Line data    Source code

       1              : //! An utilization metric which is used to decide on which pageserver to put next tenant.
       2              : //!
       3              : //! The metric is exposed via `GET /v1/utilization`. Refer and maintain it's openapi spec as the
       4              : //! truth.
       5              : 
       6              : use anyhow::Context;
       7              : use std::path::Path;
       8              : 
       9              : use pageserver_api::models::PageserverUtilization;
      10              : 
      11            0 : pub(crate) fn regenerate(tenants_path: &Path) -> anyhow::Result<PageserverUtilization> {
      12              :     // TODO: currently the http api ratelimits this to 1Hz at most, which is probably good enough
      13              : 
      14            0 :     let statvfs = nix::sys::statvfs::statvfs(tenants_path)
      15            0 :         .map_err(std::io::Error::from)
      16            0 :         .context("statvfs tenants directory")?;
      17              : 
      18              :     // https://unix.stackexchange.com/a/703650
      19            0 :     let blocksz = if statvfs.fragment_size() > 0 {
      20            0 :         statvfs.fragment_size()
      21              :     } else {
      22            0 :         statvfs.block_size()
      23              :     };
      24              : 
      25              :     #[cfg_attr(not(target_os = "macos"), allow(clippy::unnecessary_cast))]
      26            0 :     let free = statvfs.blocks_available() as u64 * blocksz;
      27            0 : 
      28            0 :     #[cfg_attr(not(target_os = "macos"), allow(clippy::unnecessary_cast))]
      29            0 :     let used = statvfs
      30            0 :         .blocks()
      31            0 :         // use blocks_free instead of available here to match df in case someone compares
      32            0 :         .saturating_sub(statvfs.blocks_free()) as u64
      33            0 :         * blocksz;
      34            0 : 
      35            0 :     let captured_at = std::time::SystemTime::now();
      36            0 : 
      37            0 :     let doc = PageserverUtilization {
      38            0 :         disk_usage_bytes: used,
      39            0 :         free_space_bytes: free,
      40            0 :         // lower is better; start with a constant
      41            0 :         //
      42            0 :         // note that u64::MAX will be output as i64::MAX as u64, but that should not matter
      43            0 :         utilization_score: u64::MAX,
      44            0 :         captured_at: utils::serde_system_time::SystemTime(captured_at),
      45            0 :     };
      46            0 : 
      47            0 :     // TODO: make utilization_score into a metric
      48            0 : 
      49            0 :     Ok(doc)
      50            0 : }