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Version: v0.3.0

src/sydra/snapshot.zig

Purpose​

Implements a simple snapshot/restore mechanism for SydraDB’s on-disk state by copying a small set of files/directories:

  • MANIFEST
  • wal/
  • segments/
  • tags.json

This is used by the CLI snapshot / restore commands in src/sydra/server.zig.

Public API​

pub fn snapshot(alloc: std.mem.Allocator, data_dir: std.fs.Dir, dst_path: []const u8) !void​

Creates (or reuses) dst_path under the current working directory and copies:

  • MANIFEST (if present)
  • wal/ recursively (if present)
  • segments/ recursively (if present)
  • tags.json (if present)

pub fn restore(alloc: std.mem.Allocator, data_dir: std.fs.Dir, src_path: []const u8) !void​

Opens src_path under the current working directory and copies back into data_dir:

  • MANIFEST (if present)
  • wal/ recursively (if present)
  • segments/ recursively (if present)
  • tags.json (if present)
snapshot/restore (excerpt)
pub fn snapshot(alloc: std.mem.Allocator, data_dir: std.fs.Dir, dst_path: []const u8) !void {
    // Simple manifested copy: copy MANIFEST, wal/, segments/, tags.json
    try std.fs.cwd().makePath(dst_path);
    var dst = try std.fs.cwd().openDir(dst_path, .{ .iterate = true });
    defer dst.close();
    try copyIfExists(data_dir, dst, "MANIFEST");
    try copyDirRecursive(alloc, data_dir, dst, "wal");
    try copyDirRecursive(alloc, data_dir, dst, "segments");
    try copyIfExists(data_dir, dst, "tags.json");
}

pub fn restore(alloc: std.mem.Allocator, data_dir: std.fs.Dir, src_path: []const u8) !void {
    var src = try std.fs.cwd().openDir(src_path, .{ .iterate = true });
    defer src.close();
    try copyIfExists(src, data_dir, "MANIFEST");
    try copyDirRecursive(alloc, src, data_dir, "wal");
    try copyDirRecursive(alloc, src, data_dir, "segments");
    try copyIfExists(src, data_dir, "tags.json");
}

Key internal helpers​

fn copyIfExists(from: std.fs.Dir, to: std.fs.Dir, name: []const u8) !void​

Copies name from from → to, ignoring error.FileNotFound.

fn copyDirRecursive(alloc: std.mem.Allocator, from: std.fs.Dir, to: std.fs.Dir, name: []const u8) !void​

Recursively copies a directory tree:

  • Opens from.openDir(name, .{ .iterate = true }); ignores error.FileNotFound.
  • Ensures the destination path exists (to.makePath(name)).
  • Iterates entries:
    • files: copyFile
    • directories: recurse

Note: alloc is currently unused by the implementation.