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Sqoop-server uses tomcat web server, it is very bare bones.
The main entry point is the TomcatToolRunner, it bootstraps the tomcat and loads all the sqoop related classes into its class path. It is invoked from the bash script .
Code Block
/sqoop.sh server start
The main hook for the sqoop server to start is this entry in the web.xml. Tomcat invokes it callbacks as it bootstraps and we use the contextInitialized callback to initialize all the related code.

Code Block

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<!-- Listeners -->
   <listener>
    <listener-class>org.apache.sqoop.server.ServerInitializer</listener-class>
  </listener>

Sqoop Server

The sqoop server is represented by the java class SqoopServer.java
SqoopServer.initialize() is the

main entry point.

called from the ServerInitiaizer
SqoopServer.destroy() is called when the tomcat server is shutdown

Sqoop Servlets

There are a bunch of servlets in web.xml : https://github.com/apache/sqoop/blob/sqoop2/server/src/main/webapp/WEB-INF/web.xml

They receive the requests and process it. Each Servlet has its corresponding handler class that handles the request for that servlet. It then internally calls the internal sqoop core/ common code.

Sqoop Request Handlers

We have servlets for each Sqoop Entity that is exposed via the REST API in web.xml. Refer to Sqoop 2 (1.99.4) Entity Nomenclature and Relationships for more details on the supported Sqoop Entities.
They receive the requests from the web or the Sqoop Client and process the request.
They delegate most of the business logic to their corresponding RequestHandler implementations.
All the rest APIs supported via the sqoop-server are documented here: http://sqoop.apache.org/docs/1.99.4/RESTAPI.html#id1

Code Block

  <!-- Version servlet -->
  <servlet>
    <servlet-name>VersionServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.VersionServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>VersionServlet</servlet-name>
    <url-pattern>/version</url-pattern>
  </servlet-mapping>
   <!-- Generic Configurable servlet -->
  <servlet>
    <servlet-name>v1.ConfigurableServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.ConfigurableServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>v1.ConfigurableServlet</servlet-name>
    <url-pattern>/v1/configurable/*</url-pattern>
  </servlet-mapping>
  <!-- Connector servlet -->
  <servlet>
    <servlet-name>v1.ConnectorServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.ConnectorServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>v1.ConnectorServlet</servlet-name>
    <url-pattern>/v1/connector/*</url-pattern>
  </servlet-mapping>
  <!-- Connectors servlet -->
  <servlet>
    <servlet-name>v1.ConnectorsServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.ConnectorServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>v1.ConnectorsServlet</servlet-name>
    <url-pattern>/v1/connectors/*</url-pattern>
  </servlet-mapping>
  <!-- Driver servlet -->
  <servlet>
    <servlet-name>v1.DriverServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.DriverServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  ......
  <!-- Job servlet -->
  <servlet>
    <servlet-name>v1.JobServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.JobServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>v1.JobServlet</servlet-name>
    <url-pattern>/v1/job/*</url-pattern>
  </servlet-mapping>
  <!-- Jobs servlet -->
  <servlet>
    <servlet-name>v1.JobsServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.JobsServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>v1.JobsServlet</servlet-name>
    <url-pattern>/v1/jobs/*</url-pattern>
  </servlet-mapping>
  <!-- Submissions servlet -->
  <servlet>
    <servlet-name>v1.SubmissionsServlet</servlet-name>
    <servlet-class>org.apache.sqoop.server.v1.SubmissionsServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>v1.SubmissionsServlet</servlet-name>
    <url-pattern>/v1/submissions/*</url-pattern>
  </servlet-mapping>

</web-app>

There is an authentication filter to authenticate all request.

Code Block
<!-- Filter --> <filter> <filter-name>authFilter</filter-name> <filter-class>org.apache.sqoop.filter.SqoopAuthenticationFilter</filter-class> </filter>

There are two authentication mode supported: simple and Kerberos, which could be set in the sqoop.properties.

Code Block

#
# Authentication configuration
#
org.apache.sqoop.security.authentication.type=SIMPLE
org.apache.sqoop.security.authentication.handler=org.apache.sqoop.security.Authentication.SimpleAuthenticationHandler
org.apache.sqoop.security.authentication.anonymous=true

#org.apache.sqoop.security.authentication.type=KERBEROS
#org.apache.sqoop.security.authentication.handler=org.apache.sqoop.security.Authentication.KerberosAuthenticationHandler
#org.apache.sqoop.security.authentication.kerberos.principal=sqoop/_HOST@NOVALOCAL
#org.apache.sqoop.security.authentication.kerberos.keytab=/home/kerberos/sqoop.keytab
#org.apache.sqoop.security.authentication.kerberos.http.principal=HTTP/_HOST@NOVALOCAL
#org.apache.sqoop.security.authentication.kerberos.http.keytab=/home/kerberos/sqoop.keytab
#org.apache.sqoop.security.authentication.enable.doAs=true
#org.apache.sqoop.security.authentication.proxyuser.#USER#.users=*
#org.apache.sqoop.security.authentication.proxyuser.#USER#.groups=*
#org.apache.sqoop.security.authentication.proxyuser.#USER#.hosts=*

Sqoop Request Handlers

Each Sqoop They receive the requests and process it. Each Servlet has its corresponding handler class that handles the request for that servlet. It then internally calls the internal sqoop core/ common code.

All the rest APIs supported via the sqoop-server are documented here: http://sqoop.apache.org/docs/1.99.4/RESTAPI.html#id1

Sqoop Client

There is also the Sqoop-client that used to invoke the Sqoop-server methods via the jersey REST client,

Code Block

public interface RequestHandler {
  static final String CONNECTOR_NAME_QUERY_PARAM = "cname";
  static final String JOB_NAME_QUERY_PARAM = "jname";
  JsonBean handleEvent(RequestContext ctx);
}
public class ConnectorRequestHandler implements RequestHandler {
...
}

Sqoop Client

Sqoop Client is represented by the java class SqoopClient.java
It has wrapper ResourceRequest classes for each sqoop entity, they encapsulate the request/postBody parameters to be sent in the request. Refer to Sqoop 2 (1.99.4) Entity Nomenclature and Relationships for more details on the supported Sqoop Entities.
It used the bare bones HttpURLConnection object to make requests to the Sqoop-server.
Code Block
HttpURLConnection conn = new DelegationTokenAuthenticatedURL().openConnection(url, authToken);
Note
SqoopClient used to use jersey REST client for making tomcat requests. Recently it was switched to Hadoop-auth/SPENGO for adding Kerberos support that are documented

herehttps

here
https://cwiki.apache.org/confluence/display/SQOOP/Security+Guide+On+Sqoop+2
Run command to start Sqoop Client.

Code Block
/sqoop.sh client

In Kerberos Authentication mode. Kinit is required to set Kerberos environment.

Code Block
kinit sqoop/server-fqdn@HADOOP.COM

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Key

Sqoop Server

Sqoop Servlets

Sqoop Request Handlers

Sqoop Request Handlers

Sqoop Client

Sqoop Client