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HACK: restore old impl, make runtime configurable (how to: reconfigure via HTTP, then kill existing walredo procs)

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This commit is contained in:
Christian Schwarz
2024-03-22 10:23:53 +00:00
parent 3aa4fc593e
commit 8265739e91
7 changed files with 872 additions and 336 deletions
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13
pageserver/src/http/routes.rs
View File

@@ -2080,6 +2080,16 @@ async fn put_io_engine_handler(
json_response(StatusCode::OK, ())
}
async fn put_walredo_process_kind(
mut r: Request<Body>,
_cancel: CancellationToken,
) -> Result<Response<Body>, ApiError> {
check_permission(&r, None)?;
let kind: crate::walredo::ProcessKind = json_request(&mut r).await?;
crate::walredo::set_process_kind(kind);
json_response(StatusCode::OK, ())
}
/// Polled by control plane.
///
/// See [`crate::utilization`].
@@ -2407,6 +2417,9 @@ pub fn make_router(
|r| api_handler(r, timeline_collect_keyspace),
)
.put("/v1/io_engine", |r| api_handler(r, put_io_engine_handler))
.put("/v1/walredo_process_kind", |r| {
api_handler(r, put_walredo_process_kind)
})
.get("/v1/utilization", |r| api_handler(r, get_utilization))
.any(handler_404))
}

14
pageserver/src/metrics.rs
View File

@@ -1805,6 +1805,20 @@ impl Default for WalRedoProcessCounters {
pub(crate) static WAL_REDO_PROCESS_COUNTERS: Lazy<WalRedoProcessCounters> =
Lazy::new(WalRedoProcessCounters::default);
#[cfg(not(test))]
pub(crate) mod wal_redo {
use super::*;
pub(crate) static PROCESS_KIND: Lazy<UIntGaugeVec> = Lazy::new(|| {
register_uint_gauge_vec!(
"pageserver_wal_redo_process_kind",
"The configured process kind for walredo",
&["kind"],
)
.unwrap()
});
}
/// Similar to `prometheus::HistogramTimer` but does not record on drop.
pub(crate) struct StorageTimeMetricsTimer {
metrics: StorageTimeMetrics,

7
pageserver/src/walredo.rs
View File

@@ -20,6 +20,7 @@
/// Process lifecycle and abstracction for the IPC protocol.
mod process;
pub(crate) use process::{Kind as ProcessKind, set_kind as set_process_kind};
/// Code to apply [`NeonWalRecord`]s.
pub(crate) mod apply_neon;
@@ -53,7 +54,7 @@ pub struct PostgresRedoManager {
tenant_shard_id: TenantShardId,
conf: &'static PageServerConf,
last_redo_at: std::sync::Mutex<Option<Instant>>,
redo_process: RwLock<Option<Arc<process::WalRedoProcess>>>,
redo_process: RwLock<Option<Arc<process::Process>>>,
}
///
@@ -194,7 +195,7 @@ impl PostgresRedoManager {
let mut n_attempts = 0u32;
loop {
// launch the WAL redo process on first use
let proc: Arc<process::WalRedoProcess> = {
let proc: Arc<process::Process> = {
let proc_guard = self.redo_process.read().unwrap();
match &*proc_guard {
None => {
@@ -205,7 +206,7 @@ impl PostgresRedoManager {
None => {
let start = Instant::now();
let proc = Arc::new(
process::WalRedoProcess::launch(
process::Process::launch(
self.conf,
self.tenant_shard_id,
pg_version,

410
pageserver/src/walredo/process.rs
View File

@@ -1,183 +1,86 @@
use self::no_leak_child::NoLeakChild;
use crate::{
config::PageServerConf,
metrics::{WalRedoKillCause, WAL_REDO_PROCESS_COUNTERS, WAL_REDO_RECORD_COUNTER},
walrecord::NeonWalRecord,
use std::{
sync::atomic::{AtomicU8, Ordering},
time::Duration,
};
use anyhow::Context;
use bytes::Bytes;
use pageserver_api::{reltag::RelTag, shard::TenantShardId};
use postgres_ffi::BLCKSZ;
#[cfg(feature = "testing")]
use std::sync::atomic::AtomicUsize;
use std::{
collections::VecDeque,
process::{Command, Stdio},
};
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tracing::{debug, error, instrument, Instrument};
use utils::{lsn::Lsn, poison::Poison};
use utils::lsn::Lsn;
use crate::{config::PageServerConf, walrecord::NeonWalRecord};
mod live_reconfig;
mod no_leak_child;
/// The IPC protocol that pageserver and walredo process speak over their shared pipe.
mod protocol;
pub struct WalRedoProcess {
#[allow(dead_code)]
conf: &'static PageServerConf,
tenant_shard_id: TenantShardId,
// Some() on construction, only becomes None on Drop.
child: Option<NoLeakChild>,
stdout: tokio::sync::Mutex<Poison<ProcessOutput>>,
stdin: tokio::sync::Mutex<Poison<ProcessInput>>,
/// Counter to separate same sized walredo inputs failing at the same millisecond.
#[cfg(feature = "testing")]
dump_sequence: AtomicUsize,
mod process_impl {
pub(super) mod process_async;
pub(super) mod process_std;
}
struct ProcessInput {
stdin: tokio::process::ChildStdin,
n_requests: usize,
#[derive(Clone, Copy, Debug, serde::Serialize, serde::Deserialize)]
#[repr(u8)]
pub(crate) enum Kind {
Sync,
Async,
}
struct ProcessOutput {
stdout: tokio::process::ChildStdout,
pending_responses: VecDeque<Option<Bytes>>,
n_processed_responses: usize,
impl TryFrom<u8> for Kind {
type Error = u8;
fn try_from(value: u8) -> Result<Self, Self::Error> {
Ok(match value {
v if v == (Kind::Sync as u8) => Kind::Sync,
v if v == (Kind::Async as u8) => Kind::Async,
x => return Err(x),
})
}
}
impl WalRedoProcess {
//
// Start postgres binary in special WAL redo mode.
