Java ProcessContext.yield方法代码示例

import org.apache.nifi.processor.ProcessContext; //导入方法依赖的package包/类
/**
 * Will construct JMS {@link Message} by extracting its body from the
 * incoming {@link FlowFile}. {@link FlowFile} attributes that represent
 * standard JMS headers will be extracted from the {@link FlowFile} and set
 * as JMS headers on the newly constructed message. For the list of
 * available message headers please see {@link JmsHeaders}. <br>
 * <br>
 * Upon success the incoming {@link FlowFile} is transferred to the'success'
 * {@link Relationship} and upon failure FlowFile is penalized and
 * transferred to the 'failure' {@link Relationship}
 *
 */
@Override
protected void rendezvousWithJms(ProcessContext context, ProcessSession processSession) throws ProcessException {
    FlowFile flowFile = processSession.get();
    if (flowFile != null) {
        try {
            String destinationName = context.getProperty(DESTINATION).evaluateAttributeExpressions(flowFile).getValue();
            this.targetResource.publish(destinationName, this.extractMessageBody(flowFile, processSession), flowFile.getAttributes());
            processSession.transfer(flowFile, REL_SUCCESS);
            processSession.getProvenanceReporter().send(flowFile, context.getProperty(DESTINATION).evaluateAttributeExpressions().getValue());
        } catch (Exception e) {
            processSession.transfer(flowFile, REL_FAILURE);
            this.getLogger().error("Failed while sending message to JMS via " + this.targetResource, e);
            context.yield();
        }
    }
}
 

import org.apache.nifi.processor.ProcessContext; //导入方法依赖的package包/类
@Override
public void onTrigger(final ProcessContext context, final ProcessSession session) {
    List<FlowFile> flowFiles = session.get(delayFilter);

    if (flowFiles.isEmpty()) {
        logger.debug("no flowFiles ready to be processed, yielding");
        context.yield();
    } else {
        for (FlowFile flowFile : flowFiles) {
            delayMap.remove(flowFile.getAttribute(CoreAttributes.UUID.key()));
        }
        logger.debug("transferring {} files to 'success': {}", new Object[]{flowFiles.size(), flowFiles});
        session.transfer(flowFiles, REL_SUCCESS);
    }
}
 

import org.apache.nifi.processor.ProcessContext; //导入方法依赖的package包/类
@Override
public void onTrigger(final ProcessContext context, final ProcessSession processSession) {
    List<FlowFile> flowFiles = processSession.get(batchSize);
    if (flowFiles.isEmpty()) {
        return;
    }

    Session jschSession = null;
    Channel channel = null;
    try {
        jschSession = openSession(context);
        final String remotePath = context.getProperty(REMOTE_PATH).evaluateAttributeExpressions().getValue();
        channel = openExecChannel(context, jschSession, "scp -r -d -t " + remotePath);

        InputStream channelIn = channel.getInputStream();
        OutputStream channelOut = channel.getOutputStream();

        channel.connect();
        waitForAck(channelIn);

        ListIterator<FlowFile> fileIt = flowFiles.listIterator();
        while (fileIt.hasNext()) {
            final FlowFile flowFile = fileIt.next();

            // conditionally reject files that are zero bytes or less
            if (context.getProperty(REJECT_ZERO_BYTE).asBoolean() && flowFile.getSize() == 0) {
                logger.warn("Rejecting {} because it is zero bytes", new Object[]{flowFile});
                processSession.transfer(processSession.penalize(flowFile), REL_REJECT);
                fileIt.remove();
                continue;
            }

            final String filename = flowFile.getAttribute(CoreAttributes.FILENAME.key());
            final String permissions = context.getProperty(PERMISSIONS).evaluateAttributeExpressions(flowFile).getValue();

            // destination path + filename
            // final String fullPath = buildFullPath(context, flowFile, filename);

            processSession.read(flowFile, new InputStreamCallback() {
                @Override
                public void process(final InputStream flowFileIn) throws IOException {
                    // send "C0644 filesize filename", where filename should not include '/'
                    StringBuilder command = new StringBuilder("C").append(permissions).append(' ');
                    command.append(flowFile.getSize()).append(' ');
                    command.append(filename).append('\n');

                    channelOut.write(command.toString().getBytes(StandardCharsets.UTF_8));
                    channelOut.flush();
                    waitForAck(channelIn);

                    IOUtils.copy(flowFileIn, channelOut);
                    channelOut.flush();
                    sendAck(channelOut);
                    waitForAck(channelIn);
                }
            });

            processSession.transfer(flowFile, REL_SUCCESS);
            processSession.getProvenanceReporter().send(flowFile, remotePath);
            fileIt.remove();
            if (logger.isDebugEnabled()) {
                logger.debug("Sent {} to remote host", new Object[]{flowFile});
            }
        }

    } catch (JSchException | IOException ex) {
        context.yield();
        logger.error("Unable to create session to remote host due to {}", new Object[]{ex}, ex);
        processSession.transfer(flowFiles, REL_FAILURE);

    } finally {
        if (channel != null) {
            channel.disconnect();
        }
        if (jschSession != null) {
            jschSession.disconnect();
        }
    }
}