Line data Source code
1 : //! An in-memory layer stores recently received key-value pairs.
2 : //!
3 : //! The "in-memory" part of the name is a bit misleading: the actual page versions are
4 : //! held in an ephemeral file, not in memory. The metadata for each page version, i.e.
5 : //! its position in the file, is kept in memory, though.
6 : //!
7 : use crate::config::PageServerConf;
8 : use crate::context::{PageContentKind, RequestContext, RequestContextBuilder};
9 : use crate::repository::{Key, Value};
10 : use crate::tenant::block_io::BlockReader;
11 : use crate::tenant::ephemeral_file::EphemeralFile;
12 : use crate::tenant::storage_layer::{ValueReconstructResult, ValueReconstructState};
13 : use crate::tenant::Timeline;
14 : use crate::walrecord;
15 : use anyhow::{ensure, Result};
16 : use pageserver_api::models::InMemoryLayerInfo;
17 : use pageserver_api::shard::TenantShardId;
18 : use std::collections::HashMap;
19 : use std::sync::{Arc, OnceLock};
20 : use tracing::*;
21 : use utils::{bin_ser::BeSer, id::TimelineId, lsn::Lsn, vec_map::VecMap};
22 : // avoid binding to Write (conflicts with std::io::Write)
23 : // while being able to use std::fmt::Write's methods
24 : use std::fmt::Write as _;
25 : use std::ops::Range;
26 : use tokio::sync::{RwLock, RwLockWriteGuard};
27 :
28 : use super::{DeltaLayerWriter, ResidentLayer};
29 :
30 : pub struct InMemoryLayer {
31 : conf: &'static PageServerConf,
32 : tenant_shard_id: TenantShardId,
33 : timeline_id: TimelineId,
34 :
35 : /// This layer contains all the changes from 'start_lsn'. The
36 : /// start is inclusive.
37 : start_lsn: Lsn,
38 :
39 : /// Frozen layers have an exclusive end LSN.
40 : /// Writes are only allowed when this is `None`.
41 : end_lsn: OnceLock<Lsn>,
42 :
43 : /// The above fields never change, except for `end_lsn`, which is only set once.
44 : /// All other changing parts are in `inner`, and protected by a mutex.
45 : inner: RwLock<InMemoryLayerInner>,
46 : }
47 :
48 : impl std::fmt::Debug for InMemoryLayer {
49 0 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
50 0 : f.debug_struct("InMemoryLayer")
51 0 : .field("start_lsn", &self.start_lsn)
52 0 : .field("end_lsn", &self.end_lsn)
53 0 : .field("inner", &self.inner)
54 0 : .finish()
55 0 : }
56 : }
57 :
58 : pub struct InMemoryLayerInner {
59 : /// All versions of all pages in the layer are kept here. Indexed
60 : /// by block number and LSN. The value is an offset into the
61 : /// ephemeral file where the page version is stored.
62 : index: HashMap<Key, VecMap<Lsn, u64>>,
63 :
64 : /// The values are stored in a serialized format in this file.
65 : /// Each serialized Value is preceded by a 'u32' length field.
66 : /// PerSeg::page_versions map stores offsets into this file.