//
#[instrument(skip_all,fields(pg_version=pg_version))]
pub(crate) fn launch(
static PROCESS_KIND: AtomicU8 = AtomicU8::new(Kind::Async as u8);
pub(crate) fn set_kind(kind: Kind) {
PROCESS_KIND.store(kind as u8, std::sync::atomic::Ordering::Relaxed);
#[cfg(not(test))]
{
let metric = &crate::metrics::wal_redo::PROCESS_KIND;
metric.reset();
metric.with_label_values(&[&format!("{kind:?}")]).set(1);
}
}
fn get() -> Kind {
Kind::try_from(PROCESS_KIND.load(Ordering::Relaxed)).unwrap()
}
pub(crate) enum Process {
Sync(process_impl::process_std::WalRedoProcess),
Async(process_impl::process_async::WalRedoProcess),
}
impl Process {
#[inline(always)]
pub fn launch(
conf: &'static PageServerConf,
tenant_shard_id: TenantShardId,
pg_version: u32,
) -> anyhow::Result<Self> {
crate::span::debug_assert_current_span_has_tenant_id();
let pg_bin_dir_path = conf.pg_bin_dir(pg_version).context("pg_bin_dir")?; // TODO these should be infallible.
let pg_lib_dir_path = conf.pg_lib_dir(pg_version).context("pg_lib_dir")?;
use no_leak_child::NoLeakChildCommandExt;
// Start postgres itself
let child = Command::new(pg_bin_dir_path.join("postgres"))
// the first arg must be --wal-redo so the child process enters into walredo mode
.arg("--wal-redo")
// the child doesn't process this arg, but, having it in the argv helps indentify the
// walredo process for a particular tenant when debugging a pagserver
.args(["--tenant-shard-id", &format!("{tenant_shard_id}")])
.stdin(Stdio::piped())
.stderr(Stdio::piped())
.stdout(Stdio::piped())
.env_clear()
.env("LD_LIBRARY_PATH", &pg_lib_dir_path)
.env("DYLD_LIBRARY_PATH", &pg_lib_dir_path)
// NB: The redo process is not trusted after we sent it the first
// walredo work. Before that, it is trusted. Specifically, we trust
// it to
// 1. close all file descriptors except stdin, stdout, stderr because
// pageserver might not be 100% diligent in setting FD_CLOEXEC on all
// the files it opens, and
// 2. to use seccomp to sandbox itself before processing the first
// walredo request.
.spawn_no_leak_child(tenant_shard_id)
.context("spawn process")?;
WAL_REDO_PROCESS_COUNTERS.started.inc();
let mut child = scopeguard::guard(child, |child| {
error!("killing wal-redo-postgres process due to a problem during launch");
child.kill_and_wait(WalRedoKillCause::Startup);
});
let stdin = child.stdin.take().unwrap();
let stdout = child.stdout.take().unwrap();
let stderr = child.stderr.take().unwrap();
let stderr = tokio::process::ChildStderr::from_std(stderr)
.context("convert to tokio::ChildStderr")?;
let stdin =
tokio::process::ChildStdin::from_std(stdin).context("convert to tokio::ChildStdin")?;
let stdout = tokio::process::ChildStdout::from_std(stdout)
.context("convert to tokio::ChildStdout")?;
// all fallible operations post-spawn are complete, so get rid of the guard
let child = scopeguard::ScopeGuard::into_inner(child);
tokio::spawn(
async move {
scopeguard::defer! {
debug!("wal-redo-postgres stderr_logger_task finished");
crate::metrics::WAL_REDO_PROCESS_COUNTERS.active_stderr_logger_tasks_finished.inc();
}
debug!("wal-redo-postgres stderr_logger_task started");
crate::metrics::WAL_REDO_PROCESS_COUNTERS.active_stderr_logger_tasks_started.inc();
use tokio::io::AsyncBufReadExt;
let mut stderr_lines = tokio::io::BufReader::new(stderr);
let mut buf = Vec::new();
let res = loop {
buf.clear();
// TODO we don't trust the process to cap its stderr length.
// Currently it can do unbounded Vec allocation.
match stderr_lines.read_until(b'\n', &mut buf).await {
Ok(0) => break Ok(()), // eof
Ok(num_bytes) => {
let output = String::from_utf8_lossy(&buf[..num_bytes]);
error!(%output, "received output");
}
Err(e) => {
break Err(e);
}
}
};
match res {
Ok(()) => (),
Err(e) => {
error!(error=?e, "failed to read from walredo stderr");
}
}
}.instrument(tracing::info_span!(parent: None, "wal-redo-postgres-stderr", pid = child.id(), tenant_id = %tenant_shard_id.tenant_id, shard_id = %tenant_shard_id.shard_slug(), %pg_version))
);
Ok(Self {
conf,
tenant_shard_id,
child: Some(child),
stdin: tokio::sync::Mutex::new(Poison::new(
"stdin",
ProcessInput {
stdin,
n_requests: 0,
},
)),
stdout: tokio::sync::Mutex::new(Poison::new(
"stdout",
ProcessOutput {
stdout,
pending_responses: VecDeque::new(),
n_processed_responses: 0,
},
)),
#[cfg(feature = "testing")]
dump_sequence: AtomicUsize::default(),
Ok(match get() {
Kind::Sync => Self::Sync(process_impl::process_std::WalRedoProcess::launch(
conf,
tenant_shard_id,
pg_version,
)?),
Kind::Async => Self::Async(process_impl::process_async::WalRedoProcess::launch(
conf,
tenant_shard_id,
pg_version,
)?),
})
}
pub(crate) fn id(&self) -> u32 {
self.child
.as_ref()
.expect("must not call this during Drop")
.id()
}
/// Apply given WAL records ('records') over an old page image. Returns
/// new page image.
