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https://issues.apache.org/jira/browse/STORM-122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13941157#comment-13941157
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Peter Klipfel commented on STORM-122:
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I'm using sbt. I've been trying to exclude any and all logging dependencies.
This error will not go away and has now cost me days of development time.
> log4j-over-slf4j in 0.9.0-rc2 breaks existing topologies
> --------------------------------------------------------
>
> Key: STORM-122
> URL: https://issues.apache.org/jira/browse/STORM-122
> Project: Apache Storm (Incubating)
> Issue Type: Bug
> Reporter: James Xu
> Priority: Minor
>
> https://github.com/nathanmarz/storm/issues/745
> Apologies if this ticket is off-base, I'm not an expert in this area. We've
> been testing an existing topology we ran on Storm 0.8.1 on a deployment of
> Storm 0.9.0-rc2. The only roadblock we've encountered so far is the presence
> of the log4j-over-slf4j jar in the newer version. It turns out that
> log4j-over-slf4j is incompatible with slf4j-log4j12.
> Basically our topology uses slf4j as the the logging facade and log4j as the
> backend, which I've heard is a common pattern. It seems that in order to
> migrate to the new Storm version we must either move our code off of log4j or
> delete the log4j-over-slf4j jar from the storm classpath.
> Are we doing something crazy here? I'm open to alternate solutions, but it
> seems like an issue to break legacy topologies over logging. My understanding
> based on #144 was that Storm was migrating completely to slf4j, is this no
> longer true? Any insight, advice, or fixes would be helpful.
> --------
> jmlogan: You're going to have to exclude log4j and log4j-over-slf4j. Storm
> calls mostly seem to be slf4j, but it is not logger-agonistic. In 0.9.0, it
> will force logback onto your classpath at runtime, and will crash if it has
> multiple adapters.
> If you see a job failing to launch, right after updating, it's probably this
> issue. We ended up just excluding log4j from the offending dependencies.
> ---------
> bakks: Hey, thanks for your response. The issue is that log4j-over-slf4j is
> now a Storm dependency, so its loaded into the topology classpath by default.
> This wasn't true in earlier Storm versions, so perhaps this is intentional,
> but our topology which used to work now doesn't. It seems like there is now
> no way to use log4j as an slf4j backend. If that is the new state of the
> world, its fine, but it seems like an issue and I'm hoping for a workaround.
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