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Comment: Re:IPv6 would make the problem worse (Score 1) 248 248

While in practice most admins configure /64s as subnets, there's nothing preventing netblocks that are smaller than /64. I have /127 point-to-point subnets on my network, and /96s going to server racks. You need a /64 in order to do RA, however, but you can use DHCPv6 instead on smaller subnets.

Comment: More likely case (Score 1) 125 125

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:Why did Python avoid some common "OO" idioms? (Score 1) 242 242

In python, that's correct. There's some method name mangling to ensure that devs writing code calling private methods know what they're doing, but otherwise it's allowed. In other languages (Java for example) private methods are completely hidden from outside classes.

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

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) 135 135

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) 135 135

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) 135 135

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).

All the simple programs have been written.

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