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[server]: Start Peers Asynchronously #1658

Merged
merged 4 commits into from Aug 16, 2018
Merged

[server]: Start Peers Asynchronously #1658

merged 4 commits into from Aug 16, 2018

Commits on Aug 14, 2018

  1. peer: add ready chan arg to WaitForDisconnect 

    This commit adds additional synchronization logic to
WaitForDisconnect, such that it can be spawned before
Start has been executed by the server. Without
modification, the current version will return
immediately since no goroutines will have been
spawned.

To solve this, we modify WaitForDisconnect to block until:
 1) the peer is disconnected,
 2) the peer is successfully started,
before watching the waitgroup.

In the first case, the waitgroup will block until all
(if any) spawned goroutines have exited. Otherwise, if
the Start is successful, we can switch to watching the
waitgroup, knowing that waitgroup counter is positive.
    @cfromknecht
    cfromknecht committed Aug 14, 2018
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  2. server: add async peer Start() + safer cleanup 

    This commit adds asynchronous starting of peers,
in order to avoid potential DOS vectors. Currently,
we block with the server's mutex while peers exchange
Init messages and perform other setup. Thus, a remote
peer that does not reply with an init message will
cause server to block for 15s per attempt.

We also modify the startup behavior to spawn
peerTerminationWatchers before starting the
peer itself, ensuring that a peer is properly
cleaned up if the initialization fails. Currently,
failing to start a peer does not execute the bulk
of the teardown logic, since it is not spawned
until after a successful Start occurs.
    @cfromknecht
    cfromknecht committed Aug 14, 2018
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  3. server: rearrange peer lifecyle helpers for readability

    @cfromknecht
    cfromknecht committed Aug 14, 2018
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  4. peer: increase peer write timeout to 50 seconds 

    Sometimes when performing an initial sync, the remote
node isn't able to pull messages off the wire because
of long running tasks and queues are saturated. With
a shorter write timeout, we will give up trying to send
messages and teardown the connection, even though the
peer is still active.
    @cfromknecht
    cfromknecht committed Aug 14, 2018
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