Create a connection to HDFS by navigating to the Connections page in the Sync App application and selecting the corresponding icon in the Add Connections panel. If the HDFS icon is not available, click the Add More icon to download and install the HDFS connector from the CData site.

Required properties are listed under the Settings tab. The Advanced tab lists connection properties that are not typically required.

Connecting to HDFS

In order to connect, set the following connection properties:

• Host: Set this value to the host of your HDFS installation.
• Port: Set this value to the port of your HDFS installation. Default port: 50070
• UseSSL: (Optional) Set this value to 'True', to negotiate TLS/SSL connections to the HDFS server. Default: 'False'.

Authenticating to HDFS

There are two authentication methods available for connecting to the HDFS data source, Anonymous Authentication and Negotiate (Kerberos) Authentication.

Anonymous Authentication

In some situations, HDFS may be connected to without any authentication connection properties. To do so, set the AuthScheme to None (default).

Kerberos

When authentication credentials are required, you can use Kerberos. See Using Kerberos for details on how to authenticate with Kerberos.

Fine Tuning Data Access

You can use the following properties to gain more control over the data returned from HDFS:

• DirectoryRetrievalDepth: How many subfolders to be recursively scanned before stopping.
  -1 specifies that all subfolders are scanned. 0 specifies that only the current folder will be scanned for items.
• Path: Limit the subfolders recursively scanned.

This section shows how to use the Sync App to authenticate using Kerberos.

Kerberos

To authenticate to HDFS using Kerberos, set the following properties:

• AuthScheme: Set this to NEGOTIATE.
• KerberosKDC: Set this to the host name or IP Address of your Kerberos KDC machine.
• KerberosSPN: Set this to the service and host of the HDFS Kerberos Principal. This is the value prior to the '@' symbol (for instance, ServiceName/MyHost) of the principal value (for instance, ServiceName/[email protected]).

Retrieve the Kerberos Ticket

You can use one of the following options to retrieve the required Kerberos ticket.

MIT Kerberos Credential Cache File

This option enables you to use the MIT Kerberos Ticket Manager or kinit command to get tickets. Note that you do not need to set the User or Password connection properties with this option.

1. Ensure that you have an environment variable created called KRB5CCNAME.
2. Set the KRB5CCNAME environment variable to a path pointing to your credential cache file (for instance, C:\krb_cache\krb5cc_0 or /tmp/krb5cc_0). This file is created when generating your ticket with MIT Kerberos Ticket Manager.
3. To obtain a ticket, open the MIT Kerberos Ticket Manager application, click Get Ticket, enter your principal name and password, then click OK. If successful, ticket information appears in Kerberos Ticket Manager and is stored in the credential cache file.
4. Now that you have created the credential cache file, the Sync App uses the cache file to obtain the Kerberos ticket to connect to HDFS.

As an alternative to setting the KRB5CCNAME environment variable, you can directly set the file path using the KerberosTicketCache property. When set, the Sync App uses the specified cache file to obtain the Kerberos ticket to connect to HDFS.

Keytab File

If the KRB5CCNAME environment variable has not been set, you can retrieve a Kerberos ticket using a Keytab File. To do so, set the User property to the desired username and set the KerberosKeytabFile property to a file path pointing to the keytab file associated with the user.

User and Password

If both the KRB5CCNAME environment variable and the KerberosKeytabFile property have not been set, you can retrieve a ticket using a user and password combination. To do this, set the User and Password properties to the user/password combination that you use to authenticate with HDFS.

Cross-Realm

More complex Kerberos environments may require cross-realm authentication where multiple realms and KDC servers are used (e.g., where one realm/KDC is used for user authentication and another realm/KDC is used for obtaining the service ticket).

In such an environment, set the KerberosRealm and KerberosKDC properties to the values required for user authentication. Also set the KerberosServiceRealm and KerberosServiceKDC properties to the values required to obtain the service ticket.

This section details a selection of advanced features of the HDFS Sync App.

