Use sendBeacon to send kernel shutdown request.

[trungleduc]

References

Support for synchronous use of XMLHTTPRequest() during page unloads is removed from Chrome (https://www.chromestatus.com/feature/4664843055398912).

Code changes

Use sendBeacon to send kernel shutdown request on beforeunload event

User-facing changes

N/A

Backwards-incompatible changes

N/A

[github-actions]

Benchmark report

The execution time (in milliseconds) are grouped by test file, test type and browser.
For each case, the following values are computed: min <- [1st quartile - median - 3rd quartile] -> max.

Results table

Test file	basics.ipynb	bqplot.ipynb	dashboard.ipynb	gridspecLayout.ipynb	interactive.ipynb	ipympl.ipynb	ipyvolume.ipynb	multiple_widgets.ipynb	query-strings.ipynb
Render
chromium
actual	2619 <- [2702 - 2783 - 2956] -> 3459	2473 <- [2525 - 2617 - 2666] -> 2785	2586 <- [2637 - 2650 - 2665] -> 2795	3146 <- [3160 - 3171 - 3221] -> 3224	1872 <- [1896 - 1905 - 1975] -> 2036	2553 <- [2589 - 2611 - 2681] -> 2758	8847 <- [10887 - 11787 - 14680] -> 15052	9442 <- [9468 - 9509 - 9539] -> 9692	1180 <- [1204 - 1278 - 1286] -> 1308
expected	3379 <- [3442 - 3517 - 3701] -> 3876	2976 <- [3227 - 3321 - 3421] -> 3604	3608 <- [3623 - 3709 - 3793] -> 3825	4453 <- [4453 - 4523 - 4661] -> 4748	2559 <- [2655 - 2656 - 2660] -> 2674	3982 <- [4079 - 4213 - 4356] -> 4743	12183 <- [18509 - 19553 - 20811] -> 21515	15319 <- [15660 - 15796 - 15912] -> 16056	1517 <- [1920 - 1997 - 2103] -> 2113

❗ Test metadata have changed

--- /dev/fd/63	2021-09-21 20:48:39.610714122 +0000
+++ /dev/fd/62	2021-09-21 20:48:39.614714197 +0000
@@ -8,27 +8,27 @@
   },
   "systemInformation": {
     "cpu": {
-      "brand": "Xeon® Platinum 8272CL",
+      "brand": "Xeon® E5-2673 v3",
       "cache": {
         "l1d": 65536,
         "l1i": 65536,
-        "l2": 2097152,
-        "l3": 36700160
+        "l2": 524288,
+        "l3": 31457280
       },
       "cores": 2,
       "family": "6",
-      "flags": "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single pti fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clflushopt avx512cd avx512bw avx512vl xsaveopt xsavec xsaves md_clear",
+      "flags": "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm invpcid_single pti fsgsbase bmi1 avx2 smep bmi2 erms invpcid xsaveopt md_clear",
       "governor": "",
       "manufacturer": "Intel®",
-      "model": "85",
+      "model": "63",
       "physicalCores": 2,
       "processors": 1,
       "revision": "",
       "socket": "",
-      "speed": 2.6,
+      "speed": 2.4,
       "speedMax": null,
       "speedMin": null,
-      "stepping": "7",
+      "stepping": "2",
       "vendor": "GenuineIntel",
       "virtualization": false,
       "voltage": ""
@@ -42,11 +42,11 @@
       "codename": "Focal Fossa",
       "codepage": "UTF-8",
       "distro": "Ubuntu",
-      "kernel": "5.8.0-1041-azure",
+      "kernel": "5.8.0-1040-azure",
       "logofile": "ubuntu",
       "platform": "linux",
       "release": "20.04.3 LTS",
-      "serial": "faac5b9e00cf4ae3b2d2c013e98d933a",
+      "serial": "cfc067bfcb844f35865e279a1b0e66c5",
       "servicepack": "",
       "uefi": false
     }

[jtpio]

Thanks @trungleduc.

Re-reading the discussion in #612, I think the original intent was to be able to set that flag to false so the request doesn't get aborted in the middle of the page unload.

[jtpio]

is removed from Chrome (https://www.chromestatus.com/feature/4664843055398912)

Given this:

"While this is reasonable, there are no good reasons to use synchronous XHR. Instead SendBeacon, Fetch keep-alive should be used (in addition to sending analytics periodically and on pagevisibility etc.)."

Maybe we should give another look at using sendBeacon which was experimented with in #612 (comment)

[trungleduc]

Thanks @jtpio, sorry for didn't read the discussion in #612 before. I'll open an issue and try the sendBeacon with this PR

[jtpio]

Thanks!

Testing on Binder with this link:

https://mybinder.org/v2/gh/trungleduc/voila/fix-kernel-shutdown?urlpath=voila%2Ftree%2Fnotebooks

It looks like the request is correctly sent, but returns a 405:

send-beacon-binder.mp4

Not sure if it's a limitation on the Binder side. Voila runs as a server extension there and the diff looks good w.r.t that.

[trungleduc]

It looks like the POST URL https://hub.gke2.mybinder.org/voila/api/shutdown/... is not correct since Voila server is exposed at https://hub.gke2.mybinder.org/user/trungleduc-voila-mxw256mu/. It should send request to something like https://hub.gke2.mybinder.org/user/trungleduc-voila-mxw256mu/voila/api/shutdown/... to make it works

[jtpio]

Ah good catch, then that would explain why.

[trungleduc]

it seems to work now in Binder

[jtpio]

Thanks @trungleduc!