Why was my relay given the Guard flag only for it to be removed an hour+ later?

Question

My relay 'angrykitteh' (the kitten is now quite frustrated!) was blessed and granted the flag 'Guard' by the Directory Authorities as its uptime is more than 8 days and the bandwidth is deemed acceptable and fast enough. Great.

The atlas link given shows a slight peak in the 'Guard probability' but dropped immediately afterwards.

Suddenly, only an hour (or two) after being granted the flag, it was gone!

Here's the consensus now, after I discovered the flag was gone: consensus after my Guard flag disappeared http://s21.postimg.org/6r6kywl5h/2013_12_30_001800_1105x134_scrot.png

Why was the flag removed? Why are some authorities still voting to give me it? What changed?

Answer 1

Each authority votes on what they think the proper flags are for your relay.

Currently it seems 5 think angrykitteh should have the Guard flag, and 4 think it shouldn't yet. Depeding on which authorities manage to vote for which consensus, the flag might end up being set in the consensus or not.

I suppose in a while the remaining 4 authorities will also conclude that your relay is sufficiently stable and give you the guard flag.

Answer 2

I am in the same situation. My relay is jobiwan. Guard flag has been wild lately.

I believe this happens when your bandwidth is just about enough to be guard. The authorities vote 4 against 5 or 5 against 4 and small fluctuations in your consensus weight fraction can flip the balance.