Realtime visits error (see #19129)

[AdamSGit]

I got exactly the same error that is described in issue #19129 after migrating my matomo installation from php 7.4 to 8.1 in a docker container. The original issue also seemed to be related to php >= 8. The issue was closed without any solution or further investigation a year ago.

Environment

• Matomo Version: 4.14.2
• PHP Version: 8.1.20
• PHP modules: Core, ctype, curl, date, dom, filter, gd, hash, json, libxml, mysqlnd, openssl, pcre, PDO, pdo_mysql, readline, Reflection, session, SimpleXML, SPL, standard, xml, Zend OPcache, zlib
• Mariadb version: 11.0.2
• Server Operating System: Alpine linux in a docker container
• Additionally installed plugins: AbTesting, Actions, Annotations, Contents, CustomAlerts, CustomDimensions, CustomJsTracker, CustomVariables, DBStats, Dashboard, DeviceDetectorCache, DeviceNetworkInformation, DevicePixelRatio, DevicePlugins, DevicesDetection, Diagnostics, DiagnosticsExtended, Ecommerce, Events, FacebookPageWidgetByAmperage, Feedback, GeoIp2, Goals, Heartbeat, HeatmapSessionRecording, ImageGraph, Insights, IntranetMeasurable, KPIWidgets, Live, Login, MarketingCampaignsReporting, Marketplace, MobileAppMeasurable, MobileMessaging, Monolog, MultiSites, Overlay, PagePerformance, PrivacyManager, ProfessionalServices, Provider, QueuedTracking, Referrers, ReferrersManager, Resolution, RssWidget, SEO, ScheduledReports, SecurityInfo, SegmentEditor, ShortcodeTracker, Sms77, TagManager, Tour, Transitions, TreemapVisualization, TwoFactorAuth, UserCountry, UserCountryMap, UserId, UserLanguage, VisitFrequency, VisitTime, VisitorInterest, VisitsSummary, Widgetize

[sgiehl]

Hey @AdamSGit, sorry to hear you have the same problem.
Unfortunatelly we were not able to reproduce it back than, nor am I having the problem right now.

Are you maybe able to provide some further details? It looks like you and the other one having that issue are both using MariaDB. As I'm currently testing with MySQL, maybe that could be the reason.
Do you have some logging in MariaDB? Could you check if you are able to look up the query that produces the error?

[AdamSGit]

Ok, found the cause. Mbstring module was missing in php installation.

The error location is in plugins/Live/Model.php on line 427. This is this part of the code :

    if (0 === stripos($query['sql'], 'SELECT')) {
        $query['sql'] = 'SELECT /* Live.getCounters */' . mb_substr($query['sql'], strlen('SELECT'));
    }

Which, without mbstring module installed, would result to the following query : SELECT /* Live.getCounters */

Don't know if this is an exception, or if others parts of the code use the same logic, but it would need either :

• To throw an error with helpful message in case of use of mbstring module if not installed
• Detecting the availability of mb_functions, with a fallback to standard functions if not
• Or, at least, list mbstring in the Other required extensions section of system checks

[sgiehl]

Thanks for the update @AdamSGit
That's quite interesting as we actually have the mbstring polyfill from symfony included, so that method shouldn't cause issues.
So guess we might need to check if the polyfill works as expected...

[sgiehl]

I've now checked that locally again. Matomo works smoothly with mbstring disabled. mbstring methods are actually even used all across Matomo so it would be weird if that only fails in the reatime reports, but work everywhere else.
I'll close this one, as it's most likely related to some server configuration issue.