SQL Client Example using KnoxShell in Apache Knox

The KnoxShell release artifact provides a small footprint client environment that removes all unnecessary server dependencies, configuration, binary scripts, etc. It is comprised a couple different things that empower different sorts of users.

• A set of SDK type classes for providing access to Hadoop resources over HTTP
• A Groovy based DSL for scripting access to Hadoop resources based on the underlying SDK classes
• A KnoxShell Token based Sessions to provide a CLI SSO session for executing multiple script

While testing the KnoxShell examples for the 0.14.0 Apache Knox release, I realized that using the KnoxShell for access to HiveServer2 was not easily done.

This is due to the fact that we are leveraging the knoxshell executable jar which makes is difficult to add additional classes and jars to the classpath for the executing script.

I needed to create a launch script that called the main class of the executable jar while also being able to set the classpath with additional jars for Apache Hive clients.

This article will go over the creation of a simple SQL client that we will call "knoxline" by using KnoxShell Groovy based DSL.

This particular article should work using the 0.14.0 knoxshell download and with previous gateway server releases as well.

Download

In the 0.14.0 release, you may get to the knoxshell download through the Apache Knox site.

From this above page click the Gateway client binary archive link or just use the one here.

Unzip this file into your preferred location which will result in a knoxshell-0.14.0 directory and we will refer to that location as the {GATEWAY_HOME}.

CD {GATEWAY_HOME}

You should see something similar to the following:

bash-3.2$ ls -l
total 160
-r--r--r--@ 1 larry staff 71714 Dec 6 18:32 LICENSE
-r--r--r--@ 1 larry staff 164 Dec 6 18:32 NOTICE
-rw-r--r--@ 1 larry staff 1452 Dec 6 18:32 README
drwxr-xr-x@ 6 larry staff 204 Dec 14 18:06 bin
drwxr--r--@ 3 larry staff 102 Dec 14 18:06 conf
drwxr-xr-x@ 19 larry staff 646 Dec 14 18:06 samples

Directory

Description

bin

contains the main knoxshell jar and related shell scripts

conf

only contains log4j config

logs

contains the knoxshell.log file

samples

has numerous examples to help you get started

Setup Truststore for Client

Get/setup truststore for the target Knox instance or fronting load balancer

• if you have access to the server you may use the command 

  • knoxcli.sh export-cert –type JKS

• copy the resulting gateway-client-identity.jks to your user home directory
• you may also ask your Knox administrator to provide you with the public cert for the gateway and create your own truststore within your user home directory

NOTE: if you see errors related to SSL and PKIX your truststore is not properly setup

Add Hive Client Libraries

Directory

Description

lib

To contain external jars to add to the classpath for things like HiveDriver

java -Dlog4j.configuration=conf/knoxshell-log4j.properties -cp bin/knoxshell.jar:lib/* org.apache.hadoop.gateway.shell.Shell bin/hive2.groovy "$@"

/**
* 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.
*/
import java.sql.DriverManager
import org.apache.hadoop.gateway.shell.Credentials

gatewayHost = "localhost";
gatewayPort = 8443;
trustStore = System.getProperty('user.home') + "/gateway-client-trust.jks";
trustStorePassword = "changeit";
contextPath = "gateway/sandbox/hive";

if (args.length == 0) {
  // accept defaults
} else if (args[0] == "?" || args[0] == "help") {
  System.out.println("\nExpected arguments: {host, port, truststore, truststore-pass, context-path}\n")
  System.exit(0);
} else if (args.length == 5) {
  gatewayHost = args[0];
  gatewayPort = args[1].toInteger();
  trustStore = args[2];
  trustStorePassword = args[3];
  contextPath = args[4];
} else if (args.length > 0) {
  System.out.println("\nERROR: Expected arguments: NONE for defaults or {host, port, truststore, truststore-pass, context-path}\n")
  System.exit(1);
}

connectionString = String.format( "jdbc:hive2://%s:%d/;ssl=true;sslTrustStore=%s;trustStorePassword=%s?hive.server2.transport.mode=http;hive.server2.thrift.http.path=/%s", gatewayHost, gatewayPort, trustStore, trustStorePassword, contextPath );

credentials = new Credentials()
credentials.add("ClearInput", "Enter username: ", "user")
.add("HiddenInput", "Enter pas" + "sword: ", "pass")
credentials.collect()

user = credentials.get("user").string()
pass = credentials.get("pass").string()

// Load Hive JDBC Driver
Class.forName( "org.apache.hive.jdbc.HiveDriver" );

// Configure JDBC connection
connection = DriverManager.getConnection( connectionString, user, pass );

while(1) {
  def sql = System.console().readLine 'knoxline> '

  if (!sql.equals("")) {
    System.out.println(sql)

    rs = true;
    statement = connection.createStatement();
    try {
      if (statement.execute( sql )) {
        resultSet = statement.getResultSet()
        int colcount = 0
        colcount = resultSet.getMetaData().getColumnCount();
        row = 0
        header = "| "
        while ( resultSet.next() ) {
          line = "| "
          for (int i = 1; i <= colcount; i++) {
            colvalue = resultSet.getString( i )
            if (colvalue == null) colvalue = ""
              colsize = colvalue.length()
              headerSize = resultSet.getMetaData().getColumnLabel( i ).length()
              if (headerSize > colsize) colsize = headerSize
                if (row == 0) {
                  header += resultSet.getMetaData().getColumnLabel( i ).center(colsize) + " | ";
                }
                line += colvalue.center(colsize) + " | ";
              }
              if (row == 0) {
                System.out.println("".padLeft(header.length(), "="))
                System.out.println(header);
                System.out.println("".padLeft(header.length(), "="))
              }
              System.out.println(line);
              row++
            }
            System.out.println("\nRows: " + row + "\n");
            resultSet.close();
          }
        }
        catch(Exception e) {
         e.printStackTrace()
         connection = DriverManager.getConnection( connectionString, user, pass );
        }
        statement.close();
     }
 }
 connection.close();

Execute a SQL Commands using KnoxLine

Let's check for existing tables:

Let's create a table by loading file from the local disk of the cluster machine:

knoxline> CREATE TABLE logs(column1 string, column2 string, column3 string, column4 string, column5 string, column6 string, column7 string) ROW FORMAT DELIMITED FIELDS TERMINATED BY ' '

Show the created table:

Show the table description:

Load the data from the samples.log file in /tmp:

knoxline> LOAD DATA LOCAL INPATH '/tmp/sample.log' OVERWRITE INTO TABLE logs

select * from logs where column2='20:11:56' and column4='[TRACE]'

Some things to note about this sample:

1. The gateway URL defaults to the sandbox topology
   • alternatives would be passing it as an argument to the script
2. Credential collectors are used to gather credentials or other input from various sources. In this sample the HiddenInput and ClearInput collectors prompt the user for the input with the provided prompt text and the values are acquired by a subsequent get call with the provided name value.
3. The standard Java classes for JDBC are used rather than the Hadoop session object used for access to the pure REST APIs
4. The resultSet is rendered in the familiar table format of other command line interfaces but shows how to access it for doing whatever scripting needs you have
5. Error handling is more or less non-existent in this example

I hope to bring "knoxline" to the KnoxShell module in a future release just as a simple way to do some quick queries from your KnoxShell environment.