diff --git a/extracturls/README.md b/extracturls/README.md
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+++ b/extracturls/README.md
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+ExtractUrlFromHttp
+===================
+
+Prepare
+-------
+
+Install and configure Apache Spark for local test.
+
+
+Build
+-----
+
+    sbt assembly
+
+Run
+---
+
+    spark-submit --master local --class cn.edu.sjtu.omnilab.cobac.ExtractUrlFromHttp\
+      target/scala-2.10/cobac-extracturls-assembly-1.0.jar \
+      input output
+
+Test script
+-----------
+
+    chmod +x bin/test_extract_urls.sh
+    ./bin/test_extract_urls.sh
+
+Enjoy!
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diff --git a/extracturls/bin/test_extract_urls.sh b/extracturls/bin/test_extract_urls.sh
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+++ b/extracturls/bin/test_extract_urls.sh
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+#!/bin/bash
+set -e
+
+if [ $# -lt 2 ]; then
+ echo "Usage: $0 <httplog.in> <out>"
+ exit -1
+fi
+
+httplog=$1
+output=$2-`date +%y%m%d-%H%M%S`
+echo "Output file:" $output
+
+# build with java 6 to be compatible with our Spark cluster
+sbt -java-home $(/usr/libexec/java_home -v '1.6*') assembly
+
+APP_NAME="cn.edu.sjtu.omnilab.cobac.ExtractUrlFromHttp"
+BINJAR="target/scala-2.10/cobac-extracturls-assembly-1.0.jar"
+
+spark-submit --master local --class $APP_NAME $BINJAR $httplog $output
+
+if [ -d $output ]; then
+    echo "Output: "
+    head -n 20 $output/part-00000
+    echo "..."
+fi
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diff --git a/extracturls/build.sbt b/extracturls/build.sbt
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+++ b/extracturls/build.sbt
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+name := "cobac-extracturls"
+
+version := "1.0"
+
+scalaVersion := "2.10.5"
+
+libraryDependencies += "org.apache.spark" %% "spark-core" % "1.2.0" % "provided"
+    
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diff --git a/extracturls/project/plugins.sbt b/extracturls/project/plugins.sbt
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+++ b/extracturls/project/plugins.sbt
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+logLevel := Level.Warn
+
+addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.12.0")
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diff --git a/extracturls/src/main/scala/cn/edu/sjtu/omnilab/cobac/DataSchema.scala b/extracturls/src/main/scala/cn/edu/sjtu/omnilab/cobac/DataSchema.scala
new file mode 100644
index 0000000..eaad97e
--- /dev/null
+++ b/extracturls/src/main/scala/cn/edu/sjtu/omnilab/cobac/DataSchema.scala
@@ -0,0 +1,47 @@
+package cn.edu.sjtu.omnilab.cobac
+
+/**
+ * Data Schema of SJTU HTTP logs
+ */
+object DataSchema {
+
+  val source_ip = 0
+  val source_port = 1
+  val dest_ip = 2
+  val dest_port = 3
+  val conn = 4
+  val conn_ts = 5
+  val close_ts = 6
+  val conn_dur = 7
+  val idle_time0 = 8
+  val request_ts = 9
+  val request_dur = 10
+  val response_ts = 11
+  val response_dur_b = 12
+  val response_dur_e = 13
+  val idle_time1 = 14
+  val request_size = 15
+  val response_size = 16
+  val request_method = 17
+  val request_url = 18
+  val request_protocol = 19
+  val request_host = 20
+  val request_user_agent = 21
+  val request_referrer = 22
+  val request_conn = 23
+  val request_keep_alive = 24
+  val response_protocol = 25
+  val response_code = 26
+  val response_server = 27
+  val response_clen = 28
+  val response_ctype = 29
+  val response_cenc = 30
+  val response_etag = 31
+  val response_cache_ctl = 32
+  val response_last_mod = 33
