I saw a spike in these errors today from 0/hour to ~500/hour from 8/22 @ 21:30 to 8/23 @ 04:00.
from /srv/parsoid-testing/src/Utils/PipelineUtils.php(415)
#0 [internal function]: MediaWiki\Exception\MWExceptionHandler::handleError(int, string, string, string)
#1 /srv/mediawiki/php-1.45.0-wmf.15/includes/debug/MWDebug.php(386): trigger_error(string, int)
#2 /srv/mediawiki/php-1.45.0-wmf.15/includes/debug/MWDebug.php(357): MediaWiki\Debug\MWDebug::sendRawDeprecated(string, bool, string)
#3 /srv/mediawiki/php-1.45.0-wmf.15/includes/debug/MWDebug.php(238): MediaWiki\Debug\MWDebug::deprecatedMsg(string, string, string, int)
#4 /srv/mediawiki/php-1.45.0-wmf.15/includes/parser/Parsoid/Config/SiteConfig.php(891): MediaWiki\Debug\MWDebug::deprecated(string, string, string, int)
#5 /srv/parsoid-testing/src/Utils/ContentUtils.php(316): MediaWiki\Parser\Parsoid\Config\SiteConfig->deprecated(string, string)
#6 /srv/parsoid-testing/src/Utils/PipelineUtils.php(415): Wikimedia\Parsoid\Utils\ContentUtils::shiftDSR(Wikimedia\Parsoid\Config\Env, Wikimedia\Parsoid\DOM\DocumentFragment, Closure, Wikimedia\Parsoid\Ext\ParsoidExtensionAPI)
#7 /srv/parsoid-testing/src/Utils/PipelineUtils.php(482): Wikimedia\Parsoid\Utils\PipelineUtils::expandAttrValueToDOM(Wikimedia\Parsoid\Config\Env, Wikimedia\Parsoid\Wt2Html\PageConfigFrame, array, bool, bool)
#8 /srv/parsoid-testing/src/Wt2Html/TT/AttributeExpander.php(612): Wikimedia\Parsoid\Utils\PipelineUtils::expandAttrValuesToDOM(Wikimedia\Parsoid\Config\Env, Wikimedia\Parsoid\Wt2Html\PageConfigFrame, array, bool, bool)
#9 /srv/parsoid-testing/src/Wt2Html/TT/AttributeExpander.php(656): Wikimedia\Parsoid\Wt2Html\TT\AttributeExpander->buildExpandedAttrs(Wikimedia\Parsoid\Tokens\TagTk, array)
#10 /srv/parsoid-testing/src/Wt2Html/TT/AttributeExpander.php(728): Wikimedia\Parsoid\Wt2Html\TT\AttributeExpander->processComplexAttributes(Wikimedia\Parsoid\Tokens\TagTk)
#11 /srv/parsoid-testing/src/Wt2Html/TT/UniversalTokenHandler.php(62): Wikimedia\Parsoid\Wt2Html\TT\AttributeExpander->onAny(Wikimedia\Parsoid\Tokens\TagTk)
#12 /srv/parsoid-testing/src/Wt2Html/TokenHandlerPipeline.php(129): Wikimedia\Parsoid\Wt2Html\TT\UniversalTokenHandler->process(array)
#13 /srv/parsoid-testing/src/Wt2Html/TokenHandlerPipeline.php(193): Wikimedia\Parsoid\Wt2Html\TokenHandlerPipeline->processChunk(array)
#14 /srv/parsoid-testing/src/Wt2Html/TokenHandlerPipeline.php(191): Wikimedia\Parsoid\Wt2Html\TokenHandlerPipeline->processChunkily(string, array)
#15 /srv/parsoid-testing/src/Wt2Html/TreeBuilder/TreeBuilderStage.php(502): Wikimedia\Parsoid\Wt2Html\TokenHandlerPipeline->processChunkily(string, array)
#16 [internal function]: Wikimedia\Parsoid\Wt2Html\TreeBuilder\TreeBuilderStage->processChunkily(string, array)
#17 /srv/parsoid-testing/src/Wt2Html/DOMProcessorPipeline.php(196): Generator->current()
#18 /srv/parsoid-testing/src/Wt2Html/ParserPipeline.php(164): Wikimedia\Parsoid\Wt2Html\DOMProcessorPipeline->processChunkily(string, array)
#19 /srv/parsoid-testing/src/Wt2Html/ParserPipelineFactory.php(619): Wikimedia\Parsoid\Wt2Html\ParserPipeline->parseChunkily(string, array)
#20 /srv/parsoid-testing/src/Wikitext/ContentModelHandler.php(187): Wikimedia\Parsoid\Wt2Html\ParserPipelineFactory->parse(string)
#21 /srv/parsoid-testing/src/Parsoid.php(198): Wikimedia\Parsoid\Wikitext\ContentModelHandler->toDOM(Wikimedia\Parsoid\Ext\ParsoidExtensionAPI, null)
#22 /srv/parsoid-testing/src/Parsoid.php(264): Wikimedia\Parsoid\Parsoid->parseWikitext(MediaWiki\Parser\Parsoid\Config\PageConfig, MediaWiki\Parser\ParserOutput, array, null)
#23 /srv/mediawiki/php-1.45.0-wmf.15/includes/parser/Parsoid/ParsoidParser.php(166): Wikimedia\Parsoid\Parsoid->wikitext2html(MediaWiki\Parser\Parsoid\Config\PageConfig, array, null, MediaWiki\Parser\ParserOutput)
#24 /srv/mediawiki/php-1.45.0-wmf.15/includes/parser/Parsoid/ParsoidParser.php(294): MediaWiki\Parser\Parsoid\ParsoidParser->genParserOutput(MediaWiki\Parser\Parsoid\Config\PageConfig, MediaWiki\Parser\ParserOptions, null)
