-
Notifications
You must be signed in to change notification settings - Fork 556
/
GlobalIdGenerator.java
94 lines (81 loc) · 3.16 KB
/
GlobalIdGenerator.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.apache.skywalking.apm.agent.core.context.ids;
import java.util.UUID;
import org.apache.skywalking.apm.util.StringUtil;
public final class GlobalIdGenerator {
private static final String PROCESS_ID = UUID.randomUUID().toString().replaceAll("-", "");
private static final ThreadLocal<IDContext> THREAD_ID_SEQUENCE = ThreadLocal.withInitial(
() -> new IDContext(System.currentTimeMillis(), (short) 0));
private GlobalIdGenerator() {
}
/**
* Generate a new id, combined by three parts.
* <p>
* The first one represents application instance id.
* <p>
* The second one represents thread id.
* <p>
* The third one also has two parts, 1) a timestamp, measured in milliseconds 2) a seq, in current thread, between
* 0(included) and 9999(included)
*
* @return unique id to represent a trace or segment
*/
public static String generate() {
return StringUtil.join(
'.',
PROCESS_ID,
String.valueOf(Thread.currentThread().getId()),
String.valueOf(THREAD_ID_SEQUENCE.get().nextSeq())
);
}
private static class IDContext {
private long lastTimestamp;
private short threadSeq;
// Just for considering time-shift-back only.
private long lastShiftTimestamp;
private int lastShiftValue;
private IDContext(long lastTimestamp, short threadSeq) {
this.lastTimestamp = lastTimestamp;
this.threadSeq = threadSeq;
}
private long nextSeq() {
return timestamp() * 10000 + nextThreadSeq();
}
private long timestamp() {
long currentTimeMillis = System.currentTimeMillis();
if (currentTimeMillis < lastTimestamp) {
// Just for considering time-shift-back by Ops or OS. @hanahmily 's suggestion.
if (lastShiftTimestamp != currentTimeMillis) {
lastShiftValue++;
lastShiftTimestamp = currentTimeMillis;
}
return lastShiftValue;
} else {
lastTimestamp = currentTimeMillis;
return lastTimestamp;
}
}
private short nextThreadSeq() {
if (threadSeq == 10000) {
threadSeq = 0;
}
return threadSeq++;
}
}
}