101 lines
3 KiB
Go
101 lines
3 KiB
Go
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// Licensed to Elasticsearch B.V. under one or more contributor
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// license agreements. See the NOTICE file distributed with
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// this work for additional information regarding copyright
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// ownership. Elasticsearch B.V. licenses this file to you under
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// the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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package cfgfile
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import (
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"os"
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"path/filepath"
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"time"
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"github.com/mitchellh/hashstructure"
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"github.com/elastic/beats/libbeat/logp"
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)
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type GlobWatcher struct {
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glob string
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lastScan time.Time
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lastHash uint64
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}
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func NewGlobWatcher(glob string) *GlobWatcher {
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return &GlobWatcher{
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lastScan: time.Time{},
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lastHash: 0,
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glob: glob,
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}
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}
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// Scan scans all files matched by the glob and checks if the number of files or the modtime of the files changed
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// It returns the list of files, a boolean if anything in the glob changed and potential errors.
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// To detect changes not only mod time is compared but also the hash of the files list. This is required to
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// also detect files which were removed.
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// The modtime is compared based on second as normally mod-time is in seconds. If it is unclear if something changed
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// the method will return true for the changes. It is strongly recommend to call scan not more frequent then 1s.
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func (gw *GlobWatcher) Scan() ([]string, bool, error) {
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globList, err := filepath.Glob(gw.glob)
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if err != nil {
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return nil, false, err
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}
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updatedFiles := false
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files := []string{}
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lastScan := time.Now()
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defer func() { gw.lastScan = lastScan }()
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for _, f := range globList {
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info, err := os.Stat(f)
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if err != nil {
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logp.Err("Error getting stats for file: %s", f)
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continue
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}
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// Directories are skipped
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if !info.Mode().IsRegular() {
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continue
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}
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// Check if one of the files was changed recently
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// File modification time can be in seconds. -1 + truncation is to cover for files which
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// were created during this second.
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// If the last scan was at 09:02:15.00001 it will pick up files which were modified also 09:02:14
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// As this scan no necessarily picked up files form 09:02:14
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// TODO: How could this be improved / simplified? Behaviour was sometimes flaky. Is ModTime updated with delay?
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if info.ModTime().After(gw.lastScan.Add(-1 * time.Second).Truncate(time.Second)) {
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updatedFiles = true
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}
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files = append(files, f)
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}
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hash, err := hashstructure.Hash(files, nil)
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if err != nil {
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return files, true, err
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}
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defer func() { gw.lastHash = hash }()
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// Check if something changed
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if !updatedFiles && hash == gw.lastHash {
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return files, false, nil
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}
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return files, true, nil
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}
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