Merge pull request 'rest-collector-plugin-with-retry' (#432) from rest-collector-plugin-with-retry into beta

Reviewed-on: #432

dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/collection/plugin/rest/RestIterator.java

@@ -18,7 +18,11 @@ import javax.xml.transform.TransformerConfigurationException;
 import javax.xml.transform.TransformerFactory;
 import javax.xml.transform.dom.DOMSource;
 import javax.xml.transform.stream.StreamResult;
-import javax.xml.xpath.*;
+import javax.xml.xpath.XPath;
+import javax.xml.xpath.XPathConstants;
+import javax.xml.xpath.XPathExpression;
+import javax.xml.xpath.XPathExpressionException;
+import javax.xml.xpath.XPathFactory;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.StringUtils;
@@ -35,7 +39,7 @@ import eu.dnetlib.dhp.common.collection.CollectorException;
 import eu.dnetlib.dhp.common.collection.HttpClientParams;
 
 /**
- * log.info(...) equal to  log.trace(...) in the application-logs
+ * log.info(...) equal to log.trace(...) in the application-logs
  * <p>
  * known bug: at resumptionType 'discover' if the (resultTotal % resultSizeValue) == 0 the collecting fails -> change the resultSizeValue
  *
@@ -47,6 +51,7 @@ public class RestIterator implements Iterator<String> {
 
 	private static final Logger log = LoggerFactory.getLogger(RestIterator.class);
 	public static final String UTF_8 = "UTF-8";
+	private static final int MAX_ATTEMPTS = 5;
 
 	private final HttpClientParams clientParams;
 
@@ -60,8 +65,9 @@ public class RestIterator implements Iterator<String> {
 	private final int resultSizeValue;
 	private int resumptionInt = 0; // integer resumption token (first record to harvest)
 	private int resultTotal = -1;
-	private String resumptionStr = Integer.toString(resumptionInt); // string resumption token (first record to harvest
-																	// or token scanned from results)
+	private String resumptionStr = Integer.toString(this.resumptionInt); // string resumption token (first record to
+																			// harvest
+	// or token scanned from results)
 	private InputStream resultStream;
 	private Transformer transformer;
 	private XPath xpath;
@@ -73,7 +79,7 @@ public class RestIterator implements Iterator<String> {
 	private final String querySize;
 	private final String authMethod;
 	private final String authToken;
-	private final Queue<String> recordQueue = new PriorityBlockingQueue<String>();
+	private final Queue<String> recordQueue = new PriorityBlockingQueue<>();
 	private int discoverResultSize = 0;
 	private int pagination = 1;
 	/*
@@ -83,8 +89,8 @@ public class RestIterator implements Iterator<String> {
 	 */
 	private final String resultOutputFormat;
 
-	/** RestIterator class
-	 *  compatible to version 1.3.33
+	/**
+	 * RestIterator class compatible to version 1.3.33
 	 */
 	public RestIterator(
 		final HttpClientParams clientParams,
@@ -108,40 +114,42 @@ public class RestIterator implements Iterator<String> {
 		this.resumptionType = resumptionType;
 		this.resumptionParam = resumptionParam;
 		this.resultFormatValue = resultFormatValue;
-		this.resultSizeValue = Integer.valueOf(resultSizeValueStr);
+		this.resultSizeValue = Integer.parseInt(resultSizeValueStr);
 		this.queryParams = queryParams;
 		this.authMethod = authMethod;
 		this.authToken = authToken;
 		this.resultOutputFormat = resultOutputFormat;
 
