tMongoDBGridFSList Standard properties

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 drop-down list, select the desired 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.

Use 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 in which the files to be listed are stored. A bucket of GridFS is similar to a folder.

Query

Enter the query to be used to select the files to be listed. You need to define how these files are sorted in the list by selecting:

• Sort by: these files can be sorted by their filename attributes, uploadDate attributes or length (the File Size option) attributes.

• Sort order: these files can be sorted in the Ascending or Descending order.

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.

CURRENT_FILEID: the value of the ObjectId (the file ID) attribute of the current file. This is an Flow variable and it returns a string.

CURRENT_FILENAME: the value of the filename attribute of the current file. This is an Flow variable and it returns a string.

CURRENT_FILEUPLOADDATE: the value of the uploadDate attribute of the current file. This is an Flow variable and it returns a date.

CURRENT_FILELENGTH: the value of the length (the size) attribute of the current file. This is an Flow variable and it returns a length.

CURRENT_FILEMD5: the value of the md5 attribute of the current file. This is an Flow variable and it returns a string.

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 iteration, thus usually used as a single-component subJob to list files stored in a given bucket in MongoDB GridFS.

Different lists are returned, each representing an attribute of these files and being stored in a specific global variable as explained above regarding the global variables provided by tMongoDBGridFSList.

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