|The Gleeful Grognard|
It lasts the whole turn.
If it had given the bonus only for the triggering attack it would had said that, like the rogue nimble dodge reaction.
PFS Legal Nimble Dodge ReactionFeat 1Rogue
Source Core Rulebook pg. 183
Requirements You are not encumbered.
Trigger A creature targets you with an attack and you can see the attacker.
You deftly dodge out of the way, gaining a +2 circumstance bonus to AC against the triggering attack.