-		queryFormat = StringUtils.isNotBlank(resultFormatParam) ? "&" + resultFormatParam + "=" + resultFormatValue
+		this.queryFormat = StringUtils.isNotBlank(resultFormatParam) ? "&" + resultFormatParam + "=" + resultFormatValue
+			: "";
+		this.querySize = StringUtils.isNotBlank(resultSizeParam) ? "&" + resultSizeParam + "=" + resultSizeValueStr
 			: "";
-		querySize = StringUtils.isNotBlank(resultSizeParam) ? "&" + resultSizeParam + "=" + resultSizeValueStr : "";
 
 		try {
 			initXmlTransformation(resultTotalXpath, resumptionXpath, entityXpath);
-		} catch (Exception e) {
+		} catch (final Exception e) {
 			throw new IllegalStateException("xml transformation init failed: " + e.getMessage());
 		}
 
 		initQueue();
 	}
 
-	private void initXmlTransformation(String resultTotalXpath, String resumptionXpath, String entityXpath)
+	private void initXmlTransformation(final String resultTotalXpath, final String resumptionXpath,
+		final String entityXpath)
 		throws TransformerConfigurationException, XPathExpressionException {
 		final TransformerFactory factory = TransformerFactory.newInstance();
-		transformer = factory.newTransformer();
-		transformer.setOutputProperty(OutputKeys.INDENT, "yes");
-		transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "3");
-		xpath = XPathFactory.newInstance().newXPath();
-		xprResultTotalPath = xpath.compile(resultTotalXpath);
-		xprResumptionPath = xpath.compile(StringUtils.isBlank(resumptionXpath) ? "/" : resumptionXpath);
-		xprEntity = xpath.compile(entityXpath);
+		this.transformer = factory.newTransformer();
+		this.transformer.setOutputProperty(OutputKeys.INDENT, "yes");
+		this.transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "3");
+		this.xpath = XPathFactory.newInstance().newXPath();
+		this.xprResultTotalPath = this.xpath.compile(resultTotalXpath);
+		this.xprResumptionPath = this.xpath.compile(StringUtils.isBlank(resumptionXpath) ? "/" : resumptionXpath);
+		this.xprEntity = this.xpath.compile(entityXpath);
 	}
 
 	private void initQueue() {
-		query = baseUrl + "?" + queryParams + querySize + queryFormat;
-		log.info("REST calls starting with {}", query);
+		this.query = this.baseUrl + "?" + this.queryParams + this.querySize + this.queryFormat;
+		log.info("REST calls starting with {}", this.query);
 	}
 
 	private void disconnect() {
@@ -154,12 +162,11 @@ public class RestIterator implements Iterator<String> {
 	 */
 	@Override
 	public boolean hasNext() {
-		if (recordQueue.isEmpty() && query.isEmpty()) {
+		if (this.recordQueue.isEmpty() && this.query.isEmpty()) {
 			disconnect();
 			return false;
-		} else {
-			return true;
 		}
+		return true;
 	}
 
 	/*
@@ -168,214 +175,241 @@ public class RestIterator implements Iterator<String> {
 	 */
 	@Override
 	public String next() {
-		synchronized (recordQueue) {
-			while (recordQueue.isEmpty() && !query.isEmpty()) {
+		synchronized (this.recordQueue) {
+			while (this.recordQueue.isEmpty() && !this.query.isEmpty()) {
 				try {
-					query = downloadPage(query);
-				} catch (CollectorException e) {
+					this.query = downloadPage(this.query, 0);
+				} catch (final CollectorException e) {
 					log.debug("CollectorPlugin.next()-Exception: {}", e);
 					throw new RuntimeException(e);
 				}
 			}
-			return recordQueue.poll();
+			return this.recordQueue.poll();
 		}
 	}
 
 	/*
-	 * download page and return nextQuery
+	 * download page and return nextQuery (with number of attempt)
 	 */
-	private String downloadPage(String query) throws CollectorException {
-		String resultJson;
-		String resultXml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
-		String nextQuery = "";
-		String emptyXml = resultXml + "<" + JsonUtils.XML_WRAP_TAG + "></" + JsonUtils.XML_WRAP_TAG + ">";
-		Node resultNode = null;
-		NodeList nodeList = null;
-		String qUrlArgument = "";
-		int urlOldResumptionSize = 0;
-		InputStream theHttpInputStream;
+	private String downloadPage(String query, final int attempt) throws CollectorException {
 
