Go-based FUSE file system for uid mapping local file access designed to be used as part of mapfs-release.
In CloudFoundry NFS volume
services, the NFS
driver will start mapfs
when the uid or gid parameters are specified when binding an NFS
mount. MapFS will expose a FUSE filesystem that is mounted into the app
container, and the app can read and write from. This is backed by an NFS
mount. MapFS replicates file access so that as far as NFS is concerned,
the file access is done with the uid and gid specified.
Because an app can potentially go faster than NFS (which is limited by network bandwidth), it's possible for requests to stack up in MapFS while it waits for NFS to respond. Currently, go-fuse does not implement backpressure or load shedding. For every request in-flight, a buffer and a goroutine will be created, so MapFS can consume high memory and processor when the app accesses the filesystem faster than NFS responds.
There is an optional configuration file that can be placed at
/var/vcap/jobs/mapfs/config/mapfs.yml that will allow MapFS to be
configured. Configuration keys are: - debug - enables go-fuse debug
mode. Logs are written to /var/vcap/sys/log/mapfs/mapfs.$$.log where
$$ is the process ID. - single_threaded - enables go-fuse single
threaded mode. Can reduce memory pressure, and may slow down access. -
cpu_profile - writes a Go pprof CPU profile to the specified path. -
mem_profile - when the process receives a SIGUSR1 a Go pprof memory
profile will be written to the path with a timestamp as a file suffix. -
soft_mem_limit - soft memory limit in bytes. Equivalent to setting
GOMEMLIMIT environment variable.
The configuration file is read on startup. To restart MapFS just
kill -9 the existing process and the NFS Driver will start a new one.
This may break running apps.
make test
See the Contributing.md for more information on how to contribute.
This repository is maintained by Service
Management
under Volume Services area.
Important
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