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
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed 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 com.google.devtools.build.lib.exec;
import static java.nio.charset.StandardCharsets.US_ASCII;
import com.google.common.base.Preconditions;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.Maps;
import com.google.common.io.BaseEncoding;
import com.google.devtools.build.lib.actions.ActionInput;
import com.google.devtools.build.lib.actions.ActionInputFileCache;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.DigestOfDirectoryException;
import com.google.devtools.build.lib.vfs.FileSystem;
import com.google.devtools.build.lib.vfs.Path;
import com.google.protobuf.ByteString;
import java.io.File;
import java.io.IOException;
import java.util.Map;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;
/**
* An in-memory cache to ensure we do I/O for source files only once during a single build.
*
* <p>Simply maintains a two-way cached mapping from digest <--> filename that may be populated
* only once.
*/
@ThreadSafe
public class SingleBuildFileCache implements ActionInputFileCache {
private final String cwd;
private final FileSystem fs;
public SingleBuildFileCache(String cwd, FileSystem fs) {
this.fs = Preconditions.checkNotNull(fs);
this.cwd = Preconditions.checkNotNull(cwd);
}
// If we can't get the digest, we store the exception. This avoids extra file IO for files
// that are allowed to be missing, as we first check a likely non-existent content file
// first. Further we won't need to unwrap the exception in getDigest().
private final LoadingCache<ActionInput, ActionInputMetadata> pathToMetadata =
CacheBuilder.newBuilder()
// We default to 10 disk read threads, but we don't expect them all to edit the map
// simultaneously.
.concurrencyLevel(8)
// Even small-ish builds, as of 11/21/2011 typically have over 10k artifacts, so it's
// unlikely that this default will adversely affect memory in most cases.
.initialCapacity(10000)
.build(new CacheLoader<ActionInput, ActionInputMetadata>() {
@Override
public ActionInputMetadata load(ActionInput input) {
Path path = null;
try {
path = fs.getPath(fullPath(input));
BaseEncoding hex = BaseEncoding.base16().lowerCase();
ByteString digest = ByteString.copyFrom(
hex.encode(path.getMD5Digest())
.getBytes(US_ASCII));
// Inject reverse mapping. Doing this unconditionally in getDigest() showed up
// as a hotspot in CPU profiling.
digestToPath.put(digest, input);
return new ActionInputMetadata(digest, path.getFileSize());
} catch (IOException e) {
if (path != null && path.isDirectory()) {
// TODO(bazel-team): This is rather presumptuous- it could have been another type of
// IOException.
return new ActionInputMetadata(new DigestOfDirectoryException(
"Input is a directory: " + input.getExecPathString()));
} else {
return new ActionInputMetadata(e);
}
}
}
});
private final Map<ByteString, ActionInput> digestToPath = Maps.newConcurrentMap();
@Nullable
@Override
public ActionInput getInputFromDigest(ByteString digest) {
return digestToPath.get(digest);
}
@Override
public Path getInputPath(ActionInput input) {
return fs.getPath(fullPath(input));
}
@Override
public long getSizeInBytes(ActionInput input) throws IOException {
return pathToMetadata.getUnchecked(input).getSize();
}
@Override
public ByteString getDigest(ActionInput input) throws IOException {
return pathToMetadata.getUnchecked(input).getDigest();
}
@Override
public boolean isFile(Artifact input) {
// We shouldn't fall back on this functionality ever.
throw new UnsupportedOperationException();
}
@Override
public boolean contentsAvailableLocally(ByteString digest) {
return digestToPath.containsKey(digest);
}
/**
* Creates a File object that refers to fileName, if fileName is an absolute path. Otherwise,
* returns a File object that refers to the fileName appended to the (absolute) current working
* directory.
*/
private String fullPath(ActionInput input) {
String relPath = input.getExecPathString();
return relPath.startsWith("/") ? relPath : new File(cwd, relPath).getPath();
}
/** Container class for caching I/O around ActionInputs. */
private static class ActionInputMetadata {
private final ByteString digest;
private final long size;
private final IOException exceptionOnAccess;
/** Constructor for a successful lookup. */
ActionInputMetadata(ByteString digest, long size) {
this.digest = digest;
this.size = size;
this.exceptionOnAccess = null;
}
/** Constructor for a failed lookup, size will be 0. */
ActionInputMetadata(IOException exceptionOnAccess) {
this.exceptionOnAccess = exceptionOnAccess;
this.digest = null;
this.size = 0;
}
/** Returns digest or throws the exception encountered calculating it/ */
ByteString getDigest() throws IOException {
maybeRaiseException();
return digest;
}
/** Returns the size. */
long getSize() throws IOException {
maybeRaiseException();
return size;
}
private void maybeRaiseException() throws IOException {
if (exceptionOnAccess != null) {
throw exceptionOnAccess;
}
}
}
}
|
