Line data Source code
1 : //! Spawns and kills background processes that are needed by Neon CLI.
2 : //! Applies common set-up such as log and pid files (if needed) to every process.
3 : //!
4 : //! Neon CLI does not run in background, so it needs to store the information about
5 : //! spawned processes, which it does in this module.
6 : //! We do that by storing the pid of the process in the "${process_name}.pid" file.
7 : //! The pid file can be created by the process itself
8 : //! (Neon storage binaries do that and also ensure that a lock is taken onto that file)
9 : //! or we create such file after starting the process
10 : //! (non-Neon binaries don't necessarily follow our pidfile conventions).
11 : //! The pid stored in the file is later used to stop the service.
12 : //!
13 : //! See the [`lock_file`](utils::lock_file) module for more info.
14 :
15 : use std::ffi::OsStr;
16 : use std::io::Write;
17 : use std::os::unix::prelude::AsRawFd;
18 : use std::os::unix::process::CommandExt;
19 : use std::path::Path;
20 : use std::process::Command;
21 : use std::time::Duration;
22 : use std::{fs, io, thread};
23 :
24 : use anyhow::Context;
25 : use camino::{Utf8Path, Utf8PathBuf};
26 : use nix::errno::Errno;
27 : use nix::fcntl::{FcntlArg, FdFlag};
28 : use nix::sys::signal::{kill, Signal};
29 : use nix::unistd::Pid;
30 : use utils::pid_file::{self, PidFileRead};
31 :
32 : // These constants control the loop used to poll for process start / stop.
33 : //
34 : // The loop waits for at most 10 seconds, polling every 100 ms.
35 : // Once a second, it prints a dot ("."), to give the user an indication that
36 : // it's waiting. If the process hasn't started/stopped after 5 seconds,
37 : // it prints a notice that it's taking long, but keeps waiting.
38 : //
39 : const RETRY_UNTIL_SECS: u64 = 10;
40 : const RETRIES: u64 = (RETRY_UNTIL_SECS * 1000) / RETRY_INTERVAL_MILLIS;
41 : const RETRY_INTERVAL_MILLIS: u64 = 100;
42 : const DOT_EVERY_RETRIES: u64 = 10;
43 : const NOTICE_AFTER_RETRIES: u64 = 50;
44 :
45 : /// Argument to `start_process`, to indicate whether it should create pidfile or if the process creates
46 : /// it itself.
47 : pub enum InitialPidFile {
48 : /// Create a pidfile, to allow future CLI invocations to manipulate the process.
49 : Create(Utf8PathBuf),
50 : /// The process will create the pidfile itself, need to wait for that event.
51 : Expect(Utf8PathBuf),
52 : }
53 :
54 : /// Start a background child process using the parameters given.
55 1864 : pub async fn start_process<F, Fut, AI, A, EI>(
56 1864 : process_name: &str,
57 1864 : datadir: &Path,
58 1864 : command: &Path,
59 1864 : args: AI,
60 1864 : envs: EI,
61 1864 : initial_pid_file: InitialPidFile,
62 1864 : process_status_check: F,
63 1864 : ) -> anyhow::Result<()>
64 1864 : where
65 1864 : F: Fn() -> Fut,
66 1864 : Fut: std::future::Future<Output = anyhow::Result<bool>>,
67 1864 : AI: IntoIterator<Item = A>,
68 1864 : A: AsRef<OsStr>,
69 1864 : // Not generic AsRef<OsStr>, otherwise empty `envs` prevents type inference
70 1864 : EI: IntoIterator<Item = (String, String)>,
71 1864 : {
72 1864 : let log_path = datadir.join(format!("{process_name}.log"));
73 1864 : let process_log_file = fs::OpenOptions::new()
74 1864 : .create(true)
75 1864 : .append(true)
76 1864 : .open(&log_path)
77 1864 : .with_context(|| {
78 0 : format!("Could not open {process_name} log file {log_path:?} for writing")
79 1864 : })?;
80 1864 : let same_file_for_stderr = process_log_file.try_clone().with_context(|| {
81 0 : format!("Could not reuse {process_name} log file {log_path:?} for writing stderr")
82 1864 : })?;
83 :
84 1864 : let mut command = Command::new(command);
85 1864 : let background_command = command
86 1864 : .stdout(process_log_file)
87 1864 : .stderr(same_file_for_stderr)
88 1864 : .args(args);
89 1864 : let filled_cmd = fill_remote_storage_secrets_vars(fill_rust_env_vars(background_command));
90 1864 : filled_cmd.envs(envs);
91 :
92 1864 : let pid_file_to_check = match &initial_pid_file {
93 731 : InitialPidFile::Create(path) => {
94 731 : pre_exec_create_pidfile(filled_cmd, path);
95 731 : path
96 : }
97 1133 : InitialPidFile::Expect(path) => path,
98 : };
99 :
100 1864 : let spawned_process = filled_cmd.spawn().with_context(|| {
101 0 : format!("Could not spawn {process_name}, see console output and log files for details.")
