Line data Source code
1 : //! Code related to evicting WAL files to remote storage.
2 : //!
3 : //! The actual upload is done by the partial WAL backup code. This file has
4 : //! code to delete and re-download WAL files, cross-validate with partial WAL
5 : //! backup if local file is still present.
6 :
7 : use anyhow::Context;
8 : use camino::Utf8PathBuf;
9 : use remote_storage::RemotePath;
10 : use tokio::{
11 : fs::File,
12 : io::{AsyncRead, AsyncWriteExt},
13 : };
14 : use tracing::{debug, info, instrument, warn};
15 : use utils::crashsafe::durable_rename;
16 :
17 : use crate::{
18 : metrics::{EvictionEvent, EVICTION_EVENTS_COMPLETED, EVICTION_EVENTS_STARTED},
19 : rate_limit::rand_duration,
20 : timeline_manager::{Manager, StateSnapshot},
21 : wal_backup,
22 : wal_backup_partial::{self, PartialRemoteSegment},
23 : wal_storage::wal_file_paths,
24 : };
25 :
26 : impl Manager {
27 : /// Returns true if the timeline is ready for eviction.
28 : /// Current criteria:
29 : /// - no active tasks
30 : /// - control file is flushed (no next event scheduled)
31 : /// - no WAL residence guards
32 : /// - no pushes to the broker
33 : /// - last partial WAL segment is uploaded
34 : /// - all local segments before the uploaded partial are committed and uploaded
35 0 : pub(crate) fn ready_for_eviction(
36 0 : &self,
37 0 : next_event: &Option<tokio::time::Instant>,
38 0 : state: &StateSnapshot,
39 0 : ) -> bool {
40 0 : let ready = self.backup_task.is_none()
41 0 : && self.recovery_task.is_none()
42 0 : && self.wal_removal_task.is_none()
43 0 : && self.partial_backup_task.is_none()
44 0 : && next_event.is_none()
45 0 : && self.access_service.is_empty()
46 0 : && !self.tli_broker_active.get()
47 : // Partial segment of current flush_lsn is uploaded up to this flush_lsn.
48 0 : && !wal_backup_partial::needs_uploading(state, &self.partial_backup_uploaded)
49 : // And it is the next one after the last removed. Given that local
50 : // WAL is removed only after it is uploaded to s3 (and pageserver
51 : // advancing remote_consistent_lsn) which happens only after WAL is
52 : // committed, true means all this is done.
53 : //
54 : // This also works for the first segment despite last_removed_segno
55 : // being 0 on init because this 0 triggers run of wal_removal_task
56 : // on success of which manager updates the horizon.
57 0 : && self
58 0 : .partial_backup_uploaded
59 0 : .as_ref()
60 0 : .unwrap()
61 0 : .flush_lsn
62 0 : .segment_number(self.wal_seg_size)
63 0 : == self.last_removed_segno + 1;
64 0 : ready
65 0 : }
66 :
67 : /// Evict the timeline to remote storage.
68 0 : #[instrument(name = "evict_timeline", skip_all)]
69 : pub(crate) async fn evict_timeline(&mut self) {
70 : assert!(!self.is_offloaded);
71 : let partial_backup_uploaded = match &self.partial_backup_uploaded {
72 : Some(p) => p.clone(),
73 : None => {
74 : warn!("no partial backup uploaded, skipping eviction");
75 : return;
76 : }
77 : };
78 :
79 : info!("starting eviction, using {:?}", partial_backup_uploaded);
80 :
81 : EVICTION_EVENTS_STARTED
82 : .with_label_values(&[EvictionEvent::Evict.into()])
83 : .inc();
84 0 : let _guard = scopeguard::guard((), |_| {
85 0 : EVICTION_EVENTS_COMPLETED
86 0 : .with_label_values(&[EvictionEvent::Evict.into()])
87 0 : .inc();
88 0 : });
89 :
90 : if let Err(e) = do_eviction(self, &partial_backup_uploaded).await {
91 : warn!("failed to evict timeline: {:?}", e);
92 : return;
93 : }
94 :
95 : info!("successfully evicted timeline");
96 : }
97 :
98 : /// Attempt to restore evicted timeline from remote storage; it must be
99 : /// offloaded.