///
/// # Cancel-Safety
///
/// Cancellation safe.
#[instrument(skip_all, level = tracing::Level::DEBUG, fields(tenant_id=%self.tenant_shard_id.tenant_id, shard_id=%self.tenant_shard_id.shard_slug(), pid=%self.id()))]
#[inline(always)]
pub(crate) async fn apply_wal_records(
&self,
rel: RelTag,
@@ -185,184 +88,25 @@ impl WalRedoProcess {
base_img: &Option<Bytes>,
records: &[(Lsn, NeonWalRecord)],
) -> anyhow::Result<Bytes> {
let tag = protocol::BufferTag { rel, blknum };
// Serialize all the messages to send the WAL redo process first.
//
// This could be problematic if there are millions of records to replay,
// but in practice the number of records is usually so small that it doesn't
// matter, and it's better to keep this code simple.
//
// Most requests start with a before-image with BLCKSZ bytes, followed by
// by some other WAL records. Start with a buffer that can hold that
// comfortably.
let mut writebuf: Vec<u8> = Vec::with_capacity((BLCKSZ as usize) * 3);
protocol::build_begin_redo_for_block_msg(tag, &mut writebuf);
if let Some(img) = base_img {
protocol::build_push_page_msg(tag, img, &mut writebuf);
}
for (lsn, rec) in records.iter() {
if let NeonWalRecord::Postgres {
will_init: _,
rec: postgres_rec,
} = rec
{
protocol::build_apply_record_msg(*lsn, postgres_rec, &mut writebuf);
} else {
anyhow::bail!("tried to pass neon wal record to postgres WAL redo");
}
}
protocol::build_get_page_msg(tag, &mut writebuf);
WAL_REDO_RECORD_COUNTER.inc_by(records.len() as u64);
let res = self.apply_wal_records0(&writebuf).await;
if res.is_err() {
// not all of these can be caused by this particular input, however these are so rare
// in tests so capture all.
self.record_and_log(&writebuf);
}
res
}
/// # Cancel-Safety
///
/// Cancellation safe (enforced through the use of [`utils::poison::Poison`]).
async fn apply_wal_records0(&self, writebuf: &[u8]) -> anyhow::Result<Bytes> {
let request_no = {
let mut lock_guard = self.stdin.lock().await;
let mut poison_guard = lock_guard.check_and_arm()?;
let input = poison_guard.data_mut();
input
.stdin
.write_all(writebuf)
match self {
Process::Sync(p) => {
p.apply_wal_records(
rel,
blknum,
base_img,
records,
Duration::from_secs(100000), /* TODO remove */
)
.await
.context("write to walredo stdin")?;
let request_no = input.n_requests;
input.n_requests += 1;
poison_guard.disarm();
request_no
};
// To improve walredo performance we separate sending requests and receiving
// responses. Them are protected by different mutexes (output and input).
// If thread T1, T2, T3 send requests D1, D2, D3 to walredo process
// then there is not warranty that T1 will first granted output mutex lock.
// To address this issue we maintain number of sent requests, number of processed
// responses and ring buffer with pending responses. After sending response
// (under input mutex), threads remembers request number. Then it releases
// input mutex, locks output mutex and fetch in ring buffer all responses until
// its stored request number. The it takes correspondent element from
// pending responses ring buffer and truncate all empty elements from the front,
// advancing processed responses number.
let mut lock_guard = self.stdout.lock().await;
let mut poison_guard = lock_guard.check_and_arm()?;
let output = poison_guard.data_mut();
let n_processed_responses = output.n_processed_responses;
while n_processed_responses + output.pending_responses.len() <= request_no {
// We expect the WAL redo process to respond with an 8k page image. We read it
// into this buffer.
let mut resultbuf = vec![0; BLCKSZ.into()];
output
.stdout
.read_exact(&mut resultbuf)
.await
.context("read walredo stdout")?;
output
.pending_responses
.push_back(Some(Bytes::from(resultbuf)));
}
// Replace our request's response with None in `pending_responses`.
// Then make space in the ring buffer by clearing out any seqence of contiguous
// `None`'s from the front of `pending_responses`.
