-
Notifications
You must be signed in to change notification settings - Fork 3
/
config-example.rs
407 lines (341 loc) · 15.6 KB
/
config-example.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
// Copyright 2020 Two Sigma Investments, LP.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use anyhow::{Result, Context};
use std::{
mem::{size_of, MaybeUninit},
os::unix::io::AsRawFd,
os::unix::fs::PermissionsExt,
path::Path,
io::prelude::*,
io::SeekFrom,
slice,
fs,
};
use nix::unistd::{lseek, Whence};
#[cfg(not(test))]
use nix::{Error, errno::Errno};
use libc::timespec;
use crate::{
consts::*,
util::pwrite_all,
};
// This file contains logic to configure libvirttime. In a nutshell, libvirttime
// is used to virtualize the CLOCK_MONOTONIC values for the application. The
// library is configured via an external file that contains all the clock time
// offsets to be applied.
//
// The config file has the following format:
// static struct virt_time_config {
// struct timespec ts_offset;
// struct timespec per_thread_ts[PID_MAX];
// };
//
// There is a global time offset, and a per thread time offset. All must be
// adjusted when migrating an app from a machine to another.
//
// More details can be found at https://github.com/twosigma/libvirttime
// `PID_MAX` is defined in the kernel in include/linux/threads.h
// We don't read /proc/sys/kernel/pid_max because it can vary
// from machine to machine.
const PID_MAX: u32 = 4_194_304;
const NSEC_IN_SEC: Nanos = 1_000_000_000;
/// File position of virt_time_config.thread_confs[0]
const PID_0_FPOS: i64 = size_of::<timespec>() as i64;
/// sizeof(struct per_thread_conf)
const PROCESS_AREA_SIZE: usize = size_of::<timespec>();
/// We represent a `timespec` with the nanosecs as a i128. It's easier to do
/// computation with. `Duration` is not suitable for us as it lack support
/// underflowing substractions.
pub type Nanos = i128;
#[cfg(not(test))]
fn clock_gettime_monotonic() -> Nanos {
let result = unsafe {
let mut ts = MaybeUninit::<timespec>::uninit();
if libc::clock_gettime(libc::CLOCK_MONOTONIC, ts.as_mut_ptr()) == 0 {
Ok(Nanos::from_timespec(ts.assume_init()))
} else {
Err(Error::Sys(Errno::last()))
}
};
result.expect("clock_gettime() failed")
}
#[cfg(test)]
fn clock_gettime_monotonic() -> Nanos {
test::clock_gettime_mock()
}
trait NanosExt {
fn to_timespec(self) -> timespec;
fn from_timespec(ts: timespec) -> Self;
}
impl NanosExt for Nanos {
fn to_timespec(self) -> timespec {
let mut ts = timespec {
tv_sec: (self / NSEC_IN_SEC) as i64,
tv_nsec: (self % NSEC_IN_SEC) as i64,
};
// nsec should always be positive as the libvirttime code assumes nsec is between 0 and
// NSEC_IN_SEC-1. See https://github.com/twosigma/libvirttime/blob/master/src/util.h#L48
if ts.tv_nsec < 0 {
ts.tv_sec -= 1;
ts.tv_nsec += NSEC_IN_SEC as i64;
}
ts
}
fn from_timespec(ts: timespec) -> Self {
ts.tv_sec as i128 * NSEC_IN_SEC + ts.tv_nsec as i128
}
}
fn read_timespec<R: Read>(reader: &mut R) -> Result<Nanos> {
unsafe {
let mut ts = MaybeUninit::<timespec>::uninit();
let mut buf = slice::from_raw_parts_mut(
ts.as_mut_ptr() as *mut u8,
size_of::<timespec>()
);
reader.read_exact(&mut buf)
.context("Failed to read from the time config file")?;
Ok(Nanos::from_timespec(ts.assume_init()))
}
}
fn write_timespec_at(file: &fs::File, nanos: Nanos, fpos: i64) -> Result<()> {
unsafe {
let ts = nanos.to_timespec();
let buf = slice::from_raw_parts(
&ts as *const timespec as *const u8,
size_of::<timespec>()
);
pwrite_all(file, &buf, fpos)
.context("Failed to write to the time config file")?;
Ok(())
}
}
pub struct ConfigPath<'a> {
path: &'a Path,
}
impl<'a> ConfigPath<'a> {
pub fn new<S: AsRef<Path>>(path: &'a S) -> Self {
// We don't open the config file at this point. Depending on the
// operation, we might create, open_read, or open_write the file.
