, and 2. it's a multithreading style problem, which makes it very difficult to narrow down to any given section of code. Things that might be relevant, aside from aforementioned browser differences: it's an AngularJS application, served to the browser from NodeJS. We're using $interval(), timeout(), $http, and Stomp websocket connections.
According to my understanding, this apparently multithreaded behavior should be impossible. How could this happen?
javascript multithreading
google-chrome firefox javascript multithreading
google-chrome firefox asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
asked Nov 24 '18 at 1:48
ErhannisErhannis
2,55711429
2,55711429
If there is any multiprocessing going on, it is likely the browser's internal operations that are multithreaded for this anomaly and not the JS runtime. So this seems simply like Mozilla's debugger works differently than Chrome's.
– Randy Casburn
Nov 24 '18 at 2:24
@RandyCasburn Perhaps, depending on what you mean. If the debugger is to be believed, there is more than one thread of execution. I can step through code in one place, all the while code continues to be executed somewhere else. It seems like this would be an actual bug in Firefox's debugger, rather than a simple difference of operation - if invoking the debugger invisibly and significantly breaks one of the fundamental principles of programming in Javascript, that seems like a bug to me.
– Erhannis
Nov 24 '18 at 2:44
Then report it after you read the third essential quality here: developer.mozilla.org/en-US/docs/Tools/Debugger-API
– Randy Casburn
Nov 24 '18 at 2:51
add a comment |
If there is any multiprocessing going on, it is likely the browser's internal operations that are multithreaded for this anomaly and not the JS runtime. So this seems simply like Mozilla's debugger works differently than Chrome's.
– Randy Casburn
Nov 24 '18 at 2:24
@RandyCasburn Perhaps, depending on what you mean. If the debugger is to be believed, there is more than one thread of execution. I can step through code in one place, all the while code continues to be executed somewhere else. It seems like this would be an actual bug in Firefox's debugger, rather than a simple difference of operation - if invoking the debugger invisibly and significantly breaks one of the fundamental principles of programming in Javascript, that seems like a bug to me.
– Erhannis
Nov 24 '18 at 2:44
Then report it after you read the third essential quality here: developer.mozilla.org/en-US/docs/Tools/Debugger-API
– Randy Casburn
Nov 24 '18 at 2:51
If there is any multiprocessing going on, it is likely the browser's internal operations that are multithreaded for this anomaly and not the JS runtime. So this seems simply like Mozilla's debugger works differently than Chrome's.
– Randy Casburn
Nov 24 '18 at 2:24
If there is any multiprocessing going on, it is likely the browser's internal operations that are multithreaded for this anomaly and not the JS runtime. So this seems simply like Mozilla's debugger works differently than Chrome's.
– Randy Casburn
Nov 24 '18 at 2:24
@RandyCasburn Perhaps, depending on what you mean. If the debugger is to be believed, there is more than one thread of execution. I can step through code in one place, all the while code continues to be executed somewhere else. It seems like this would be an actual bug in Firefox's debugger, rather than a simple difference of operation - if invoking the debugger invisibly and significantly breaks one of the fundamental principles of programming in Javascript, that seems like a bug to me.
– Erhannis
Nov 24 '18 at 2:44
@RandyCasburn Perhaps, depending on what you mean. If the debugger is to be believed, there is more than one thread of execution. I can step through code in one place, all the while code continues to be executed somewhere else. It seems like this would be an actual bug in Firefox's debugger, rather than a simple difference of operation - if invoking the debugger invisibly and significantly breaks one of the fundamental principles of programming in Javascript, that seems like a bug to me.
– Erhannis
Nov 24 '18 at 2:44
Then report it after you read the third essential quality here: developer.mozilla.org/en-US/docs/Tools/Debugger-API
– Randy Casburn
Nov 24 '18 at 2:51
Then report it after you read the third essential quality here: developer.mozilla.org/en-US/docs/Tools/Debugger-API
– Randy Casburn
Nov 24 '18 at 2:51
add a comment |
1 Answer
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Nodejs in fact is not single threaded. It has basically two parts:
- Javascript part. Basically Event loop processes (single threaded).
- C++ part (libuv library), thanks to V8. This part implements a thread pool with multiple thread to compute costly operations. This way we don't block the event loop.
So, maybe you can check all the modules that you are using and check their implementation. Anyone implemented in C++ uses the thread pool on the background.
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
add a comment |
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1 Answer
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Nodejs in fact is not single threaded. It has basically two parts:
- Javascript part. Basically Event loop processes (single threaded).
- C++ part (libuv library), thanks to V8. This part implements a thread pool with multiple thread to compute costly operations. This way we don't block the event loop.
So, maybe you can check all the modules that you are using and check their implementation. Anyone implemented in C++ uses the thread pool on the background.
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
add a comment |
Nodejs in fact is not single threaded. It has basically two parts:
- Javascript part. Basically Event loop processes (single threaded).
- C++ part (libuv library), thanks to V8. This part implements a thread pool with multiple thread to compute costly operations. This way we don't block the event loop.
So, maybe you can check all the modules that you are using and check their implementation. Anyone implemented in C++ uses the thread pool on the background.
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
add a comment |
Nodejs in fact is not single threaded. It has basically two parts:
- Javascript part. Basically Event loop processes (single threaded).
- C++ part (libuv library), thanks to V8. This part implements a thread pool with multiple thread to compute costly operations. This way we don't block the event loop.
So, maybe you can check all the modules that you are using and check their implementation. Anyone implemented in C++ uses the thread pool on the background.
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
Nodejs in fact is not single threaded. It has basically two parts:
- Javascript part. Basically Event loop processes (single threaded).
- C++ part (libuv library), thanks to V8. This part implements a thread pool with multiple thread to compute costly operations. This way we don't block the event loop.
So, maybe you can check all the modules that you are using and check their implementation. Anyone implemented in C++ uses the thread pool on the background.
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
answered Dec 2 '18 at 16:31
Dr. CooperDr. Cooper
12
12
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
add a comment |
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
Hmm. Except, it appears multithreaded even on the client-side. Are the C++ libraries executed client-side? I'd be very surprised; that seems like a very dangerous thing to allow a website to execute.
– Erhannis
Dec 4 '18 at 5:42
add a comment |
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If there is any multiprocessing going on, it is likely the browser's internal operations that are multithreaded for this anomaly and not the JS runtime. So this seems simply like Mozilla's debugger works differently than Chrome's.
– Randy Casburn
Nov 24 '18 at 2:24
@RandyCasburn Perhaps, depending on what you mean. If the debugger is to be believed, there is more than one thread of execution. I can step through code in one place, all the while code continues to be executed somewhere else. It seems like this would be an actual bug in Firefox's debugger, rather than a simple difference of operation - if invoking the debugger invisibly and significantly breaks one of the fundamental principles of programming in Javascript, that seems like a bug to me.
– Erhannis
Nov 24 '18 at 2:44
Then report it after you read the third essential quality here: developer.mozilla.org/en-US/docs/Tools/Debugger-API
– Randy Casburn
Nov 24 '18 at 2:51