/*
* Copyright 2013 Cloudera Inc.
*
* 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.cloudera.cdk.morphline.stdlib;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import com.cloudera.cdk.morphline.api.Command;
import com.cloudera.cdk.morphline.api.CommandBuilder;
import com.cloudera.cdk.morphline.api.MorphlineContext;
import com.cloudera.cdk.morphline.api.MorphlineRuntimeException;
import com.cloudera.cdk.morphline.api.Record;
import com.cloudera.cdk.morphline.base.AbstractCommand;
import com.codahale.metrics.Meter;
import com.typesafe.config.Config;
/**
* A tryRules command consists of zero or more rules.
*
* A rule consists of zero or more commands.
*
* The rules of a tryRules command are processed in top-down order. If one of the commands in a rule
* fails, the tryRules command stops processing of this rule, backtracks and tries the next rule,
* and so on, until a rule is found that runs all its commands to completion without failure (the
* rule succeeds). If a rule succeeds the remaining rules of the current tryRules command are
* skipped. If no rule succeeds the record remains unchanged, but a warning may be issued (the
* warning can be turned off) or an exception may be thrown (which is logged and ignored in
* production mode).
*
* Because a command can itself be a tryRules command, there can be tryRules commands with commands,
* nested inside tryRules, inside tryRules, recursively. This helps to implement arbitrarily complex
* functionality for advanced usage.
*/
public final class TryRulesBuilder implements CommandBuilder {
@Override
public Collection<String> getNames() {
return Collections.singletonList("tryRules");
}
@Override
public Command build(Config config, Command parent, Command child, MorphlineContext context) {
return new TryRules(this, config, parent, child, context);
}
///////////////////////////////////////////////////////////////////////////////
// Nested classes:
///////////////////////////////////////////////////////////////////////////////
private static final class TryRules extends AbstractCommand {
private final List<Command> childRules = new ArrayList();
private final boolean throwExceptionIfAllRulesFailed;
private final boolean catchExceptions;
private final boolean copyRecords;
private final Meter numExceptionsCaught;
public TryRules(CommandBuilder builder, Config config, Command parent, Command child, MorphlineContext context) {
super(builder, config, parent, child, context);
this.throwExceptionIfAllRulesFailed = getConfigs().getBoolean(config, "throwExceptionIfAllRulesFailed", true);
this.catchExceptions = getConfigs().getBoolean(config, "catchExceptions", false);
this.copyRecords = getConfigs().getBoolean(config, "copyRecords", true);
List<? extends Config> ruleConfigs = getConfigs().getConfigList(config, "rules", Collections.EMPTY_LIST);
for (Config ruleConfig : ruleConfigs) {
List<Command> commands = buildCommandChain(ruleConfig, "commands", child, true);
if (commands.size() > 0) {
childRules.add(commands.get(0));
}
}
validateArguments();
numExceptionsCaught = getMeter("numExceptionsCaught");
}
@Override
protected void doNotify(Record notification) {
for (Command childRule : childRules) {
childRule.notify(notification);
}
super.doNotify(notification);
}
@Override
protected boolean doProcess(Record record) {
for (Command childRule : childRules) {
Record copy = copyRecords ? record.copy() : record;
if (!catchExceptions) {
if (childRule.process(copy)) {
return true; // rule was executed successfully; no need to try the other remaining rules
}
} else {
try {
if (childRule.process(copy)) {
return true; // rule was executed successfully; no need to try the other remaining rules
}
} catch (RuntimeException e) {
numExceptionsCaught.mark();
LOG.warn("tryRules command caught rule exception. Continuing to try other remaining rules", e);
// continue and try the other remaining rules
}
}
}
LOG.warn("tryRules command found no successful rule");
if (throwExceptionIfAllRulesFailed) {
throw new MorphlineRuntimeException("tryRules command found no successful rule for record: " + record);
}
return false;
}
}
}