Self { path: path.as_ref() }
}
/// Returns the current configured time offset
fn read_configured_offset(&self) -> Result<Nanos> {
let mut config_file = fs::File::open(&self.path)
.with_context(|| format!("Failed to open {}. \
It is normally created when running the application for the \
first time via the 'run' command", self.path.display()))?;
let ts_offset = read_timespec(&mut config_file)?;
Ok(ts_offset)
}
/// Returns the offset to write in the time config file so that if the
/// application were to call `clock_gettime(CLOCK_MONOTONIC)` immediately, it
/// would get `app_clock`.
fn config_time_offset(app_clock: Nanos) -> Nanos {
let machine_clock = clock_gettime_monotonic();
machine_clock - app_clock
}
/// `read_current_app_clock()` returns the same result as what the application,
/// virtualized with libvirttime, would get if it were to call
/// `clock_gettime(CLOCK_MONOTONIC)`.
pub fn read_current_app_clock(&self) -> Result<Nanos> {
let config_offset = self.read_configured_offset()?;
let machine_clock = clock_gettime_monotonic();
let app_clock = machine_clock - config_offset;
Ok(app_clock)
}
pub fn write_intial(&self) -> Result<()> {
|| -> Result<_> {
// We arbitrarily start the app clock at 0.
let app_clock = 0;
// The time config file must be writable by all users as we are
// applying a system-wide virtualization configuration.
let mut config_file = fs::File::create(&self.path)
.with_context(|| format!("Failed to create {}", self.path.display()))?;
// We `set_permissions()` after `create()` because our umask may get in the way of
// the flags we specify in create(). We don't want to change our umask as it is a
// process-wide setting, and not thread local. So it would be unsafe to restore the
// previous umask.
fs::set_permissions(self.path, fs::Permissions::from_mode(0o777))
.with_context(|| format!("Failed to chmod {}", self.path.display()))?;
// The config_file has the layout of the `struct virt_time_config`
write_timespec_at(&config_file, Self::config_time_offset(app_clock), 0)?;
// Write a 0 at the end of the file to make it the right size
// without using much space. We add a page to avoid making the hole
// ends too early.
config_file.seek(SeekFrom::Current(
Self::pid_to_fpos(PID_MAX+1) + PAGE_SIZE as i64))?;
config_file.write_all(&[0])?;
Ok(())
}().with_context(|| format!("Failed to write to {}", self.path.display()))
}
/// PID to file position in the config file
fn pid_to_fpos(pid: u32) -> i64 {
PID_0_FPOS + (pid as i64)*(PROCESS_AREA_SIZE as i64)
}
/// file position to PID (rounded down)
fn fpos_to_pid(fpos: i64) -> u32 {
((fpos - PID_0_FPOS)/(PROCESS_AREA_SIZE as i64)) as u32
}
/// Rewrite time offsets with the desired `app_clock`
pub fn adjust_timespecs(&self, app_clock: Nanos) -> Result<()> {
|| -> Result<_> {
let mut config_file = fs::OpenOptions::new()
.read(true)
.write(true)
.open(&self.path)?;
let new_time_offset = Self::config_time_offset(app_clock);
let old_time_offset = read_timespec(&mut config_file)?;
let old_to_new_time_offset = new_time_offset - old_time_offset;
// Adjust the global timespec offset
write_timespec_at(&config_file, new_time_offset, 0)?;
let mut pid: u32 = 1; // pid=0 does not exist
// Adjust the threads timespec offsets
loop {
// With SEEK_DATA, we'll be skipping pages that have no pids.
