I'm using the built-in Mediawiki search engine. We just updated from 1.30.0 to 1.31.0. Since the update, search results are unstable. The same search term gives different results in different web browsers. We also see different results across browser sessions. Any advice on how I can troubleshoot this?
Thank you!
-Michael
Hi!
I'm using the built-in Mediawiki search engine. We just updated from 1.30.0 to 1.31.0. Since the update, search results are unstable. The same search term gives different results in different web browsers. We also see different results across browser sessions. Any advice on how I can troubleshoot this?
Could you provide more info - which search you're talking about (URL might help, or description of the sequence of actions), which terms, what you're getting in different cases? Some search results might depend on your preferences or user language selected, so there might be difference, e.g. for different logged-in users.
Thanks,
I'm running a self-hosted wiki, so unfortunately can't provide a URL. The search is performed on the standard [[Special:Search]] page. It may matter that we're running the wiki on two servers, using Percona MySQL for data replication between the servers. A load balancer sends users to whichever server has the fewest active connections.
-----Original Message----- From: Stas Malyshev [mailto:smalyshev@wikimedia.org] Sent: Tuesday, March 05, 2019 5:39 PM To: Wikimedia developers wikitech-l@lists.wikimedia.org; Hogan (US), Michael C Michael.C.Hogan2@boeing.com Subject: Re: [Wikitech-l] Unstable search results - possible causes
Hi!
I'm using the built-in Mediawiki search engine. We just updated from 1.30.0 to 1.31.0. Since the update, search results are unstable. The same search term gives different results in different web browsers. We also see different results across browser sessions. Any advice on how I can troubleshoot this?
Could you provide more info - which search you're talking about (URL might help, or description of the sequence of actions), which terms, what you're getting in different cases? Some search results might depend on your preferences or user language selected, so there might be difference, e.g. for different logged-in users.
Thanks, -- Stas Malyshev smalyshev@wikimedia.org
"Hogan (US), Michael C" Michael.C.Hogan2@boeing.com writes:
It may matter that we're running the wiki on two servers, using Percona MySQL for data replication between the servers.
I'm guessing that this is the cause.
If you're using the XtraDB Cluster, you have probably set PXC Strict Mode to permissive or disabled it and, as a result, there is some inconsistency between the two databases.
Mark.
A load balancer sends users to whichever server has the fewest active connections.
That could be it- I don't think there has been a lot of focus on full read-read stability on Mediawiki, so some stickiness may be needed for some queries. Things that worry about that is: potential non deterministic queries, which can return results differently depending on the physical distribution of the rows. Those are mistakes and are corrected when detected (I am trying to force strict sql mode into our CI), but because not many people run mediawiki in large clusters AND use the internal search engine it could have been missed. To verify it is that- without any writes, rebuild the tables involved and they would return results in different order.
Please share details about versions, url and queries, or contact us privately in Phabricator if you cannot share those details publicly.
Percona Cluster/Galera is not officially supported as far as I know, and while it should work with no problem because it has the same sql interface, there are no specific controls for the distributed nature of such cluster (unlike regular replication, which has specific functionality). Enabling the chronology protector with heartbeat may work for PXC, but I have not tested it. Another option is to use PXC in a failover-only mode, being sticky to a primary server and leaving the other nodes for failover, backups, etc.
On Wed, Mar 6, 2019 at 3:05 AM Hogan (US), Michael C Michael.C.Hogan2@boeing.com wrote:
I'm running a self-hosted wiki, so unfortunately can't provide a URL. The search is performed on the standard [[Special:Search]] page. It may matter that we're running the wiki on two servers, using Percona MySQL for data replication between the servers. A load balancer sends users to whichever server has the fewest active connections.
-----Original Message----- From: Stas Malyshev [mailto:smalyshev@wikimedia.org] Sent: Tuesday, March 05, 2019 5:39 PM To: Wikimedia developers wikitech-l@lists.wikimedia.org; Hogan (US), Michael C Michael.C.Hogan2@boeing.com Subject: Re: [Wikitech-l] Unstable search results - possible causes
Hi!
I'm using the built-in Mediawiki search engine. We just updated from 1.30.0 to 1.31.0. Since the update, search results are unstable. The same search term gives different results in different web browsers. We also see different results across browser sessions. Any advice on how I can troubleshoot this?
Could you provide more info - which search you're talking about (URL might help, or description of the sequence of actions), which terms, what you're getting in different cases? Some search results might depend on your preferences or user language selected, so there might be difference, e.g. for different logged-in users.
Thanks,
Stas Malyshev smalyshev@wikimedia.org _______________________________________________ Wikitech-l mailing list Wikitech-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l
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