User Defined Views

The Sync App allows you to define virtual tables, called user defined views, whose contents are decided by a pre-configured query. These views are useful when you cannot directly control queries being issued to the drivers. See User Defined Views for an overview of creating and configuring custom views.

SSL Configuration

Use SSL Configuration to adjust how Sync App handles TLS/SSL certificate negotiations. You can choose from various certificate formats; see the SSLServerCert property under "Connection String Options" for more information.

Firewall and Proxy

Configure the Sync App for compliance with Firewall and Proxy, including Windows proxies and HTTP proxies. You can also set up tunnel connections.

Query Processing

The Sync App offloads as much of the SELECT statement processing as possible to HDFS and then processes the rest of the query in memory (client-side).

See Query Processing for more information.

Logging

See Logging for an overview of configuration settings that can be used to refine CData logging. For basic logging, you only need to set two connection properties, but there are numerous features that support more refined logging, where you can select subsets of information to be logged using the LogModules connection property.

Customizing the SSL Configuration

By default, the Sync App attempts to negotiate SSL/TLS by checking the server's certificate against the system's trusted certificate store.

To specify another certificate, see the SSLServerCert property for the available formats to do so.

Connecting Through a Firewall or Proxy

HTTP Proxies

To connect through the Windows system proxy, you do not need to set any additional connection properties. To connect to other proxies, set ProxyAutoDetect to false.

In addition, to authenticate to an HTTP proxy, set ProxyAuthScheme, ProxyUser, and ProxyPassword, in addition to ProxyServer and ProxyPort.

Other Proxies

Set the following properties:

• To use a proxy-based firewall, set FirewallType, FirewallServer, and FirewallPort.
• To tunnel the connection, set FirewallType to TUNNEL.
• To authenticate, specify FirewallUser and FirewallPassword.
• To authenticate to a SOCKS proxy, additionally set FirewallType to SOCKS5.

The CData Sync App models HDFS objects as relational tables and views. HDFS objects have relationships to other objects; in the tables, these relationships are expressed through foreign keys. The following sections show the available API objects and provide more information on executing SQL to HDFS APIs.

Schemas for most database objects are defined in simple, text-based configuration files.

Key Features

• The Sync App models HDFS entities such as files and permissions as relational views, allowing you to write SQL to query HDFS data.
• Stored procedures allow you to execute operations to HDFS
• Live connectivity to these objects means any changes to your HDFS account are immediately reflected when using the Sync App.

The Sync App offloads as much of the SELECT statement processing as possible to the HDFS APIs and then processes the rest of the query in memory. See SupportEnhancedSQL for more information on how the Sync App circumvents API limitations with in-memory client-side processing.

Views are composed of columns and pseudo columns. Views are similar to tables in the way that data is represented; however, views do not support updates. Entities that are represented as views are typically read-only entities. Often, a stored procedure is available to update the data if such functionality is applicable to the data source.

Queries can be executed against a view as if it were a normal table, and the data that comes back is similar in that regard.

Dynamic views, such as queries exposed as views, and views for looking up specific combinations of project_team work items are supported.

HDFS Connector for CData Sync Views

Lists the contents of the supplied path.

Table Specific Information

Select

This will return a list of all the files and directories in your system. By default all subfolders are recursively scanned to list their children. You can configure the depth of subfolders you want to be recursively scanned with DirectoryRetrievalDepth property. All filters are executed client side within the Sync App.

Columns

Lists the permissions of the files/file specified in the path.

Table Specific Information

Select

This will return a list of permissions of all the files and directories in your system. All filters are executed client side within the Sync App.

Columns

The connection string properties are the various options that can be used to establish a connection. This section provides a complete list of the options you can configure in the connection string for this provider. Click the links for further details.

Authentication

Connection

Kerberos

SSL

Firewall

Proxy

Logging

Schema

Miscellaneous

This section provides a complete list of the Authentication properties you can configure in the connection string for this provider.