67 : file: EphemeralFile,
68 : }
69 :
70 : impl std::fmt::Debug for InMemoryLayerInner {
71 0 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
72 0 : f.debug_struct("InMemoryLayerInner").finish()
73 0 : }
74 : }
75 :
76 : impl InMemoryLayer {
77 337 : pub(crate) fn get_timeline_id(&self) -> TimelineId {
78 337 : self.timeline_id
79 337 : }
80 :
81 4 : pub(crate) fn info(&self) -> InMemoryLayerInfo {
82 4 : let lsn_start = self.start_lsn;
83 :
84 4 : if let Some(&lsn_end) = self.end_lsn.get() {
85 0 : InMemoryLayerInfo::Frozen { lsn_start, lsn_end }
86 : } else {
87 4 : InMemoryLayerInfo::Open { lsn_start }
88 : }
89 4 : }
90 :
91 2932753 : pub(crate) fn assert_writable(&self) {
92 2932753 : assert!(self.end_lsn.get().is_none());
93 2932753 : }
94 :
95 29921801 : pub(crate) fn end_lsn_or_max(&self) -> Lsn {
96 29921801 : self.end_lsn.get().copied().unwrap_or(Lsn::MAX)
97 29921801 : }
98 :
99 29916198 : pub(crate) fn get_lsn_range(&self) -> Range<Lsn> {
100 29916198 : self.start_lsn..self.end_lsn_or_max()
101 29916198 : }
102 :
103 : /// debugging function to print out the contents of the layer
104 : ///
105 : /// this is likely completly unused
106 0 : pub async fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
107 0 : let inner = self.inner.read().await;
108 :
109 0 : let end_str = self.end_lsn_or_max();
110 0 :
111 0 : println!(
112 0 : "----- in-memory layer for tli {} LSNs {}-{} ----",
113 0 : self.timeline_id, self.start_lsn, end_str,
114 0 : );
115 0 :
116 0 : if !verbose {
117 0 : return Ok(());
118 0 : }
119 0 :
120 0 : let cursor = inner.file.block_cursor();
121 0 : let mut buf = Vec::new();
122 0 : for (key, vec_map) in inner.index.iter() {
123 0 : for (lsn, pos) in vec_map.as_slice() {
124 0 : let mut desc = String::new();
125 0 : cursor.read_blob_into_buf(*pos, &mut buf, ctx).await?;
126 0 : let val = Value::des(&buf);
127 0 : match val {
128 0 : Ok(Value::Image(img)) => {
129 0 : write!(&mut desc, " img {} bytes", img.len())?;
130 : }
131 0 : Ok(Value::WalRecord(rec)) => {
132 0 : let wal_desc = walrecord::describe_wal_record(&rec).unwrap();
133 0 : write!(
134 0 : &mut desc,
135 0 : " rec {} bytes will_init: {} {}",
136 0 : buf.len(),
137 0 : rec.will_init(),
138 0 : wal_desc
139 0 : )?;
140 : }
141 0 : Err(err) => {
142 0 : write!(&mut desc, " DESERIALIZATION ERROR: {}", err)?;
143 : }
144 : }
145 0 : println!(" key {} at {}: {}", key, lsn, desc);
146 : }
147 : }
148 :
149 0 : Ok(())
150 0 : }
151 :
152 : /// Look up given value in the layer.
153 6962343 : pub(crate) async fn get_value_reconstruct_data(
154 6962343 : &self,
155 6962343 : key: Key,
156 6962343 : lsn_range: Range<Lsn>,
157 6962343 : reconstruct_state: &mut ValueReconstructState,
158 6962343 : ctx: &RequestContext,
159 6962343 : ) -> anyhow::Result<ValueReconstructResult> {
160 6962339 : ensure!(lsn_range.start >= self.start_lsn);
161 6962339 : let mut need_image = true;
162 6962339 :
163 6962339 : let ctx = RequestContextBuilder::extend(ctx)
164 6962339 : .page_content_kind(PageContentKind::InMemoryLayer)
165 6962339 : .build();
166 :
167 6962339 : let inner = self.inner.read().await;
168 :
169 6962339 : let reader = inner.file.block_cursor();
170 :
171 : // Scan the page versions backwards, starting from `lsn`.
172 6962339 : if let Some(vec_map) = inner.index.get(&key) {
173 4203246 : let slice = vec_map.slice_range(lsn_range);
174 34868495 : for (entry_lsn, pos) in slice.iter().rev() {
175 34868495 : let buf = reader.read_blob(*pos, &ctx).await?;
176 34868495 : let value = Value::des(&buf)?;
177 34868495 : match value {
178 1577349 : Value::Image(img) => {
179 1577349 : reconstruct_state.img = Some((*entry_lsn, img));
180 1577349 : return Ok(ValueReconstructResult::Complete);
181 : }
182 33291146 : Value::WalRecord(rec) => {
183 33291146 : let will_init = rec.will_init();
184 33291146 : reconstruct_state.records.push((*entry_lsn, rec));
185 33291146 : if will_init {
186 : // This WAL record initializes the page, so no need to go further back
187 537941 : need_image = false;
188 537941 : break;
189 32753205 : }
190 : }
191 : }
192 : }
193 2759093 : }
194 :
195 : // release lock on 'inner'
196 :
197 : // If an older page image is needed to reconstruct the page, let the
198 : // caller know.
