[HADOOP-8361] Avoid out-of-memory problems when deserializing strings

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.0.0-alpha
• Fix Version/s: 2.0.2-alpha
• Hadoop Flags: Reviewed
• Assignee: Colin McCabe
• Reporter: Colin McCabe
• Created: 04/May/12 21:18
• Updated: 11/Oct/12 17:45
• Resolved: 11/May/12 20:45

Description

In HDFS, we want to be able to read the edit log without crashing on an OOM condition. Unfortunately, we currently cannot do this, because there are no limits on the length of certain data types we pull from the edit log. We often read strings without setting any upper limit on the length we're prepared to accept.

It's not that we don't have limits on strings-- for example, HDFS limits the maximum path length to 8000 UCS-2 characters. Linux limits the maximum user name length to either 64 or 128 bytes, depending on what version you are running. It's just that we're not exposing these limits to the deserialization functions that need to be aware of them.

Issue Links

• blocks: HDFS-3134 Harden edit log loader against malformed or malicious input
• is related to: HADOOP-8388 Remove unused BlockLocation serialization