#25 /srv/mediawiki/php-1.45.0-wmf.15/includes/content/WikitextContentHandler.php(389): MediaWiki\Parser\Parsoid\ParsoidParser->parse(string, MediaWiki\Title\Title, MediaWiki\Parser\ParserOptions, bool, bool, int, null)
#26 /srv/mediawiki/php-1.45.0-wmf.15/includes/content/ContentHandler.php(1695): MediaWiki\Content\WikitextContentHandler->fillParserOutput(MediaWiki\Content\WikitextContent, MediaWiki\Content\Renderer\ContentParseParams, MediaWiki\Parser\ParserOutput)
#27 /srv/mediawiki/php-1.45.0-wmf.15/includes/content/Renderer/ContentRenderer.php(75): MediaWiki\Content\ContentHandler->getParserOutput(MediaWiki\Content\WikitextContent, MediaWiki\Content\Renderer\ContentParseParams)
#28 /srv/mediawiki/php-1.45.0-wmf.15/includes/Revision/RenderedRevision.php(261): MediaWiki\Content\Renderer\ContentRenderer->getParserOutput(MediaWiki\Content\WikitextContent, MediaWiki\Page\PageIdentityValue, MediaWiki\Revision\MutableRevisionRecord, MediaWiki\Parser\ParserOptions, array)
#29 /srv/mediawiki/php-1.45.0-wmf.15/includes/Revision/RenderedRevision.php(233): MediaWiki\Revision\RenderedRevision->getSlotParserOutputUncached(MediaWiki\Content\WikitextContent, array)
#30 /srv/mediawiki/php-1.45.0-wmf.15/includes/Revision/RevisionRenderer.php(237): MediaWiki\Revision\RenderedRevision->getSlotParserOutput(string, array)
#31 /srv/mediawiki/php-1.45.0-wmf.15/includes/Revision/RevisionRenderer.php(170): MediaWiki\Revision\RevisionRenderer->combineSlotOutput(MediaWiki\Revision\RenderedRevision, MediaWiki\Parser\ParserOptions, array)
#32 /srv/mediawiki/php-1.45.0-wmf.15/includes/Revision/RenderedRevision.php(196): MediaWiki\Revision\RevisionRenderer->MediaWiki\Revision\{closure}(MediaWiki\Revision\RenderedRevision, array)
#33 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Handler/Helper/HtmlOutputRendererHelper.php(992): MediaWiki\Revision\RenderedRevision->getRevisionParserOutput()
#34 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Handler/Helper/HtmlOutputRendererHelper.php(944): MediaWiki\Rest\Handler\Helper\HtmlOutputRendererHelper->parseUncacheable(MediaWiki\Page\PageStoreRecord, MediaWiki\Revision\MutableRevisionRecord, bool)
#35 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Handler/Helper/HtmlOutputRendererHelper.php(661): MediaWiki\Rest\Handler\Helper\HtmlOutputRendererHelper->getParserOutputInternal()
#36 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Handler/Helper/HtmlOutputRendererHelper.php(755): MediaWiki\Rest\Handler\Helper\HtmlOutputRendererHelper->getParserOutput()
#37 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Handler/ParsoidHandler.php(741): MediaWiki\Rest\Handler\Helper\HtmlOutputRendererHelper->getPageBundle()
#38 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Handler/TransformHandler.php(213): MediaWiki\Rest\Handler\ParsoidHandler->wt2html(MediaWiki\Parser\Parsoid\Config\PageConfig, array, string)
#39 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Module/Module.php(418): MediaWiki\Rest\Handler\TransformHandler->execute()
#40 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Module/Module.php(301): MediaWiki\Rest\Module\Module->executeHandler(MWParsoid\Rest\Handler\TransformHandler)
#41 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Router.php(485): MediaWiki\Rest\Module\Module->execute(string, MediaWiki\Rest\RequestFromGlobals)
#42 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/Router.php(444): MediaWiki\Rest\Router->doExecute(string, MediaWiki\Rest\RequestFromGlobals)
#43 /srv/mediawiki/php-1.45.0-wmf.15/includes/Rest/EntryPoint.php(207): MediaWiki\Rest\Router->execute(MediaWiki\Rest\RequestFromGlobals)
#44 /srv/mediawiki/php-1.45.0-wmf.15/includes/MediaWikiEntryPoint.php(198): MediaWiki\Rest\EntryPoint->execute()
#45 /srv/mediawiki/php-1.45.0-wmf.15/rest.php(39): MediaWiki\MediaWikiEntryPoint->run()
#46 /srv/mediawiki/w/rest.php(3): require(string)
#47 {main}