100 0 : #[instrument(name = "unevict_timeline", skip_all)]
101 : pub(crate) async fn unevict_timeline(&mut self) {
102 : assert!(self.is_offloaded);
103 : let partial_backup_uploaded = match &self.partial_backup_uploaded {
104 : Some(p) => p.clone(),
105 : None => {
106 : warn!("no partial backup uploaded, cannot unevict");
107 : return;
108 : }
109 : };
110 :
111 : info!("starting uneviction, using {:?}", partial_backup_uploaded);
112 :
113 : EVICTION_EVENTS_STARTED
114 : .with_label_values(&[EvictionEvent::Restore.into()])
115 : .inc();
116 0 : let _guard = scopeguard::guard((), |_| {
117 0 : EVICTION_EVENTS_COMPLETED
118 0 : .with_label_values(&[EvictionEvent::Restore.into()])
119 0 : .inc();
120 0 : });
121 :
122 : if let Err(e) = do_uneviction(self, &partial_backup_uploaded).await {
123 : warn!("failed to unevict timeline: {:?}", e);
124 : return;
125 : }
126 :
127 : self.evict_not_before =
128 : tokio::time::Instant::now() + rand_duration(&self.conf.eviction_min_resident);
129 :
130 : info!("successfully restored evicted timeline");
131 : }
132 : }
133 :
134 : /// Ensure that content matches the remote partial backup, if local segment exists.
135 : /// Then change state in control file and in-memory. If `delete_offloaded_wal` is set,
136 : /// delete the local segment.
137 0 : async fn do_eviction(mgr: &mut Manager, partial: &PartialRemoteSegment) -> anyhow::Result<()> {
138 0 : compare_local_segment_with_remote(mgr, partial).await?;
139 :
140 0 : mgr.tli.switch_to_offloaded(partial).await?;
141 : // switch manager state as soon as possible
142 0 : mgr.is_offloaded = true;
143 0 :
144 0 : if mgr.conf.delete_offloaded_wal {
145 0 : delete_local_segment(mgr, partial).await?;
146 0 : }
147 :
148 0 : Ok(())
149 0 : }
150 :
151 : /// Ensure that content matches the remote partial backup, if local segment exists.
152 : /// Then download segment to local disk and change state in control file and in-memory.
153 0 : async fn do_uneviction(mgr: &mut Manager, partial: &PartialRemoteSegment) -> anyhow::Result<()> {
154 0 : // if the local segment is present, validate it
155 0 : compare_local_segment_with_remote(mgr, partial).await?;
156 :
157 : // atomically download the partial segment
158 0 : redownload_partial_segment(mgr, partial).await?;
159 :
160 0 : mgr.tli.switch_to_present().await?;
161 : // switch manager state as soon as possible
162 0 : mgr.is_offloaded = false;
163 0 :
164 0 : Ok(())
165 0 : }
166 :
167 : /// Delete local WAL segment.
168 0 : async fn delete_local_segment(mgr: &Manager, partial: &PartialRemoteSegment) -> anyhow::Result<()> {
169 0 : let local_path = local_segment_path(mgr, partial);
170 0 :
171 0 : info!("deleting WAL file to evict: {}", local_path);
172 0 : tokio::fs::remove_file(&local_path).await?;
173 0 : Ok(())
174 0 : }
175 :
176 : /// Redownload partial segment from remote storage.
177 : /// The segment is downloaded to a temporary file and then renamed to the final path.
178 0 : async fn redownload_partial_segment(
179 0 : mgr: &Manager,
180 0 : partial: &PartialRemoteSegment,
181 0 : ) -> anyhow::Result<()> {
182 0 : let tmp_file = mgr.tli.timeline_dir().join("remote_partial.tmp");
183 0 : let remote_segfile = remote_segment_path(mgr, partial);
184 0 :
185 0 : debug!(
186 0 : "redownloading partial segment: {} -> {}",
187 : remote_segfile, tmp_file
188 : );
189 :
190 0 : let mut reader = wal_backup::read_object(&remote_segfile, 0).await?;
191 0 : let mut file = File::create(&tmp_file).await?;
192 :
193 0 : let actual_len = tokio::io::copy(&mut reader, &mut file).await?;
194 0 : let expected_len = partial.flush_lsn.segment_offset(mgr.wal_seg_size);
195 0 :
196 0 : if actual_len != expected_len as u64 {
197 0 : anyhow::bail!(
198 0 : "partial downloaded {} bytes, expected {}",
199 0 : actual_len,
200 0 : expected_len
201 0 : );
202 0 : }
203 0 :
204 0 : if actual_len > mgr.wal_seg_size as u64 {
205 0 : anyhow::bail!(
206 0 : "remote segment is too long: {} bytes, expected {}",
207 0 : actual_len,
208 0 : mgr.wal_seg_size
209 0 : );
210 0 : }
211 0 : file.set_len(mgr.wal_seg_size as u64).await?;
212 0 : file.flush().await?;
213 :
214 0 : let final_path = local_segment_path(mgr, partial);
215 0 : info!("downloaded {actual_len} bytes, renaming to {final_path}");
216 0 : if let Err(e) = durable_rename(&tmp_file, &final_path, !mgr.conf.no_sync).await {
217 : // Probably rename succeeded, but fsync of it failed. Remove
218 : // the file then to avoid using it.