-		// check if cursor=* is initial set otherwise add it to the queryParam URL
-		if (resumptionType.equalsIgnoreCase("deep-cursor")) {
-			log.debug("check resumptionType deep-cursor and check cursor=*?{}", query);
-			if (!query.contains("&cursor=")) {
-				query += "&cursor=*";
+		if (attempt > MAX_ATTEMPTS) {
+			throw new CollectorException("Max Number of attempts reached, query:" + query);
+		}
+
+		if (attempt > 0) {
+			final int delay = (attempt * 5000);
+			log.debug("Attempt {} with delay {}", attempt, delay);
+			try {
+				Thread.sleep(delay);
+			} catch (final InterruptedException e) {
+				new CollectorException(e);
 			}
 		}
 
 		try {
-			log.info("requestig URL [{}]", query);
+			String resultJson;
+			String resultXml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
+			String nextQuery = "";
+			final String emptyXml = resultXml + "<" + JsonUtils.XML_WRAP_TAG + "></" + JsonUtils.XML_WRAP_TAG + ">";
+			Node resultNode = null;
+			NodeList nodeList = null;
+			String qUrlArgument = "";
+			int urlOldResumptionSize = 0;
+			InputStream theHttpInputStream;
 
-			URL qUrl = new URL(query);
-			log.debug("authMethod: {}", authMethod);
-			if ("bearer".equalsIgnoreCase(this.authMethod)) {
-				log.trace("authMethod before inputStream: {}", resultXml);
-				HttpURLConnection conn = (HttpURLConnection) qUrl.openConnection();
-				conn.setRequestProperty(HttpHeaders.AUTHORIZATION, "Bearer " + authToken);
-				conn.setRequestProperty(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_JSON.getMimeType());
-				conn.setRequestMethod("GET");
-				theHttpInputStream = conn.getInputStream();
-			} else if (BASIC.equalsIgnoreCase(this.authMethod)) {
-				log.trace("authMethod before inputStream: {}", resultXml);
-				HttpURLConnection conn = (HttpURLConnection) qUrl.openConnection();
-				conn.setRequestProperty(HttpHeaders.AUTHORIZATION, "Basic " + authToken);
-				conn.setRequestProperty(HttpHeaders.ACCEPT, ContentType.APPLICATION_XML.getMimeType());
-				conn.setRequestMethod("GET");
-				theHttpInputStream = conn.getInputStream();
-			} else {
-				theHttpInputStream = qUrl.openStream();
-			}
-
-			resultStream = theHttpInputStream;
-			if ("json".equals(resultOutputFormat)) {
-				resultJson = IOUtils.toString(resultStream, StandardCharsets.UTF_8);
-				resultXml = JsonUtils.convertToXML(resultJson);
-				resultStream = IOUtils.toInputStream(resultXml, UTF_8);
-			}
-
-			if (!(emptyXml).equalsIgnoreCase(resultXml)) {
-				resultNode = (Node) xpath.evaluate("/", new InputSource(resultStream), XPathConstants.NODE);
-				nodeList = (NodeList) xprEntity.evaluate(resultNode, XPathConstants.NODESET);
-				log.debug("nodeList.length: {}", nodeList.getLength());
-				for (int i = 0; i < nodeList.getLength(); i++) {
-					StringWriter sw = new StringWriter();
-					transformer.transform(new DOMSource(nodeList.item(i)), new StreamResult(sw));
-					String toEnqueue = sw.toString();
-					if (toEnqueue == null || StringUtils.isBlank(toEnqueue) || emptyXml.equalsIgnoreCase(toEnqueue)) {
-						log.warn("The following record resulted in empty item for the feeding queue: {}", resultXml);
-					} else {
-						recordQueue.add(sw.toString());
-					}
+			// check if cursor=* is initial set otherwise add it to the queryParam URL
+			if ("deep-cursor".equalsIgnoreCase(this.resumptionType)) {
+				log.debug("check resumptionType deep-cursor and check cursor=*?{}", query);
+				if (!query.contains("&cursor=")) {
+					query += "&cursor=*";
 				}
-			} else {
-				log.warn("resultXml is equal with emptyXml");
 			}
 