The scheme used for authentication. Accepted entries are None, and Negotiate (Kerberos). None is the default.

Remarks

This field is used to authenticate against the server. Use the following options to select your authentication scheme:

• None: Set this to use anonymous authentication and connect to the HDFS data source without specifying the user credentials.
• Negotiate: If AuthScheme is set to Negotiate, the Sync App will negotiate an authentication mechanism with the server. Set AuthScheme to Negotiate if you want to use Kerberos authentication.
• Token: Set this to authenticate using an AccessToken.

This property specifies the host of your HDFS installation.

Remarks

This property specifies the host of your HDFS installation.

This property specifies the port of your HDFS installation.

Remarks

This property specifies the port of your HDFS installation.

The user name to login to the HDFS server.

Remarks

The user name to login to the HDFS server. If AuthScheme=None, it is used as the authenticated user. If AuthScheme=Negotiate, it is used in the Kerberos Authentication as a client principal.

The password used to authenticate to the HDFS server. Only used when Kerberos authentication is selected.

Remarks

The password used to authenticate to the HDFS server. Only used when Kerberos authentication is selected.

The HDFS Access Token.

Remarks

The HDFS Access Token used to authenticate the requests.

This field sets whether SSL is enabled.

Remarks

This field sets whether the Sync App will attempt to negotiate TLS/SSL connections to the server. By default, the Sync App checks the server's certificate against the system's trusted certificate store. To specify another certificate, set SSLServerCert.

This section provides a complete list of the Connection properties you can configure in the connection string for this provider.

This property specifies the HDFS path which will be used as the working directory.

Remarks

This property specifies the HDFS path which will be used as the working directory. Used in views Files and Permissions.

Limit the subfolders recursively scanned.

Remarks

DirectoryRetrievalDepth specifies how many subfolders will be recursively scanned before stopping. -1 specifies that all subfolders are scanned. 0 specifies that only the current folder will be scanned for items.

This section provides a complete list of the Kerberos properties you can configure in the connection string for this provider.

The Kerberos Key Distribution Center (KDC) service used to authenticate the user.

Remarks

The Kerberos properties are used when using SPNEGO or Windows Authentication. The Sync App will request session tickets and temporary session keys from the Kerberos KDC service. The Kerberos KDC service is conventionally colocated with the domain controller.

If Kerberos KDC is not specified, the Sync App will attempt to detect these properties automatically from the following locations:

• KRB5 Config File (krb5.ini/krb5.conf): If the KRB5_CONFIG environment variable is set and the file exists, the Sync App will obtain the KDC from the specified file. Otherwise, it will attempt to read from the default MIT location based on the OS: C:\ProgramData\MIT\Kerberos5\krb5.ini (Windows) or /etc/krb5.conf (Linux).
• Domain Name and Host: If the Kerberos Realm and Kerberos KDC could not be inferred from another location, the Sync App will infer them from the configured domain name and host.

The Kerberos Realm used to authenticate the user.

Remarks

The Kerberos properties are used when using SPNEGO or Windows Authentication. The Kerberos Realm is used to authenticate the user with the Kerberos Key Distribution Service (KDC). The Kerberos Realm can be configured by an administrator to be any string, but conventionally it is based on the domain name.

If Kerberos Realm is not specified, the Sync App will attempt to detect these properties automatically from the following locations:

• KRB5 Config File (krb5.ini/krb5.conf): If the KRB5_CONFIG environment variable is set and the file exists, the Sync App will obtain the default realm from the specified file. Otherwise, it will attempt to read from the default MIT location based on the OS: C:\ProgramData\MIT\Kerberos5\krb5.ini (Windows) or /etc/krb5.conf (Linux)
• Domain Name and Host: If the Kerberos Realm and Kerberos KDC could not be inferred from another location, the Sync App will infer them from the user-configured domain name and host. This might work in some Windows environments.

The service principal name (SPN) for the Kerberos Domain Controller.

Remarks

If the SPN on the Kerberos Domain Controller is not the same as the URL that you are authenticating to, use this property to set the SPN.