199 5384990 : if need_image {
200 4847049 : Ok(ValueReconstructResult::Continue)
201 : } else {
202 537941 : Ok(ValueReconstructResult::Complete)
203 : }
204 6962339 : }
205 : }
206 :
207 : impl std::fmt::Display for InMemoryLayer {
208 5603 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
209 5603 : let end_lsn = self.end_lsn_or_max();
210 5603 : write!(f, "inmem-{:016X}-{:016X}", self.start_lsn.0, end_lsn.0)
211 5603 : }
212 : }
213 :
214 : impl InMemoryLayer {
215 : /// Get layer size.
216 1400622 : pub async fn size(&self) -> Result<u64> {
217 1400622 : let inner = self.inner.read().await;
218 1400622 : Ok(inner.file.len())
219 1400622 : }
220 :
221 : /// Create a new, empty, in-memory layer
222 5713 : pub async fn create(
223 5713 : conf: &'static PageServerConf,
224 5713 : timeline_id: TimelineId,
225 5713 : tenant_shard_id: TenantShardId,
226 5713 : start_lsn: Lsn,
227 5713 : ) -> Result<InMemoryLayer> {
228 0 : trace!("initializing new empty InMemoryLayer for writing on timeline {timeline_id} at {start_lsn}");
229 :
230 5713 : let file = EphemeralFile::create(conf, tenant_shard_id, timeline_id).await?;
231 :
232 5713 : Ok(InMemoryLayer {
233 5713 : conf,
234 5713 : timeline_id,
235 5713 : tenant_shard_id,
236 5713 : start_lsn,
237 5713 : end_lsn: OnceLock::new(),
238 5713 : inner: RwLock::new(InMemoryLayerInner {
239 5713 : index: HashMap::new(),
240 5713 : file,
241 5713 : }),
242 5713 : })
243 5713 : }
244 :
245 : // Write operations
246 :
247 : /// Common subroutine of the public put_wal_record() and put_page_image() functions.
248 : /// Adds the page version to the in-memory tree
249 1214102 : pub(crate) async fn put_value(
250 1214102 : &self,
251 1214102 : key: Key,
252 1214102 : lsn: Lsn,
253 1214102 : val: &Value,
254 1214102 : ctx: &RequestContext,
255 1214102 : ) -> Result<()> {
256 1214102 : let mut inner = self.inner.write().await;
257 1214102 : self.assert_writable();
258 1214102 : self.put_value_locked(&mut inner, key, lsn, val, ctx).await
259 1214102 : }
260 :
261 1718651 : pub(crate) async fn put_values(
262 1718651 : &self,
263 1718651 : values: &HashMap<Key, Vec<(Lsn, Value)>>,
264 1718651 : ctx: &RequestContext,
265 1718651 : ) -> Result<()> {
266 1718651 : let mut inner = self.inner.write().await;
267 1718651 : self.assert_writable();
268 12342190 : for (key, vals) in values {
269 74717538 : for (lsn, val) in vals {
270 64093999 : self.put_value_locked(&mut inner, *key, *lsn, val, ctx)
271 71121 : .await?;
272 : }
273 : }
274 1718650 : Ok(())
275 1718650 : }
276 :
277 65308101 : async fn put_value_locked(
278 65308101 : &self,
279 65308101 : locked_inner: &mut RwLockWriteGuard<'_, InMemoryLayerInner>,
280 65308101 : key: Key,
281 65308101 : lsn: Lsn,
282 65308101 : val: &Value,
283 65308101 : ctx: &RequestContext,
284 65308101 : ) -> Result<()> {
285 0 : trace!("put_value key {} at {}/{}", key, self.timeline_id, lsn);
286 :
287 65308100 : let off = {
288 : // Avoid doing allocations for "small" values.
289 : // In the regression test suite, the limit of 256 avoided allocations in 95% of cases:
290 : // https://github.com/neondatabase/neon/pull/5056#discussion_r1301975061
291 65308101 : let mut buf = smallvec::SmallVec::<[u8; 256]>::new();
292 65308101 : buf.clear();
293 65308101 : val.ser_into(&mut buf)?;
294 65308101 : locked_inner
295 65308101 : .file
296 65308101 : .write_blob(
297 65308101 : &buf,
298 65308101 : &RequestContextBuilder::extend(ctx)
299 65308101 : .page_content_kind(PageContentKind::InMemoryLayer)
300 65308101 : .build(),
301 65308101 : )
302 71480 : .await?