102 1864 : })?;
103 1864 : let pid = spawned_process.id();
104 1864 : let pid = Pid::from_raw(
105 1864 : i32::try_from(pid)
106 1864 : .with_context(|| format!("Subprocess {process_name} has invalid pid {pid}"))?,
107 : );
108 : // set up a scopeguard to kill & wait for the child in case we panic or bail below
109 1864 : let spawned_process = scopeguard::guard(spawned_process, |mut spawned_process| {
110 0 : println!("SIGKILL & wait the started process");
111 0 : (|| {
112 0 : // TODO: use another signal that can be caught by the child so it can clean up any children it spawned (e..g, walredo).
113 0 : spawned_process.kill().context("SIGKILL child")?;
114 0 : spawned_process.wait().context("wait() for child process")?;
115 0 : anyhow::Ok(())
116 0 : })()
117 0 : .with_context(|| format!("scopeguard kill&wait child {process_name:?}"))
118 0 : .unwrap();
119 1864 : });
120 :
121 3780 : for retries in 0..RETRIES {
122 8419 : match process_started(pid, pid_file_to_check, &process_status_check).await {
123 : Ok(true) => {
124 1864 : println!("\n{process_name} started and passed status check, pid: {pid}");
125 1864 : // leak the child process, it'll outlive this neon_local invocation
126 1864 : drop(scopeguard::ScopeGuard::into_inner(spawned_process));
127 1864 : return Ok(());
128 : }
129 : Ok(false) => {
130 1916 : if retries == NOTICE_AFTER_RETRIES {
131 0 : // The process is taking a long time to start up. Keep waiting, but
132 0 : // print a message
133 0 : print!("\n{process_name} has not started yet, continuing to wait");
134 1916 : }
135 1916 : if retries % DOT_EVERY_RETRIES == 0 {
136 1862 : print!(".");
137 1862 : io::stdout().flush().unwrap();
138 1862 : }
139 1916 : thread::sleep(Duration::from_millis(RETRY_INTERVAL_MILLIS));
140 : }
141 0 : Err(e) => {
142 0 : println!("error starting process {process_name:?}: {e:#}");
143 0 : return Err(e);
144 : }
145 : }
146 : }
147 0 : println!();
148 0 : anyhow::bail!(
149 0 : "{process_name} did not start+pass status checks within {RETRY_UNTIL_SECS} seconds"
150 0 : );
151 1864 : }
152 :
153 : /// Stops the process, using the pid file given. Returns Ok also if the process is already not running.
154 1541 : pub fn stop_process(
155 1541 : immediate: bool,
156 1541 : process_name: &str,
157 1541 : pid_file: &Utf8Path,
158 1541 : ) -> anyhow::Result<()> {
159 1541 : let pid = match pid_file::read(pid_file)
160 1541 : .with_context(|| format!("read pid_file {pid_file:?}"))?
161 : {
162 : PidFileRead::NotExist => {
163 0 : println!("{process_name} is already stopped: no pid file present at {pid_file:?}");
164 0 : return Ok(());
165 : }
166 : PidFileRead::NotHeldByAnyProcess(_) => {
167 : // Don't try to kill according to file contents beacuse the pid might have been re-used by another process.
168 : // Don't delete the file either, it can race with new pid file creation.
169 : // Read `pid_file` module comment for details.
170 47 : println!(
171 47 : "No process is holding the pidfile. The process must have already exited. Leave in place to avoid race conditions: {pid_file:?}"
172 47 : );
173 47 : return Ok(());
174 : }
175 1494 : PidFileRead::LockedByOtherProcess(pid) => pid,
176 : };
177 : // XXX the pid could become invalid (and recycled) at any time before the kill() below.
178 :
179 : // send signal
180 1494 : let sig = if immediate {
181 1189 : print!("Stopping {process_name} with pid {pid} immediately..");
182 1189 : Signal::SIGQUIT
183 : } else {
184 305 : print!("Stopping {process_name} with pid {pid} gracefully..");
185 305 : Signal::SIGTERM
186 : };
187 1494 : io::stdout().flush().unwrap();
188 1494 : match kill(pid, sig) {
189 1494 : Ok(()) => (),
190 : Err(Errno::ESRCH) => {
191 : // Again, don't delete the pid file. The unlink can race with a new pid file being created.
