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File Reader

File Reader

.This page is no longer maintained (Nov 12, 2025). For the most current information, go to https://docs.snaplogic.com/snaps/snaps-core/sp-binary/file-reader.html.

In this article

Overview

You can use this Snap to read data from various sources (such as SLDB, HTTP, S3, SFTP, HDFS, etc.) and produce a binary data stream at the output.

You must install the AzCopy utility, if you use the ABFS (Azure Blob File Storage) file protocol Azure Data Lake Gen 2 for bulk operation. The utility must be installed in Snaplex to fetch the file path. If the path is null, the native Azure Storage SDK is used for all operations. Learn more about the AzCopy command. If AzCopy Utility is not installed for ABS file transfer, the file transfer will not be as fast as using AzCopy because a REST call will be invoked for each file content instead of a bulk operation.

The SnapLogic Platform does not support the installation of utilities or processes on Cloudplexes. Learn more.

 

 

Snap Type

The File Reader Snap is a Read type Snap.

Prerequisites

Support for Ultra Pipelines 

Works in Ultra Pipelines. 

Limitations

  • For most file protocols, the Snap behaves the same in both Snaplex and Groundplex. However, the HDFS protocol works only in the Groundplex. The Hadoop cluster must be open to the Groundplex server instance without any authentication.

  • When reading a file over HTTP, the File Reader Snap displays an error if the number of bytes consumed does not match the Content-Length header value present in the response.

  • Do not use sldb as a file system or storage. File Assets are intended only for specialized files that a pipeline uses to reference specific data, such as accounts, expressions, or JAR files. Use a Cloud storage provider to store production data. File Assets should not be used as a file source or as a destination in production pipelines. When you configure the File Reader Snap, set the file path to a cloud provider or an external file system.

Known Issues

  • This Snap fails for SMB file path with the error: unable to create new native thread.

  • This Snap Pack does not natively support SHA1-based algorithms to connect to SFTP endpoints. With the August 2023 GA release, you can now leverage the properties specified in the Configuration settings for Snaps to add support for ones that are disabled on your Snaplex. 

  • If the Snap encounters a file with the same name as your Project Space, it can result in an error when you attempt to use that file's name within the Mapper Snap. For instance, if your Project Space is named "servicenow/to_snowflake" and the file being read is named "servicenow_to_snowflake_demo.json," you may encounter issues.
    Consider using the complete file path instead of just the file name as a workaround.

 

Snap Views

Type

Format

Number of Views

Examples of Upstream and Downstream Snaps

Description

Input 

Document

  • Min: 0

  • Max: 1

Upstream Snap is optional. Any Snap with a document output view can be connected upstream.

Input may contain value(s) to evaluate the JavaScript expression in the File property.

Output

Binary

 

  • Min: 1

  • Max: 1

  • File Writer

  • CSV Parser

  • JSON Parser

  • XML Parser

Binary data read from the source specified in the File property with header information about the binary stream. 

When reading a file, all the characters in the filename (except dot, hyphen, underscore, space, alphabet, and digit) are replaced with an underscore (_) in the content-disposition column of the output. If you want to get the exact file name in the output column, consider using content-location as the identifier instead of content-disposition.

An example of the output preview on the File property value of "http://www.facebook.com" is as follows:

[ { "": "Preview binary0...", "content-type": "text/html; charset=utf-8", "x-frame-options": "DENY", "connection": "keep-alive", "transfer-encoding": "chunked", "date": "Thu, 23 Oct 2014 00:24:40 GMT", "content-location": "https://www.facebook.com", "pragma": "no-cache", "p3p": "CP=\"Facebook does not have a P3P policy. Learn why here: http://fb.me/p3p\"", "cache-control": "private, no- cache, no-store, must-revalidate", "x-xss-protection": "0", "x-content-type-options": "nosniff", "x- fb-debug": "N6wiHWAvz9kzpPUoM5vTm+yZzCZyiSrHXFXumHQixfMd0Qi+VDm514PkrrmQu2ISuuMTTFtUTqDZgDVG4blPTw==", "expires": "Sat, 01 Jan 2000 00:00:00 GMT", "set-cookie": "reg_ext_ref=deleted; expires=Thu, 01-Jan- 1970 00:00:01 GMT; Max-Age=0; path=/; domain=.facebook.com" } ]

Error

Error handling is a generic way to handle errors without losing data or failing the Snap execution. You can handle the errors that the Snap might encounter when running the Pipeline by choosing one of the following options from the When errors occur list under the Views tab:

  • Stop Pipeline Execution: Stops the current pipeline execution when the Snap encounters an error.

