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wrenn-releases/envd-rs/src/http/snapshot.rs
pptx704 78f2ea603f v0.1.6 (#45)
## What's New?
Performance updates for large capsules, admin panel enhancement and bug fixes

### Envd
- Fixed bug with sandbox metrics calculation
- Page cache drop and balloon inflation to reduce memfile snapshot
- Updated rpc timeout logic for better control
- Added tests

### Admin Panel
- Add/Remove platform admin
- Updated template deletion logic for fine grained permission

### Others
- Minor frontend visual improvement
- Minor bugfixes
- Version bump

Co-authored-by: Tasnim Kabir Sadik <tksadik92@gmail.com>
Reviewed-on: wrenn/wrenn#45
Co-authored-by: pptx704 <rafeed@omukk.dev>
Co-committed-by: pptx704 <rafeed@omukk.dev>
2026-05-13 22:24:13 +06:00

50 lines
1.7 KiB
Rust

use std::sync::Arc;
use std::sync::atomic::Ordering;
use axum::extract::State;
use axum::http::{StatusCode, header};
use axum::response::IntoResponse;
use crate::state::AppState;
/// POST /snapshot/prepare — quiesce subsystems before Firecracker snapshot.
///
/// In Rust there is no GC dance. We just:
/// 1. Drop page cache to shrink snapshot size
/// 2. Stop port subsystem
/// 3. Close idle connections via conntracker
/// 4. Set needs_restore flag
pub async fn post_snapshot_prepare(State(state): State<Arc<AppState>>) -> impl IntoResponse {
// Drop page cache BEFORE blocking the reclaimer — avoids snapshotting
// gigabytes of stale cache that inflates the memory dump on disk.
// "1" = pagecache only (keep dentries/inodes for faster resume).
if let Err(e) = std::fs::write("/proc/sys/vm/drop_caches", "1") {
tracing::warn!(error = %e, "snapshot/prepare: drop_caches failed");
} else {
tracing::info!("snapshot/prepare: page cache dropped");
}
// Block memory reclaimer — prevents drop_caches from running mid-freeze
// which would corrupt kernel page table state.
state.snapshot_in_progress.store(true, Ordering::Release);
if let Some(ref ps) = state.port_subsystem {
ps.stop();
tracing::info!("snapshot/prepare: port subsystem stopped");
}
state.conn_tracker.prepare_for_snapshot();
tracing::info!("snapshot/prepare: connections prepared");
// Sync filesystem buffers so dirty pages are flushed before freeze.
unsafe { libc::sync(); }
state.needs_restore.store(true, Ordering::Release);
tracing::info!("snapshot/prepare: ready for freeze");
(
StatusCode::NO_CONTENT,
[(header::CACHE_CONTROL, "no-store")],
)
}