com.streamsets.pipeline.api.interceptor.Interceptor Maven / Gradle / Ivy
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/*
* Copyright 2018 StreamSets 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.streamsets.pipeline.api.interceptor;
import com.streamsets.pipeline.api.BlobStore;
import com.streamsets.pipeline.api.ConfigIssue;
import com.streamsets.pipeline.api.Configuration;
import com.streamsets.pipeline.api.ErrorCode;
import com.streamsets.pipeline.api.MetricContext;
import com.streamsets.pipeline.api.Record;
import com.streamsets.pipeline.api.Stage;
import com.streamsets.pipeline.api.StageException;
import java.util.List;
import java.util.Map;
/**
* Interceptor is a plugable component similar to Stage. However unlike stage, it's not visible to user but rather is
* run "hidden" inside the execution framework. This allows interceptors perform job that user should not be able to
* disable.
*/
public interface Interceptor {
/**
* Context that provides runtime information and services to the interceptor.
*/
public interface Context extends MetricContext {
/**
* Creates a configuration issue for the interceptor (at initialization time).
*
* @param errorCode the ErrorCode for the issue.
* @param args the arguments for the ErrorCode message.
* @return the configuration issue to report back.
*/
ConfigIssue createConfigIssue(ErrorCode errorCode, Object... args);
/**
* Return value for given configuration option from data collector main configuration.
*
* @param configName Configuration option name
* @return String representation of the value or null if it's not defined.
* @deprecated Use getConfiguration() instead.
*/
@Deprecated
public String getConfig(String configName);
/**
* Return configuration object corresponding to the data collector main configuration files.
*/
public Configuration getConfiguration();
/**
* Returns SDC singleton instance for the BLOB store
*/
public BlobStore getBlobStore();
/**
* Instantiate and initialize given stage definition. The stage must be of a type klass.
*
* This method can be only called from init() method. The created stage will be initialized by framework (e.g. the
* method init() will be already called). If the initialization failed from whatever reason, this method will return
* null and the framework will propagate the validation issues up.
*
* Similarly the destroy() method on the created stage is called by the framework when required.
*
* @param jsonDefinition Json definition as is usually generated by data collector framework.
* @param klass Subclass of stage (Processor, Source, Target, ...)
* @param Subclass of stage (Processor, Source, Target, ...)
* @return New instance of the stage or null if the stage can't be created from any reason
*/
public S createStage(String jsonDefinition, Class klass);
/**
* Indicates if the pipeline is running in preview mode or not.
*
* @return if the pipeline is running in preview mode or not.
*/
public boolean isPreview();
/**
* Return unique id that identifies this data collector.
*
* @return unique id that identifies this data collector.
*/
public String getSdcId();
/**
* Return unique id of stage that this interceptor is associated with.
*
* @return Return unique id of stage that this interceptor is associated with.
*/
public String getStageInstanceName();
/**
* Return unique id that identifies this pipeline.
*
* @return unique id that identifies this pipeline.
*/
public String getPipelineId();
}
/**
* Initializes the interceptor.
*
* This method is called once when the pipeline is being initialized before the processing any data.
*
* If the method returns empty list then it is considered ready to process data. Else it is considered mis-configured or
* that there is a problem and the interceptor is not ready to process data, thus aborting the pipeline initialization.
*
* @param context the stage context.
*/
public List init(Context context);
/**
* Intercept records and perform operations that need to be performed.
*
* @param records List of input records
* @return List of records that should be passed down to the processing.
*/
public List intercept(List records) throws StageException;
/**
* Destroys the interceptor. It should be used to release any resources held by the interceptor after initialization or
* processing.
*
* This method is called once when the pipeline is being shutdown. After this method is called, the interceptor will not
* be called to process any more data.
*
* This method is also called after a failed initialization to allow releasing resources created before the
* initialization failed.
*/
void destroy();
}