  • Discard Error Data and Continue: Ignores the error, discards that record, and continues with the remaining records.

  • Route Error Data to Error View: Routes the error data to an error view without stopping the Snap execution.

Learn more about Error handling in Pipelines.

 

Snap Settings

Field

Field Type

Description

Label*

 

Default Value: File Reader
Example: File Reader

String

File*

 

Default Value: N/A
Example: 

 

String/Expression

Specify the URL for a regular file that must begin with a file protocol. The supported file protocols are:

  • http:

  • https:

  • s3:

  • ftp:

  • ftps:

  • sftp: 

  • hdfs:

  • sldb: 

  • smb:

  • file: (only for use with a Groundplex)

  • wasb:

  • wasbs:

  • gs:

  • adl:

You can also upload a file from using the Upload 

icon. You can preview the uploaded file using the preview
icon. Learn more about Previewing File.

 

Reading files from Project and Shared Project Spaces

  • If a Pipeline is created in a project other than the shared project and you want to read the "asset.json" file from the same project, enter "asset.json" or "sldb:///asset.json".

  • If a Pipeline is created in the shared project and you want to read the "asset.json" file from the shared project, enter "asset.json" or "sldb:///asset.json".

  • If a Pipeline is created in a project other than the shared project and you want to read the "asset.json" file from the shared project, enter "shared/asset.json" or "sldb:///shared/asset.json".

  • Ensure the file name, folder name, or the file path does not contain '?' character because it is not fully supported and when present, the Snap might fail.

File value as an Expression

The File value can be a JavaScript expression which is evaluated with values from the input view document and the pipeline parameters. The syntax for file value is: [protocol]://[host][:port]/[path]

  • $filename (The value of the $filename is obtained from the input document and the document should have an entry with the "filename" key.)

  • _filename (A key/value pair with "filename" key should be defined as a pipeline parameter.)

The File value should be an absolute path for all protocols except for SLDB. For files in SLDB, the Snap can read only files in the same Project Directory or the Shared Project Directory. It cannot access files from other Projects. Typically, the file names in the Reader Snaps are read from incoming document which might have a structure different from the relative path. For optimal results, we recommend that you build absolute paths to their projects and then add the file name.
Note: When you provide a file path that contains more than five entities (for example, entity1/entity2/entity3/entity4/file1.json) the Snap displays a Lint Warning in your Pipeline.

  • "://" is a separator between the file protocol and the rest of the URL and the host name and the port number should be between "://" and "/". The hostname and port number are omitted in the SLDB and s3 protocols. If the port number is omitted, a default port for the protocol is used.

  • The file:/// protocol is supported only on Groundplex. In Cloudplex configurations, use SLDB or other file protocols. When using the file:/// protocol, the file access is done using the permissions of the user assigned or associated with the Snaplex (by default Snapuser). File system access is to be used with caution, and it is the customer's own responsibility to ensure that file system is cleaned up after use. 

 

 

Prevent URL encoding

 

Default value: Deselected  

Checkbox

When enabled, this will prevent the Snap from automatically URL encoding the file path (including the query string if it exists). Enable this setting to use the file path value as-is.  

When disabled, the following are some of the common characters that are automatically encoded by the Snap: 

Character name 

Character  

URL Encoded value

backslash    

  \

 %5C

Pound

 #   

 %23

space       



 %20 

percent   

 %   

  %25 

Left-angle

<

%3C

Right-angle

>

%3E

Left-square

[

%5B

Right-square

]

%5D

Left-curly

{

%7B

Right-curly

}

%7D

And these are some of the characters that are not automatically encoded by the Snap:

Character name 

Character  

URL Encoded value

semi-colon    

 ;   

 %3B

question mark     

?

 %3F

forward slash      

/

 %2F

colon       

 : 

  %3A 

ampersand      

 &  

%26

equals   

 =  

%3D

plus        

+  

%2B

dollar   

 $    

 %24

comma  

   ,     

%2C

Enable staging

 

Default value: Deselected

Checkbox

If selected, the Snap downloads the source file into a local temporary file. When the download is completed, it streams the data from the temporary file to the output view. This property prevents the Snap from being blocked by slow downstream pipeline. The local disk should have sufficient free space as large as the expected file size. 

Some Snaps may take a long time to process large amounts of data. This, in turn, could lead to connection timeouts, causing the pipeline to fail. Selecting this property saves the data on your local disk, enabling you to avoid such timeouts.