// NB: We can't pop_front() because other requests' responses because another
// requester might have grabbed the output mutex before us:
// T1: grab input mutex
// T1: send request_no 23
// T1: release input mutex
// T2: grab input mutex
// T2: send request_no 24
// T2: release input mutex
// T2: grab output mutex
// T2: n_processed_responses + output.pending_responses.len() <= request_no
// 23 0 24
// T2: enters poll loop that reads stdout
// T2: put response for 23 into pending_responses
// T2: put response for 24 into pending_resposnes
// pending_responses now looks like this: Front Some(response_23) Some(response_24) Back
// T2: takes its response_24
// pending_responses now looks like this: Front Some(response_23) None Back
// T2: does the while loop below
// pending_responses now looks like this: Front Some(response_23) None Back
// T2: releases output mutex
// T1: grabs output mutex
// T1: n_processed_responses + output.pending_responses.len() > request_no
// 23 2 23
// T1: skips poll loop that reads stdout
// T1: takes its response_23
// pending_responses now looks like this: Front None None Back
// T2: does the while loop below
// pending_responses now looks like this: Front Back
// n_processed_responses now has value 25
let res = output.pending_responses[request_no - n_processed_responses]
.take()
.expect("we own this request_no, nobody else is supposed to take it");
while let Some(front) = output.pending_responses.front() {
if front.is_none() {
output.pending_responses.pop_front();
output.n_processed_responses += 1;
} else {
break;
}
}
poison_guard.disarm();
Ok(res)
}
#[cfg(feature = "testing")]
fn record_and_log(&self, writebuf: &[u8]) {
use std::sync::atomic::Ordering;
let millis = std::time::SystemTime::now()
.duration_since(std::time::SystemTime::UNIX_EPOCH)
.unwrap()
.as_millis();
let seq = self.dump_sequence.fetch_add(1, Ordering::Relaxed);
// these files will be collected to an allure report
let filename = format!("walredo-{millis}-{}-{seq}.walredo", writebuf.len());
let path = self.conf.tenant_path(&self.tenant_shard_id).join(&filename);
use std::io::Write;
let res = std::fs::OpenOptions::new()
.write(true)
.create_new(true)
.read(true)
.open(path)
.and_then(|mut f| f.write_all(writebuf));
// trip up allowed_errors
if let Err(e) = res {
tracing::error!(target=%filename, length=writebuf.len(), "failed to write out the walredo errored input: {e}");
} else {
tracing::error!(filename, "erroring walredo input saved");
Process::Async(p) => p.apply_wal_records(rel, blknum, base_img, records).await,
}
}
#[cfg(not(feature = "testing"))]
fn record_and_log(&self, _: &[u8]) {}
}
impl Drop for WalRedoProcess {
fn drop(&mut self) {
self.child
.take()
.expect("we only do this once")
.kill_and_wait(WalRedoKillCause::WalRedoProcessDrop);
// no way to wait for stderr_logger_task from Drop because that is async only
pub(crate) fn id(&self) -> u32 {
match self {
Process::Sync(p) => p.id(),
Process::Async(p) => p.id(),
}
}
}

0
pageserver/src/walredo/process/live_reconfig.rs Normal file
View File

362
pageserver/src/walredo/process/process_impl/process_async.rs Normal file
View File

@@ -0,0 +1,362 @@
use self::no_leak_child::NoLeakChild;
use crate::{
config::PageServerConf, metrics::{WalRedoKillCause, WAL_REDO_PROCESS_COUNTERS, WAL_REDO_RECORD_COUNTER}, walrecord::NeonWalRecord, walredo::process::{no_leak_child, protocol}
};
use anyhow::Context;
use bytes::Bytes;
use pageserver_api::{reltag::RelTag, shard::TenantShardId};
use postgres_ffi::BLCKSZ;
#[cfg(feature = "testing")]
use std::sync::atomic::AtomicUsize;
use std::{
collections::VecDeque,
process::{Command, Stdio},
};
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tracing::{debug, error, instrument, Instrument};
use utils::{lsn::Lsn, poison::Poison};
pub struct WalRedoProcess {
#[allow(dead_code)]
conf: &'static PageServerConf,
tenant_shard_id: TenantShardId,
// Some() on construction, only becomes None on Drop.
child: Option<NoLeakChild>,
stdout: tokio::sync::Mutex<Poison<ProcessOutput>>,
stdin: tokio::sync::Mutex<Poison<ProcessInput>>,
/// Counter to separate same sized walredo inputs failing at the same millisecond.
#[cfg(feature = "testing")]
dump_sequence: AtomicUsize,
}
struct ProcessInput {
stdin: tokio::process::ChildStdin,
n_requests: usize,
}
struct ProcessOutput {
stdout: tokio::process::ChildStdout,
pending_responses: VecDeque<Option<Bytes>>,
n_processed_responses: usize,
}
impl WalRedoProcess {
//
// Start postgres binary in special WAL redo mode.
//
#[instrument(skip_all,fields(pg_version=pg_version))]
pub(crate) fn launch(
conf: &'static PageServerConf,
tenant_shard_id: TenantShardId,
pg_version: u32,
) -> anyhow::Result<Self> {
crate::span::debug_assert_current_span_has_tenant_id();
let pg_bin_dir_path = conf.pg_bin_dir(pg_version).context("pg_bin_dir")?; // TODO these should be infallible.
let pg_lib_dir_path = conf.pg_lib_dir(pg_version).context("pg_lib_dir")?;
use no_leak_child::NoLeakChildCommandExt;
// Start postgres itself
let child = Command::new(pg_bin_dir_path.join("postgres"))
// the first arg must be --wal-redo so the child process enters into walredo mode
.arg("--wal-redo")
// the child doesn't process this arg, but, having it in the argv helps indentify the
// walredo process for a particular tenant when debugging a pagserver
.args(["--tenant-shard-id", &format!("{tenant_shard_id}")])
.stdin(Stdio::piped())
.stderr(Stdio::piped())
.stdout(Stdio::piped())
.env_clear()
.env("LD_LIBRARY_PATH", &pg_lib_dir_path)
.env("DYLD_LIBRARY_PATH", &pg_lib_dir_path)
// NB: The redo process is not trusted after we sent it the first
// walredo work. Before that, it is trusted. Specifically, we trust
// it to
// 1. close all file descriptors except stdin, stdout, stderr because
// pageserver might not be 100% diligent in setting FD_CLOEXEC on all
// the files it opens, and
// 2. to use seccomp to sandbox itself before processing the first
// walredo request.
.spawn_no_leak_child(tenant_shard_id)
.context("spawn process")?;
WAL_REDO_PROCESS_COUNTERS.started.inc();
let mut child = scopeguard::guard(child, |child| {
error!("killing wal-redo-postgres process due to a problem during launch");
child.kill_and_wait(WalRedoKillCause::Startup);
});
let stdin = child.stdin.take().unwrap();
let stdout = child.stdout.take().unwrap();
let stderr = child.stderr.take().unwrap();
let stderr = tokio::process::ChildStderr::from_std(stderr)
.context("convert to tokio::ChildStderr")?;
let stdin =
tokio::process::ChildStdin::from_std(stdin).context("convert to tokio::ChildStdin")?;
let stdout = tokio::process::ChildStdout::from_std(stdout)
.context("convert to tokio::ChildStdout")?;
// all fallible operations post-spawn are complete, so get rid of the guard
let child = scopeguard::ScopeGuard::into_inner(child);
tokio::spawn(
async move {
scopeguard::defer! {
debug!("wal-redo-postgres stderr_logger_task finished");
crate::metrics::WAL_REDO_PROCESS_COUNTERS.active_stderr_logger_tasks_finished.inc();
}
debug!("wal-redo-postgres stderr_logger_task started");
crate::metrics::WAL_REDO_PROCESS_COUNTERS.active_stderr_logger_tasks_started.inc();
use tokio::io::AsyncBufReadExt;
let mut stderr_lines = tokio::io::BufReader::new(stderr);
let mut buf = Vec::new();
let res = loop {
buf.clear();
// TODO we don't trust the process to cap its stderr length.