192 0 : println!(
193 0 : "{process_name} with pid {pid} does not exist, but a pid file {pid_file:?} was found. Likely the pid got recycled. Lucky we didn't harm anyone."
194 0 : );
195 0 : return Ok(());
196 : }
197 0 : Err(e) => anyhow::bail!("Failed to send signal to {process_name} with pid {pid}: {e}"),
198 : }
199 :
200 : // Wait until process is gone
201 1494 : wait_until_stopped(process_name, pid)?;
202 1494 : Ok(())
203 1541 : }
204 :
205 2066 : pub fn wait_until_stopped(process_name: &str, pid: Pid) -> anyhow::Result<()> {
206 3662 : for retries in 0..RETRIES {
207 3662 : match process_has_stopped(pid) {
208 : Ok(true) => {
209 2066 : println!("\n{process_name} stopped");
210 2066 : return Ok(());
211 : }
212 : Ok(false) => {
213 1596 : if retries == NOTICE_AFTER_RETRIES {
214 0 : // The process is taking a long time to start up. Keep waiting, but
215 0 : // print a message
216 0 : print!("\n{process_name} has not stopped yet, continuing to wait");
217 1596 : }
218 1596 : if retries % DOT_EVERY_RETRIES == 0 {
219 1502 : print!(".");
220 1502 : io::stdout().flush().unwrap();
221 1502 : }
222 1596 : thread::sleep(Duration::from_millis(RETRY_INTERVAL_MILLIS));
223 : }
224 0 : Err(e) => {
225 0 : println!("{process_name} with pid {pid} failed to stop: {e:#}");
226 0 : return Err(e);
227 : }
228 : }
229 : }
230 0 : println!();
231 0 : anyhow::bail!("{process_name} with pid {pid} did not stop in {RETRY_UNTIL_SECS} seconds");
232 2066 : }
233 :
234 1864 : fn fill_rust_env_vars(cmd: &mut Command) -> &mut Command {
235 1864 : // If RUST_BACKTRACE is set, pass it through. But if it's not set, default
236 1864 : // to RUST_BACKTRACE=1.
237 1864 : let backtrace_setting = std::env::var_os("RUST_BACKTRACE");
238 1864 : let backtrace_setting = backtrace_setting
239 1864 : .as_deref()
240 1864 : .unwrap_or_else(|| OsStr::new("1"));
241 1864 :
242 1864 : let mut filled_cmd = cmd.env_clear().env("RUST_BACKTRACE", backtrace_setting);
243 :
244 : // Pass through these environment variables to the command
245 5592 : for var in ["LLVM_PROFILE_FILE", "FAILPOINTS", "RUST_LOG"] {
246 5592 : if let Some(val) = std::env::var_os(var) {
247 1872 : filled_cmd = filled_cmd.env(var, val);
248 3720 : }
249 : }
250 :
251 1864 : filled_cmd
252 1864 : }
253 :
254 1864 : fn fill_remote_storage_secrets_vars(mut cmd: &mut Command) -> &mut Command {
255 11184 : for env_key in [
256 : "AWS_ACCESS_KEY_ID",
257 1864 : "AWS_SECRET_ACCESS_KEY",
258 1864 : "AWS_PROFILE",
259 1864 : // HOME is needed in combination with `AWS_PROFILE` to pick up the SSO sessions.
260 1864 : "HOME",
261 1864 : "AZURE_STORAGE_ACCOUNT",
262 1864 : "AZURE_STORAGE_ACCESS_KEY",
263 : ] {
264 11184 : if let Ok(value) = std::env::var(env_key) {
265 5592 : cmd = cmd.env(env_key, value);
266 5592 : }
267 : }
268 1864 : cmd
269 1864 : }
270 :
271 : /// Add a `pre_exec` to the cmd that, inbetween fork() and exec(),
272 : /// 1. Claims a pidfile with a fcntl lock on it and
273 : /// 2. Sets up the pidfile's file descriptor so that it (and the lock)
274 : /// will remain held until the cmd exits.
275 731 : fn pre_exec_create_pidfile<P>(cmd: &mut Command, path: P) -> &mut Command
276 731 : where
277 731 : P: Into<Utf8PathBuf>,
278 731 : {
279 731 : let path: Utf8PathBuf = path.into();
280 731 : // SAFETY:
281 731 : // pre_exec is marked unsafe because it runs between fork and exec.