The Keytab file containing your pairs of Kerberos principals and encrypted keys.

Remarks

The Keytab file containing your pairs of Kerberos principals and encrypted keys.

The Kerberos realm of the service.

Remarks

The KerberosServiceRealm is the specify the service Kerberos realm when using cross-realm Kerberos authentication.

In most cases, a single realm and KDC machine are used to perform the Kerberos authentication and this property is not required.

This property is available for complex setups where a different realm and KDC machine are used to obtain an authentication ticket (AS request) and a service ticket (TGS request).

The Kerberos KDC of the service.

Remarks

The KerberosServiceKDC is used to specify the service Kerberos KDC when using cross-realm Kerberos authentication.

In most cases, a single realm and KDC machine are used to perform the Kerberos authentication and this property is not required.

This property is available for complex setups where a different realm and KDC machine are used to obtain an authentication ticket (AS request) and a service ticket (TGS request).

The full file path to an MIT Kerberos credential cache file.

Remarks

This property can be set if you wish to use a credential cache file that was created using the MIT Kerberos Ticket Manager or kinit command.

This section provides a complete list of the SSL properties you can configure in the connection string for this provider.

The certificate to be accepted from the server when connecting using TLS/SSL.

Remarks

If using a TLS/SSL connection, this property can be used to specify the TLS/SSL certificate to be accepted from the server. Any other certificate that is not trusted by the machine is rejected.

This property can take the following forms:

If not specified, any certificate trusted by the machine is accepted.

Use '*' to signify to accept all certificates. Note that this is not recommended due to security concerns.

This section provides a complete list of the Firewall properties you can configure in the connection string for this provider.

The protocol used by a proxy-based firewall.

Remarks

This property specifies the protocol that the Sync App will use to tunnel traffic through the FirewallServer proxy. Note that by default, the Sync App connects to the system proxy; to disable this behavior and connect to one of the following proxy types, set ProxyAutoDetect to false.

To connect to HTTP proxies, use ProxyServer and ProxyPort. To authenticate to HTTP proxies, use ProxyAuthScheme, ProxyUser, and ProxyPassword.

The name or IP address of a proxy-based firewall.

Remarks

This property specifies the IP address, DNS name, or host name of a proxy allowing traversal of a firewall. The protocol is specified by FirewallType: Use FirewallServer with this property to connect through SOCKS or do tunneling. Use ProxyServer to connect to an HTTP proxy.

Note that the Sync App uses the system proxy by default. To use a different proxy, set ProxyAutoDetect to false.

The TCP port for a proxy-based firewall.

Remarks

This specifies the TCP port for a proxy allowing traversal of a firewall. Use FirewallServer to specify the name or IP address. Specify the protocol with FirewallType.

The user name to use to authenticate with a proxy-based firewall.

Remarks

The FirewallUser and FirewallPassword properties are used to authenticate against the proxy specified in FirewallServer and FirewallPort, following the authentication method specified in FirewallType.

A password used to authenticate to a proxy-based firewall.

Remarks

This property is passed to the proxy specified by FirewallServer and FirewallPort, following the authentication method specified by FirewallType.

This section provides a complete list of the Proxy properties you can configure in the connection string for this provider.

This indicates whether to use the system proxy settings or not. This takes precedence over other proxy settings, so you'll need to set ProxyAutoDetect to FALSE in order use custom proxy settings.

Remarks

This takes precedence over other proxy settings, so you'll need to set ProxyAutoDetect to FALSE in order use custom proxy settings.

To connect to an HTTP proxy, see ProxyServer. For other proxies, such as SOCKS or tunneling, see FirewallType.

The hostname or IP address of a proxy to route HTTP traffic through.

Remarks

The hostname or IP address of a proxy to route HTTP traffic through. The Sync App can use the HTTP, Windows (NTLM), or Kerberos authentication types to authenticate to an HTTP proxy.