// Currently it can do unbounded Vec allocation.
match stderr_lines.read_until(b'\n', &mut buf).await {
Ok(0) => break Ok(()), // eof
Ok(num_bytes) => {
let output = String::from_utf8_lossy(&buf[..num_bytes]);
error!(%output, "received output");
}
Err(e) => {
break Err(e);
}
}
};
match res {
Ok(()) => (),
Err(e) => {
error!(error=?e, "failed to read from walredo stderr");
}
}
}.instrument(tracing::info_span!(parent: None, "wal-redo-postgres-stderr", pid = child.id(), tenant_id = %tenant_shard_id.tenant_id, shard_id = %tenant_shard_id.shard_slug(), %pg_version))
);
Ok(Self {
conf,
tenant_shard_id,
child: Some(child),
stdin: tokio::sync::Mutex::new(Poison::new(
"stdin",
ProcessInput {
stdin,
n_requests: 0,
},
)),
stdout: tokio::sync::Mutex::new(Poison::new(
"stdout",
ProcessOutput {
stdout,
pending_responses: VecDeque::new(),
n_processed_responses: 0,
},
)),
#[cfg(feature = "testing")]
dump_sequence: AtomicUsize::default(),
})
}
pub(crate) fn id(&self) -> u32 {
self.child
.as_ref()
.expect("must not call this during Drop")
.id()
}
/// Apply given WAL records ('records') over an old page image. Returns
/// new page image.
///
/// # Cancel-Safety
///
/// Cancellation safe.
#[instrument(skip_all, level = tracing::Level::DEBUG, fields(tenant_id=%self.tenant_shard_id.tenant_id, shard_id=%self.tenant_shard_id.shard_slug(), pid=%self.id()))]
pub(crate) async fn apply_wal_records(
&self,
rel: RelTag,
blknum: u32,
base_img: &Option<Bytes>,
records: &[(Lsn, NeonWalRecord)],
) -> anyhow::Result<Bytes> {
let tag = protocol::BufferTag { rel, blknum };
// Serialize all the messages to send the WAL redo process first.
//
// This could be problematic if there are millions of records to replay,
// but in practice the number of records is usually so small that it doesn't
// matter, and it's better to keep this code simple.
//
// Most requests start with a before-image with BLCKSZ bytes, followed by
// by some other WAL records. Start with a buffer that can hold that
// comfortably.
let mut writebuf: Vec<u8> = Vec::with_capacity((BLCKSZ as usize) * 3);
protocol::build_begin_redo_for_block_msg(tag, &mut writebuf);
if let Some(img) = base_img {
protocol::build_push_page_msg(tag, img, &mut writebuf);
}
for (lsn, rec) in records.iter() {
if let NeonWalRecord::Postgres {
will_init: _,
rec: postgres_rec,
} = rec
{
protocol::build_apply_record_msg(*lsn, postgres_rec, &mut writebuf);
} else {
anyhow::bail!("tried to pass neon wal record to postgres WAL redo");
}
}
protocol::build_get_page_msg(tag, &mut writebuf);
WAL_REDO_RECORD_COUNTER.inc_by(records.len() as u64);
let res = self.apply_wal_records0(&writebuf).await;
if res.is_err() {
// not all of these can be caused by this particular input, however these are so rare
// in tests so capture all.
self.record_and_log(&writebuf);
}
res
}
/// # Cancel-Safety
///
/// Cancellation safe (enforced through the use of [`utils::poison::Poison`]).
async fn apply_wal_records0(&self, writebuf: &[u8]) -> anyhow::Result<Bytes> {
let request_no = {
let mut lock_guard = self.stdin.lock().await;
let mut poison_guard = lock_guard.check_and_arm()?;
let input = poison_guard.data_mut();
input
.stdin
.write_all(writebuf)
.await
.context("write to walredo stdin")?;
let request_no = input.n_requests;
input.n_requests += 1;
poison_guard.disarm();
request_no
};
// To improve walredo performance we separate sending requests and receiving
// responses. Them are protected by different mutexes (output and input).
// If thread T1, T2, T3 send requests D1, D2, D3 to walredo process
// then there is not warranty that T1 will first granted output mutex lock.
// To address this issue we maintain number of sent requests, number of processed
// responses and ring buffer with pending responses. After sending response
// (under input mutex), threads remembers request number. Then it releases
// input mutex, locks output mutex and fetch in ring buffer all responses until
// its stored request number. The it takes correspondent element from
// pending responses ring buffer and truncate all empty elements from the front,
// advancing processed responses number.
let mut lock_guard = self.stdout.lock().await;
let mut poison_guard = lock_guard.check_and_arm()?;
let output = poison_guard.data_mut();
let n_processed_responses = output.n_processed_responses;
while n_processed_responses + output.pending_responses.len() <= request_no {
// We expect the WAL redo process to respond with an 8k page image. We read it
// into this buffer.
let mut resultbuf = vec![0; BLCKSZ.into()];
output
.stdout
.read_exact(&mut resultbuf)
.await
.context("read walredo stdout")?;
output
.pending_responses
.push_back(Some(Bytes::from(resultbuf)));
}
// Replace our request's response with None in `pending_responses`.
// Then make space in the ring buffer by clearing out any seqence of contiguous
// `None`'s from the front of `pending_responses`.
