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std.cache_hash: don't trust mtime granularity to be better than 1ms

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I empirically observed mtime not changing when rapidly writing the same
file name within the same millisecond of wall clock time, despite the
mtime field having nanosecond precision.

I believe this fixes the CI test failures.
This commit is contained in:
Andrew Kelley 2020-08-17 21:24:38 -07:00
parent 27cb23cbc5
commit ce8b9c0c5c
1 changed files with 22 additions and 10 deletions
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32
lib/std/cache_hash.zig
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@ -466,7 +466,16 @@ fn isProblematicTimestamp(fs_clock: i128) bool {
} else {
wall_nsec &= @as(i64, -1) << @intCast(u6, @ctz(i64, fs_nsec));
}
return wall_nsec == fs_nsec and wall_sec == fs_sec;
if (wall_nsec == fs_nsec and wall_sec == fs_sec)
return true;
// I have also observed precision problems at a millisecond granularity.
const fs_msec = @intCast(i64, @divFloor(fs_clock, std.time.ns_per_ms * 2));
const wall_msec = @intCast(i64, @divFloor(wall_clock, std.time.ns_per_ms * 2));
if (fs_msec == wall_msec)
return true;
return false;
}
test "cache file and then recall it" {
@ -479,9 +488,10 @@ test "cache file and then recall it" {
const temp_file = "test.txt";
const temp_manifest_dir = "temp_manifest_dir";
const ts = std.time.nanoTimestamp();
try cwd.writeFile(temp_file, "Hello, world!\n");
while (isProblematicTimestamp(std.time.nanoTimestamp())) {
while (isProblematicTimestamp(ts)) {
std.time.sleep(1);
}
@ -545,9 +555,13 @@ test "check that changing a file makes cache fail" {
const original_temp_file_contents = "Hello, world!\n";
const updated_temp_file_contents = "Hello, world; but updated!\n";
try cwd.deleteTree(temp_manifest_dir);
try cwd.deleteTree(temp_file);
const ts = std.time.nanoTimestamp();
try cwd.writeFile(temp_file, original_temp_file_contents);
while (isProblematicTimestamp(std.time.nanoTimestamp())) {
while (isProblematicTimestamp(ts)) {
std.time.sleep(1);
}
@ -571,10 +585,6 @@ test "check that changing a file makes cache fail" {
try cwd.writeFile(temp_file, updated_temp_file_contents);
while (isProblematicTimestamp(std.time.nanoTimestamp())) {
std.time.sleep(1);
}
{
var ch = try CacheHash.init(testing.allocator, cwd, temp_manifest_dir);
defer ch.release();
@ -594,7 +604,7 @@ test "check that changing a file makes cache fail" {
testing.expect(!mem.eql(u8, digest1[0..], digest2[0..]));
try cwd.deleteTree(temp_manifest_dir);
try cwd.deleteFile(temp_file);
try cwd.deleteTree(temp_file);
}
test "no file inputs" {
@ -643,10 +653,11 @@ test "CacheHashes with files added after initial hash work" {
const temp_file2 = "cache_hash_post_file_test2.txt";
const temp_manifest_dir = "cache_hash_post_file_manifest_dir";
const ts1 = std.time.nanoTimestamp();
try cwd.writeFile(temp_file1, "Hello, world!\n");
try cwd.writeFile(temp_file2, "Hello world the second!\n");
while (isProblematicTimestamp(std.time.nanoTimestamp())) {
while (isProblematicTimestamp(ts1)) {
std.time.sleep(1);
}
@ -680,9 +691,10 @@ test "CacheHashes with files added after initial hash work" {
testing.expect(mem.eql(u8, &digest1, &digest2));
// Modify the file added after initial hash
const ts2 = std.time.nanoTimestamp();
try cwd.writeFile(temp_file2, "Hello world the second, updated\n");
while (isProblematicTimestamp(std.time.nanoTimestamp())) {
while (isProblematicTimestamp(ts2)) {
std.time.sleep(1);
}