+  val response_age = 34
+  val response_expire = 35
+  val response_connval  = 36
+  val response_keep_alive = 37
+
+}
diff --git a/extracturls/src/main/scala/cn/edu/sjtu/omnilab/cobac/ExtractUrlFromHttp.scala b/extracturls/src/main/scala/cn/edu/sjtu/omnilab/cobac/ExtractUrlFromHttp.scala
new file mode 100644
index 0000000..57ac265
--- /dev/null
+++ b/extracturls/src/main/scala/cn/edu/sjtu/omnilab/cobac/ExtractUrlFromHttp.scala
@@ -0,0 +1,116 @@
+package cn.edu.sjtu.omnilab.cobac
+
+import java.util.regex.{Matcher, Pattern}
+
+import org.apache.spark.storage.StorageLevel
+import org.apache.spark.{SparkContext, SparkConf}
+import org.apache.spark.SparkContext._
+import org.omg.CORBA.PERSIST_STORE
+
+object ExtractUrlFromHttp {
+
+  final val httpProtoPattern = Pattern.compile("^(\\w+:?//)?(.*)$", Pattern.CASE_INSENSITIVE)
+  final val httpParamPattern = Pattern.compile("^((\\w+://)?([^\\?&]+))\\??", Pattern.CASE_INSENSITIVE)
+
+  def main( args: Array[String] ): Unit = {
+
+    // parse command options
+    if (args.length < 2){
+      println("Usage: ExtractUrlFromHttp <HTTPLOG> <OUTPUT>")
+      sys.exit(0)
+    }
+
+    val httplog = args(0)
+    val output = args(1)
+
+    // configure spark
+    val conf = new SparkConf()
+      .setAppName("Extracting unique urls from http logs")
+    val spark = new SparkContext(conf)
+
+    // extract fields from raw logs and validate input data
+    val allUrlRDD = spark.textFile(httplog).map(cleanseLog(_))
+      .filter( line => line != null &&
+        line(DataSchema.request_host) != null &&
+        line(DataSchema.request_url) != null)
+      .map( line => {
+        val url = combineHostUri(line(DataSchema.request_host), line(DataSchema.request_url))
+        val curl = stripUrlParam(stripUrlProto(url))
+        (curl, url)
+      }).groupBy(_._1)
+      .map { case (curl, pairs) => {
+        val tnum = pairs.size
+        if (tnum > 500 ) { // about TOP-60K in one month
+          val oneurl = pairs.toList(1)._2
+          (tnum, oneurl)
+        } else {
+          null
+        }
+      }}.filter(m => m != null)
+      .sortByKey(false)
+      .zipWithIndex
+      .map { case ((tnum, url), index) => "%d|%d|%s".format(index, tnum, url) }
+      .saveAsTextFile(output)
+
+    spark.stop()
+    
+  }
+
+  def cleanseLog(line: String): Array[String] = {
+    // get HTTP header fields
+    val chops = line.split("""\"\s\"""");
+    if ( chops.length != 21 )
+      return null
+
+    // get timestamps
+    val timestamps = chops(0).split(" ");
+    if (timestamps.length != 18 )
+      return null
+
+    val results = timestamps ++ chops.slice(1, 21)
+
+    // remove N/A values and extrat quote
+    results.transform( field => {
+      var new_field = field.replaceAll("\"", "")
+      if (new_field == "N/A")
+        new_field = null
+      new_field
+    })
+
+    results
+  }
+
+  def hasProtoPrefix(uri: String): Boolean = {
+    if ( uri.matches("^(\\w+:?//).*"))
+      return true
+    return false
+  }
+
+  def combineHostUri(host: String, uri: String): String = {
+    if ( hasProtoPrefix(uri) ){
+      return uri;
+    } else {
+      return host+uri;
+    }
+  }
+
+  def stripUrlProto(url: String): String = {
+    val matcher = httpProtoPattern.matcher(url);
+    if ( matcher.find() ){
+      return matcher.group(2);
+    } else {
+      return url;
+    }
+  }
+
+  def stripUrlParam(url: String): String = {
+    val matcher = httpParamPattern.matcher(url);
+    if ( matcher.find() ){
+      return matcher.group(1);
+    } else {
+      return url;
+    }
+  }
+
+
+}
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