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::RequestContext;
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::walrecord;
14 : use anyhow::{ensure, Result};
15 : use pageserver_api::models::InMemoryLayerInfo;
16 : use std::collections::HashMap;
17 : use std::sync::OnceLock;
18 : use tracing::*;
19 : use utils::{
20 : bin_ser::BeSer,
21 : id::{TenantId, TimelineId},
22 : lsn::Lsn,
23 : vec_map::VecMap,
24 : };
25 : // avoid binding to Write (conflicts with std::io::Write)
26 : // while being able to use std::fmt::Write's methods
27 : use std::fmt::Write as _;
28 : use std::ops::Range;
29 : use tokio::sync::RwLock;
30 :
31 : use super::{DeltaLayer, DeltaLayerWriter, Layer};
32 :
33 : pub struct InMemoryLayer {
34 : conf: &'static PageServerConf,
35 : tenant_id: TenantId,
36 : timeline_id: TimelineId,
37 :
38 : /// This layer contains all the changes from 'start_lsn'. The
39 : /// start is inclusive.
40 : start_lsn: Lsn,
41 :
42 : /// Frozen layers have an exclusive end LSN.
43 : /// Writes are only allowed when this is `None`.
44 : end_lsn: OnceLock<Lsn>,
45 :
46 : /// The above fields never change, except for `end_lsn`, which is only set once.
47 : /// All other changing parts are in `inner`, and protected by a mutex.
48 : inner: RwLock<InMemoryLayerInner>,
49 : }
50 :
51 : impl std::fmt::Debug for InMemoryLayer {
52 0 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
53 0 : f.debug_struct("InMemoryLayer")
54 0 : .field("start_lsn", &self.start_lsn)
55 0 : .field("end_lsn", &self.end_lsn)
56 0 : .field("inner", &self.inner)
57 0 : .finish()
58 0 : }
59 : }
60 :
61 : pub struct InMemoryLayerInner {
62 : /// All versions of all pages in the layer are kept here. Indexed
63 : /// by block number and LSN. The value is an offset into the
64 : /// ephemeral file where the page version is stored.
65 : index: HashMap<Key, VecMap<Lsn, u64>>,
66 :
67 : /// The values are stored in a serialized format in this file.
68 : /// Each serialized Value is preceded by a 'u32' length field.
69 : /// PerSeg::page_versions map stores offsets into this file.
70 : file: EphemeralFile,
71 : }
72 :
73 : impl std::fmt::Debug for InMemoryLayerInner {
74 0 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
75 0 : f.debug_struct("InMemoryLayerInner").finish()
76 0 : }
77 : }
78 :
79 : impl InMemoryLayer {
80 2 : pub(crate) fn get_timeline_id(&self) -> TimelineId {
81 2 : self.timeline_id
82 2 : }
83 :
84 23 : pub(crate) fn info(&self) -> InMemoryLayerInfo {
85 23 : let lsn_start = self.start_lsn;
86 :
87 23 : if let Some(&lsn_end) = self.end_lsn.get() {
88 0 : InMemoryLayerInfo::Frozen { lsn_start, lsn_end }
89 : } else {
90 23 : InMemoryLayerInfo::Open { lsn_start }
91 : }
92 23 : }
93 :
94 82545974 : pub(crate) fn assert_writable(&self) {
95 82545974 : assert!(self.end_lsn.get().is_none());
96 82545974 : }
97 :
98 131619481 : pub(crate) fn end_lsn_or_max(&self) -> Lsn {
99 131619481 : self.end_lsn.get().copied().unwrap_or(Lsn::MAX)
100 131619481 : }
101 :
102 131612965 : pub(crate) fn get_lsn_range(&self) -> Range<Lsn> {
103 131612965 : self.start_lsn..self.end_lsn_or_max()
104 131612965 : }
105 :
106 : /// debugging function to print out the contents of the layer
107 : ///
108 : /// this is likely completly unused
109 0 : pub async fn dump(&self, verbose: bool, _ctx: &RequestContext) -> Result<()> {
110 0 : let inner = self.inner.read().await;
111 :
112 0 : let end_str = self.end_lsn_or_max();
113 0 :
114 0 : println!(
115 0 : "----- in-memory layer for tli {} LSNs {}-{} ----",
116 0 : self.timeline_id, self.start_lsn, end_str,
117 0 : );
118 0 :
119 0 : if !verbose {
120 0 : return Ok(());
121 0 : }
122 0 :
123 0 : let cursor = inner.file.block_cursor();
124 0 : let mut buf = Vec::new();
125 0 : for (key, vec_map) in inner.index.iter() {
126 0 : for (lsn, pos) in vec_map.as_slice() {
127 0 : let mut desc = String::new();
128 0 : cursor.read_blob_into_buf(*pos, &mut buf).await?;
129 0 : let val = Value::des(&buf);
130 0 : match val {
131 0 : Ok(Value::Image(img)) => {
132 0 : write!(&mut desc, " img {} bytes", img.len())?;
133 : }
134 0 : Ok(Value::WalRecord(rec)) => {
135 0 : let wal_desc = walrecord::describe_wal_record(&rec).unwrap();
136 0 : write!(
137 0 : &mut desc,
138 0 : " rec {} bytes will_init: {} {}",
139 0 : buf.len(),
140 0 : rec.will_init(),
141 0 : wal_desc
142 0 : )?;
143 : }
144 0 : Err(err) => {
145 0 : write!(&mut desc, " DESERIALIZATION ERROR: {}", err)?;
146 : }
147 : }
148 0 : println!(" key {} at {}: {}", key, lsn, desc);
149 : }
150 : }
151 :
152 0 : Ok(())
153 0 : }
154 :
155 : /// Look up given value in the layer.
