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Add tests for truncated and symlinked files #24425

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merged 3 commits into from
Apr 14, 2021
Merged

Add tests for truncated and symlinked files #24425

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371b1ba
Fix support of symlinking in filestream input
kvch Mar 8, 2021
280f4d2
remove accidentally added files from paths
kvch Apr 8, 2021
179a7a1
add missing new symlinking
kvch Apr 13, 2021
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164 changes: 164 additions & 0 deletions filebeat/input/filestream/input_integration_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ import (
"context"
"os"
"runtime"
"strconv"
"testing"
"time"

Expand Down Expand Up @@ -736,3 +737,166 @@ func TestFilestreamTruncateBlockedOutput(t *testing.T) {
cancelInput()
env.waitUntilInputStops()
}

// test_symlinks_enabled from test_harvester.py
func TestFilestreamSymlinksEnabled(t *testing.T) {
env := newInputTestingEnvironment(t)

testlogName := "test.log"
symlinkName := "test.log.symlink"
inp := env.mustCreateInput(map[string]interface{}{
"paths": []string{
env.abspath(symlinkName),
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},
"prospector.scanner.symlinks": "true",
})

testlines := []byte("first line\n")
env.mustWriteLinesToFile(testlogName, testlines)

env.mustSymlink(testlogName, symlinkName)

ctx, cancelInput := context.WithCancel(context.Background())
env.startInput(ctx, inp)

env.waitUntilEventCount(1)

cancelInput()
env.waitUntilInputStops()

env.requireOffsetInRegistry(testlogName, len(testlines))
}

// test_symlink_rotated from test_harvester.py
func TestFilestreamSymlinkRotated(t *testing.T) {
env := newInputTestingEnvironment(t)

firstTestlogName := "test1.log"
secondTestlogName := "test2.log"
symlinkName := "test.log"
inp := env.mustCreateInput(map[string]interface{}{
"paths": []string{
env.abspath(symlinkName),
},
"prospector.scanner.check_interval": "1ms",
"prospector.scanner.symlinks": "true",
"close.on_state_change.removed": "false",
"clean_removed": "false",
})

commonLine := "first line in file "
for i, path := range []string{firstTestlogName, secondTestlogName} {
env.mustWriteLinesToFile(path, []byte(commonLine+strconv.Itoa(i)+"\n"))
}

env.mustSymlink(firstTestlogName, symlinkName)

ctx, cancelInput := context.WithCancel(context.Background())
env.startInput(ctx, inp)

env.waitUntilEventCount(1)

expectedOffset := len(commonLine) + 2
env.requireOffsetInRegistry(firstTestlogName, expectedOffset)

// rotate symlink
env.mustRemoveFile(symlinkName)
env.mustSymlink(secondTestlogName, symlinkName)
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Interesting. I would not expect the symlink to be removed when rotating it. Just change the location it points to. What would happen in that case? What would happen if the new log file is larger then the old one when we update the link?

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I have just ported blindly the test from the original Python one. There should not be any change in behaviour of Filebeat if the symlink is renamed.

If the log file is bigger than the previous, Filebeat cannot detect truncation regardless of what we do with the file symlink, rename, remove and create again. That is why we need the special copytruncate prospector.

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@urso urso Apr 12, 2021 •
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I see. So we do track the inode of the symlink file, and not the inode of the target file.

I have just ported blindly the test from the original Python one. There should not be any change in behaviour of Filebeat if the symlink is renamed.

I still would expect a slight difference. If we remove the symlink file before, then the symlink is a new file with a new inode. If we just overwrite the symlink with a new file the inode is not changed and filebeat would/should see it as a truncation event. Also the observable result (collect from offset 0) should be the same, the internal handling of these 2 cases differ, right? So it would be nice to have additonal tests for symlinks, but I would say these cases can be tested as unit tests in the prospector or file watcher.

I guess we need to rethink symlink support to some extent. Detecting changes on a symlink should not only depend on the file size. Have we also considered the case of a symlink becoming an actual file (or the other way around)?

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Is it OK if I add a test for the scenario you had described in a follow up PR? You are raising valid points. However, we should decide what we want to tackle in the default prospector and what we want to cover in the copytruncate prospector. I would rather give us a bit more time for that and address your concerns in a new PR. WDYT?


moreLines := "second line in file 2\nthird line in file 2\n"
env.mustAppendLinesToFile(secondTestlogName, []byte(moreLines))

env.waitUntilEventCount(4)
env.requireOffsetInRegistry(firstTestlogName, expectedOffset)
env.requireOffsetInRegistry(secondTestlogName, expectedOffset+len(moreLines))

cancelInput()
env.waitUntilInputStops()

env.requireRegistryEntryCount(2)
}

// test_symlink_removed from test_harvester.py
func TestFilestreamSymlinkRemoved(t *testing.T) {
env := newInputTestingEnvironment(t)

testlogName := "test.log"
symlinkName := "test.log.symlink"
inp := env.mustCreateInput(map[string]interface{}{
"paths": []string{
env.abspath(symlinkName),
},
"prospector.scanner.check_interval": "1ms",
"prospector.scanner.symlinks": "true",
"close.on_state_change.removed": "false",
"clean_removed": "false",
})

line := []byte("first line\n")
env.mustWriteLinesToFile(testlogName, line)

env.mustSymlink(testlogName, symlinkName)

ctx, cancelInput := context.WithCancel(context.Background())
env.startInput(ctx, inp)

env.waitUntilEventCount(1)

env.requireOffsetInRegistry(testlogName, len(line))

// remove symlink
env.mustRemoveFile(symlinkName)
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What happens if I don't remove/update the symlink, but the file the symlink points to? Do we even detect that case?

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Yes, the reader opens the original file and tracks everything the same way as done in ordinary files.


env.mustAppendLinesToFile(testlogName, line)

env.waitUntilEventCount(2)
env.requireOffsetInRegistry(testlogName, 2*len(line))
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What would happen if we have close...removed: true? Will remove act on the symlink state, or on the resolved file?

What happens on close...renamed?

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Filebeat cares about the original file, not the symlink. The setting has no impact on the behaviour of the reader if the symlink is deleted. I am not sure why the original test contains it.


cancelInput()
env.waitUntilInputStops()

env.requireRegistryEntryCount(1)
}

// test_truncate from test_harvester.py
func TestFilestreamTruncate(t *testing.T) {
env := newInputTestingEnvironment(t)

testlogName := "test.log"
symlinkName := "test.log.symlink"
inp := env.mustCreateInput(map[string]interface{}{
"paths": []string{
env.abspath("*"),
},
"prospector.scanner.check_interval": "1ms",
"prospector.scanner.symlinks": "true",
})

lines := []byte("first line\nsecond line\nthird line\n")
env.mustWriteLinesToFile(testlogName, lines)

env.mustSymlink(testlogName, symlinkName)

ctx, cancelInput := context.WithCancel(context.Background())
env.startInput(ctx, inp)

env.waitUntilEventCount(3)

env.requireOffsetInRegistry(testlogName, len(lines))

// remove symlink
env.mustRemoveFile(symlinkName)
env.mustTruncateFile(testlogName, 0)
env.waitUntilOffsetInRegistry(testlogName, 0)
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moreLines := []byte("forth line\nfifth line\n")
env.mustWriteLinesToFile(testlogName, moreLines)

env.waitUntilEventCount(5)
env.requireOffsetInRegistry(testlogName, len(moreLines))

cancelInput()
env.waitUntilInputStops()

env.requireRegistryEntryCount(1)
}