Removes old, empty directories from datatype root directories (#99)

* Removes old, empty directories

Pusher did not remove old directories. Every extant directory creates an
inotify watch in pusher. Over time and/or for experiments (e.g., wehe)
that create a large amount of directories, this can create a very large
number of useless watches, which eat up memory, and eventually may run
up against fs.inotify.max_user_watches, causing other containers on the
system to fail.

This commit also fixes an apparent variable name bug in which the value
for maxFileAge was put into a variable named minFileAge.

* Removes old, empty directories when walking dir

Previously, directories were not touched. On long-running containers
directories would begin to pile up causing a large amount of useless
pusher inotify directories watches.

* Uses Go v1.18 to build Docker image, and Alpine 3.15

* Updates Go modules

* Reverts prometheus/client_golang to v1.11.0

I was running into this with newer versions:

prometheus/prometheus#10574

* Updates Travis to use Go v1.18

* Reverts Go to v1.17 (from v1.18)

The travis build was failing with something like this:

mattn/goveralls#207

... and the Docker build was failing with this error:

Step 8/10 : COPY --from=build /go/bin/pusher /
COPY failed: stat go/bin/pusher: file does not exist

* Adds a clarifying comment about removing dirs

* Simplifies dir removal logic, removes branching

.travis.yml

@@ -1,7 +1,7 @@
 language: go
 
 go:
-- "1.13"
+- "1.17"
 
 services:
 - docker

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13 as build
+FROM golang:1.17 as build
 # Add the local files to be sure we are building the local source code instead
 # of downloading from GitHub.
 # Don't add any of the other libraries, because we live at HEAD.
@@ -13,7 +13,7 @@ RUN go get \
       github.com/m-lab/pusher
 
 # Now copy the built binary into a minimal base image.
-FROM alpine:3.7
+FROM alpine:3.15
 # By default, alpine has no root certs. Add them so pusher can use PKI to
 # verify that Google Cloud Storage is actually Google Cloud Storage.
 RUN apk add --no-cache ca-certificates

finder/findfiles.go

@@ -15,6 +15,7 @@ package finder
 
 import (
 	"context"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
@@ -27,6 +28,11 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
+// The minimum age of a directory before it will be considered for removal, if
+// it is also empty. 25h should ensure that the current day's directory is never
+// removed prematurely.
+const minDirectoryAge time.Duration = 25 * time.Hour
+
 // Set up the prometheus metrics.
 var (
 	pusherFinderRuns = promauto.NewCounter(prometheus.CounterOpts{
@@ -52,20 +58,22 @@ var (
 
 // findFiles recursively searches through a given directory to find all the files which are old enough to be eligible for upload.
 // The list of files returned is sorted by mtime.
-func findFiles(datatype string, directory filename.System, minFileAge time.Duration) []filename.System {
+func findFiles(datatype string, directory filename.System, maxFileAge time.Duration) []filename.System {
 	// Give an initial capacity to the slice. 1024 chosen because it's a nice round number.
 	// TODO: Choose a better default.
 	eligibleFiles := make(map[filename.System]os.FileInfo)
-	eligibleTime := time.Now().Add(-minFileAge)
+	eligibleTime := time.Now().Add(-maxFileAge)
 	totalEligibleSize := int64(0)
 
 	err := filepath.Walk(string(directory), func(path string, info os.FileInfo, err error) error {
 		if err != nil {
 			// Any error terminates the walk.
 			return err
 		}
+		// Check whether a directory is very old and empty, and removes it if so.
 		if info.IsDir() {
-			return nil
+			err = checkDirectory(datatype, path, info.ModTime())
+			return err
 		}
 		if eligibleTime.After(info.ModTime()) {
 			eligibleFiles[filename.System(path)] = info
@@ -100,6 +108,45 @@ func findFiles(datatype string, directory filename.System, minFileAge time.Durat
 	return fileList
 }
 
+// checkDirectory checks to see if a directory is sufficiently old and empty.
+// If so, it removes the directory from the filesystem to prevent old, empty
+// directories from piling up in the filesystem.
+func checkDirectory(datatype string, path string, mTime time.Time) error {
+	// Do not delete the root datatype directory.
+	if datatype == filepath.Base(path) {
+		return nil
+	}
+	// Do nothing if the directory is less than constant minDirectoryAge.  This
+	// could probably be more aggressive.
+	eligibleTime := time.Now().Add(-minDirectoryAge)
+	if mTime.After(eligibleTime) {
+		return nil
+	}
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// Read the contents of the directory, looking only as far as the first file
+	// found. We don't care how many files there are, only that at least one
+	// exists. An error of type io.EOF indicates an empty directory.
+	// https://pkg.go.dev/os#File.Readdirnames
+	// https://stackoverflow.com/a/30708914
+	// Implementation note: we are using Readdirnames() instead of Readdir()
+	// because the former does not stat each file, but only returns file names,
+	// which is more efficient for our use case.
+	_, err = f.Readdirnames(1)
+	if err != io.EOF {
+		return err
+	}
+	err = os.Remove(path)
+	if err != nil {
+		return err
+	}
+	log.Printf("Removed old, empty directory %s.", path)
+	return nil
+}
+
 // FindForever repeatedly runs FindFiles until its context is canceled.
 //
 // It randomizes the inter-`find` sleep time in an effort to avoid thundering

