Re-Validate aufs crawling on Armada

[canturkisci]

Description

We have an issue on crawling aufs backed containers. Let us validate we can crawl containers backed by aufs.

Previously we had issues on 'detecting' new containers on an aufs-backed system. We should better understand and document the current state.

How to Reproduce

• Deploy crawler on armada worked, backed by aufs
• Validate it (a) discovers and (b) crawls existing containers
• Check if it (a) discovers and (b) crawls newly-created containers

Related Issues

#112 #167 #275

[nadgowdas]

@canturkisci
Summary of Discussion with Alan:

1. There is a scenario in which setns fails if called from multi-threaded process. And in namespace.py -> run_as_another_process() the multi-threaded context fails the setns to mount namespace of container. And this is specific to aufs. We don't expect this will be fixed in aufs since its development seems to be stagnant.

2. Alan mentioned, he has a solution for that and he will create a PR to add that fix into this OSS code.

3. We also have few gaps in terms of porting few other changes regarding package crawling that we will perform after aufs fix.