156 6248109 : pub(crate) async fn get_value_reconstruct_data(
157 6248109 : &self,
158 6248109 : key: Key,
159 6248109 : lsn_range: Range<Lsn>,
160 6248109 : reconstruct_state: &mut ValueReconstructState,
161 6248109 : _ctx: &RequestContext,
162 6248112 : ) -> anyhow::Result<ValueReconstructResult> {
163 6248112 : ensure!(lsn_range.start >= self.start_lsn);
164 6248112 : let mut need_image = true;
165 :
166 6248112 : let inner = self.inner.read().await;
167 :
168 6248112 : let reader = inner.file.block_cursor();
169 :
170 : // Scan the page versions backwards, starting from `lsn`.
171 6248112 : if let Some(vec_map) = inner.index.get(&key) {
172 3434973 : let slice = vec_map.slice_range(lsn_range);
173 33295413 : for (entry_lsn, pos) in slice.iter().rev() {
174 33295413 : let buf = reader.read_blob(*pos).await?;
175 33295412 : let value = Value::des(&buf)?;
176 33295412 : match value {
177 1641578 : Value::Image(img) => {
178 1641578 : reconstruct_state.img = Some((*entry_lsn, img));
179 1641578 : return Ok(ValueReconstructResult::Complete);
180 : }
181 31653834 : Value::WalRecord(rec) => {
182 31653834 : let will_init = rec.will_init();
183 31653834 : reconstruct_state.records.push((*entry_lsn, rec));
184 31653834 : if will_init {
185 : // This WAL record initializes the page, so no need to go further back
186 444686 : need_image = false;
187 444686 : break;
188 31209148 : }
189 : }
190 : }
191 : }
192 2813139 : }
193 :
194 : // release lock on 'inner'
195 :
196 : // If an older page image is needed to reconstruct the page, let the
197 : // caller know.
198 4606533 : if need_image {
199 4161847 : Ok(ValueReconstructResult::Continue)
200 : } else {
201 444686 : Ok(ValueReconstructResult::Complete)
202 : }
203 6248111 : }
204 : }
205 :
206 : #[async_trait::async_trait]
207 : impl Layer for InMemoryLayer {
208 0 : async fn get_value_reconstruct_data(
209 0 : &self,
210 0 : key: Key,
211 0 : lsn_range: Range<Lsn>,
212 0 : reconstruct_data: &mut ValueReconstructState,
213 0 : ctx: &RequestContext,
214 0 : ) -> Result<ValueReconstructResult> {
215 0 : self.get_value_reconstruct_data(key, lsn_range, reconstruct_data, ctx)
216 0 : .await
217 0 : }
218 : }
219 :
220 : impl std::fmt::Display for InMemoryLayer {
221 6516 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
222 6516 : let end_lsn = self.end_lsn_or_max();
223 6516 : write!(f, "inmem-{:016X}-{:016X}", self.start_lsn.0, end_lsn.0)
224 6516 : }
225 : }
226 :
227 : impl InMemoryLayer {
228 : ///
229 : /// Get layer size.
230 : ///
231 733761 : pub async fn size(&self) -> Result<u64> {
232 733761 : let inner = self.inner.read().await;
233 733761 : Ok(inner.file.len())
234 733761 : }
235 :
236 : ///
237 : /// Create a new, empty, in-memory layer
238 : ///
239 6868 : pub fn create(
240 6868 : conf: &'static PageServerConf,
241 6868 : timeline_id: TimelineId,
242 6868 : tenant_id: TenantId,
243 6868 : start_lsn: Lsn,
244 6868 : ) -> Result<InMemoryLayer> {
245 6868 : trace!("initializing new empty InMemoryLayer for writing on timeline {timeline_id} at {start_lsn}");
246 :
247 6868 : let file = EphemeralFile::create(conf, tenant_id, timeline_id)?;
248 :
249 6868 : Ok(InMemoryLayer {
250 6868 : conf,
251 6868 : timeline_id,
252 6868 : tenant_id,
253 6868 : start_lsn,
254 6868 : end_lsn: OnceLock::new(),
255 6868 : inner: RwLock::new(InMemoryLayerInner {
256 6868 : index: HashMap::new(),
257 6868 : file,
258 6868 : }),
259 6868 : })
260 6868 : }
261 :
262 : // Write operations
263 :
264 : /// Common subroutine of the public put_wal_record() and put_page_image() functions.