219 0 : tokio::fs::remove_file(tmp_file)
220 0 : .await
221 0 : .or_else(utils::fs_ext::ignore_not_found)?;
222 0 : return Err(e.into());
223 0 : }
224 0 :
225 0 : Ok(())
226 0 : }
227 :
228 : /// Compare local WAL segment with partial WAL backup in remote storage.
229 : /// If the local segment is not present, the function does nothing.
230 : /// If the local segment is present, it compares the local segment with the remote one.
231 0 : async fn compare_local_segment_with_remote(
232 0 : mgr: &Manager,
233 0 : partial: &PartialRemoteSegment,
234 0 : ) -> anyhow::Result<()> {
235 0 : let local_path = local_segment_path(mgr, partial);
236 0 :
237 0 : match File::open(&local_path).await {
238 0 : Ok(mut local_file) => do_validation(mgr, &mut local_file, mgr.wal_seg_size, partial)
239 0 : .await
240 0 : .context("validation failed"),
241 : Err(_) => {
242 0 : info!(
243 0 : "local WAL file {} is not present, skipping validation",
244 : local_path
245 : );
246 0 : Ok(())
247 : }
248 : }
249 0 : }
250 :
251 : /// Compare opened local WAL segment with partial WAL backup in remote storage.
252 : /// Validate full content of both files.
253 0 : async fn do_validation(
254 0 : mgr: &Manager,
255 0 : file: &mut File,
256 0 : wal_seg_size: usize,
257 0 : partial: &PartialRemoteSegment,
258 0 : ) -> anyhow::Result<()> {
259 0 : let local_size = file.metadata().await?.len() as usize;
260 0 : if local_size != wal_seg_size {
261 0 : anyhow::bail!(
262 0 : "local segment size is invalid: found {}, expected {}",
263 0 : local_size,
264 0 : wal_seg_size
265 0 : );
266 0 : }
267 0 :
268 0 : let remote_segfile = remote_segment_path(mgr, partial);
269 0 : let mut remote_reader: std::pin::Pin<Box<dyn AsyncRead + Send + Sync>> =
270 0 : wal_backup::read_object(&remote_segfile, 0).await?;
271 :
272 : // remote segment should have bytes excatly up to `flush_lsn`
273 0 : let expected_remote_size = partial.flush_lsn.segment_offset(mgr.wal_seg_size);
274 0 : // let's compare the first `expected_remote_size` bytes
275 0 : compare_n_bytes(&mut remote_reader, file, expected_remote_size).await?;
276 : // and check that the remote segment ends here
277 0 : check_end(&mut remote_reader).await?;
278 :
279 : // if local segment is longer, the rest should be zeroes
280 0 : read_n_zeroes(file, mgr.wal_seg_size - expected_remote_size).await?;
281 : // and check that the local segment ends here
282 0 : check_end(file).await?;
283 :
284 0 : Ok(())
285 0 : }
286 :
287 0 : fn local_segment_path(mgr: &Manager, partial: &PartialRemoteSegment) -> Utf8PathBuf {
288 0 : let flush_lsn = partial.flush_lsn;
289 0 : let segno = flush_lsn.segment_number(mgr.wal_seg_size);
290 0 : let (_, local_partial_segfile) =
291 0 : wal_file_paths(mgr.tli.timeline_dir(), segno, mgr.wal_seg_size);
292 0 : local_partial_segfile
293 0 : }
294 :
295 0 : fn remote_segment_path(mgr: &Manager, partial: &PartialRemoteSegment) -> RemotePath {
296 0 : partial.remote_path(&mgr.tli.remote_path)
297 0 : }
298 :
299 : /// Compare first `n` bytes of two readers. If the bytes differ, return an error.
