Hi there I need some help on an issue we have been having since we upgrading from silverstripe 3.1 to 3.4. We also changed hosting companies to siteground.
We are getting an internal server error every 4 hours for about 3 minutes. About 80% of our web page will display an internal server error. After 3 minutes everything will come right again. The timing is exactly at 1:00pm 5:00pm 9:00pm 1:00am and 5:00am.
I enabled silverstripe logging on monday
In the log,
The error that occur is

[24-Nov-2016 02:03:10] Error at framework/model/connect/DBConnector.php line 55: Uncaught SS_DatabaseException: Couldn't run query:

SELECT DISTINCT "SiteTree_Live"."ClassName", "SiteTree_Live"."LastEdited", "SiteTree_Live"."Created", "SiteTree_Live"."URLSegment", "SiteTree_Live"."Title", "SiteTree_Live"."MenuTitle", "SiteTree_Live"."Content", "SiteTree_Live"."MetaDescription", "SiteTree_Live"."ExtraMeta", "SiteTree_Live"."ShowInMenus", "SiteTree_Live"."ShowInSearch", "SiteTree_Live"."Sort", "SiteTree_Live"."HasBrokenFile", "SiteTree_Live"."HasBrokenLink", "SiteTree_Live"."ReportClass", "SiteTree_Live"."CanViewType", "SiteTree_Live"."CanEditType", "SiteTree_Live"."HideOnSitemap", "SiteTree_Live"."Version", "SiteTree_Live"."ParentID", "SiteTree_Live"."ID",
CASE WHEN "SiteTree_Live"."ClassName" IS NOT NULL THEN "SiteTree_Live"."ClassName"
ELSE 'SiteTree' END AS "RecordClassName"

FROM "SiteTree_Live"

WHERE ("SiteTree_Live"."URLSegment" = ?)
AND ("SiteTree_Live"."ParentID" = ?)

ORDER BY "SiteTree_Live"."Sort" ASC

LIMIT 1

Prepared statement needs to be re-prepared (http://www.pertronic.com.au/news/)

[24-Nov-2016 02:03:24] Error at framework/model/connect/DBConnector.php line 55: Uncaught SS_DatabaseException: Couldn't run query:

SELECT DISTINCT "SiteTree_Live"."ClassName", "SiteTree_Live"."LastEdited", "SiteTree_Live"."Created", "SiteTree_Live"."URLSegment", "SiteTree_Live"."Title", "SiteTree_Live"."MenuTitle", "SiteTree_Live"."Content", "SiteTree_Live"."MetaDescription", "SiteTree_Live"."ExtraMeta", "SiteTree_Live"."ShowInMenus", "SiteTree_Live"."ShowInSearch", "SiteTree_Live"."Sort", "SiteTree_Live"."HasBrokenFile", "SiteTree_Live"."HasBrokenLink", "SiteTree_Live"."ReportClass", "SiteTree_Live"."CanViewType", "SiteTree_Live"."CanEditType", "SiteTree_Live"."HideOnSitemap", "SiteTree_Live"."Version", "SiteTree_Live"."ParentID", "SiteTree_Live"."ID",
CASE WHEN "SiteTree_Live"."ClassName" IS NOT NULL THEN "SiteTree_Live"."ClassName"
ELSE 'SiteTree' END AS "RecordClassName"

FROM "SiteTree_Live"

WHERE ("SiteTree_Live"."URLSegment" = ?)
AND ("SiteTree_Live"."ParentID" = ?)

ORDER BY "SiteTree_Live"."Sort" ASC

LIMIT 1

Prepared statement needs to be re-prepared (http://pertronic.com.au/resources/online-tools/)

Has anyone come accross this error before?

I have done a bit if searching on google and wondered if this is a MYSQL bug
and happens during auto back of the database. Which would explain why our site goes down exactly at the precise times above .

Any help would be greatly appreciated.

Stu

Looks like a lot of people have ran into this at some point - I see a lot of comments referring to mysqldump being in progress so you may be right. It shouldn't be a SilverStripe upgrade problem, I think.

You could try temporary downgrading back to 3.2 to see if it's maybe a difference in how MySQL queries are executed in 3.5, but I doubt that...

We have sorted the issue out now.
I switched from MySQLi to PDO by updating the mysite/_config.php file.
This stop the errors.
Info about the issue in the link below

http://bugs.mysql.com/bug.php?id=42041

Stu