// NB: We can't pop_front() because other requests' responses because another
// requester might have grabbed the output mutex before us:
// T1: grab input mutex
// T1: send request_no 23
// T1: release input mutex
// T2: grab input mutex
// T2: send request_no 24
// T2: release input mutex
// T2: grab output mutex
// T2: n_processed_responses + output.pending_responses.len() <= request_no
// 23 0 24
// T2: enters poll loop that reads stdout
// T2: put response for 23 into pending_responses
// T2: put response for 24 into pending_resposnes
// pending_responses now looks like this: Front Some(response_23) Some(response_24) Back
// T2: takes its response_24
// pending_responses now looks like this: Front Some(response_23) None Back
// T2: does the while loop below
// pending_responses now looks like this: Front Some(response_23) None Back
// T2: releases output mutex
// T1: grabs output mutex
// T1: n_processed_responses + output.pending_responses.len() > request_no
// 23 2 23
// T1: skips poll loop that reads stdout
// T1: takes its response_23
// pending_responses now looks like this: Front None None Back
// T2: does the while loop below
// pending_responses now looks like this: Front Back
// n_processed_responses now has value 25
let res = output.pending_responses[request_no - n_processed_responses]
.take()
.expect("we own this request_no, nobody else is supposed to take it");
while let Some(front) = output.pending_responses.front() {
if front.is_none() {
output.pending_responses.pop_front();
output.n_processed_responses += 1;
} else {
break;
}
}
poison_guard.disarm();
Ok(res)
}
#[cfg(feature = "testing")]
fn record_and_log(&self, writebuf: &[u8]) {
use std::sync::atomic::Ordering;
let millis = std::time::SystemTime::now()
.duration_since(std::time::SystemTime::UNIX_EPOCH)
.unwrap()
.as_millis();
let seq = self.dump_sequence.fetch_add(1, Ordering::Relaxed);
// these files will be collected to an allure report
let filename = format!("walredo-{millis}-{}-{seq}.walredo", writebuf.len());
let path = self.conf.tenant_path(&self.tenant_shard_id).join(&filename);
use std::io::Write;
let res = std::fs::OpenOptions::new()
.write(true)
.create_new(true)
.read(true)
.open(path)
.and_then(|mut f| f.write_all(writebuf));
// trip up allowed_errors
if let Err(e) = res {
tracing::error!(target=%filename, length=writebuf.len(), "failed to write out the walredo errored input: {e}");
} else {
tracing::error!(filename, "erroring walredo input saved");
}
}
#[cfg(not(feature = "testing"))]
fn record_and_log(&self, _: &[u8]) {}
}
impl Drop for WalRedoProcess {
fn drop(&mut self) {
self.child
.take()
.expect("we only do this once")
.kill_and_wait(WalRedoKillCause::WalRedoProcessDrop);
// no way to wait for stderr_logger_task from Drop because that is async only
}
}

402
pageserver/src/walredo/process/process_impl/process_std.rs Normal file
View File

@@ -0,0 +1,402 @@
use self::no_leak_child::NoLeakChild;
use crate::{
config::PageServerConf, metrics::{WalRedoKillCause, WAL_REDO_PROCESS_COUNTERS, WAL_REDO_RECORD_COUNTER}, walrecord::NeonWalRecord, walredo::process::{no_leak_child, protocol}
};
use anyhow::Context;
use bytes::Bytes;
use nix::poll::{PollFd, PollFlags};
use pageserver_api::{reltag::RelTag, shard::TenantShardId};
use postgres_ffi::BLCKSZ;
use std::os::fd::AsRawFd;
#[cfg(feature = "testing")]
use std::sync::atomic::AtomicUsize;
use std::{
collections::VecDeque,
io::{Read, Write},
process::{ChildStdin, ChildStdout, Command, Stdio},
sync::{Mutex, MutexGuard},
time::Duration,
};
use tracing::{debug, error, instrument, Instrument};
use utils::{lsn::Lsn, nonblock::set_nonblock};
pub struct WalRedoProcess {
#[allow(dead_code)]
conf: &'static PageServerConf,
tenant_shard_id: TenantShardId,
// Some() on construction, only becomes None on Drop.
child: Option<NoLeakChild>,
stdout: Mutex<ProcessOutput>,
stdin: Mutex<ProcessInput>,
/// Counter to separate same sized walredo inputs failing at the same millisecond.
#[cfg(feature = "testing")]
dump_sequence: AtomicUsize,
}
struct ProcessInput {
stdin: ChildStdin,
n_requests: usize,
}
struct ProcessOutput {
stdout: ChildStdout,
pending_responses: VecDeque<Option<Bytes>>,
n_processed_responses: usize,
}
impl WalRedoProcess {
//
// Start postgres binary in special WAL redo mode.
//
#[instrument(skip_all,fields(pg_version=pg_version))]
pub(crate) fn launch(
conf: &'static PageServerConf,
tenant_shard_id: TenantShardId,
pg_version: u32,
) -> anyhow::Result<Self> {
crate::span::debug_assert_current_span_has_tenant_id();
let pg_bin_dir_path = conf.pg_bin_dir(pg_version).context("pg_bin_dir")?; // TODO these should be infallible.
let pg_lib_dir_path = conf.pg_lib_dir(pg_version).context("pg_lib_dir")?;
use no_leak_child::NoLeakChildCommandExt;
// Start postgres itself
let child = Command::new(pg_bin_dir_path.join("postgres"))
// the first arg must be --wal-redo so the child process enters into walredo mode
.arg("--wal-redo")
// the child doesn't process this arg, but, having it in the argv helps indentify the
// walredo process for a particular tenant when debugging a pagserver
.args(["--tenant-shard-id", &format!("{tenant_shard_id}")])
.stdin(Stdio::piped())
.stderr(Stdio::piped())
.stdout(Stdio::piped())
.env_clear()
.env("LD_LIBRARY_PATH", &pg_lib_dir_path)
.env("DYLD_LIBRARY_PATH", &pg_lib_dir_path)
// NB: The redo process is not trusted after we sent it the first
// walredo work. Before that, it is trusted. Specifically, we trust
// it to
// 1. close all file descriptors except stdin, stdout, stderr because
// pageserver might not be 100% diligent in setting FD_CLOEXEC on all
// the files it opens, and
// 2. to use seccomp to sandbox itself before processing the first
// walredo request.