// It seeks to the earlist file position that has data. Typically,
// we'll be hitting a page boundary.
let fpos = lseek(config_file.as_raw_fd(), Self::pid_to_fpos(pid),
Whence::SeekData)?;
// Note: performance could be better as we are doing two
// syscalls (read+write) per pid. We could improve this to only
// do two syscalls per page. But that's for another time.
// Compute the pid corresponding to the file position
pid = Self::fpos_to_pid(fpos);
if pid > PID_MAX {
break;
}
// `fpos_to_pid()` rounds down. If the returned `fpos` does not
// correspond to the file position of the `pid`, the file
// position is at a data page boundary. We can skip that pid as
// we are sure that pid is unused.
//
// |pid ......|pid+1 ......|
// ... hole >|< data ...
// ^
// \ file_offset
//
if fpos == Self::pid_to_fpos(pid) {
// Read the current timespec, adjust it, and write it back
let mut offset = read_timespec(&mut config_file)?;
offset += old_to_new_time_offset;
write_timespec_at(&mut config_file, offset, fpos)?;
}
pid += 1;
}
Ok(())
}().with_context(|| format!(
"Failed to adjust timespecs in {}", self.path.display()))
}
}
impl<'a> Default for ConfigPath<'a> {
fn default() -> Self {
Self::new(&*VIRT_TIME_CONF_PATH)
}
}
#[cfg(test)]
mod test {
use super::*;
use std::sync::Mutex;
lazy_static! {
static ref MACHINE_CLOCK: Mutex<Nanos> = Mutex::new(-1);
}
pub fn clock_gettime_mock() -> Nanos {
*MACHINE_CLOCK.lock().unwrap()
}
#[test]
fn test() -> Result<()> {
let config_path = Path::new("/tmp/ff-test-time-conf");
let _ = std::fs::remove_file(&config_path);
let config = ConfigPath::new(&config_path);
fn read_pid_ts(config_file: &mut fs::File, pid: u32) -> Result<Nanos> {
config_file.seek(SeekFrom::Start(ConfigPath::pid_to_fpos(pid) as u64))?;
read_timespec(config_file)
}
assert!(config.read_configured_offset().is_err());
// Clock offset is set to 100, app clock is 0.
let mut machine_clock = NSEC_IN_SEC + 100;
let mut app_clock = 0;
*MACHINE_CLOCK.lock().unwrap() = machine_clock;
config.write_intial()?;
let mut config_file = fs::OpenOptions::new()
.read(true)
.write(true)
.open(&config.path)?;
assert_eq!(config.read_configured_offset()?, machine_clock);
assert_eq!(config.read_current_app_clock()?, 0);
// Clock advances by 1000, so app_clock should be 1000
machine_clock += 1000;
app_clock += 1000;
*MACHINE_CLOCK.lock().unwrap() = machine_clock;
assert_eq!(config.read_current_app_clock()?, app_clock);
write_timespec_at(&config_file, machine_clock + 100, ConfigPath::pid_to_fpos(1))?;
write_timespec_at(&config_file, machine_clock + 101, ConfigPath::pid_to_fpos(10000))?;
write_timespec_at(&config_file, machine_clock + 102, ConfigPath::pid_to_fpos(20000))?;
write_timespec_at(&config_file, machine_clock + 103, ConfigPath::pid_to_fpos(20001))?;
write_timespec_at(&config_file, machine_clock + 104, ConfigPath::pid_to_fpos(PID_MAX))?;
assert_eq!(machine_clock + 100, read_pid_ts(&mut config_file, 1)?);
assert_eq!(machine_clock + 101, read_pid_ts(&mut config_file, 10000)?);
assert_eq!(machine_clock + 102, read_pid_ts(&mut config_file, 20000)?);
assert_eq!(machine_clock + 103, read_pid_ts(&mut config_file, 20001)?);
assert_eq!(machine_clock + 104, read_pid_ts(&mut config_file, PID_MAX)?);
// Now let's pretend we checkpoint and move to another machine.
