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Coordinatool

Lustre "coordinator in userspace" implemented as a copytool which takes in all requests from coordinator and redispatches them to real lhsm agent, wrapped around with a LD_PRELOAD lib

Usage

coordinatool configuration

arguments

The server takes command line options, and must be given a mount point to register as agent last.

Options:

  • --host / --port : host and port to bind to
  • --archive archive id to listen to, additive. defaults to any.
  • --verbose / --quiet

systemd service

A systemd unit is provided, and should be started/enabled with, for example, coordinatool@mnt-lustre (the argument is an absolute path with the first slash removed, see systemd-escape)

Arguments can then be specified in either /etc/sysconfig/coordinatool or /etc/sysconfig/coordinatool.mnt-lustre

pitfalls

The server is stateless, that is, it won't remember requests it has already accepted if the service is restarted, but lustre will consider these to have been started and refuse to do anything with the files for a long time.

To work around this, the standalone client should be used to feed the server with 'leftovers' requests from the hsm/active_requests file whenever the server is restarted. For example:

cat /sys/kernel/debug/lustre/mdt/lustre0-MDT*/hsm/active_requests |
    coordinatool-client -Q

Also, if many requests are queued and a request times out the original request will be lost and clients can see errors, for this reason it is recommended to increase the timeout and usual loop period settings:

lctl set_param -P mdt.lustre0-MDT*.hsm.active_request_timeout=$((3600*24*31))
lctl set_param -P mdt.lustre0-MDT*.hsm.loop_period=1
lctl set_param -P mdt.lustre0-MDT*.hsm.max_requests=1000

client configuration

Clients read configuration from /etc/coordinatool.conf, or environment variables (priority over config file)

See client_common/coordinatool.conf for config file example, which is a simple "key value" format separated by new lines. Comments are accepted on their own lines with a sharp (#).

Environment variables use the same name in full caps prefixed by COORDINATOOL_ e.g. where host is used in the config file, COORDINATOOL_HOST will have the same effect.

knobs:

  • host: define what dns name to connect to
  • port: define ports to connect to
  • max_restore, max_archive, max_remove: maximum number of simultaneous requests accepted for each type
  • hal_size buffer size used for internal receive buffer, defaults to 1MB like lustre. Accepts optional K/M/G suffix.
  • archive_id: archive id to request if set, default to any
  • verbose: loglevel, can be one of DEBUG, INFO, NORMAL, WARN, ERROR, OFF.

standalone client

The standalone client also abides by config file and environment variables, then:

  • default just prints status and exist
  • --queue/-Q parse stdin for active_requests and send these to coordinatool
  • other options for debug are listed in --help

Tests

see tests' readme

TODO

  • systemd post-start action to ssh to mds and get a client to feed server?
  • TLS + some kind of auth
  • priority/fair queueing (stat file to get uid etc)