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Comment: More likely case (Score 1) 125

by rekoil (#46071387) Attached to: How Google Broke Itself and Fixed Itself, Automatically

What's more likely - I've run into exactly this scenario before, in fact - is that the configuration generation system regenerates configs on a regular schedule, and at one point encountered a failure or spurious bug that caused it to push an invalid config. On the next run - right as the SREs started poking around - the generator ran again, the bug wasn't encountered, and it generated and pushed a correct config, clearing the error and allowing apps to recover.

Comment: Re:Silly priorities (Score 3, Informative) 274

Disclaimer: Another Twitter engineer here. What my apparently former colleague said, plus X.

Also: Don't be afraid to add caching layers when you see your web server or DBs start to run hot. Putting a memcached instance in place in "front of" your database layer is much easier than sharding the database layers to relieve load - eventually you'll have to do both, but you'll definitely want the memcache layer first. Same with web caches/proxies - putting varnish or squid in front will take some pressure off before you need to implement load balancers.

Comment: Re:Not so fast...YET (Score 1) 135

by rekoil (#40356211) Attached to: SPDY Not As Speedy As Hyped?

In fact, if SPDY support was ubiquitous tommorrow, I would be surprised to see SPDY+TLS used for third party ad serving for this very reason.

Good news here: Google's DoubleClick and AdSense ads are served over SPDY today. In fact, I'm not aware of any Google properties that don't use SPDY, since they're all routed through the same GFE (Google FrontEnd) proxy farms.

Comment: Re:The problem with the test ... (Score 5, Informative) 135

by rekoil (#40352749) Attached to: SPDY Not As Speedy As Hyped?

SPDY as implemented requires SSL, since the protocol capability is negotiated by a TLS extension on port 443. There's no spec for negotiating SPDY on a standard HTTP port - it would only work if the capability was assumed on both sides before the connection (for example, URLs that start with spdy:// instead of http:/// which connects to a different TCP port on the server).

Comment: Re:Single domain? (Score 1) 135

by rekoil (#40352719) Attached to: SPDY Not As Speedy As Hyped?

That only works if all of those hostnames resolve to the same IP addresses. The main optimization in SPDY is the elimination of the need to make multiple TCP connections simultaneously, but all of those resources must live on the same server. If the resources have different hostnames, you might be able to detect hostnames that point to the same IP and then interleave those, but I don't know if the current implementations do that yet.

Most CDNs, however, return different IPs for nearly every query, and web developers use multiple hostnames pointing to the same resources to get non-SPDY multiplexing today. This sounds like an optimization that's easy to accomplish dynamically, though (if request is SPDY, don't spread the resources across different hostnames).

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