[jira] [Commented] (KAFKA-2614) No more clients can connect after `TooManyConnectionsException` threshold (max.connections.per.ip) is reached

["Ismael Juma (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-2614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14946786#comment-14946786 ] 

Ismael Juma commented on KAFKA-2614:
------------------------------------

Thanks for filing this, there is indeed an issue where we are not handling disconnections properly. I have fixed it locally and will push a PR soon for discussion.

> No more clients can connect after `TooManyConnectionsException` threshold (max.connections.per.ip) is reached
> -------------------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-2614
>                 URL: https://issues.apache.org/jira/browse/KAFKA-2614
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 0.8.2.1
>         Environment: Debian Jessie
>            Reporter: Stephen Chu
>            Assignee: Ismael Juma
>            Priority: Critical
>             Fix For: 0.9.0.0
>
>
> It seems no more clients can connect to Kafka after `max.connections.per.ip` is reached, even if previous clients were already disconnected.
> Using 0.8.3 (9c936b18), upon starting a fresh Kafka server that is configured with (max.connections.per.ip = 24), I noticed that I can cause the server to hit the error case of {{INFO Rejected connection from /0:0:0:0:0:0:0:1, address already has the configured maximum of 24 connections.}} very quickly, by simply looping through a bunch of simple clients against the server:
> {noformat}
> #! /bin/bash
> for i in {1..30}; do
>     # either:
>     nc -vz 127.0.0.1 9092;
>     # or:
>     ( telnet 127.0.0.1 9092; ) &
> done
> # if using telnet, kill all connected jobs now via:
> kill %{2..31}
> {noformat}
> The problem seems to be that the counter for such short-lived client connections aren't properly decrementing when using the `max.connections.per.ip` feature.
> Turning on DEBUG logs, I cannot see the log lines "Closing connection from xxx" on [this line|https://github.com/apache/kafka/blob/0.8.2/core/src/main/scala/kafka/network/SocketServer.scala#L164] from the first few still-under-threshold short-lived connections, but starts showing *after* I hit the limit per that config.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)