265 : /// Adds the page version to the in-memory tree
266 82545974 : pub async fn put_value(&self, key: Key, lsn: Lsn, val: &Value) -> Result<()> {
267 0 : trace!("put_value key {} at {}/{}", key, self.timeline_id, lsn);
268 82546097 : let inner: &mut _ = &mut *self.inner.write().await;
269 82546097 : self.assert_writable();
270 :
271 82546095 : let off = {
272 : // Avoid doing allocations for "small" values.
273 : // In the regression test suite, the limit of 256 avoided allocations in 95% of cases:
274 : // https://github.com/neondatabase/neon/pull/5056#discussion_r1301975061
275 82546097 : let mut buf = smallvec::SmallVec::<[u8; 256]>::new();
276 82546097 : buf.clear();
277 82546097 : val.ser_into(&mut buf)?;
278 82546097 : inner.file.write_blob(&buf).await?
279 : };
280 :
281 82546095 : let vec_map = inner.index.entry(key).or_default();
282 82546095 : let old = vec_map.append_or_update_last(lsn, off).unwrap().0;
283 82546095 : if old.is_some() {
284 : // We already had an entry for this LSN. That's odd..
285 0 : warn!("Key {} at {} already exists", key, lsn);
286 82546095 : }
287 :
288 82546095 : Ok(())
289 82546095 : }
290 :
291 17794 : pub async fn put_tombstone(&self, _key_range: Range<Key>, _lsn: Lsn) -> Result<()> {
292 17794 : // TODO: Currently, we just leak the storage for any deleted keys
293 17794 :
294 17794 : Ok(())
295 17794 : }
296 :
297 : /// Make the layer non-writeable. Only call once.
298 : /// Records the end_lsn for non-dropped layers.
299 : /// `end_lsn` is exclusive
300 6562 : pub async fn freeze(&self, end_lsn: Lsn) {
301 6562 : let inner = self.inner.write().await;
302 :
303 6562 : assert!(self.start_lsn < end_lsn);
304 6562 : self.end_lsn.set(end_lsn).expect("end_lsn set only once");
305 :
306 5263399 : for vec_map in inner.index.values() {
307 59430639 : for (lsn, _pos) in vec_map.as_slice() {
308 59430639 : assert!(*lsn < end_lsn);
309 : }
310 : }
311 6562 : }
312 :
313 : /// Write this frozen in-memory layer to disk.
314 : ///
315 : /// Returns a new delta layer with all the same data as this in-memory layer
316 6477 : pub(crate) async fn write_to_disk(&self) -> Result<DeltaLayer> {
317 : // Grab the lock in read-mode. We hold it over the I/O, but because this
318 : // layer is not writeable anymore, no one should be trying to acquire the
319 : // write lock on it, so we shouldn't block anyone. There's one exception
320 : // though: another thread might have grabbed a reference to this layer
321 : // in `get_layer_for_write' just before the checkpointer called
322 : // `freeze`, and then `write_to_disk` on it. When the thread gets the
323 : // lock, it will see that it's not writeable anymore and retry, but it
324 : // would have to wait until we release it. That race condition is very
325 : // rare though, so we just accept the potential latency hit for now.
326 6477 : let inner = self.inner.read().await;
327 :
328 6477 : let end_lsn = *self.end_lsn.get().unwrap();
329 :
330 6477 : let mut delta_layer_writer = DeltaLayerWriter::new(
331 6477 : self.conf,
332 6477 : self.timeline_id,
333 6477 : self.tenant_id,
334 6477 : Key::MIN,
335 6477 : self.start_lsn..end_lsn,
336 6477 : )
337 0 : .await?;
338 :
339 6477 : let mut buf = Vec::new();
340 6477 :
341 6477 : let cursor = inner.file.block_cursor();
342 6477 :
343 6477 : let mut keys: Vec<(&Key, &VecMap<Lsn, u64>)> = inner.index.iter().collect();
344 118417390 : keys.sort_by_key(|k| k.0);
345 :
346 5242685 : for (key, vec_map) in keys.iter() {
347 5242685 : let key = **key;
348 : // Write all page versions
349 59022791 : for (lsn, pos) in vec_map.as_slice() {
350 59022791 : cursor.read_blob_into_buf(*pos, &mut buf).await?;
351 59022790 : let will_init = Value::des(&buf)?.will_init();
352 59022790 : delta_layer_writer
353 59022790 : .put_value_bytes(key, *lsn, &buf, will_init)
354 0 : .await?;
355 : }
356 : }
357 :
358 6476 : let delta_layer = delta_layer_writer.finish(Key::MAX).await?;
359 6476 : Ok(delta_layer)
360 6476 : }
361 : }
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