/**
* Activation strategy that enables features for a given percentage of users. This strategy is
* typically used to implement gradual rollouts. The implementation is based on a hashcode created
* from the name of the acting user which is calculated by {@link #calculateHashCode(FeatureUser)}.
*
* @author Christian Kaltepoth
*/
public class GradualActivationStrategy implements ActivationStrategy {
private final Log log = LogFactory.getLog(GradualActivationStrategy.class);
public static final String ID = "gradual";
public static final String PARAM_PERCENTAGE = "percentage";
@Override
public String getId() {
return ID;
}
@Override
public String getName() {
return "Gradual rollout";
}
@Override
public boolean isActive(FeatureState state, FeatureUser user) {
if (user != null && Strings.isNotBlank(user.getName())) {
String percentageAsString = state.getParameter(PARAM_PERCENTAGE);
try {
int percentage = Integer.valueOf(percentageAsString);
if (percentage > 0) {
int hashCode = Math.abs(calculateHashCode(user, state.getFeature()));
return (hashCode % 100) < percentage;
}
} catch (NumberFormatException e) {
log.error(
"Invalid gradual rollout percentage for feature "
+ state.getFeature().name()
+ ": "
+ percentageAsString);
}
}
return false;
}
/** @deprecated Use {@link #calculateHashCode(FeatureUser, Feature)} instead */
@Deprecated
protected int calculateHashCode(FeatureUser user) {
return calculateHashCode(user, null);
}
protected int calculateHashCode(FeatureUser user, Feature feature) {
Validate.notNull(user, "user is required");
return new StringBuilder()
.append(user.getName().toLowerCase(Locale.ENGLISH).trim())
.append(":")
.append(feature != null ? feature.name() : "")
.toString()
.hashCode();
}
@Override
public Parameter[] getParameters() {
return new Parameter[] {
ParameterBuilder.create(PARAM_PERCENTAGE)
.label("Percentage")
.matching("\\d{1,3}")
.description(
"Percentage of users for which the feature should be active (i.e. '25' for every fourth user).")
};
}
}
public class ScriptEngineActivationStrategy implements ActivationStrategy {
private final Log log = LogFactory.getLog(ScriptEngineActivationStrategy.class);
public static final String ID = "script";
public static final String PARAM_SCRIPT = "script";
public static final String PARAM_LANG = "lang";
private final ScriptEngineManager engineManager;
public ScriptEngineActivationStrategy() {
engineManager = new ScriptEngineManager();
}
@Override
public String getId() {
return ID;
}
@Override
public String getName() {
return "Java Scripting API";
}
@Override
public boolean isActive(FeatureState featureState, FeatureUser user) {
String lang = featureState.getParameter(PARAM_LANG);
String script = featureState.getParameter(PARAM_SCRIPT);
ScriptEngine engine = engineManager.getEngineByName(lang);
if (engine == null) {
log.error("Could not find script engine for: " + lang);
return false;
}
engine.put("user", user);
engine.put("date", new Date());
try {
Object result = engine.eval(script);
if (result instanceof Boolean) {
return ((Boolean) result).booleanValue();
}
} catch (ScriptException e) {
log.error(
"Could not evaluate script for feature "
+ featureState.getFeature().name()
+ ": "
+ e.getMessage());
}
return false;
}
@Override
public Parameter[] getParameters() {
return new Parameter[] {
new ScriptLanguageParameter(engineManager),
ParameterBuilder.create(PARAM_SCRIPT)
.label("Script")
.largeText()
.description(
"The script to check if the feature is active. "
+ "The script context provides access to some default objects. "
+ "The variable 'user' refers to the current acting FeatureUser "
+ "and 'date' to the current time represented as a java.util.Date.")
};
}
private static class ScriptLanguageParameter implements Parameter {
private List<String> languages = new ArrayList<String>();
public ScriptLanguageParameter(ScriptEngineManager engineManager) {
for (ScriptEngineFactory factory : engineManager.getEngineFactories()) {
languages.add(factory.getLanguageName());
}
}
@Override
public String getName() {
return PARAM_LANG;
}
@Override
public String getLabel() {
return "Language";
}
@Override
public String getDescription() {
return "The script language to use. Your system seems to support the following languages: "
+ Strings.join(languages, ", ");
}
@Override
public boolean isOptional() {
return false;
}
@Override
public boolean isLargeText() {
return false;
}
@Override
public boolean isValid(String value) {
return Strings.isNotBlank(value) && languages.contains(value);
}
}
}