Issue #4579 has been reported by Nigel Kersten.
----------------------------------------
Bug #4579: Symlink file type can issue potentially expensive stat calls rather
than lstat
http://projects.puppetlabs.com/issues/4579
Author: Nigel Kersten
Status: Unreviewed
Priority: Normal
Assigned to:
Category:
Target version:
Affected version:
Keywords:
Branch:
I've only briefly looked at the relevant Puppet code here, but wanted to get
this bug in as it took a little while for us to work out what was triggering
this.
Given the following simple manifest saved to /tmp/test.pp
<pre>
file { "/tmp/symlink":
ensure => symlink,
target => "/tmp/target",
force => true,
}
</pre>
There are a bunch of cases that can cause Puppet to stat the symlink rather
than lstat'ing it. If the symlink target is on a slow filesystem, this can be
very expensive.
Shell script to indicate issue:
<pre>
#!/bin/bash
#
SYM=/tmp/symlink
TAR=/tmp/target
touch $TAR
if stat $SYM &>/dev/null ; then
echo "Symlink exists"
# check if target exists
if stat -L $SYM &>/dev/null; then
# output target
stat -c "%N" $SYM
# output target type
echo "Target is a $(stat -L -c "%F" $SYM)"
else
echo "Target is missing"
fi
else
echo "Symlink missing"
fi
strace -e trace=stat,lstat -f /usr/bin/puppet /tmp/test.pp 2>&1 | grep -E
"/tmp/(symlink|target)"
</pre>
Some examples:
Symlink doesn't exist, target does.
lstat: 1
stat: 1
<pre>
nig...@wittgenstein:~ $ rm -f /tmp/{symlink,target}
nig...@wittgenstein:~ $ ~/symlink-test.sh
Symlink missing
[pid 30115] lstat("/tmp/symlink", 0x7fff33457420) = -1 ENOENT (No such file or
directory)
[pid 30115] stat("/tmp/symlink", 0x7fff334549b0) = -1 ENOENT (No such file or
directory)
notice: //File[/tmp/symlink]/ensure: created
</pre>
Symlink exists, points to desired target.
lstat: 1
<pre>
nig...@wittgenstein:~ $ ~/symlink-test.sh
Symlink exists
`/tmp/symlink' -> `/tmp/target'
Target is a regular empty file
[pid 30435] lstat("/tmp/symlink", {st_mode=S_IFLNK|0777, st_size=11, ...}) = 0
</pre>
Symlink exists, points to undesired file.
lstat: 1
stat: 4
<pre>
nig...@wittgenstein:~ $ ~/symlink-test.sh
Symlink exists
`/tmp/symlink' -> `/etc/fstab'
Target is a regular file
[pid 30524] lstat("/tmp/symlink", {st_mode=S_IFLNK|0777, st_size=10, ...}) = 0
[pid 30524] stat("/tmp/symlink", {st_mode=S_IFREG|0644, st_size=811, ...}) = 0
[pid 30524] stat("/tmp/symlink", {st_mode=S_IFREG|0644, st_size=811, ...}) = 0
[pid 30524] stat("/tmp/symlink", {st_mode=S_IFREG|0644, st_size=811, ...}) = 0
[pid 30524] stat("/tmp/symlink", 0x7fffb5d1b370) = -1 ENOENT (No such file or
directory)
notice: //File[/tmp/symlink]/target: target changed '/etc/fstab' to
'/tmp/target'
</pre>
Symlink exists, points to undesired directory.
lstat: 2
stat: 5
<pre>
nig...@wittgenstein:~ $ ~/symlink-test.sh
Symlink exists
`/tmp/symlink' -> `/usr'
Target is a directory
[pid 30790] lstat("/tmp/symlink", {st_mode=S_IFLNK|0777, st_size=4, ...}) = 0
[pid 30790] stat("/tmp/symlink", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
[pid 30790] stat("/tmp/symlink", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
[pid 30790] stat("/tmp/symlink", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
[pid 30790] stat("/tmp/symlink", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
[pid 30790] lstat("/tmp/symlink", {st_mode=S_IFLNK|0777, st_size=4, ...}) = 0
[pid 30790] stat("/tmp/symlink", 0x7fff06901ab0) = -1 ENOENT (No such file or
directory)
notice: //File[/tmp/symlink]/target: target changed '/usr' to '/tmp/target'
</pre>
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