1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.kubernetes;
18
19 import java.io.File;
20 import java.io.IOException;
21 import java.nio.file.Files;
22 import java.nio.file.Path;
23 import java.util.Objects;
24
25 import org.apache.logging.log4j.Logger;
26 import org.apache.logging.log4j.status.StatusLogger;
27
28 /**
29 * Locate the current docker container.
30 */
31 public class ContainerUtil {
32 private static final Logger LOGGER = StatusLogger.getLogger();
33 private static final int MAXLENGTH = 65;
34
35 /**
36 * Returns the container id when running in a Docker container.
37 *
38 * This inspects /proc/self/cgroup looking for a Kubernetes Control Group. Once it finds one it attempts
39 * to isolate just the docker container id. There doesn't appear to be a standard way to do this, but
40 * it seems to be the only way to determine what the current container is in a multi-container pod. It would have
41 * been much nicer if Kubernetes would just put the container id in a standard environment variable.
42 *
43 * @see <a href="http://stackoverflow.com/a/25729598/12916">Stackoverflow</a> for a discussion on retrieving the containerId.
44 * @see <a href="https://github.com/jenkinsci/docker-workflow-plugin/blob/master/src/main/java/org/jenkinsci/plugins/docker/workflow/client/ControlGroup.java>ControlGroup</a>
45 * for the original version of this. Not much is actually left but it provided good inspiration.
46 */
47 public static String getContainerId() {
48 try {
49 File file = new File("/proc/self/cgroup");
50 if (file.exists()) {
51 Path path = file.toPath();
52 String id = Files.lines(path).map(ContainerUtil::getContainerId).filter(Objects::nonNull)
53 .findFirst().orElse(null);
54 LOGGER.debug("Found container id {}", id);
55 return id;
56 }
57 LOGGER.warn("Unable to access container information");
58 } catch (IOException ioe) {
59 LOGGER.warn("Error obtaining container id: {}", ioe.getMessage());
60 }
61 return null;
62 }
63
64 private static String getContainerId(String line) {
65 // Every control group in Kubernetes will use
66 if (line.contains("/kubepods")) {
67 // Strip off everything up to the last slash.
68 int i = line.lastIndexOf('/');
69 if (i < 0) {
70 return null;
71 }
72 // If the remainder has a period then take everything up to it.
73 line = line.substring(i + 1);
74 i = line.lastIndexOf('.');
75 if (i > 0) {
76 line = line.substring(0, i);
77 }
78 // Everything ending with a '/' has already been stripped but the remainder might start with "docker-"
79 if (line.contains("docker-")) {
80 // 8:cpuset:/kubepods.slice/kubepods-pod9c26dfb6_b9c9_11e7_bfb9_02c6c1fc4861.slice/docker-3dd988081e7149463c043b5d9c57d7309e079c5e9290f91feba1cc45a04d6a5b.scope
81 i = line.lastIndexOf("docker-");
82 line = line.substring(i + 7);
83 }
84 return line.length() <= MAXLENGTH ? line : line.substring(0, MAXLENGTH);
85 }
86
87 return null;
88 }
89 }