org.apache.kafka.common.config.ConfigTransformer Maven / Gradle / Ivy
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/*
* 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.kafka.common.config;
import org.apache.kafka.common.config.provider.ConfigProvider;
import org.apache.kafka.common.config.provider.FileConfigProvider;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* This class wraps a set of {@link ConfigProvider} instances and uses them to perform
* transformations.
*
* The default variable pattern is of the form ${provider:[path:]key},
* where the provider corresponds to a {@link ConfigProvider} instance, as passed to
* {@link ConfigTransformer#ConfigTransformer(Map)}. The pattern will extract a set
* of paths (which are optional) and keys and then pass them to {@link ConfigProvider#get(String, Set)} to obtain the
* values with which to replace the variables.
*
*
For example, if a Map consisting of an entry with a provider name "file" and provider instance
* {@link FileConfigProvider} is passed to the {@link ConfigTransformer#ConfigTransformer(Map)}, and a Properties
* file with contents
*
* fileKey=someValue
*
* resides at the path "/tmp/properties.txt", then when a configuration Map which has an entry with a key "someKey" and
* a value "${file:/tmp/properties.txt:fileKey}" is passed to the {@link #transform(Map)} method, then the transformed
* Map will have an entry with key "someKey" and a value "someValue".
*
* This class only depends on {@link ConfigProvider#get(String, Set)} and does not depend on subscription support
* in a {@link ConfigProvider}, such as the {@link ConfigProvider#subscribe(String, Set, ConfigChangeCallback)} and
* {@link ConfigProvider#unsubscribe(String, Set, ConfigChangeCallback)} methods.
*/
public class ConfigTransformer {
public static final Pattern DEFAULT_PATTERN = Pattern.compile("\\$\\{([^}]*?):(([^}]*?):)?([^}]*?)\\}");
private static final String EMPTY_PATH = "";
private final Map configProviders;
/**
* Creates a ConfigTransformer with the default pattern, of the form ${provider:[path:]key}.
*
* @param configProviders a Map of provider names and {@link ConfigProvider} instances.
*/
public ConfigTransformer(Map configProviders) {
this.configProviders = configProviders;
}
/**
* Transforms the given configuration data by using the {@link ConfigProvider} instances to
* look up values to replace the variables in the pattern.
*
* @param configs the configuration values to be transformed
* @return an instance of {@link ConfigTransformerResult}
*/
public ConfigTransformerResult transform(Map configs) {
Map>> keysByProvider = new HashMap<>();
Map>> lookupsByProvider = new HashMap<>();
// Collect the variables from the given configs that need transformation
for (Map.Entry config : configs.entrySet()) {
if (config.getValue() != null) {
List configVars = getVars(config.getValue(), DEFAULT_PATTERN);
for (ConfigVariable configVar : configVars) {
Map> keysByPath = keysByProvider.computeIfAbsent(configVar.providerName, k -> new HashMap<>());
Set keys = keysByPath.computeIfAbsent(configVar.path, k -> new HashSet<>());
keys.add(configVar.variable);
}
}
}
// Retrieve requested variables from the ConfigProviders
Map ttls = new HashMap<>();
for (Map.Entry>> entry : keysByProvider.entrySet()) {
String providerName = entry.getKey();
ConfigProvider provider = configProviders.get(providerName);
Map> keysByPath = entry.getValue();
if (provider != null && keysByPath != null) {
for (Map.Entry> pathWithKeys : keysByPath.entrySet()) {
String path = pathWithKeys.getKey();
Set keys = new HashSet<>(pathWithKeys.getValue());
ConfigData configData = provider.get(path, keys);
Map data = configData.data();
Long ttl = configData.ttl();
if (ttl != null && ttl >= 0) {
ttls.put(path, ttl);
}
Map> keyValuesByPath =
lookupsByProvider.computeIfAbsent(providerName, k -> new HashMap<>());
keyValuesByPath.put(path, data);
}
}
}
// Perform the transformations by performing variable replacements
Map data = new HashMap<>(configs);
for (Map.Entry config : configs.entrySet()) {
data.put(config.getKey(), replace(lookupsByProvider, config.getValue(), DEFAULT_PATTERN));
}
return new ConfigTransformerResult(data, ttls);
}
private static List getVars(String value, Pattern pattern) {
List configVars = new ArrayList<>();
Matcher matcher = pattern.matcher(value);
while (matcher.find()) {
configVars.add(new ConfigVariable(matcher));
}
return configVars;
}
private static String replace(Map>> lookupsByProvider,
String value,
Pattern pattern) {
if (value == null) {
return null;
}
Matcher matcher = pattern.matcher(value);
StringBuilder builder = new StringBuilder();
int i = 0;
while (matcher.find()) {
ConfigVariable configVar = new ConfigVariable(matcher);
Map> lookupsByPath = lookupsByProvider.get(configVar.providerName);
if (lookupsByPath != null) {
Map keyValues = lookupsByPath.get(configVar.path);
String replacement = keyValues.get(configVar.variable);
builder.append(value, i, matcher.start());
if (replacement == null) {
// No replacements will be performed; just return the original value
builder.append(matcher.group(0));
} else {
builder.append(replacement);
}
i = matcher.end();
}
}
builder.append(value, i, value.length());
return builder.toString();
}
private static class ConfigVariable {
final String providerName;
final String path;
final String variable;
ConfigVariable(Matcher matcher) {
this.providerName = matcher.group(1);
this.path = matcher.group(3) != null ? matcher.group(3) : EMPTY_PATH;
this.variable = matcher.group(4);
}
public String toString() {
return "(" + providerName + ":" + (path != null ? path + ":" : "") + variable + ")";
}
}
}