WiFi problems on Yosemite I've seen a few posts around wifi problems with Yosemite, especially after an update from Mavericks. I've only started seeing WiFi problems about 3 days ago (update was 3-6 months ago), and my issues are happening on a number of routers.

Looking on the console, I see a number of the following messages:

&gt; 06/06/2015 17:07:03.691 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
&gt; 06/06/2015 17:07:04.443 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.
&gt; 06/06/2015 17:07:07.277 com.apple.WebKit.WebContent[2260]: dnssd_clientstub write_all(16) failed -1/64 32 Broken pipe
&gt; 06/06/2015 17:07:07.277 com.apple.WebKit.WebContent[2260]: dnssd_clientstub write_all(16) failed -1/28 32 Broken pipe
&gt; 06/06/2015 17:07:19.113 discoveryd[2360]: Basic DNSResolver UDNS Send(): UDP Sendto() failed to DNSNameServer 8.8.8.8 Port 53 errno 65, fd 53, ErrLogCount 1 ResolverIntf:0
&gt; 06/06/2015 17:07:19.114 discoveryd[2360]: Basic DNSResolver UDNS Send(): UDP Sendto() failed to DNSNameServer 8.8.8.8 Port 53 errno 65, fd 51, ErrLogCount 2 ResolverIntf:0
&gt; 06/06/2015 17:07:19.477 discoveryd[2360]: Basic DNSResolver UDNS Send(): UDP Sendto() failed to DNSNameServer 8.8.4.4 Port 53 errno 65, fd 52, ErrLogCount 3 ResolverIntf:0
&gt; 06/06/2015 17:07:20.177 discoveryd[2360]: Basic DNSResolver UDNS Send(): UDP Sendto() failed to DNSNameServer 8.8.4.4 Port 53 errno 65, fd 37, ErrLogCount 4 ResolverIntf:0
&gt; 06/06/2015 17:07:20.178 discoveryd[2360]: Basic DNSResolver UDNS Send(): UDP Sendto() failed to DNSNameServer 8.8.4.4 Port 53 errno 65, fd 37, ErrLogCount 5 ResolverIntf:0


WiFi otherwise "appears" normal (wifi symbol in the status bar shows no error, and network config says I'm still connected); however, no connectivity (not even through ping). 

I can at this point disconnect and reconnect to the wifi, which will work for about 1 minute before disconnecting again. 

Only long-term solution is to reboot. Unsure what triggers it!

I've tried, but no luck with,
- restart discoveryd
- clear safari cache
- change dns servers

Help would be appreciated - I'd rather avoid having to fresh-install the OS!
The latest OS X 10.10.4 public beta, build 14E26a, totally gets rid of discoveryd. Go to this Apple link and sign up for the public beta program, where you'll be given a link to download a piece of software that'll get the App Store to pick up beta updates. Take a backup of everything, install Beta Access Utility, and then install and enjoy a discoveryd-free Yosemite!