Wikimedia Release Engineering Team/Logspam

What it is
#Logspam is the term we use to describe the category of noisy error messages in our logs. These usually do not represent actual error conditions or the errors are being ignored/purposefully not prioritized by the responsible parties (when any exist). Specific error messages that have been identified by Release Engineering are tracked in the #Wikimedia-Log-Errors Phabricator project.

Why it's a problem
Logspam is a problem because noisy logs make it more difficult to detect real problems quickly when looking at a log dashboard, for example fatalmonitor.

All deployers need to be able to quickly detect any new problems that are introduced by their newly deployed code. If important error messages are drowned out by this logspam then they might not detect more serious issues.

Incorrectly categorized log messages
The most common example of this type would be expected (or known) conditions being recorded as exceptional conditions, eg:  notices or   being logged as. This is incorrect use of logging and should be corrected.

Undefined index notices
These are a common occurrence in php code. Whenever you attempt to access an index of an array but the array does not contain the specified key, HHVM will log a notice. These are coding errors and they need to be fixed. If the array index is not always expected to exist then the code needs to check with  or   before referencing the key.