300 : /// If the readers are shorter than `n`, return an error.
301 0 : async fn compare_n_bytes<R1, R2>(reader1: &mut R1, reader2: &mut R2, n: usize) -> anyhow::Result<()>
302 0 : where
303 0 : R1: AsyncRead + Unpin,
304 0 : R2: AsyncRead + Unpin,
305 0 : {
306 : use tokio::io::AsyncReadExt;
307 :
308 : const BUF_SIZE: usize = 32 * 1024;
309 :
310 0 : let mut buffer1 = vec![0u8; BUF_SIZE];
311 0 : let mut buffer2 = vec![0u8; BUF_SIZE];
312 0 :
313 0 : let mut offset = 0;
314 :
315 0 : while offset < n {
316 0 : let bytes_to_read = std::cmp::min(BUF_SIZE, n - offset);
317 :
318 0 : let bytes_read1 = reader1
319 0 : .read(&mut buffer1[..bytes_to_read])
320 0 : .await
321 0 : .with_context(|| format!("failed to read from reader1 at offset {}", offset))?;
322 0 : if bytes_read1 == 0 {
323 0 : anyhow::bail!("unexpected EOF from reader1 at offset {}", offset);
324 0 : }
325 :
326 0 : let bytes_read2 = reader2
327 0 : .read_exact(&mut buffer2[..bytes_read1])
328 0 : .await
329 0 : .with_context(|| {
330 0 : format!(
331 0 : "failed to read {} bytes from reader2 at offset {}",
332 0 : bytes_read1, offset
333 0 : )
334 0 : })?;
335 0 : assert!(bytes_read2 == bytes_read1);
336 :
337 0 : if buffer1[..bytes_read1] != buffer2[..bytes_read2] {
338 0 : let diff_offset = buffer1[..bytes_read1]
339 0 : .iter()
340 0 : .zip(buffer2[..bytes_read2].iter())
341 0 : .position(|(a, b)| a != b)
342 0 : .expect("mismatched buffers, but no difference found");
343 0 : anyhow::bail!("mismatch at offset {}", offset + diff_offset);
344 0 : }
345 0 :
346 0 : offset += bytes_read1;
347 : }
348 :
349 0 : Ok(())
350 0 : }
351 :
352 0 : async fn check_end<R>(mut reader: R) -> anyhow::Result<()>
353 0 : where
354 0 : R: AsyncRead + Unpin,
355 0 : {
356 : use tokio::io::AsyncReadExt;
357 :
358 0 : let mut buffer = [0u8; 1];
359 0 : let bytes_read = reader.read(&mut buffer).await?;
360 0 : if bytes_read != 0 {
361 0 : anyhow::bail!("expected EOF, found bytes");
362 0 : }
363 0 : Ok(())
364 0 : }
365 :
366 0 : async fn read_n_zeroes<R>(reader: &mut R, n: usize) -> anyhow::Result<()>
367 0 : where
368 0 : R: AsyncRead + Unpin,
369 0 : {
370 : use tokio::io::AsyncReadExt;
371 :
372 : const BUF_SIZE: usize = 32 * 1024;
373 0 : let mut buffer = vec![0u8; BUF_SIZE];
374 0 : let mut offset = 0;
375 :
376 0 : while offset < n {
377 0 : let bytes_to_read = std::cmp::min(BUF_SIZE, n - offset);
378 :
379 0 : let bytes_read = reader
380 0 : .read(&mut buffer[..bytes_to_read])
381 0 : .await
382 0 : .context("expected zeroes, got read error")?;
383 0 : if bytes_read == 0 {
384 0 : anyhow::bail!("expected zeroes, got EOF");
385 0 : }
386 0 :
387 0 : if buffer[..bytes_read].iter().all(|&b| b == 0) {
388 0 : offset += bytes_read;
389 0 : } else {
390 0 : anyhow::bail!("non-zero byte found");
391 : }
392 : }
393 :
394 0 : Ok(())
395 0 : }
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