Фото: IMAGO / Leco Viana / Reuters
Continue reading...。PDF资料对此有专业解读
Go to BBCAfrica.com for more news from the African continent.，推荐阅读电影获取更多信息
The commit protocol in the paper actually starts simple: clients send log records straight to Pending Update (PU) queues. But the problem with this naive direct-write approach is that if the client crashes mid-commit, only some records might make it to the queue, and this breaks atomicity. To fix this issue, the paper proposes an Atomicity protocol: clients first dump all logs plus a final “commit” token into a private ATOMIC queue, then push everything to the public PU queues. This guarantees all-or-nothing transactions, but it’s pricey, since every extra SQS message adds up. At $2.90 per 1,000 transactions, it’s almost twenty times the $0.15 of the naive direct-write approach. So here, consistency comes at a literal monetary cost!
The Apple event, for instance, that’s a pseudo-event. That’s not an event in the same way that a helicopter crash is an event. Because everybody at Apple knows what’s going to happen ahead of time. There might be a couple of surprises if the audience acts up, but they know what they’re announcing, they know roughly when they’re going to announce it, they’ve rehearsed. And so this is a knowable pseudo-event.