Add support for http proxy (#450)

Adds support for Http Proxy when reading data from storage

sample configuration:

```
spark.delta.sharing.network.proxyHost=1.2.3.4
spark.delta.sharing.network.proxyPort=3128
spark.delta.sharing.network.noProxyHosts=5.6.7.8,12.13.14.15
```

client/src/main/scala/io/delta/sharing/client/DeltaSharingFileSystem.scala

@@ -22,37 +22,69 @@ import java.util.concurrent.TimeUnit
 import org.apache.hadoop.fs._
 import org.apache.hadoop.fs.permission.FsPermission
 import org.apache.hadoop.util.Progressable
+import org.apache.http.{HttpHost, HttpRequest}
+import org.apache.http.auth.{AuthScope, UsernamePasswordCredentials}
 import org.apache.http.client.config.RequestConfig
-import org.apache.http.impl.client.HttpClientBuilder
+import org.apache.http.conn.routing.HttpRoute
+import org.apache.http.impl.client.{BasicCredentialsProvider, HttpClientBuilder}
+import org.apache.http.impl.conn.{DefaultRoutePlanner, DefaultSchemePortResolver}
+import org.apache.http.protocol.HttpContext
 import org.apache.spark.SparkEnv
 import org.apache.spark.delta.sharing.{PreSignedUrlCache, PreSignedUrlFetcher}
-import org.apache.spark.network.util.JavaUtils
 
 import io.delta.sharing.client.model.FileAction
-import io.delta.sharing.client.util.{ConfUtils, RetryUtils}
+import io.delta.sharing.client.util.ConfUtils
 
 /** Read-only file system for delta paths. */
 private[sharing] class DeltaSharingFileSystem extends FileSystem {
+
   import DeltaSharingFileSystem._
 
   lazy private val numRetries = ConfUtils.numRetries(getConf)
   lazy private val maxRetryDurationMillis = ConfUtils.maxRetryDurationMillis(getConf)
   lazy private val timeoutInSeconds = ConfUtils.timeoutInSeconds(getConf)
+  lazy private val httpClient = createHttpClient()
 
-  lazy private val httpClient = {
+  private[sharing] def createHttpClient() = {
+    val proxyConfigOpt = ConfUtils.getProxyConfig(getConf)
     val maxConnections = ConfUtils.maxConnections(getConf)
     val config = RequestConfig.custom()
       .setConnectTimeout(timeoutInSeconds * 1000)
       .setConnectionRequestTimeout(timeoutInSeconds * 1000)
       .setSocketTimeout(timeoutInSeconds * 1000).build()
-    HttpClientBuilder.create()
+
+    val clientBuilder = HttpClientBuilder.create()
       .setMaxConnTotal(maxConnections)
       .setMaxConnPerRoute(maxConnections)
       .setDefaultRequestConfig(config)
       // Disable the default retry behavior because we have our own retry logic.
       // See `RetryUtils.runWithExponentialBackoff`.
       .disableAutomaticRetries()
-      .build()
+
+    // Set proxy if provided.
+    proxyConfigOpt.foreach { proxyConfig =>
+
+      val proxy = new HttpHost(proxyConfig.host, proxyConfig.port)
+      clientBuilder.setProxy(proxy)
+
+      if (proxyConfig.noProxyHosts.nonEmpty) {
+        val routePlanner = new DefaultRoutePlanner(DefaultSchemePortResolver.INSTANCE) {
+          override def determineRoute(target: HttpHost,
+                                      request: HttpRequest,
+                                      context: HttpContext): HttpRoute = {
+            if (proxyConfig.noProxyHosts.contains(target.getHostName)) {
+              // Direct route (no proxy)
+              new HttpRoute(target)
+            } else {
+              // Route via proxy
+              new HttpRoute(target, proxy)
+            }
+          }
+        }
+        clientBuilder.setRoutePlanner(routePlanner)
+      }
+    }
+    clientBuilder.build()
   }
 
   private lazy val refreshThresholdMs = getConf.getLong(

client/src/main/scala/io/delta/sharing/client/util/ConfUtils.scala

@@ -64,6 +64,27 @@ object ConfUtils {
   val LIMIT_PUSHDOWN_ENABLED_CONF = "spark.delta.sharing.limitPushdown.enabled"
   val LIMIT_PUSHDOWN_ENABLED_DEFAULT = "true"
 
