Was the concern that a better solution was possible that could fully repair the issue instead of a partial fix?
On Mon, Oct 3, 2016 at 3:41 AM, Pavlos Parissis <[email protected]> wrote: > On 29/09/2016 07:13 μμ, Joseph Lynch wrote: > > You can always dynamically remove servers via the stats socket by > > downing them. If your server pool is relatively well behaved you can > > just pre-allocate and up and down as needed. > > > > If you need to add new servers, afaik you have to reload, which > > won't drop existing connections but may drop new connections for a > > very brief moment (10-20ms). Old instances of HAProxy will hang > > around until all connections through them drain so you have to be > > careful if you're restarting a lot with long timeouts not to run out > > of memory. > > > > Seehttps://engineeringblog.yelp.com/2015/04/true-zero- > downtime-haproxy-reloads.html > > > > > <https://engineeringblog.yelp.com/2015/04/true-zero- > downtime-haproxy-reloads.html> > > for a deep dive into why reloading is a tricky problem. You'll note > > that existing connections are never dropped with -sf , but there are > > a very small number of new connections that are. The community has > > been working on it though! > > > > Most notably within HAProxy the DNS work Baptiste is doing will > > hopefully eventually allow complete dynamic re-assignment of the > > hosts and ports within a backend, meaning you just have to reload > > when your pool size is too high. I believe changing host is supported > > and port is in the works (double check me on this, might have > > changed). > > > > Willy nearly had a Linux kernel patch in to 4.2 that fixed the > > underlying problem with the Linux kernel, but then it got a bit > > derailed by the BPF changes that got merged. > > Seehttps://marc.info/?t=144331405900001&r=1&w=2 > > <https://marc.info/?t=144331405900001&r=1&w=2> for the story there. > > Guys proposed to use BPF resolve the issue, but they didn't provide a > workable solution, which Willy's patch fixed the problem, at least > partially. > > I know you can do a lot of interesting and useful things with BPF, like > stracing application in production without performance degradation, but > they could have accepted Willy's patch until a permanent solution arrives. > > May be I am missing something here. > > Cheers, > Pavlos > >
