The filch implementation is fairly broken:
* When Filch.cur exceeds MaxFileSize, it calls moveContents
to copy the entirety of cur into alt (while holding the write lock).
By nature, this is the movement of a lot of data in a hot path,
meaning that all log calls will be globally blocked!
It also means that log uploads will be blocked during the move.
* The implementation of moveContents is buggy in that
it copies data from cur into the start of alt,
but fails to truncate alt to the number of bytes copied.
Consequently, there are unrelated lines near the end,
leading to out-of-order lines when being read back.
* Data filched via stderr do not directly respect MaxFileSize,
which is only checked every 100 Filch.Write calls.
This means that it is possible that the file grows far beyond
the specified max file size before moveContents is called.
* If both log files have data when New is called,
it also copies the entirety of cur into alt.
This can block the startup of a process copying lots of data
before the process can do any useful work.
* TryReadLine is implemented using bufio.Scanner.
Unfortunately, it will choke on any lines longer than
bufio.MaxScanTokenSize, rather than gracefully skip over them.
The re-implementation avoids a lot of these problems
by fundamentally eliminating the need for moveContent.
We enforce MaxFileSize by simply rotating the log files
whenever the current file exceeds MaxFileSize/2.
This is a constant-time operation regardless of file size.
To more gracefully handle lines longer than bufio.MaxScanTokenSize,
we skip over these lines (without growing the read buffer)
and report an error. This allows subsequent lines to be read.
In order to improve debugging, we add a lot of metrics.
Note that the the mechanism of dup2 with stderr
is inherently racy with a the two file approach.
The order of operations during a rotation is carefully chosen
to reduce the race window to be as short as possible.
Thus, this is slightly less racy than before.
Updates tailscale/corp#21363
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
I'm not saying it works, but it compiles.
Updates #5794
Change-Id: I2f3c99732e67fe57a05edb25b758d083417f083e
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
The //go:build syntax was introduced in Go 1.17:
https://go.dev/doc/go1.17#build-lines
gofmt has kept the +build and go:build lines in sync since
then, but enough time has passed. Time to remove them.
Done with:
perl -i -npe 's,^// \+build.*\n,,' $(git grep -l -F '+build')
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Initialize logtail and provide an uploader that works in the
browser (we make a no-cors cross-origin request to avoid having to
open up the logcatcher servers to CORS).
Fixes#5147
Signed-off-by: Mihai Parparita <mihai@tailscale.com>
In particular, the Dup2 syscall is not defined in the syscall
package on arm64, but is defined in x/sys/unix.
Signed-off-by: David Anderson <dave@natulte.net>
Joe Tsai
Andrea Barisani
Brad Fitzpatrick
Will Norris
Mihai Parparita
Josh Bleecher Snyder
David Anderson
Earl Lee