If you need to connect through a SOCKS proxy or tunnel the connection, see FirewallType.

By default, the Sync App uses the system proxy. If you need to use another proxy, set ProxyAutoDetect to false.

The TCP port the ProxyServer proxy is running on.

Remarks

The port the HTTP proxy is running on that you want to redirect HTTP traffic through. Specify the HTTP proxy in ProxyServer. For other proxy types, see FirewallType.

The authentication type to use to authenticate to the ProxyServer proxy.

Remarks

This value specifies the authentication type to use to authenticate to the HTTP proxy specified by ProxyServer and ProxyPort.

Note that the Sync App will use the system proxy settings by default, without further configuration needed; if you want to connect to another proxy, you will need to set ProxyAutoDetect to false, in addition to ProxyServer and ProxyPort. To authenticate, set ProxyAuthScheme and set ProxyUser and ProxyPassword, if needed.

The authentication type can be one of the following:

• BASIC: The Sync App performs HTTP BASIC authentication.
• DIGEST: The Sync App performs HTTP DIGEST authentication.
• NEGOTIATE: The Sync App retrieves an NTLM or Kerberos token based on the applicable protocol for authentication.
• PROPRIETARY: The Sync App does not generate an NTLM or Kerberos token. You must supply this token in the Authorization header of the HTTP request.

If you need to use another authentication type, such as SOCKS 5 authentication, see FirewallType.

A user name to be used to authenticate to the ProxyServer proxy.

Remarks

The ProxyUser and ProxyPassword options are used to connect and authenticate against the HTTP proxy specified in ProxyServer.

You can select one of the available authentication types in ProxyAuthScheme. If you are using HTTP authentication, set this to the user name of a user recognized by the HTTP proxy. If you are using Windows or Kerberos authentication, set this property to a user name in one of the following formats:

user@domain
domain\user

A password to be used to authenticate to the ProxyServer proxy.

Remarks

This property is used to authenticate to an HTTP proxy server that supports NTLM (Windows), Kerberos, or HTTP authentication. To specify the HTTP proxy, you can set ProxyServer and ProxyPort. To specify the authentication type, set ProxyAuthScheme.

If you are using HTTP authentication, additionally set ProxyUser and ProxyPassword to HTTP proxy.

If you are using NTLM authentication, set ProxyUser and ProxyPassword to your Windows password. You may also need these to complete Kerberos authentication.

For SOCKS 5 authentication or tunneling, see FirewallType.

By default, the Sync App uses the system proxy. If you want to connect to another proxy, set ProxyAutoDetect to false.

The SSL type to use when connecting to the ProxyServer proxy.

Remarks

This property determines when to use SSL for the connection to an HTTP proxy specified by ProxyServer. This value can be AUTO, ALWAYS, NEVER, or TUNNEL. The applicable values are the following:

A semicolon separated list of destination hostnames or IPs that are exempt from connecting through the ProxyServer .

Remarks

The ProxyServer is used for all addresses, except for addresses defined in this property. Use semicolons to separate entries.

Note that the Sync App uses the system proxy settings by default, without further configuration needed; if you want to explicitly configure proxy exceptions for this connection, you need to set ProxyAutoDetect = false, and configure ProxyServer and ProxyPort. To authenticate, set ProxyAuthScheme and set ProxyUser and ProxyPassword, if needed.

This section provides a complete list of the Logging properties you can configure in the connection string for this provider.

Core modules to be included in the log file.

Remarks

Only the modules specified (separated by ';') will be included in the log file. By default all modules are included.

See the Logging page for an overview.

This section provides a complete list of the Schema properties you can configure in the connection string for this provider.

A path to the directory that contains the schema files defining tables, views, and stored procedures.

Remarks

The path to a directory which contains the schema files for the Sync App (.rsd files for tables and views, .rsb files for stored procedures). The folder location can be a relative path from the location of the executable. The Location property is only needed if you want to customize definitions (for example, change a column name, ignore a column, and so on) or extend the data model with new tables, views, or stored procedures.

