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PR adds a simple at most 1Hz refreshed informational API for querying pageserver utilization. In this first phase, no actual background calculation is performed. Instead, the worst possible score is always returned. The returned bytes information is however correct. Cc: #6835 Cc: #5331
39 lines
1.3 KiB
Rust
39 lines
1.3 KiB
Rust
//! An utilization metric which is used to decide on which pageserver to put next tenant.
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//!
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//! The metric is exposed via `GET /v1/utilization`. Refer and maintain it's openapi spec as the
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//! truth.
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use anyhow::Context;
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use std::path::Path;
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use pageserver_api::models::PageserverUtilization;
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pub(crate) fn regenerate(tenants_path: &Path) -> anyhow::Result<PageserverUtilization> {
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// TODO: currently the http api ratelimits this to 1Hz at most, which is probably good enough
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let statvfs = nix::sys::statvfs::statvfs(tenants_path)
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.map_err(std::io::Error::from)
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.context("statvfs tenants directory")?;
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let blocksz = statvfs.block_size();
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#[cfg_attr(not(target_os = "macos"), allow(clippy::unnecessary_cast))]
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let free = statvfs.blocks_available() as u64 * blocksz;
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let used = crate::metrics::RESIDENT_PHYSICAL_SIZE_GLOBAL.get();
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let captured_at = std::time::SystemTime::now();
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let doc = PageserverUtilization {
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disk_usage_bytes: used,
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free_space_bytes: free,
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// lower is better; start with a constant
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//
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// note that u64::MAX will be output as i64::MAX as u64, but that should not matter
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utilization_score: u64::MAX,
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captured_at,
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};
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// TODO: make utilization_score into a metric
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Ok(doc)
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}
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