conntrackd filling up var

##### ISSUE TYPE
* Bug Report

##### COMPONENT NAME
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VR
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##### CLOUDSTACK VERSION
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latest
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##### CONFIGURATION
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N/A
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##### OS / ENVIRONMENT
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KVM
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##### SUMMARY
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We have large customers with a lot of VR traffic traversing the VRs. Logrotate cannot keep up and /var fills up to 100%, causing the VR to exhibit problems when attempting to start/restart instances in the VPC and/or traffic stops flowing. Conntrackd is logging verbosely to daemon.log.
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##### STEPS TO REPRODUCE
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1. Construct a VPC with a redundant VR pair with a private gateway or tunnel
2. Create a large amount of traffic to/from a VPC over gateway or tunnel

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##### EXPECTED RESULTS
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/var should not fill up regardless of traffic load
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##### ACTUAL RESULTS
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/var fills up
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使用冗余 VR 对、私有网关或隧道以及高流量重现该问题，然后检查 daemon.log 中的 conntrackd 日志记录以及 logrotate 的行为。在报告的流量负载下，VR 的 /var 未达到容量上限，且实例操作和流量继续正常运行，即表示完成。

由索引模型根据 Issue 内容生成。