+  val PROXY_HOST = "spark.delta.sharing.network.proxyHost"
+  val PROXY_PORT = "spark.delta.sharing.network.proxyPort"
+  val NO_PROXY_HOSTS = "spark.delta.sharing.network.noProxyHosts"
+
+  def getProxyConfig(conf: Configuration): Option[ProxyConfig] = {
+    val proxyHost = conf.get(PROXY_HOST, null)
+    val proxyPortAsString = conf.get(PROXY_PORT, null)
+
+    if (proxyHost == null && proxyPortAsString == null) {
+      return None
+    }
+
+    validateNonEmpty(proxyHost, PROXY_HOST)
+    validateNonEmpty(proxyPortAsString, PROXY_PORT)
+    val proxyPort = proxyPortAsString.toInt
+    validatePortNumber(proxyPort, PROXY_PORT)
+
+    val noProxyList = conf.getTrimmedStrings(NO_PROXY_HOSTS).toSeq
+    Some(ProxyConfig(proxyHost, proxyPort, noProxyHosts = noProxyList))
+  }
+
   def numRetries(conf: Configuration): Int = {
     val numRetries = conf.getInt(NUM_RETRIES_CONF, NUM_RETRIES_DEFAULT)
     validateNonNeg(numRetries, NUM_RETRIES_CONF)
@@ -170,4 +191,21 @@ object ConfUtils {
       throw new IllegalArgumentException(conf + " must be positive")
     }
   }
+
+  private def validateNonEmpty(value: String, conf: String): Unit = {
+    if (value == null || value.isEmpty) {
+      throw new IllegalArgumentException(conf + " must be defined")
+    }
+  }
+
+  private def validatePortNumber(value: Int, conf: String): Unit = {
+    if (value <= 0 || value > 65535) {
+      throw new IllegalArgumentException(conf + " must be a valid port number")
+    }
+  }
+
+  case class ProxyConfig(host: String,
+                         port: Int,
+                         noProxyHosts: Seq[String] = Seq.empty
+                        )
 }

client/src/test/scala/io/delta/sharing/client/DeltaSharingFileSystemSuite.scala

@@ -16,11 +16,17 @@
 
 package io.delta.sharing.client
 
+import javax.servlet.http.{HttpServlet, HttpServletRequest, HttpServletResponse}
+
 import org.apache.hadoop.conf.Configuration
-import org.apache.hadoop.fs.Path
+import org.apache.http.client.methods.HttpGet
+import org.apache.http.util.EntityUtils
 import org.apache.spark.SparkFunSuite
+import org.sparkproject.jetty.server.Server
+import org.sparkproject.jetty.servlet.{ServletHandler, ServletHolder}
 
-import io.delta.sharing.client.model.{AddCDCFile, AddFile, AddFileForCDF, FileAction, RemoveFile}
+import io.delta.sharing.client.model._
+import io.delta.sharing.client.util.{ConfUtils, ProxyServer}
 
