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brotskydotcom / susen.go

A simple sudoku game.
GNU General Public License v2.0
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Server has no session persistence #11

Closed brotskydotcom closed 8 years ago

brotskydotcom commented 8 years ago

Leaving a solver window open and idle for a few hours (or a few days) causes the free Heroku dyno to go idle and shut down. This flushes the server-side session, although the cookie persists on the client side.

brotskydotcom commented 8 years ago

Going to try to fix this by adding redis, to see if its free level add-on works across dyno idle and perhaps even restart.

brotskydotcom commented 8 years ago

So the fix doesn't work due to concurrent redis access problems. Reopening.

brotskydotcom commented 8 years ago

So the concurrency problems were solved with 7bdceea but there is a new issue: dropped redis connections. When I connect to the redis server from the command line, I can see the server's client connection drop:

herring.redistogo.com:9763> client list
id=75 addr=10.180.86.27:60505 fd=6 name= age=143 idle=140 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=rpush
id=76 addr=50.136.220.100:56694 fd=7 name= age=5 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=client
herring.redistogo.com:9763> client list
id=76 addr=50.136.220.100:56694 fd=7 name= age=69 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=client
herring.redistogo.com:9763>

After this happens, the server crashes trying to talk down the broken connection. Reopening.

brotskydotcom commented 8 years ago

Fixed this with 12cde9f (merged with pull #14 and fixed with pull #15 fa9b98b). Now every redis operation is preceded with a PING to see if the connection has dropped, and if so it is properly closed and reopened. Now we get server logs that look like this:

Nov 26 09:59:02 susen-staging heroku/web.1:  Starting process with command `susen` 
Nov 26 09:59:05 susen-staging app/web.1:  2015/11/26 17:59:04 Connected to redis at "redis://redistogo:693c0d12329f8c825669c7338ad993da@herring.redistogo.com:9763/0" 
Nov 26 09:59:07 susen-staging heroku/router:  at=info method=POST path="/api/assign/" host=susen-staging.herokuapp.com request_id=cb075e59-17df-498b-9145-236649f31050 fwd="50.136.220.100" dyno=web.1 connect=1ms service=14ms status=200 bytes=369 
Nov 26 09:59:07 susen-staging app/web.1:  2015/11/26 17:59:06 Added session 54e9399d-1c07-4ca4-80e2-92e5f1610466 step 4. 
Nov 26 09:59:07 susen-staging app/web.1:  2015/11/26 17:59:06 Reloaded session 54e9399d-1c07-4ca4-80e2-92e5f1610466, puzzle "3-star", through step 3. 
Nov 26 10:03:56 susen-staging heroku/router:  at=info method=POST path="/api/assign/" host=susen-staging.herokuapp.com request_id=f295fc89-e575-4b74-a452-4a4135bac1a4 fwd="50.136.220.100" dyno=web.1 connect=2ms service=12ms status=200 bytes=339 
Nov 26 10:03:56 susen-staging app/web.1:  2015/11/26 18:03:55 Lost connection to redis: EOF 
Nov 26 10:03:56 susen-staging app/web.1:  2015/11/26 18:03:55 Reconnected to redis at "redis://redistogo:693c0d12329f8c825669c7338ad993da@herring.redistogo.com:9763/0" 
Nov 26 10:03:56 susen-staging app/web.1:  2015/11/26 18:03:55 Added session 54e9399d-1c07-4ca4-80e2-92e5f1610466 step 5.

I don't know whether these connection failures happen with paid levels of Redis To Go or if they are a consequence of using the free level. I also need to do research on whether redigo can give me a heads-up when the connection closes, so I don't have to always PING first. But this does seem really fixed for now. Closing the issue.