Number of retries

 

Default Value: 0
Example: 3

Integer/Expression

Specify the maximum number of retry attempts that the Snap must make in case there is a network failure, and the Snap is unable to read the target file.

Minimum value: 0

 

Retry interval (seconds)

 

Default Value: 1
Example: 3

Integer/Expression

Specify the minimum number of seconds for which the Snap must wait before attempting recovery from a network failure.

Minimum value: 1

Additional output headers

Use this field set to define key-value pairs as additional headers in the binary output.

If the downstream Snap is HTTP Client Snap, these headers are used to evaluate expressions and perform the multipart file upload from various file protocols multiple times.

Key

String

Specify the key name for the additional output header.

Value

String/Expression

Specify the value for the additional output header.

Advanced properties

Use this field set to define specific settings for polling files. Click

to add a new row for defining an advanced property. This field set contains the following fields:

  • Properties

  • Values

Properties

Dropdown list

Values

 

Default Value: N/A

Example: https://myaccount.blob.core.windows.net/sascontainer/sasblob.txt?sv=2015-04-05&st=2015-04-
29T22%3A18%3A26Z&se=2015-04-30T02%3A23%3A26Z&sr=b&sp=rw&sip=168.1.5.60
-168.1.5.70&spr=https&sig=Z%2FRHIX5Xcg0Mq2rqI3OlWTjEg2tYkboXr1P9ZUXDtkk%3D

String/Expression

Specify the value for the SAS URI.

Ensure that the URI is specified in the format described here. 

If the SAS URI value is provided in the Snap settings, then the settings provided in the account (if any account is attached) are ignored.

Snap Execution


Default Value: Execute only
Example: Validate & Execute

Dropdown list

Select one of the following three modes in which the Snap executes:

  • Validate & Execute: Performs limited execution of the Snap, and generates a data preview during Pipeline validation. Subsequently, performs full execution of the Snap (unlimited records) during Pipeline runtime.

  • Execute only: Performs full execution of the Snap during Pipeline execution without generating preview data.

  • Disabled: Disables the Snap and all Snaps that are downstream from it.

Preview File

To preview a file, in the File field, click the Preview 

 icon. 

The Preview Type contains the following options:

  • Hex: Displays the preview data in hexadecimal format.

  • Text: Displays the preview data in text format.

  • Render text with whitespace: Renders whitespaces as dots "." and tabs as underscores "_" in the preview data.

 

Examples

HDFS

For hdfs:// file access, please use a SnapLogic on-premises Groundplex and make sure that its instance is within the Hadoop cluster and SSH authentication has already been established. You can access HDFS files in the same way as other file protocols in File Reader and File Writer Snaps. There is no need to use any account in the Snap.

HDFS 2.4.0 is supported for the hdfs protocol.

hdfs://<hostname>:<port number>/<path to folder>/<filename>

An example for HDFS is: 

hdfs://<hostname>:<port number>/<path to folder>/<filename>


If Cloudera Hadoop Namenode is installed in AWS EC2 and its hostname is "ec2-54-198-212-134.compute-1.amazonaws.com" and its port number is 8020, then you would enter:

hdfs://ec2-54-198-212-134.compute-1.amazonaws.com:8020/user/john/input/sample.csv

SFTP File Read

Example pipeline for an SFTP file read as shown below:

 

  • The 'IAM_CREDENTIAL_FOR_S3' feature is to access S3 files from EC2 Groundplex without  Access-key  ID and Secret key in the AWS S3 account in the Snap. The IAM credential stored in the EC2 metadata is used to gain the access rights to the S3 buckets. To enable this feature, the following line should be added to global properties and restart the JCC:

     jcc.jvm_options = -DIAM_CREDENTIAL_FOR_S3=TRUE

  • This feature is supported in the EC2-type Groundplex only.

Sample for AWS S3 Support

Troubleshooting

Error

Reason

Resolution

Response code: 400, unable to import the file <file name>

Request from elastic.snaplogic.com returned an error.

The name of the file that is being read by the Snap cannot be the same as the Project Space name.

Provide the complete path of the file (instead of only the file name) in this format: “/orgname/projectspace/project/filename”

For example: /snaplogic/shared/analytics/ga4.json

Response code: 400, unable to import expression library: <file_ProjectSpace>

Request from elastic.snaplogic.com returned an error.


Path names at root level are not allowed.

Provide the complete path of the file (instead of only the file name) in this format: “/orgname/projectspace/project/filename”

For example: /snaplogic/shared/analytics/ga4.json

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