Property type

Either Built-In or Repository.

Built-In: No property data stored centrally.

Repository: Select the repository file where the
properties are stored.

Use an existing connection

Select this check box and in the Component List click the relevant connection component to
reuse the connection details you already defined.

Note that when a Job contains the parent Job and the child Job,
Component List presents only the
connection components in the same Job level.

Use replica set address or multiple query routers

Select this check box to show the Server
addresses table.

In the Server addresses table, define the sharded
MongoDB databases or the MongoDB replica sets you want to connect
to.

Server and Port

IP address and listening port of the database server.

Available when the Use replica set
address check box is not selected.

Note that if you use the authentication mechanisms to connect to this MongoDB
database, you must enter the name, rather than the IP address, of the host of the database
server.

Database

Name of the database.

Use SSL connection

Select this check box to enable the SSL or TLS encrypted connection.

Then you need to use the tSetKeystore
component in the same Job to specify the encryption information.

Note that the SSL connection is available only for the version 2.4 + of
MongoDB.

Set read preference

Select this check box and from the Read preference
drop-down list that is displayed, select the member to which you need to direct the read
operations.

If you leave this check box clear, the Job uses the default Read preference, that is to
say, uses the primary member in a replica set.

For further information, see MongoDB’s documentation about Replication and its Read
preferences.

Required authentication

Select this check box to enable the database authentication.

Among the mechanisms listed on the Authentication mechanism
drop-down list, the NEGOTIATE one is recommended if
you are not using Kerberos, because it automatically select the authentication mechanism
the most adapted to the MongoDB version you are using.

For details about the other mechanisms in this list, see MongoDB Authentication from the MongoDB
documentation.

Set Authentication database

If the username to be used to connect to MongoDB has been created in a specific
Authentication database of MongoDB, select this check box to enter the name of this
Authentication database in the Authentication database
field that is displayed.

For further information about the MongoDB Authentication database, see User Authentication database.

Username and Password

DB user authentication data.

To enter the password, click the […] button next to the
password field, and then in the pop-up dialog box enter the password between double quotes
and click OK to save the settings.

Available when the Required
authentication check box is selected.

If the security system you have selected from the Authentication mechanism drop-down list is Kerberos, you need to
enter the User principal, the Realm and the KDC
server fields instead of the Username and the Password
fields.

Bucket

Enter the name of the bucket you need to read files from. A bucket of
GridFS is similar to a folder.

Query type

Select the type of the query you want tMongoDBGridFSGet to perform to select the data to be
copied.

• Filename: you need to enter
  the name of the file to be copied. This name is the value of the
  filename attribute used by
  this file. Note that only one name is allowed.

  In GridFS, a file is identified only by its unique identifier
  (its object ID); its file name is not necessarily unique.

• Mongo Query: enter the query
  to be used to select the files to be copied.

  The default query, {} within double quotation marks provided with this
  component, means to select all of the files. You can also apply a regular expression by
  putting {'filename':{'$regex':'REGEX_PATTERN'}} to define the file names to be
  used.

It is recommended to use your query along with the Overwrite local files and the Use Document ID as output filename check boxes to
avoid any file name conflict issue.

Local Folder

Enter the path to the folder in which the data copied from GridFS is to be
written.

Overwrite local files

Select this check box to overwrite the file using the same file name
in the local folder being used. Otherwise, an exception will be returned
in this type of situation.

Use Document ID as output
filename

Select this box to rename the incoming files on the fly using the
values of their object IDs. This allows you keep the files that have the
same file names.

tStatCatcher Statistics

Select this check box to collect the log data at the component
level.

No query timeout

Select this check box to prevent MongoDB servers from stopping idle
cursors at the end of 10-minute inactivity of these cursors. In this
situation, an idle cursor will stay open until either the results of
this cursor are exhausted or you manually close it using the
cursor.close() method.

A cursor for MongoDB is a pointer to the result set of a query. By
default, that is to say, with this check box being clear, a MongoDB
server automatically stops idle cursors after a given inactivity period
to avoid excess memory use. For further information about MongoDB
cursors, see https://docs.mongodb.org/manual/core/cursors/.

Global Variables

NB_FILE: the number of files processed. This is an After
variable and it returns an integer.

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
Space to access the variable list and choose the variable to use from it.

For further information about variables, see
Talend Studio

User Guide.

Usage rule

This component combines MongoDB GridFS connection and data extraction, thus usually
used as a single-component subJob to copy data from GridFS to a
user-defined local directory.

It is often connected to the Job using OnSubjobOk or OnComponentOk link, depending on the context.