Repair (*Broadcaster).run goroutine leak

[ityangchen]

Repair (*Broadcaster).run goroutine leak

When execute 'docker swarm init' and 'docker swarm leave -f' on a node
repeatedly, the (*Broadcaster).run goroutine leak.

•What I did
Execute 'docker swarm init' and 'docker swarm leave -f' on a node
repeatedly

•How I did it
while true; do docker swarm init ; sleep 3 ; docker swarm leave -f ; done &

•How to verify it
'free -m', watch the 'available' item . constant loss explans the goroutine leak.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@1b42826). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #1958   +/-   ##
=========================================
  Coverage          ?   37.94%           
=========================================
  Files             ?      137           
  Lines             ?    27309           
  Branches          ?        0           
=========================================
  Hits              ?    10363           
  Misses            ?    15673           
  Partials          ?     1273

Impacted Files	Coverage Δ
networkdb/networkdb.go	60.11% <100%> (ø)

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[fcrisciani]

LGTM, can you actually squash all your commits into 1?

[ityangchen]

ok, I will squash them

[abhi]

Does broadcaster.Remove() takes care of this ? Or Should this be added in here ?
https://github.com/docker/libnetwork/blob/0bce3e17ca9572955e6b83d5b7431767492133c1/networkdb/watch.go#L86

[fcrisciani]

@abhi no the broadcaster is only one per networkdb and the Add/Remove allows you to add and remove listeners.
The close instead is the one that destroy the broadcaster and freed up the go routine that is dispatching events to listeners

[abhi]

@fcrisciani got it makes sense. LGTM