282 731 : // Why is that dangerous in various ways?
283 731 : // Long answer: https://github.com/rust-lang/rust/issues/39575
284 731 : // Short answer: in a multi-threaded program, other threads may have
285 731 : // been inside of critical sections at the time of fork. In the
286 731 : // original process, that was allright, assuming they protected
287 731 : // the critical sections appropriately, e.g., through locks.
288 731 : // Fork adds another process to the mix that
289 731 : // 1. Has a single thread T
290 731 : // 2. In an exact copy of the address space at the time of fork.
291 731 : // A variety of problems scan occur now:
292 731 : // 1. T tries to grab a lock that was locked at the time of fork.
293 731 : // It will wait forever since in its address space, the lock
294 731 : // is in state 'taken' but the thread that would unlock it is
295 731 : // not there.
296 731 : // 2. A rust object that represented some external resource in the
297 731 : // parent now got implicitly copied by the the fork, even though
298 731 : // the object's type is not `Copy`. The parent program may use
299 731 : // non-copyability as way to enforce unique ownership of an
300 731 : // external resource in the typesystem. The fork breaks that
301 731 : // assumption, as now both parent and child process have an
302 731 : // owned instance of the object that represents the same
303 731 : // underlying resource.
304 731 : // While these seem like niche problems, (1) in particular is
305 731 : // highly relevant. For example, `malloc()` may grab a mutex internally,
306 731 : // and so, if we forked while another thread was mallocing' and our
307 731 : // pre_exec closure allocates as well, it will block on the malloc
308 731 : // mutex forever
309 731 : //
310 731 : // The proper solution is to only use C library functions that are marked
311 731 : // "async-signal-safe": https://man7.org/linux/man-pages/man7/signal-safety.7.html
312 731 : //
313 731 : // With this specific pre_exec() closure, the non-error path doesn't allocate.
314 731 : // The error path uses `anyhow`, and hence does allocate.
315 731 : // We take our chances there, hoping that any potential disaster is constrained
316 731 : // to the child process (e.g., malloc has no state ourside of the child process).
317 731 : // Last, `expect` prints to stderr, and stdio is not async-signal-safe.
318 731 : // Again, we take our chances, making the same assumptions as for malloc.
319 731 : unsafe {
320 731 : cmd.pre_exec(move || {
321 0 : let file = pid_file::claim_for_current_process(&path).expect("claim pid file");
322 0 : // Remove the FD_CLOEXEC flag on the pidfile descriptor so that the pidfile
323 0 : // remains locked after exec.
324 0 : nix::fcntl::fcntl(file.as_raw_fd(), FcntlArg::F_SETFD(FdFlag::empty()))
325 0 : .expect("remove FD_CLOEXEC");
326 0 : // Don't run drop(file), it would close the file before we actually exec.
327 0 : std::mem::forget(file);
328 0 : Ok(())
329 731 : });
330 731 : }
331 731 : cmd
332 731 : }
333 :
334 3780 : async fn process_started<F, Fut>(
335 3780 : pid: Pid,
336 3780 : pid_file_to_check: &Utf8Path,
337 3780 : status_check: &F,
338 3780 : ) -> anyhow::Result<bool>
339 3780 : where
340 3780 : F: Fn() -> Fut,
341 3780 : Fut: std::future::Future<Output = anyhow::Result<bool>>,
342 3780 : {
343 8419 : match status_check().await {
344 1864 : Ok(true) => match pid_file::read(pid_file_to_check)? {
345 0 : PidFileRead::NotExist => Ok(false),
346 1864 : PidFileRead::LockedByOtherProcess(pid_in_file) => Ok(pid_in_file == pid),
347 0 : PidFileRead::NotHeldByAnyProcess(_) => Ok(false),
348 : },
349 1916 : Ok(false) => Ok(false),
350 0 : Err(e) => anyhow::bail!("process failed to start: {e}"),
351 : }
352 3780 : }
353 :
354 3662 : fn process_has_stopped(pid: Pid) -> anyhow::Result<bool> {
355 3662 : match kill(pid, None) {
356 : // Process exists, keep waiting
357 1596 : Ok(_) => Ok(false),
358 : // Process not found, we're done
359 2066 : Err(Errno::ESRCH) => Ok(true),
360 0 : Err(err) => anyhow::bail!("Failed to send signal to process with pid {pid}: {err}"),
361 : }
362 3662 : }
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