finder/findfiles_test.go

@@ -2,6 +2,8 @@ package finder_test
 
 import (
 	"context"
+	"errors"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -25,6 +27,21 @@ func TestFindForever(t *testing.T) {
 	rtx.Must(ioutil.WriteFile(tempdir+"/next_oldest_file", []byte("moredata\n"), 0644), "WriteFile failed")
 	newtime = time.Now().Add(time.Duration(-12) * time.Hour)
 	rtx.Must(os.Chtimes(tempdir+"/next_oldest_file", newtime, newtime), "Chtimes failed")
+	// Set up the directories.
+	//
+	// An old, empty directory.
+	rtx.Must(os.Mkdir(tempdir+"/old_empty_dir", 0750), "Mkdir failed")
+	newtime = time.Now().Add(time.Duration(-26) * time.Hour)
+	rtx.Must(os.Chtimes(tempdir+"/old_empty_dir", newtime, newtime), "Chtimes failed")
+	// An old directory, but not empty.
+	rtx.Must(os.Mkdir(tempdir+"/old_not_empty_dir", 0750), "Mkdir failed")
+	newtime = time.Now().Add(time.Duration(-30) * time.Hour)
+	rtx.Must(os.Chtimes(tempdir+"/old_not_empty_dir", newtime, newtime), "Chtimes failed")
+	rtx.Must(ioutil.WriteFile(tempdir+"/old_not_empty_dir/test_file", []byte("data\n"), 0644), "WriteFile failed")
+	newtime = time.Now().Add(time.Duration(-27) * time.Hour)
+	rtx.Must(os.Chtimes(tempdir+"/old_not_empty_dir/test_file", newtime, newtime), "Chtimes failed")
+	// A new directory.
+	rtx.Must(os.Mkdir(tempdir+"/new_dir", 0750), "Mkdir failed")
 	// Set up the receiver channel.
 	foundFiles := make(chan filename.System)
 	ctx, cancel := context.WithCancel(context.Background())
@@ -38,15 +55,30 @@ func TestFindForever(t *testing.T) {
 	localfiles := []filename.System{
 		<-foundFiles,
 		<-foundFiles,
+		<-foundFiles,
 	}
-	if len(localfiles) != 2 {
+	// Test files.
+	if len(localfiles) != 3 {
 		t.Errorf("len(localfiles) (%d) != 2", len(localfiles))
 	}
-	if string(localfiles[0]) != tempdir+"/oldest_file" {
-		t.Errorf("wrong name[0]: %s", localfiles[0])
+	if string(localfiles[0]) != tempdir+"/old_not_empty_dir/test_file" {
+		t.Errorf("wrong name[1]: %s", localfiles[0])
+	}
+	if string(localfiles[1]) != tempdir+"/oldest_file" {
+		t.Errorf("wrong name[1]: %s", localfiles[0])
+	}
+	if string(localfiles[2]) != tempdir+"/next_oldest_file" {
+		t.Errorf("wrong name[2]: %s", localfiles[1])
+	}
+	// Test directories.
+	if _, err = os.Stat(tempdir + "/old_empty_dir"); errors.Is(err, fs.ErrExist) {
+		t.Errorf("Directory %s/old_empty_dir exists, but shouldn't", tempdir)
+	}
+	if _, err = os.Stat(tempdir + "/old_not_empty_dir"); errors.Is(err, fs.ErrNotExist) {
+		t.Errorf("Directory %s/old_not_empty_dir does not exist, but should", tempdir)
 	}
-	if string(localfiles[1]) != tempdir+"/next_oldest_file" {
-		t.Errorf("wrong name[1]: %s", localfiles[1])
+	if _, err = os.Stat(tempdir + "/new_dir"); errors.Is(err, fs.ErrNotExist) {
+		t.Errorf("Directory %s/new_dir does not exist, but should", tempdir)
 	}
 }
 

go.mod

@@ -3,13 +3,20 @@ module github.com/m-lab/pusher
 go 1.13
 
 require (
-	cloud.google.com/go/storage v1.6.0
-	github.com/go-test/deep v1.0.5 // indirect
-	github.com/googleapis/google-cloud-go-testing v0.0.0-20191008195207-8e1d251e947d
-	github.com/m-lab/go v1.3.0
-	github.com/prometheus/client_golang v1.3.0
+	cloud.google.com/go v0.101.1 // indirect
+	cloud.google.com/go/storage v1.22.0
+	github.com/araddon/dateparse v0.0.0-20210429162001-6b43995a97de // indirect
+	github.com/cespare/xxhash/v2 v2.1.2 // indirect
+	github.com/go-kit/log v0.2.0 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/googleapis/google-cloud-go-testing v0.0.0-20210719221736-1c9a4c676720
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/m-lab/go v0.1.47
+	github.com/prometheus/client_golang v1.11.0
+	github.com/prometheus/common v0.32.1 // indirect
+	github.com/prometheus/procfs v0.7.3 // indirect
 	github.com/rjeczalik/notify v0.9.2
-	golang.org/x/net v0.0.0-20200222125558-5a598a2470a0
-	golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae
-	google.golang.org/api v0.21.0
+	golang.org/x/net v0.0.0-20220425223048-2871e0cb64e4
+	golang.org/x/sys v0.0.0-20220503163025-988cb79eb6c6
+	google.golang.org/api v0.79.0
 )