.spawn_no_leak_child(tenant_shard_id)
.context("spawn process")?;
WAL_REDO_PROCESS_COUNTERS.started.inc();
let mut child = scopeguard::guard(child, |child| {
error!("killing wal-redo-postgres process due to a problem during launch");
child.kill_and_wait(WalRedoKillCause::Startup);
});
let stdin = child.stdin.take().unwrap();
let stdout = child.stdout.take().unwrap();
let stderr = child.stderr.take().unwrap();
let stderr = tokio::process::ChildStderr::from_std(stderr)
.context("convert to tokio::ChildStderr")?;
macro_rules! set_nonblock_or_log_err {
($file:ident) => {{
let res = set_nonblock($file.as_raw_fd());
if let Err(e) = &res {
error!(error = %e, file = stringify!($file), pid = child.id(), "set_nonblock failed");
}
res
}};
}
set_nonblock_or_log_err!(stdin)?;
set_nonblock_or_log_err!(stdout)?;
// all fallible operations post-spawn are complete, so get rid of the guard
let child = scopeguard::ScopeGuard::into_inner(child);
tokio::spawn(
async move {
scopeguard::defer! {
debug!("wal-redo-postgres stderr_logger_task finished");
crate::metrics::WAL_REDO_PROCESS_COUNTERS.active_stderr_logger_tasks_finished.inc();
}
debug!("wal-redo-postgres stderr_logger_task started");
crate::metrics::WAL_REDO_PROCESS_COUNTERS.active_stderr_logger_tasks_started.inc();
use tokio::io::AsyncBufReadExt;
let mut stderr_lines = tokio::io::BufReader::new(stderr);
let mut buf = Vec::new();
let res = loop {
buf.clear();
// TODO we don't trust the process to cap its stderr length.
// Currently it can do unbounded Vec allocation.
match stderr_lines.read_until(b'\n', &mut buf).await {
Ok(0) => break Ok(()), // eof
Ok(num_bytes) => {
let output = String::from_utf8_lossy(&buf[..num_bytes]);
error!(%output, "received output");
}
Err(e) => {
break Err(e);
}
}
};
match res {
Ok(()) => (),
Err(e) => {
error!(error=?e, "failed to read from walredo stderr");
}
}
}.instrument(tracing::info_span!(parent: None, "wal-redo-postgres-stderr", pid = child.id(), tenant_id = %tenant_shard_id.tenant_id, shard_id = %tenant_shard_id.shard_slug(), %pg_version))
);
Ok(Self {
conf,
tenant_shard_id,
child: Some(child),
stdin: Mutex::new(ProcessInput {
stdin,
n_requests: 0,
}),
stdout: Mutex::new(ProcessOutput {
stdout,
pending_responses: VecDeque::new(),
n_processed_responses: 0,
}),
#[cfg(feature = "testing")]
dump_sequence: AtomicUsize::default(),
})
}
pub(crate) fn id(&self) -> u32 {
self.child
.as_ref()
.expect("must not call this during Drop")
.id()
}
// Apply given WAL records ('records') over an old page image. Returns
// new page image.
//
#[instrument(skip_all, fields(tenant_id=%self.tenant_shard_id.tenant_id, shard_id=%self.tenant_shard_id.shard_slug(), pid=%self.id()))]
pub(crate) async fn apply_wal_records(
&self,
rel: RelTag,
blknum: u32,
base_img: &Option<Bytes>,
records: &[(Lsn, NeonWalRecord)],
wal_redo_timeout: Duration,
) -> anyhow::Result<Bytes> {
let tag = protocol::BufferTag { rel, blknum };
let input = self.stdin.lock().unwrap();
// Serialize all the messages to send the WAL redo process first.
//
// This could be problematic if there are millions of records to replay,
// but in practice the number of records is usually so small that it doesn't
// matter, and it's better to keep this code simple.
//
// Most requests start with a before-image with BLCKSZ bytes, followed by
// by some other WAL records. Start with a buffer that can hold that
// comfortably.
let mut writebuf: Vec<u8> = Vec::with_capacity((BLCKSZ as usize) * 3);
protocol::build_begin_redo_for_block_msg(tag, &mut writebuf);
if let Some(img) = base_img {
protocol::build_push_page_msg(tag, img, &mut writebuf);
}
for (lsn, rec) in records.iter() {
if let NeonWalRecord::Postgres {
will_init: _,
rec: postgres_rec,
} = rec
{
protocol::build_apply_record_msg(*lsn, postgres_rec, &mut writebuf);
} else {
anyhow::bail!("tried to pass neon wal record to postgres WAL redo");
}
}
protocol::build_get_page_msg(tag, &mut writebuf);
WAL_REDO_RECORD_COUNTER.inc_by(records.len() as u64);
let res = self.apply_wal_records0(&writebuf, input, wal_redo_timeout);
if res.is_err() {
// not all of these can be caused by this particular input, however these are so rare
// in tests so capture all.
self.record_and_log(&writebuf);
}
res
}
fn apply_wal_records0(
&self,
writebuf: &[u8],
input: MutexGuard<ProcessInput>,
wal_redo_timeout: Duration,
) -> anyhow::Result<Bytes> {
let mut proc = { input }; // TODO: remove this legacy rename, but this keep the patch small.