If left unspecified, the default location is "%APPDATA%\\CData\\HDFS Data Provider\\Schema" with %APPDATA% being set to the user's configuration directory:

This property restricts the schemas reported to a subset of the available schemas. For example, BrowsableSchemas=SchemaA,SchemaB,SchemaC.

Remarks

Listing the schemas from databases can be expensive. Providing a list of schemas in the connection string improves the performance.

This property restricts the tables reported to a subset of the available tables. For example, Tables=TableA,TableB,TableC.

Remarks

Listing the tables from some databases can be expensive. Providing a list of tables in the connection string improves the performance of the Sync App.

This property can also be used as an alternative to automatically listing views if you already know which ones you want to work with and there would otherwise be too many to work with.

Specify the tables you want in a comma-separated list. Each table should be a valid SQL identifier with any special characters escaped using square brackets, double-quotes or backticks. For example, Tables=TableA,[TableB/WithSlash],WithCatalog.WithSchema.`TableC With Space`.

Note that when connecting to a data source with multiple schemas or catalogs, you will need to provide the fully qualified name of the table in this property, as in the last example here, to avoid ambiguity between tables that exist in multiple catalogs or schemas.

Restricts the views reported to a subset of the available tables. For example, Views=ViewA,ViewB,ViewC.

Remarks

Listing the views from some databases can be expensive. Providing a list of views in the connection string improves the performance of the Sync App.

This property can also be used as an alternative to automatically listing views if you already know which ones you want to work with and there would otherwise be too many to work with.

Specify the views you want in a comma-separated list. Each view should be a valid SQL identifier with any special characters escaped using square brackets, double-quotes or backticks. For example, Views=ViewA,[ViewB/WithSlash],WithCatalog.WithSchema.`ViewC With Space`.

Note that when connecting to a data source with multiple schemas or catalogs, you will need to provide the fully qualified name of the table in this property, as in the last example here, to avoid ambiguity between tables that exist in multiple catalogs or schemas.

This section provides a complete list of the Miscellaneous properties you can configure in the connection string for this provider.

Limits the number of rows returned rows when no aggregation or group by is used in the query. This helps avoid performance issues at design time.

Remarks

Limits the number of rows returned rows when no aggregation or group by is used in the query. This helps avoid performance issues at design time.

These hidden properties are used only in specific use cases.

Remarks

The properties listed below are available for specific use cases. Normal driver use cases and functionality should not require these properties.

Specify multiple properties in a semicolon-separated list.

Integration and Formatting

This property indicates whether or not to include pseudo columns as columns to the table.

Remarks

This setting is particularly helpful in Entity Framework, which does not allow you to set a value for a pseudo column unless it is a table column. The value of this connection setting is of the format "Table1=Column1, Table1=Column2, Table2=Column3". You can use the "*" character to include all tables and all columns; for example, "*=*".

The value in seconds until the timeout error is thrown, canceling the operation.

Remarks

If Timeout = 0, operations do not time out. The operations run until they complete successfully or until they encounter an error condition.

If Timeout expires and the operation is not yet complete, the Sync App throws an exception.

A filepath pointing to the JSON configuration file containing your custom views.

Remarks

User Defined Views are defined in a JSON-formatted configuration file called UserDefinedViews.json. The Sync App automatically detects the views specified in this file.

You can also have multiple view definitions and control them using the UserDefinedViews connection property. When you use this property, only the specified views are seen by the Sync App.

This User Defined View configuration file is formatted as follows:

• Each root element defines the name of a view.
• Each root element contains a child element, called query, which contains the custom SQL query for the view.

For example:

{
	"MyView": {
		"query": "SELECT * FROM Files WHERE MyColumn = 'value'"
	},
	"MyView2": {
		"query": "SELECT * FROM MyTable WHERE Id IN (1,2,3)"
	}
}

"UserDefinedViews", "C:\\Users\\yourusername\\Desktop\\tmp\\UserDefinedViews.json"