// app clock is still 1000, but we land on a machine whose clock with a clock in the future
machine_clock = 10*NSEC_IN_SEC + 100;
*MACHINE_CLOCK.lock().unwrap() = machine_clock;
config.adjust_timespecs(app_clock)?; // the app clock we want
assert_eq!(config.read_current_app_clock()?, app_clock);
assert_eq!(machine_clock + 100, read_pid_ts(&mut config_file, 1)?);
assert_eq!(machine_clock + 101, read_pid_ts(&mut config_file, 10000)?);
assert_eq!(machine_clock + 102, read_pid_ts(&mut config_file, 20000)?);
assert_eq!(machine_clock + 103, read_pid_ts(&mut config_file, 20001)?);
assert_eq!(machine_clock + 104, read_pid_ts(&mut config_file, PID_MAX)?);
assert_eq!(0, read_pid_ts(&mut config_file, 100000)?); // should be not touched
// What if we go on a machine which time is earlier than ours. This
// will test overflowing substractions.
machine_clock = 100;
*MACHINE_CLOCK.lock().unwrap() = machine_clock;
config.adjust_timespecs(app_clock)?; // the app clock we want
assert_eq!(config.read_current_app_clock()?, app_clock);
assert_eq!(machine_clock + 100, read_pid_ts(&mut config_file, 1)?);
assert_eq!(machine_clock + 101, read_pid_ts(&mut config_file, 10000)?);
assert_eq!(machine_clock + 102, read_pid_ts(&mut config_file, 20000)?);
assert_eq!(machine_clock + 103, read_pid_ts(&mut config_file, 20001)?);
assert_eq!(machine_clock + 104, read_pid_ts(&mut config_file, PID_MAX)?);
assert_eq!(0, read_pid_ts(&mut config_file, 100000)?);
// Time passes
machine_clock += 500;
app_clock += 500;
*MACHINE_CLOCK.lock().unwrap() = machine_clock;
// App do some calls that use the clock
write_timespec_at(&config_file, machine_clock + 100, ConfigPath::pid_to_fpos(1))?;
write_timespec_at(&config_file, machine_clock + 101, ConfigPath::pid_to_fpos(10000))?;
write_timespec_at(&config_file, machine_clock + 102, ConfigPath::pid_to_fpos(20000))?;
write_timespec_at(&config_file, machine_clock + 103, ConfigPath::pid_to_fpos(20001))?;
write_timespec_at(&config_file, machine_clock + 104, ConfigPath::pid_to_fpos(PID_MAX))?;
// We checkpoint
assert_eq!(config.read_current_app_clock()?, app_clock);
// And restore an another machine
machine_clock = 77;
*MACHINE_CLOCK.lock().unwrap() = machine_clock;
config.adjust_timespecs(app_clock)?; // the app clock we want
assert_eq!(config.read_current_app_clock()?, app_clock);
assert_eq!(machine_clock + 100, read_pid_ts(&mut config_file, 1)?);
assert_eq!(machine_clock + 101, read_pid_ts(&mut config_file, 10000)?);
assert_eq!(machine_clock + 102, read_pid_ts(&mut config_file, 20000)?);
assert_eq!(machine_clock + 103, read_pid_ts(&mut config_file, 20001)?);
assert_eq!(machine_clock + 104, read_pid_ts(&mut config_file, PID_MAX)?);
assert_eq!(0, read_pid_ts(&mut config_file, 100000)?);
Ok(())
}
}