Basic stream solution

solr/core/src/java/org/apache/solr/handler/StreamHandler.java

@@ -35,6 +35,7 @@
 import org.apache.solr.client.solrj.io.comp.StreamComparator;
 import org.apache.solr.client.solrj.io.stream.DaemonStream;
 import org.apache.solr.client.solrj.io.stream.ExceptionStream;
+import org.apache.solr.client.solrj.io.stream.MonitorStream;
 import org.apache.solr.client.solrj.io.stream.StreamContext;
 import org.apache.solr.client.solrj.io.stream.TupleStream;
 import org.apache.solr.client.solrj.io.stream.expr.Explanation;
@@ -239,6 +240,9 @@ public void handleRequestBody(SolrQueryRequest req, SolrQueryResponse rsp) throw
       rsp.add("explanation", tupleStream.toExplanation(this.streamFactory));
     }
 
+    if (tupleStream instanceof MonitorStream) {
+      tupleStream = ((MonitorStream)tupleStream).getDaemonStream();
+    }
     if (tupleStream instanceof DaemonStream) {
       DaemonStream daemonStream = (DaemonStream) tupleStream;
       if (daemons.containsKey(daemonStream.getId())) {
@@ -247,7 +251,8 @@ public void handleRequestBody(SolrQueryRequest req, SolrQueryResponse rsp) throw
       daemonStream.setDaemons(daemons);
       daemonStream.open(); // This will start the deamonStream
       daemons.put(daemonStream.getId(), daemonStream);
-      rsp.add("result-set", new DaemonResponseStream("Deamon:" + daemonStream.getId() + " started on " + coreName));
+      rsp.add("result-set", new DaemonResponseStream("Daemon:" + daemonStream.getId() + " started on " + coreName));
+
     } else {
       rsp.add("result-set", new TimerStream(new ExceptionStream(tupleStream)));
     }

solr/server/solr/configsets/_default/conf/solrconfig.xml

@@ -368,11 +368,11 @@
   <query>
 
     <!-- Maximum number of clauses allowed when parsing a boolean query string.
-         
+
          This limit only impacts boolean queries specified by a user as part of a query string,
          and provides per-collection controls on how complex user specified boolean queries can
          be.  Query strings that specify more clauses then this will result in an error.
-         
+
          If this per-collection limit is greater then the global `maxBooleanClauses` limit
          specified in `solr.xml`, it will have no effect, as that setting also limits the size
          of user specified boolean queries.
@@ -686,10 +686,10 @@
       <str name="echoParams">explicit</str>
       <int name="rows">10</int>
       <!-- Default search field
-         <str name="df">text</str> 
+         <str name="df">text</str>
         -->
       <!-- Change from JSON to XML format (the default prior to Solr 7.0)
-         <str name="wt">xml</str> 
+         <str name="wt">xml</str>
         -->
     </lst>
     <!-- In addition to defaults, "appends" params can be specified

solr/solrj/src/java/org/apache/solr/client/solrj/io/Lang.java

@@ -45,6 +45,8 @@ public static void register(StreamFactory streamFactory) {
         .withFunctionName("commit", CommitStream.class)
         .withFunctionName("random", RandomFacadeStream.class)
         .withFunctionName("knnSearch", KnnStream.class)
+        .withFunctionName("monitor", MonitorStream.class)
+        .withFunctionName("alert", AlertStream.class)
 
