Database queries via PHP - Cloud

6 Oct 2017

I'm trying to debug a PHP script that runs various queries against the enwiki_p
database on the new server (enwiki.analytics.db.svc.eqiad.wmflabs), and I've run into
a wall. To simplify the question, I'm running three SQL queries in succession using
mysqli_query. The first two queries return results as expected, but the third one
doesn't. It just hangs the script indefinitely until the server times out. If I go
into the MariaDB client while the script is running and try SHOW FULL PROCESSLIST, it
shows the script's connection is sleeping. 

Here's what has me stumped: if I comment out the first two queries and just submit the
third, it runs fine and returns the data I am looking for. So I know it's not an error
in my query string or in PHP syntax. Am I running up against some limit on successive
queries? What should I be doing differently?

If it makes a difference, none of these are extremely slow queries. Each one separately
completes in about 30-60 seconds depending on server load. 

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