-			resumptionInt += resultSizeValue;
+			try {
+				log.info("requesting URL [{}]", query);
 
-			switch (resumptionType.toLowerCase()) {
-				case "scan": // read of resumptionToken , evaluate next results, e.g. OAI, iterate over items
-					resumptionStr = xprResumptionPath.evaluate(resultNode);
-					break;
+				final URL qUrl = new URL(query);
+				log.debug("authMethod: {}", this.authMethod);
+				if ("bearer".equalsIgnoreCase(this.authMethod)) {
+					log.trace("authMethod before inputStream: {}", resultXml);
+					final HttpURLConnection conn = (HttpURLConnection) qUrl.openConnection();
+					conn.setRequestProperty(HttpHeaders.AUTHORIZATION, "Bearer " + this.authToken);
+					conn.setRequestProperty(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_JSON.getMimeType());
+					conn.setRequestMethod("GET");
+					theHttpInputStream = conn.getInputStream();
+				} else if (this.BASIC.equalsIgnoreCase(this.authMethod)) {
+					log.trace("authMethod before inputStream: {}", resultXml);
+					final HttpURLConnection conn = (HttpURLConnection) qUrl.openConnection();
+					conn.setRequestProperty(HttpHeaders.AUTHORIZATION, "Basic " + this.authToken);
+					conn.setRequestProperty(HttpHeaders.ACCEPT, ContentType.APPLICATION_XML.getMimeType());
+					conn.setRequestMethod("GET");
+					theHttpInputStream = conn.getInputStream();
+				} else {
+					theHttpInputStream = qUrl.openStream();
+				}
 
-				case "count": // begin at one step for all records, iterate over items
-					resumptionStr = Integer.toString(resumptionInt);
-					break;
+				this.resultStream = theHttpInputStream;
+				if ("json".equals(this.resultOutputFormat)) {
+					resultJson = IOUtils.toString(this.resultStream, StandardCharsets.UTF_8);
+					resultXml = JsonUtils.convertToXML(resultJson);
+					this.resultStream = IOUtils.toInputStream(resultXml, UTF_8);
+				}
 
-				case "discover": // size of result items unknown, iterate over items (for openDOAR - 201808)
-					if (resultSizeValue < 2) {
-						throw new CollectorException("Mode: discover, Param 'resultSizeValue' is less than 2");
+				if (!(emptyXml).equalsIgnoreCase(resultXml)) {
+					resultNode = (Node) this.xpath
+						.evaluate("/", new InputSource(this.resultStream), XPathConstants.NODE);
+					nodeList = (NodeList) this.xprEntity.evaluate(resultNode, XPathConstants.NODESET);
+					log.debug("nodeList.length: {}", nodeList.getLength());
+					for (int i = 0; i < nodeList.getLength(); i++) {
+						final StringWriter sw = new StringWriter();
+						this.transformer.transform(new DOMSource(nodeList.item(i)), new StreamResult(sw));
+						final String toEnqueue = sw.toString();
+						if ((toEnqueue == null) || StringUtils.isBlank(toEnqueue)
+							|| emptyXml.equalsIgnoreCase(toEnqueue)) {
+							log
+								.warn(
+									"The following record resulted in empty item for the feeding queue: {}", resultXml);
+						} else {
+							this.recordQueue.add(sw.toString());
+						}
 					}
-					qUrlArgument = qUrl.getQuery();
-					String[] arrayQUrlArgument = qUrlArgument.split("&");
-					for (String arrayUrlArgStr : arrayQUrlArgument) {
-						if (arrayUrlArgStr.startsWith(resumptionParam)) {
-							String[] resumptionKeyValue = arrayUrlArgStr.split("=");
-							if (isInteger(resumptionKeyValue[1])) {
-								urlOldResumptionSize = Integer.parseInt(resumptionKeyValue[1]);
-								log.debug("discover OldResumptionSize from Url (int): {}", urlOldResumptionSize);
-							} else {
-								log.debug("discover OldResumptionSize from Url (str): {}", resumptionKeyValue[1]);
+				} else {
+					log.warn("resultXml is equal with emptyXml");
+				}
+
+				this.resumptionInt += this.resultSizeValue;
+
+				switch (this.resumptionType.toLowerCase()) {
+					case "scan": // read of resumptionToken , evaluate next results, e.g. OAI, iterate over items
+						this.resumptionStr = this.xprResumptionPath.evaluate(resultNode);
+						break;
+
+					case "count": // begin at one step for all records, iterate over items
+						this.resumptionStr = Integer.toString(this.resumptionInt);
+						break;
+
+					case "discover": // size of result items unknown, iterate over items (for openDOAR - 201808)
+						if (this.resultSizeValue < 2) {
+							throw new CollectorException("Mode: discover, Param 'resultSizeValue' is less than 2");
+						}
+						qUrlArgument = qUrl.getQuery();
+						final String[] arrayQUrlArgument = qUrlArgument.split("&");
+						for (final String arrayUrlArgStr : arrayQUrlArgument) {
+							if (arrayUrlArgStr.startsWith(this.resumptionParam)) {
+								final String[] resumptionKeyValue = arrayUrlArgStr.split("=");
+								if (isInteger(resumptionKeyValue[1])) {
+									urlOldResumptionSize = Integer.parseInt(resumptionKeyValue[1]);
+									log.debug("discover OldResumptionSize from Url (int): {}", urlOldResumptionSize);
+								} else {
+									log.debug("discover OldResumptionSize from Url (str): {}", resumptionKeyValue[1]);
+								}
 							}
 						}
-					}
 