303 : };
304 :
305 65308100 : let vec_map = locked_inner.index.entry(key).or_default();
306 65308100 : let old = vec_map.append_or_update_last(lsn, off).unwrap().0;
307 65308100 : if old.is_some() {
308 : // We already had an entry for this LSN. That's odd..
309 0 : warn!("Key {} at {} already exists", key, lsn);
310 65308100 : }
311 :
312 65308100 : Ok(())
313 65308100 : }
314 :
315 19216 : pub(crate) async fn put_tombstones(&self, _key_ranges: &[(Range<Key>, Lsn)]) -> Result<()> {
316 19216 : // TODO: Currently, we just leak the storage for any deleted keys
317 19216 : Ok(())
318 19216 : }
319 :
320 : /// Records the end_lsn for non-dropped layers.
321 : /// `end_lsn` is exclusive
322 5288 : pub async fn freeze(&self, end_lsn: Lsn) {
323 5288 : let inner = self.inner.write().await;
324 :
325 5288 : assert!(self.start_lsn < end_lsn);
326 5288 : self.end_lsn.set(end_lsn).expect("end_lsn set only once");
327 :
328 5263643 : for vec_map in inner.index.values() {
329 35681071 : for (lsn, _pos) in vec_map.as_slice() {
330 35681071 : assert!(*lsn < end_lsn);
331 : }
332 : }
333 5288 : }
334 :
335 : /// Write this frozen in-memory layer to disk.
336 : ///
337 : /// Returns a new delta layer with all the same data as this in-memory layer
338 5186 : pub(crate) async fn write_to_disk(
339 5186 : &self,
340 5186 : timeline: &Arc<Timeline>,
341 5186 : ctx: &RequestContext,
342 5186 : ) -> Result<ResidentLayer> {
343 : // Grab the lock in read-mode. We hold it over the I/O, but because this
344 : // layer is not writeable anymore, no one should be trying to acquire the
345 : // write lock on it, so we shouldn't block anyone. There's one exception
346 : // though: another thread might have grabbed a reference to this layer
347 : // in `get_layer_for_write' just before the checkpointer called
348 : // `freeze`, and then `write_to_disk` on it. When the thread gets the
349 : // lock, it will see that it's not writeable anymore and retry, but it
350 : // would have to wait until we release it. That race condition is very
351 : // rare though, so we just accept the potential latency hit for now.
352 5186 : let inner = self.inner.read().await;
353 :
354 5186 : let end_lsn = *self.end_lsn.get().unwrap();
355 :
356 5186 : let mut delta_layer_writer = DeltaLayerWriter::new(
357 5186 : self.conf,
358 5186 : self.timeline_id,
359 5186 : self.tenant_shard_id,
360 5186 : Key::MIN,
361 5186 : self.start_lsn..end_lsn,
362 5186 : )
363 205 : .await?;
364 :
365 5186 : let mut buf = Vec::new();
366 5186 :
367 5186 : let cursor = inner.file.block_cursor();
368 5186 :
369 5186 : // Sort the keys because delta layer writer expects them sorted.
370 5186 : //
371 5186 : // NOTE: this sort can take up significant time if the layer has millions of
372 5186 : // keys. To speed up all the comparisons we convert the key to i128 and
373 5186 : // keep the value as a reference.
374 5213016 : let mut keys: Vec<_> = inner.index.iter().map(|(k, m)| (k.to_i128(), m)).collect();
375 136844622 : keys.sort_unstable_by_key(|k| k.0);
376 5186 :
377 5186 : let ctx = RequestContextBuilder::extend(ctx)
378 5186 : .page_content_kind(PageContentKind::InMemoryLayer)
379 5186 : .build();
380 5193826 : for (key, vec_map) in keys.iter() {
381 5193826 : let key = Key::from_i128(*key);
382 : // Write all page versions
383 35035862 : for (lsn, pos) in vec_map.as_slice() {
384 35035862 : cursor.read_blob_into_buf(*pos, &mut buf, &ctx).await?;
385 35035861 : let will_init = Value::des(&buf)?.will_init();
386 35035861 : delta_layer_writer
387 35035861 : .put_value_bytes(key, *lsn, &buf, will_init)
388 48979 : .await?;
389 : }
390 : }
391 :
392 : // MAX is used here because we identify L0 layers by full key range
393 5184 : let delta_layer = delta_layer_writer.finish(Key::MAX, timeline).await?;
394 5184 : Ok(delta_layer)
395 5184 : }
396 : }
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