 
             // decorator streams

solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/AlertStream.java

@@ -0,0 +1,160 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.solr.client.solrj.io.stream;
+
+import java.io.IOException;
+import java.net.URI;
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.http.client.ClientProtocolException;
+import org.apache.http.client.methods.HttpPost;
+import org.apache.http.entity.StringEntity;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.solr.client.solrj.io.Tuple;
+import org.apache.solr.client.solrj.io.comp.StreamComparator;
+import org.apache.solr.client.solrj.io.stream.expr.Explanation;
+import org.apache.solr.client.solrj.io.stream.expr.Expressible;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExplanation;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionNamedParameter;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionParameter;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionValue;
+import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
+import org.apache.solr.common.SolrException;
+import org.apache.solr.common.util.SuppressForbidden;
+
+
+public class AlertStream extends TupleStream implements Expressible {
+  CloseableHttpClient httpClient;
+  TupleStream tupleStream;
+  String targetURL;
+
+  public AlertStream(StreamExpression expression, StreamFactory factory) throws IOException {
+    List<StreamExpression> streamExpressions = factory.getExpressionOperandsRepresentingTypes(expression, Expressible.class, TupleStream.class);
+
+    String targetURL = null;
+
+    // parameters by position
+    TupleStream tupleStream = factory.constructStream(streamExpressions.get(0));
+    StreamExpressionNamedParameter urlExpression = factory.getNamedOperand(expression, "url");
+
+    if (urlExpression != null) {
+      targetURL = ((StreamExpressionValue) urlExpression.getParameter()).getValue();
+    }
+
+    init(tupleStream, targetURL);
+  }
+
+  public AlertStream(TupleStream tupleStream, String targetURL) {
+    init(tupleStream, targetURL);
+  }
+
+  public void init(TupleStream tupleStream, String targetURL) {
+    this.tupleStream = tupleStream;
+    this.targetURL = targetURL;
+  }
+
+  @Override
+  public void setStreamContext(StreamContext context) {
+    tupleStream.setStreamContext(context);
+  }
+
+  @Override
+  public List<TupleStream> children() {
+    ArrayList<TupleStream> list = new ArrayList<>();
+    list.add(tupleStream);
+    return list;
+  }
+
+  @Override
+  public void open() throws IOException {
+    tupleStream.open();
+    httpClient = HttpClients.createDefault();
+  }
+
+  @Override
+  public void close() throws IOException {
+    tupleStream.close();
+    httpClient.close();
+  }
+
+  @Override
+  public Tuple read() throws IOException {
+    Tuple tuple = tupleStream.read();
+
+    if (!tuple.EOF) {
+      alert(tuple);
+    }
+    return tuple;
+  }
+
+  @Override
+  public StreamComparator getStreamSort() {
+    return tupleStream.getStreamSort();
+  }
+
+  @Override
+  public StreamExpressionParameter toExpression(StreamFactory factory) throws IOException {
+    StreamExpression expression = new StreamExpression(factory.getFunctionName(this.getClass()));
+    expression.addParameter(((Expressible) tupleStream).toExpression(factory));
+    return expression;
+  }
+
+  @Override
+  public Explanation toExplanation(StreamFactory factory) throws IOException {
+    return new StreamExplanation(getStreamNodeId().toString())
+      .withChildren(new Explanation[]{
+        tupleStream.toExplanation(factory)
+      })
+      .withFunctionName(factory.getFunctionName(this.getClass()))
+      .withImplementingClass(this.getClass().getName())
+      .withExpressionType(Explanation.ExpressionType.STREAM_DECORATOR)
+      .withExpression(toExpression(factory).toString());
+  }
+
+  @SuppressForbidden(reason = "Needs currentTimeMillis to send request time")
+  void alert(Tuple tuple) throws IOException {
+    try {
+      Map<String, String> requestBody = new HashMap<String, String>();
+      requestBody.put("matches", tuple.fields.toString());
+      requestBody.put("requestTime", new Timestamp(System.currentTimeMillis()).toString());
+
+
+      HttpPost httpPost= new HttpPost((URI.create(targetURL)));
+      httpPost.setEntity(new StringEntity(requestBody.toString()));
+
+      httpClient.execute(httpPost);
+      //TODO: Error handling for non-successful response code
+    } catch (ClientProtocolException cpe) {
+      // Currently detecting authentication by string-matching the HTTP response
+      // Perhaps SolrClient should have thrown an exception itself??
+      if (cpe.getMessage().contains("HTTP ERROR 401") || cpe.getMessage().contentEquals("HTTP ERROR 403")) {
+        int code = cpe.getMessage().contains("HTTP ERROR 401") ? 401 : 403;
+        throw new SolrException(SolrException.ErrorCode.getErrorCode(code),
+          "Solr requires authentication for " + targetURL + ". Please supply valid credentials. HTTP code=" + code);
+      } else {
+        throw new SolrException(SolrException.ErrorCode.UNKNOWN, cpe);
+      }
+    }
+  }
+}