-					if (((emptyXml).equalsIgnoreCase(resultXml))
-						|| ((nodeList != null) && (nodeList.getLength() < resultSizeValue))) {
-						// resumptionStr = "";
-						if (nodeList != null) {
-							discoverResultSize += nodeList.getLength();
+						if (((emptyXml).equalsIgnoreCase(resultXml))
+							|| ((nodeList != null) && (nodeList.getLength() < this.resultSizeValue))) {
+							// resumptionStr = "";
+							if (nodeList != null) {
+								this.discoverResultSize += nodeList.getLength();
+							}
+							this.resultTotal = this.discoverResultSize;
+						} else {
+							this.resumptionStr = Integer.toString(this.resumptionInt);
+							this.resultTotal = this.resumptionInt + 1;
+							if (nodeList != null) {
+								this.discoverResultSize += nodeList.getLength();
+							}
 						}
-						resultTotal = discoverResultSize;
-					} else {
-						resumptionStr = Integer.toString(resumptionInt);
-						resultTotal = resumptionInt + 1;
+						log.info("discoverResultSize: {}", this.discoverResultSize);
+						break;
+
+					case "pagination":
+					case "page": // pagination, iterate over page numbers
+						this.pagination += 1;
 						if (nodeList != null) {
-							discoverResultSize += nodeList.getLength();
+							this.discoverResultSize += nodeList.getLength();
+						} else {
+							this.resultTotal = this.discoverResultSize;
+							this.pagination = this.discoverResultSize;
 						}
-					}
-					log.info("discoverResultSize: {}", discoverResultSize);
-					break;
+						this.resumptionInt = this.pagination;
+						this.resumptionStr = Integer.toString(this.resumptionInt);
+						break;
 
-				case "pagination":
-				case "page": // pagination, iterate over page numbers
-					pagination += 1;
-					if (nodeList != null) {
-						discoverResultSize += nodeList.getLength();
-					} else {
-						resultTotal = discoverResultSize;
-						pagination = discoverResultSize;
-					}
-					resumptionInt = pagination;
-					resumptionStr = Integer.toString(resumptionInt);
-					break;
+					case "deep-cursor": // size of result items unknown, iterate over items (for supporting deep cursor
+										// in
+										// solr)
+						// isn't relevant -- if (resultSizeValue < 2) {throw new CollectorServiceException("Mode:
+						// deep-cursor, Param 'resultSizeValue' is less than 2");}
 
-				case "deep-cursor": // size of result items unknown, iterate over items (for supporting deep cursor in
-									// solr)
-					// isn't relevant -- if (resultSizeValue < 2) {throw new CollectorServiceException("Mode:
-					// deep-cursor, Param 'resultSizeValue' is less than 2");}
+						this.resumptionStr = encodeValue(this.xprResumptionPath.evaluate(resultNode));
+						this.queryParams = this.queryParams.replace("&cursor=*", "");
 
-					resumptionStr = encodeValue(xprResumptionPath.evaluate(resultNode));
-					queryParams = queryParams.replace("&cursor=*", "");
+						// terminating if length of nodeList is 0
+						if ((nodeList != null) && (nodeList.getLength() < this.discoverResultSize)) {
+							this.resumptionInt += ((nodeList.getLength() + 1) - this.resultSizeValue);
+						} else {
+							this.resumptionInt += (nodeList.getLength() - this.resultSizeValue); // subtract the
+																									// resultSizeValue
+							// because the iteration is over
+							// real length and the
+							// resultSizeValue is added before
+							// the switch()
+						}
 
-					// terminating if length of nodeList is 0
-					if ((nodeList != null) && (nodeList.getLength() < discoverResultSize)) {
-						resumptionInt += (nodeList.getLength() + 1 - resultSizeValue);
-					} else {
-						resumptionInt += (nodeList.getLength() - resultSizeValue); // subtract the resultSizeValue
-																					// because the iteration is over
-																					// real length and the
-																					// resultSizeValue is added before
-																					// the switch()
-					}
+						this.discoverResultSize = nodeList.getLength();
 
-					discoverResultSize = nodeList.getLength();
+						log
+							.debug(
+								"downloadPage().deep-cursor: resumptionStr=" + this.resumptionStr + " ; queryParams="
+									+ this.queryParams + " resumptionLengthIncreased: " + this.resumptionInt);
 
-					log
-						.debug(
-							"downloadPage().deep-cursor: resumptionStr=" + resumptionStr + " ; queryParams="
-								+ queryParams + " resumptionLengthIncreased: " + resumptionInt);
+						break;
 
-					break;
+					default: // otherwise: abort
+						// resultTotal = resumptionInt;
+						break;
+				}
 
-				default: // otherwise: abort
-					// resultTotal = resumptionInt;
-					break;
+			} catch (final Exception e) {
+				log.error(e.getMessage(), e);
+				throw new IllegalStateException("collection failed: " + e.getMessage());
 			}
 
-		} catch (Exception e) {
-			log.error(e.getMessage(), e);
-			throw new IllegalStateException("collection failed: " + e.getMessage());
-		}
-
-		try {
-			if (resultTotal == -1) {
-				resultTotal = Integer.parseInt(xprResultTotalPath.evaluate(resultNode));
-				if (resumptionType.equalsIgnoreCase("page") && !BASIC.equalsIgnoreCase(authMethod)) {
-					resultTotal += 1;
-				} // to correct the upper bound
-				log.info("resultTotal was -1 is now: " + resultTotal);
+			try {
+				if (this.resultTotal == -1) {
+					this.resultTotal = Integer.parseInt(this.xprResultTotalPath.evaluate(resultNode));
+					if ("page".equalsIgnoreCase(this.resumptionType) && !this.BASIC.equalsIgnoreCase(this.authMethod)) {
+						this.resultTotal += 1;
+					} // to correct the upper bound
+					log.info("resultTotal was -1 is now: " + this.resultTotal);
+				}
+			} catch (final Exception e) {
+				log.error(e.getMessage(), e);
+				throw new IllegalStateException("downloadPage resultTotal couldn't parse: " + e.getMessage());
 			}
-		} catch (Exception e) {
-			log.error(e.getMessage(), e);
-			throw new IllegalStateException("downloadPage resultTotal couldn't parse: " + e.getMessage());
+			log.debug("resultTotal: " + this.resultTotal);
+			log.debug("resInt: " + this.resumptionInt);
+			if (this.resumptionInt <= this.resultTotal) {
+				nextQuery = this.baseUrl + "?" + this.queryParams + this.querySize + "&" + this.resumptionParam + "="
+					+ this.resumptionStr
+					+ this.queryFormat;
+			} else {
+				nextQuery = "";
+				// if (resumptionType.toLowerCase().equals("deep-cursor")) { resumptionInt -= 1; } // correct the
+				// resumptionInt and prevent a NullPointer Exception at mdStore
+			}
+			log.debug("nextQueryUrl: " + nextQuery);
+			return nextQuery;
+		} catch (final Throwable e) {
+			log.warn(e.getMessage(), e);
+			return downloadPage(query, attempt + 1);
 		}
-		log.debug("resultTotal: " + resultTotal);
-		log.debug("resInt: " + resumptionInt);
-		if (resumptionInt <= resultTotal) {
-			nextQuery = baseUrl + "?" + queryParams + querySize + "&" + resumptionParam + "=" + resumptionStr
-				+ queryFormat;
-		} else {
-			nextQuery = "";
-			// if (resumptionType.toLowerCase().equals("deep-cursor")) { resumptionInt -= 1; } // correct the
-			// resumptionInt and prevent a NullPointer Exception at mdStore
-		}
-		log.debug("nextQueryUrl: " + nextQuery);
-		return nextQuery;
 
 	}
 
-	private boolean isInteger(String s) {
+	private boolean isInteger(final String s) {
 		boolean isValidInteger = false;
 		try {
 			Integer.parseInt(s);
@@ -383,7 +417,7 @@ public class RestIterator implements Iterator<String> {
 			// s is a valid integer
 
 			isValidInteger = true;
-		} catch (NumberFormatException ex) {
+		} catch (final NumberFormatException ex) {
 			// s is not an integer
 		}
 
@@ -391,20 +425,20 @@ public class RestIterator implements Iterator<String> {
 	}
 
 	// Method to encode a string value using `UTF-8` encoding scheme
-	private String encodeValue(String value) {
+	private String encodeValue(final String value) {
 		try {
 			return URLEncoder.encode(value, StandardCharsets.UTF_8.toString());
-		} catch (UnsupportedEncodingException ex) {
+		} catch (final UnsupportedEncodingException ex) {
 			throw new RuntimeException(ex.getCause());
 		}
 	}
 
 	public String getResultFormatValue() {
-		return resultFormatValue;
+		return this.resultFormatValue;
 	}
 
 	public String getResultOutputFormat() {
-		return resultOutputFormat;
+		return this.resultOutputFormat;
 	}
 
 }

dhp-workflows/dhp-aggregation/src/test/java/eu/dnetlib/dhp/collection/plugin/rest/OsfPreprintCollectorTest.java

@@ -3,6 +3,7 @@ package eu.dnetlib.dhp.collection.plugin.rest;
 
 import java.util.HashMap;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.Assertions;
@@ -69,7 +70,7 @@ public class OsfPreprintCollectorTest {
 
 	@Test
 	@Disabled
-	void test() throws CollectorException {
+	void test_limited() throws CollectorException {
 		final AtomicInteger i = new AtomicInteger(0);
 		final Stream<String> stream = this.rcp.collect(this.api, new AggregatorReport());
 
@@ -82,4 +83,23 @@ public class OsfPreprintCollectorTest {
 		log.info("{}", i.intValue());
 		Assertions.assertTrue(i.intValue() > 0);
 	}
+
+	@Test
+	@Disabled
+	void test_all() throws CollectorException {
+		final AtomicLong i = new AtomicLong(0);
+		final Stream<String> stream = this.rcp.collect(this.api, new AggregatorReport());
+
+		stream.forEach(s -> {
+			Assertions.assertTrue(s.length() > 0);
+			if ((i.incrementAndGet() % 1000) == 0) {
+				log.info("COLLECTED: {}", i.get());
+			}
+
+		});
+
+		log.info("TOTAL: {}", i.get());
+		Assertions.assertTrue(i.get() > 0);
+	}
+
 }