v1.4.0

Added

• Changed license from the MIT License to the GNU General Public License v3.0
• Support for cgroup v2 was added to the Docker container statistics collection.
  • Motivation: Cgroup v2 handles accounting for writeback I/O better than cgroup v1, and is slowly replacing cgroup v1 as the more modern system.
  • Support: Docker added support for Cgroup v2 in its 20.10 release, and most low-level container runtimes added support for it by the end of 2021. Additionally Cgroup v2 is the default-mounted cgroup version in Ubuntu starting in 21.10, and in most other popular distros starting around 2021.
  • Changes:
    • The schema for the CSV data in the log-file is different in cgroup v1 and cgroup v2, since the kernel exposes different statistics for each.
    • The CollectorType log metadata field was added to distinguish whether a log file contains statistics from cgroup_v1 or cgroup_v2
    • Cgroup and CgroupDriver log metadata fields were moved under CollectorMetadata
    • (internal) A new abstraction was introduced, Collector, which defines a trait that is used to collect resource utilization statistics for a running target. Both cgroup_v1::Collector and cgroup_v2::Collector implement this trait.