As I mentioned last time, I ran into some challengesincredibly annoying problems setting up a dhcpd failover server. 1. Dhcpd doesn’t record full data for foreign leases. At first I thought it would be enough to run dhcpd with a failover peer and use djb_update.pl to create the host list for tinydns. But then I […]
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Here are the before and after pictures. We used to have two independent single points of failure. If boris was down, nobody could get an IP address, and internal name resolution didn’t work because the cache couldn’t see the tinydns server (on boris) that is authoritative for the internal network. If draco the firewall was […]
djbdns and DHCP server
19-Jul-08There is a script for extracting DNS data from dhcpd.leases that I’ve been using for a few years. It generates a tinydns data file which can be merged with the static file. But I am not content with only one DHCP server. I have implemented a backup/failover server. Now I have twice the problems! The […]
DHCP and djbdns
17-Jul-08DHCP assigns IPs to hosts; DNS reports IPs by hostname. The popular dhcp server is even written by the folks who brought you BIND. But in our shop, we run djbdns. I am not a full convert to the djb way. (We run postfix, for example.). I have never met the man in person. I […]
Testing a list<int> is pretty much the worst possible case for STL’s lower bound algorithm. Recall from the analysis that STL’s lower_bound uses a binary search algorithm even when the cost of advancing an iterator N steps is O(N). The advantage of this algorithm is that it only performs O( log N ) comparisons, as […]
Update: This is a known bug. In the process of gathering my data for the next post in the stl lower_bound() series, I ran into some weird timings. Basically I was seeing a linear increase until there were 32000 elements in my list, and then at 33000 the timing suddenly dropped by a factor of […]
I criticized an STL algorithm in a previous entry, calling it “unintuitive but correct.”. That’s pretty arrogant of me, considering the STL has been published for fifteen or so years. You’d think that if an STL algorithm were incorrect, someone would have noticed by now. Or taken differently, STL doesn’t need an obscure blogger’s approval. […]
When I was looking for a C lower-bound algorithm — after I wound up writing it myself — I realized that there was an implementation in STL. A Detour into STL STL, in case your programming life is lived under a rock labeled “C#”, is an awesome set of template routines for C++, for having […]
I only learned how to use precompiled headers recently — even though I remember reading this paper about how to do it back in the late 90’s. It seemed like too much effort, then, and my then-blazing fast Windows NT 4.0 machine didn’t seem to need the help. Somehow, ten years later with a dual-core […]