 class DeltaSharingFileSystemSuite extends SparkFunSuite {
   import DeltaSharingFileSystem._
@@ -58,4 +64,173 @@ class DeltaSharingFileSystemSuite extends SparkFunSuite {
       assert(fs eq path.getFileSystem(conf))
     })
   }
+
+  test("traffic goes through a proxy when a proxy configured") {
+    // Create a local HTTP server.
+    val server = new Server(0)
+    val handler = new ServletHandler()
+    server.setHandler(handler)
+    handler.addServletWithMapping(new ServletHolder(new HttpServlet {
+      override def doGet(req: HttpServletRequest, resp: HttpServletResponse): Unit = {
+        resp.setContentType("text/plain")
+        resp.setStatus(HttpServletResponse.SC_OK)
+
+        // scalastyle:off println
+        resp.getWriter.println("Hello, World!")
+        // scalastyle:on println
+      }
+    }), "/*")
+    server.start()
+    do {
+      Thread.sleep(100)
+    } while (!server.isStarted())
+
+    // Create a local HTTP proxy server.
+    val proxyServer = new ProxyServer(0)
+    proxyServer.initialize()
+
+    try {
+
+      // Create a ProxyConfig with the host and port of the local proxy server.
+      val conf = new Configuration
+      conf.set(ConfUtils.PROXY_HOST, proxyServer.getHost())
+      conf.set(ConfUtils.PROXY_PORT, proxyServer.getPort().toString)
+
+      // Configure the httpClient to use the ProxyConfig.
+      val fs = new DeltaSharingFileSystem() {
+        override def getConf = {
+          conf
+        }
+      }
+
+      // Get http client instance.
+      val httpClient = fs.createHttpClient()
+
+      // Send a request to the local server through the httpClient.
+      val response = httpClient.execute(new HttpGet(server.getURI.toString))
+
+      // Assert that the request is successful.
+      assert(response.getStatusLine.getStatusCode == HttpServletResponse.SC_OK)
+      val content = EntityUtils.toString(response.getEntity)
+      assert(content.trim == "Hello, World!")
+
+      // Assert that the request is passed through proxy.
+      assert(proxyServer.getCapturedRequests().size == 1)
+    } finally {
+      server.stop()
+      proxyServer.stop()
+    }
+  }
+
+  test("traffic skips the proxy when a noProxyHosts configured") {
+    // Create a local HTTP server.
+    val server = new Server(0)
+    val handler = new ServletHandler()
+    server.setHandler(handler)
+    handler.addServletWithMapping(new ServletHolder(new HttpServlet {
+      override def doGet(req: HttpServletRequest, resp: HttpServletResponse): Unit = {
+        resp.setContentType("text/plain")
+        resp.setStatus(HttpServletResponse.SC_OK)
+
+        // scalastyle:off println
+        resp.getWriter.println("Hello, World!")
+        // scalastyle:on println
+      }
+    }), "/*")
+    server.start()
+    do {
+      Thread.sleep(100)
+    } while (!server.isStarted())
+
+    // Create a local HTTP proxy server.
+    val proxyServer = new ProxyServer(0)
+    proxyServer.initialize()
+    try {
+      // Create a ProxyConfig with the host and port of the local proxy server and noProxyHosts.
+      val conf = new Configuration
+      conf.set(ConfUtils.PROXY_HOST, proxyServer.getHost())
+      conf.set(ConfUtils.PROXY_PORT, proxyServer.getPort().toString)
+      conf.set(ConfUtils.NO_PROXY_HOSTS, server.getURI.getHost)
+
+      // Configure the httpClient to use the ProxyConfig.
+      val fs = new DeltaSharingFileSystem() {
+        override def getConf = {
+          conf
+        }
+      }
+
+      // Get http client instance.
+      val httpClient = fs.createHttpClient()
+
+      // Send a request to the local server through the httpClient.
+      val response = httpClient.execute(new HttpGet(server.getURI.toString))
+
+      // Assert that the request is successful.
+      assert(response.getStatusLine.getStatusCode == HttpServletResponse.SC_OK)
+      val content = EntityUtils.toString(response.getEntity)
+      assert(content.trim == "Hello, World!")
+
+      // Assert that the request is not passed through proxy.
+      assert(proxyServer.getCapturedRequests().isEmpty)
+    } finally {
+      server.stop()
+      proxyServer.stop()
+    }
+  }
+
+  test("traffic goes through the proxy when noProxyHosts does not include destination") {
+    // Create a local HTTP server.
+    val server = new Server(0)
+    val handler = new ServletHandler()
+    server.setHandler(handler)
+    handler.addServletWithMapping(new ServletHolder(new HttpServlet {
+      override def doGet(req: HttpServletRequest, resp: HttpServletResponse): Unit = {
+        resp.setContentType("text/plain")
+        resp.setStatus(HttpServletResponse.SC_OK)
+
+        // scalastyle:off println
+        resp.getWriter.println("Hello, World!")
+        // scalastyle:on println
+      }
+    }), "/*")
+    server.start()
+    do {
+      Thread.sleep(100)
+    } while (!server.isStarted())
+
+    // Create a local HTTP proxy server.
+    val proxyServer = new ProxyServer(0)
+    proxyServer.initialize()
+    try {
+      // Create a ProxyConfig with the host and port of the local proxy server and noProxyHosts.
+      val conf = new Configuration
+      conf.set(ConfUtils.PROXY_HOST, proxyServer.getHost())
+      conf.set(ConfUtils.PROXY_PORT, proxyServer.getPort().toString)
+      conf.set(ConfUtils.NO_PROXY_HOSTS, "1.2.3.4")
+
+      // Configure the httpClient to use the ProxyConfig.
+      val fs = new DeltaSharingFileSystem() {
+        override def getConf = {
+          conf
+        }
+      }
+
+      // Get http client instance.
+      val httpClient = fs.createHttpClient()
+
+      // Send a request to the local server through the httpClient.
+      val response = httpClient.execute(new HttpGet(server.getURI.toString))
+
+      // Assert that the request is successful.
+      assert(response.getStatusLine.getStatusCode == HttpServletResponse.SC_OK)
+      val content = EntityUtils.toString(response.getEntity)
+      assert(content.trim == "Hello, World!")
+
+      // Assert that the request is not passed through proxy.
+      assert(proxyServer.getCapturedRequests().size == 1)
+    } finally {
+      server.stop()
+      proxyServer.stop()
+    }
+  }
 }