server-side client-side configuration

# 13.6. File Dispatcher Event Handler

## 13.6.1. Introduction

The file dispatcher is a generic event handler which is used to perform various actions on the files on which SFTPPlus operates.

As any event handler you can define all the available filtering rules for defining the scope on which the handler should be triggered.

It can be used for both server-side and client-side operations.

A common server-side use case is to move the file outside of a single inbox used by a remote account to push the files, and forward the files to a different internal team which needs a copy of the pushed file.

For the client-side, a common use case is to move or copy the pulled files to various local folders, once the file was copied from the remote server.

In this way there is a separation of concerns among various components which take part in a managed file transfer process.

One component will make sure the files are received and handled using various file transfer protocols like SFTP or FTPS. Once the files are received via the protocols, a separate component can be configured to further process the files, outside of the realm of FTPS or HTTPS file transfer protocols.

## 13.6.2. Operation Principle

The file-dispatcher event handler, when configured to be triggered for an event will use the path attribute associated with the event and perform an action on that path.

Not all events can be used with this event handler. Only events which have have an associated path on the local filesystem can be used.

For example, the events from the group file-operation can be used together with the file-dispatcher event handler, since those events have an event attribute pointing to path on the local filesystem.

Using the dispatch_attribute configuration you can define which attribute of the event to use for triggering the actions.

When used for server-side operations, the file transfer actions have both a real and virtual path. A remote file transfer client authenticated as username `johnd`, will upload a file using a path like `/inbox/REPORT_123.PDF`, this is the virtual path. On the server, that file is actually stored as `/storage/users/john/inbox/REPORT_123.PDF`, this is the real path. The dispatch_attribute should be configured with the real path of the file to be handled. Using a virtual path will cause the file not to be dispatched appropriately as it will use the virtual (non-existent) path as the source.

The file dispatching will fail if the event does not have the configured attribute.

Note

Please make sure that you are not attaching this event handler to file events for which the path was not yet closed. In such scenarios the move operation will fail.

When the event handler starts, it will try to validate the current configuration. The event handler will fail to start when the configuration is invalid.

Some configuration options can only be validated at execution time, at the moment when a certain action is triggered for an event. In such cases the event handling will fail and the failure count will be increased. Such a condition can be found when configuring the dispatch handler for an event ID which has no associated paths.

## 13.6.3. Matching expressions

The dispatch_rules will have a matching expression defined as the second member of the configuration.

This is used to decide the paths for which the action is triggered.

The matching expression is checked against the full path of the file.

As an example, if you want to match files based on the naming convention INV_NNNN.csv (like INV_0023.csv or INV_1202.csv), located in any directory, use a configuration similar to:

    [event-handlers/a0cf-d14500774340]
    dispatch_rules = move, */INV_*.csv, /srv/teams/invoicing

When you want to match only files inside a certain folder, make sure to include that folder as part of the matching expression. For example, a file named `REPORT_123.csv` will be moved to `/srv/teams/invoicing` when placed into the source folder `/invoicing` and moved to `/srv/teams/ops` when placed into the source folder `/operations`:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, /invoicing/REPORT_*.csv, /srv/teams/invoicing
        move, /operations/REPORT_*.csv, /srv/teams/ops

Note

The fallback_rule has no configuration for the matching expression since this is used for files which are not matching any of the configured expressions.

For more details about the available expressions see the matching expression documentation.

## 13.6.4. Regular Expressions and Grouping

When regular expressions are defined for the path matching expression, you can use the parentheses for grouping parts of the source path which, once matched, can be used to dynamically define the destination path based on the source path.

Note

The exclusion regular expression mode (`e/some/.*.pdf`) is not supported for group substitution.

Note

The group substitution is not available for the fallback rule as there is no matching expression for that configuration.

For the purpose of this section, it is assumed that you are already familiar with the regular expression. Here you can read more about the regular expressions.

For example, to have a file which is pushed to a path `/inbox/accounting/john/SRV_123.PDF` and moved to the path `/reports/john/teams/accounting/SRV_123.PDF` use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, m/inbox/(.+)/(.+)/SRV_.+\.PDF/, /reports/{2}/teams/{1}/

The first pair of parentheses will match the source team name and the second pair will match the source username. You can then used the matched valued as {1} or {2} etc to generate the destination path.

The first group to be matched is {1}.

The group matching can be used the dynamically generate the destination directory or the generate the full destination path.

When groups are used in the configured destination and the configuration does not end with a path separator, it will use the configuration to generate the full path for the destination. Otherwise, it will dynamically generate only the destination directory and use the source filename to generate the full path.

For example, to have a file which is pushed to a path `/users/john/SRV_123.PDF` and moved to the path `/staging/john-SRV_123.PDF.in` use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, m/users/(.+)/(SRV_.+\.PDF)/, /staging/{1}-{2}.in

To let SFTPPlus generate the destination path and for example have the file pushed as `/user/john/SRV_123.PDF` moved to the path `/staging/john/SRV_123.PDF`, use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, m/users/(.+)/SRV_.+\.PDF/, /staging/{1}/

## 13.6.5. Destination path variables

The destination path can be defined to include values from a set of dynamic variables based on each event.

Assume you have 2 accounts named `john-d` and `jane-r` with home directories in `C:\SFTP-In\john-d` and `C:\SFTP-In\jane-r` respectively.

When `john-d` or `jane-r` uploads a file named `/reports.xml` inside their root folder, the actual file is received on disk as `C:\SFTP-In\john-d\app\report.xml` or `C:\SFTP-In\jane-r\app\report.xml`.

You might need to move both reports into a common internal application inbox directory with file names like `C:\App-In\john-d_report.xml` or `C:\App-In\jane-r_report.xml`.

This can be done using the following configuration, in which only the files placed inside the app sub-directories are moved:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, g/C:\SFTP-In\*\app\*/, C:\App-In\{account.name}-{data.file_name}

You can also define the following configuration, in which any file uploaded by a user is moved:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, g/.*/, C:\App-In\{account.name}-{data.file_name}

or defined using regular expression syntax with matching groups enabled:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, m/(.*)/i, C:\App-In\{account.name}-{data.file_name}

Note

The usage of explicit g/EXPRESSION/ globbing matching syntax or regular expression with groups is required for destination path variables.

This is required for backward compatibility with older configurations in which the destination configuration was defining only the base destination directory.

## 13.6.6. