Happens time to time on bb causing tests of further builds to fail. Sometimes it happens immediately after bb exception.
At least one way to leave stale mysqld is easily reproducible:
1. ssh to a remote host
2. run mtr and wait till tests are started
3. close session: ~.
4. get back to the host and observe stale mysqld
{"report":{"fcp":865.5,"ttfb":119.39999985694885,"pageVisibility":"visible","entityId":49611,"key":"jira.project.issue.view-issue","isInitial":true,"threshold":1000,"elementTimings":{},"userDeviceMemory":8,"userDeviceProcessors":64,"apdex":1,"journeyId":"bae3cb14-a54d-4c31-91d2-e8272f9267dc","navigationType":0,"readyForUser":932.5,"redirectCount":0,"resourceLoadedEnd":1020.1999998092651,"resourceLoadedStart":124.59999990463257,"resourceTiming":[{"duration":284.90000009536743,"initiatorType":"link","name":"https://jira.mariadb.org/s/2c21342762a6a02add1c328bed317ffd-CDN/lu2bu7/820016/12ta74/0a8bac35585be7fc6c9cc5a0464cd4cf/_/download/contextbatch/css/_super/batch.css","startTime":124.59999990463257,"connectEnd":0,"connectStart":0,"domainLookupEnd":0,"domainLookupStart":0,"fetchStart":124.59999990463257,"redirectEnd":0,"redirectStart":0,"requestStart":0,"responseEnd":409.5,"responseStart":0,"secureConnectionStart":0},{"duration":284.7000000476837,"initiatorType":"link","name":"https://jira.mariadb.org/s/7ebd35e77e471bc30ff0eba799ebc151-CDN/lu2bu7/820016/12ta74/8679b4946efa1a0bb029a3a22206fb5d/_/download/contextbatch/css/jira.browse.project,project.issue.navigator,jira.view.issue,jira.general,jira.global,atl.general,-_super/batch.css?agile_global_admin_condition=true&jag=true&jira.create.linked.issue=true&slack-enabled=true","startTime":124.89999985694885,"connectEnd":0,"connectStart":0,"domainLookupEnd":0,"domainLookupStart":0,"fetchStart":124.89999985694885,"redirectEnd":0,"redirectStart":0,"requestStart":0,"responseEnd":409.59999990463257,"responseStart":0,"secureConnectionStart":0},{"duration":293.59999990463257,"initiatorType":"script","name":"https://jira.mariadb.org/s/fbf975c0cce4b1abf04784eeae9ba1f4-CDN/lu2bu7/820016/12ta74/0a8bac35585be7fc6c9cc5a0464cd4cf/_/download/contextbatch/js/_super/batch.js?locale=en","startTime":125,"connectEnd":125,"connectStart":125,"domainLookupEnd":125,"domainLookupStart":125,"fetchStart":125,"redirectEnd":0,"redirectStart":0,"requestStart":125,"responseEnd":418.59999990463257,"responseStart":418.59999990463257,"secureConnectionStart":125},{"duration":382.7999999523163,"initiatorType":"script","name":"https://jira.mariadb.org/s/099b33461394b8015fc36c0a4b96e19f-CDN/lu2bu7/820016/12ta74/8679b4946efa1a0bb029a3a22206fb5d/_/download/contextbatch/js/jira.browse.project,project.issue.navigator,jira.view.issue,jira.general,jira.global,atl.general,-_super/batch.js?agile_global_admin_condition=true&jag=true&jira.create.linked.issue=true&locale=en&slack-enabled=true","startTime":125.09999990463257,"connectEnd":125.09999990463257,"connectStart":125.09999990463257,"domainLookupEnd":125.09999990463257,"domainLookupStart":125.09999990463257,"fetchStart":125.09999990463257,"redirectEnd":0,"redirectStart":0,"requestStart":125.09999990463257,"responseEnd":507.89999985694885,"responseStart":507.89999985694885,"secureConnectionStart":125.09999990463257},{"duration":386.5,"initiatorType":"script","name":"https://jira.mariadb.org/s/94c15bff32baef80f4096a08aceae8bc-CDN/lu2bu7/820016/12ta74/c92c0caa9a024ae85b0ebdbed7fb4bd7/_/download/contextbatch/js/atl.global,-_super/batch.js?locale=en","startTime":125.19999980926514,"connectEnd":125.19999980926514,"connectStart":125.19999980926514,"domainLookupEnd":125.19999980926514,"domainLookupStart":125.19999980926514,"fetchStart":125.19999980926514,"redirectEnd":0,"redirectStart":0,"requestStart":125.19999980926514,"responseEnd":511.69999980926514,"responseStart":511.69999980926514,"secureConnectionStart":125.19999980926514},{"duration":386.90000009536743,"initiatorType":"script","name":"https://jira.mariadb.org/s/d41d8cd98f00b204e9800998ecf8427e-CDN/lu2bu7/820016/12ta74/1.0/_/download/batch/jira.webresources:calendar-en/jira.webresources:calendar-en.js","startTime":125.39999985694885,"connectEnd":125.39999985694885,"connectStart":125.39999985694885,"domainLookupEnd":125.39999985694885,"domainLookupStart":125.39999985694885,"fetchStart":125.39999985694885,"redirectEnd":0,"redirectStart":0,"requestStart":125.39999985694885,"responseEnd":512.2999999523163,"responseStart":512.2999999523163,"secureConnectionStart":125.39999985694885},{"duration":387.5,"initiatorType":"link","name":"https://jira.mariadb.org/s/b04b06a02d1959df322d9cded3aeecc1-CDN/lu2bu7/820016/12ta74/a2ff6aa845ffc9a1d22fe23d9ee791fc/_/download/contextbatch/css/jira.global.look-and-feel,-_super/batch.css","startTime":125.5,"connectEnd":0,"connectStart":0,"domainLookupEnd":0,"domainLookupStart":0,"fetchStart":125.5,"redirectEnd":0,"redirectStart":0,"requestStart":0,"responseEnd":513,"responseStart":0,"secureConnectionStart":0},{"duration":387.09999990463257,"initiatorType":"script","name":"https://jira.mariadb.org/s/d41d8cd98f00b204e9800998ecf8427e-CDN/lu2bu7/820016/12ta74/1.0/_/download/batch/jira.webresources:calendar-localisation-moment/jira.webresources:calendar-localisation-moment.js","startTime":125.5,"connectEnd":125.5,"connectStart":125.5,"domainLookupEnd":125.5,"domainLookupStart":125.5,"fetchStart":125.5,"redirectEnd":0,"redirectStart":0,"requestStart":125.5,"responseEnd":512.5999999046326,"responseStart":512.5999999046326,"secureConnectionStart":125.5},{"duration":387.40000009536743,"initiatorType":"script","name":"https://jira.mariadb.org/rest/api/1.0/shortcuts/820016/47140b6e0a9bc2e4913da06536125810/shortcuts.js?context=issuenavigation&context=issueaction","startTime":125.59999990463257,"connectEnd":125.59999990463257,"connectStart":125.59999990463257,"domainLookupEnd":125.59999990463257,"domainLookupStart":125.59999990463257,"fetchStart":125.59999990463257,"redirectEnd":0,"redirectStart":0,"requestStart":125.59999990463257,"responseEnd":513,"responseStart":513,"secureConnectionStart":125.59999990463257},{"duration":387.80000019073486,"initiatorType":"link","name":"https://jira.mariadb.org/s/3ac36323ba5e4eb0af2aa7ac7211b4bb-CDN/lu2bu7/820016/12ta74/d176f0986478cc64f24226b3d20c140d/_/download/contextbatch/css/com.atlassian.jira.projects.sidebar.init,-_super,-project.issue.navigator,-jira.view.issue/batch.css?jira.create.linked.issue=true","startTime":125.69999980926514,"connectEnd":0,"connectStart":0,"domainLookupEnd":0,"domainLookupStart":0,"fetchStart":125.69999980926514,"redirectEnd":0,"redirectStart":0,"requestStart":0,"responseEnd":513.5,"responseStart":0,"secureConnectionStart":0},{"duration":387.7000000476837,"initiatorType":"script","name":"https://jira.mariadb.org/s/3339d87fa2538a859872f2df449bf8d0-CDN/lu2bu7/820016/12ta74/d176f0986478cc64f24226b3d20c140d/_/download/contextbatch/js/com.atlassian.jira.projects.sidebar.init,-_super,-project.issue.navigator,-jira.view.issue/batch.js?jira.create.linked.issue=true&locale=en","startTime":125.89999985694885,"connectEnd":125.89999985694885,"connectStart":125.89999985694885,"domainLookupEnd":125.89999985694885,"domainLookupStart":125.89999985694885,"fetchStart":125.89999985694885,"redirectEnd":0,"redirectStart":0,"requestStart":125.89999985694885,"responseEnd":513.5999999046326,"responseStart":513.5999999046326,"secureConnectionStart":125.89999985694885},{"duration":477.40000009536743,"initiatorType":"script","name":"https://jira.mariadb.org/s/d41d8cd98f00b204e9800998ecf8427e-CDN/lu2bu7/820016/12ta74/1.0/_/download/batch/jira.webresources:bigpipe-js/jira.webresources:bigpipe-js.js","startTime":131.09999990463257,"connectEnd":131.09999990463257,"connectStart":131.09999990463257,"domainLookupEnd":131.09999990463257,"domainLookupStart":131.09999990463257,"fetchStart":131.09999990463257,"redirectEnd":0,"redirectStart":0,"requestStart":131.09999990463257,"responseEnd":608.5,"responseStart":608.5,"secureConnectionStart":131.09999990463257},{"duration":889,"initiatorType":"script","name":"https://jira.mariadb.org/s/d41d8cd98f00b204e9800998ecf8427e-CDN/lu2bu7/820016/12ta74/1.0/_/download/batch/jira.webresources:bigpipe-init/jira.webresources:bigpipe-init.js","startTime":131.19999980926514,"connectEnd":131.19999980926514,"connectStart":131.19999980926514,"domainLookupEnd":131.19999980926514,"domainLookupStart":131.19999980926514,"fetchStart":131.19999980926514,"redirectEnd":0,"redirectStart":0,"requestStart":131.19999980926514,"responseEnd":1020.1999998092651,"responseStart":1020.1999998092651,"secureConnectionStart":131.19999980926514},{"duration":41.39999985694885,"initiatorType":"xmlhttprequest","name":"https://jira.mariadb.org/rest/webResources/1.0/resources","startTime":568.2999999523163,"connectEnd":568.2999999523163,"connectStart":568.2999999523163,"domainLookupEnd":568.2999999523163,"domainLookupStart":568.2999999523163,"fetchStart":568.2999999523163,"redirectEnd":0,"redirectStart":0,"requestStart":568.2999999523163,"responseEnd":609.6999998092651,"responseStart":609.6999998092651,"secureConnectionStart":568.2999999523163}],"fetchStart":0,"domainLookupStart":0,"domainLookupEnd":0,"connectStart":0,"connectEnd":0,"requestStart":2,"responseStart":119,"responseEnd":124,"domLoading":122,"domInteractive":1037,"domContentLoadedEventStart":1037,"domContentLoadedEventEnd":1074,"domComplete":1931,"loadEventStart":1931,"loadEventEnd":1933,"userAgent":"Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)","marks":[{"name":"bigPipe.sidebar-id.start","time":1022.2999999523163},{"name":"bigPipe.sidebar-id.end","time":1023.0999999046326},{"name":"bigPipe.activity-panel-pipe-id.start","time":1023.1999998092651},{"name":"bigPipe.activity-panel-pipe-id.end","time":1025.3999998569489},{"name":"activityTabFullyLoaded","time":1080}],"measures":[],"correlationId":"94425cc66d74ee","effectiveType":"4g","downlink":10,"rtt":0,"serverDuration":68,"dbReadsTimeInMs":12,"dbConnsTimeInMs":20,"applicationHash":"9d11dbea5f4be3d4cc21f03a88dd11d8c8687422","experiments":[]}}