let mut nwrite = 0usize;
while nwrite < writebuf.len() {
let mut stdin_pollfds = [PollFd::new(&proc.stdin, PollFlags::POLLOUT)];
let n = loop {
match nix::poll::poll(&mut stdin_pollfds[..], wal_redo_timeout.as_millis() as i32) {
Err(nix::errno::Errno::EINTR) => continue,
res => break res,
}
}?;
if n == 0 {
anyhow::bail!("WAL redo timed out");
}
// If 'stdin' is writeable, do write.
let in_revents = stdin_pollfds[0].revents().unwrap();
if in_revents & (PollFlags::POLLERR | PollFlags::POLLOUT) != PollFlags::empty() {
nwrite += proc.stdin.write(&writebuf[nwrite..])?;
}
if in_revents.contains(PollFlags::POLLHUP) {
// We still have more data to write, but the process closed the pipe.
anyhow::bail!("WAL redo process closed its stdin unexpectedly");
}
}
let request_no = proc.n_requests;
proc.n_requests += 1;
drop(proc);
// To improve walredo performance we separate sending requests and receiving
// responses. Them are protected by different mutexes (output and input).
// If thread T1, T2, T3 send requests D1, D2, D3 to walredo process
// then there is not warranty that T1 will first granted output mutex lock.
// To address this issue we maintain number of sent requests, number of processed
// responses and ring buffer with pending responses. After sending response
// (under input mutex), threads remembers request number. Then it releases
// input mutex, locks output mutex and fetch in ring buffer all responses until
// its stored request number. The it takes correspondent element from
// pending responses ring buffer and truncate all empty elements from the front,
// advancing processed responses number.
let mut output = self.stdout.lock().unwrap();
let n_processed_responses = output.n_processed_responses;
while n_processed_responses + output.pending_responses.len() <= request_no {
// We expect the WAL redo process to respond with an 8k page image. We read it
// into this buffer.
let mut resultbuf = vec![0; BLCKSZ.into()];
let mut nresult: usize = 0; // # of bytes read into 'resultbuf' so far
while nresult < BLCKSZ.into() {
let mut stdout_pollfds = [PollFd::new(&output.stdout, PollFlags::POLLIN)];
// We do two things simultaneously: reading response from stdout
// and forward any logging information that the child writes to its stderr to the page server's log.
let n = loop {
match nix::poll::poll(
&mut stdout_pollfds[..],
wal_redo_timeout.as_millis() as i32,
) {
Err(nix::errno::Errno::EINTR) => continue,
res => break res,
}
}?;
if n == 0 {
anyhow::bail!("WAL redo timed out");
}
// If we have some data in stdout, read it to the result buffer.
let out_revents = stdout_pollfds[0].revents().unwrap();
if out_revents & (PollFlags::POLLERR | PollFlags::POLLIN) != PollFlags::empty() {
nresult += output.stdout.read(&mut resultbuf[nresult..])?;
}
if out_revents.contains(PollFlags::POLLHUP) {
anyhow::bail!("WAL redo process closed its stdout unexpectedly");
}
}
output
.pending_responses
.push_back(Some(Bytes::from(resultbuf)));
}
// Replace our request's response with None in `pending_responses`.
// Then make space in the ring buffer by clearing out any seqence of contiguous
// `None`'s from the front of `pending_responses`.
// NB: We can't pop_front() because other requests' responses because another
// requester might have grabbed the output mutex before us:
// T1: grab input mutex
// T1: send request_no 23
// T1: release input mutex
// T2: grab input mutex
// T2: send request_no 24
// T2: release input mutex
// T2: grab output mutex
// T2: n_processed_responses + output.pending_responses.len() <= request_no
// 23 0 24
// T2: enters poll loop that reads stdout
// T2: put response for 23 into pending_responses
// T2: put response for 24 into pending_resposnes
// pending_responses now looks like this: Front Some(response_23) Some(response_24) Back
// T2: takes its response_24
// pending_responses now looks like this: Front Some(response_23) None Back
// T2: does the while loop below
// pending_responses now looks like this: Front Some(response_23) None Back
// T2: releases output mutex
// T1: grabs output mutex
// T1: n_processed_responses + output.pending_responses.len() > request_no
// 23 2 23
// T1: skips poll loop that reads stdout
// T1: takes its response_23
// pending_responses now looks like this: Front None None Back
// T2: does the while loop below
// pending_responses now looks like this: Front Back
// n_processed_responses now has value 25
let res = output.pending_responses[request_no - n_processed_responses]
.take()
.expect("we own this request_no, nobody else is supposed to take it");
while let Some(front) = output.pending_responses.front() {
if front.is_none() {
output.pending_responses.pop_front();
output.n_processed_responses += 1;
} else {
break;
}
}
Ok(res)
}
#[cfg(feature = "testing")]
fn record_and_log(&self, writebuf: &[u8]) {
use std::sync::atomic::Ordering;
let millis = std::time::SystemTime::now()
.duration_since(std::time::SystemTime::UNIX_EPOCH)
.unwrap()
.as_millis();
let seq = self.dump_sequence.fetch_add(1, Ordering::Relaxed);
// these files will be collected to an allure report
let filename = format!("walredo-{millis}-{}-{seq}.walredo", writebuf.len());
let path = self.conf.tenant_path(&self.tenant_shard_id).join(&filename);
let res = std::fs::OpenOptions::new()
.write(true)
.create_new(true)
.read(true)
.open(path)
.and_then(|mut f| f.write_all(writebuf));
// trip up allowed_errors
if let Err(e) = res {
tracing::error!(target=%filename, length=writebuf.len(), "failed to write out the walredo errored input: {e}");
} else {
tracing::error!(filename, "erroring walredo input saved");
}
}
#[cfg(not(feature = "testing"))]
fn record_and_log(&self, _: &[u8]) {}
}
impl Drop for WalRedoProcess {
fn drop(&mut self) {
self.child
.take()
.expect("we only do this once")
.kill_and_wait(WalRedoKillCause::WalRedoProcessDrop);
// no way to wait for stderr_logger_task from Drop because that is async only
}
}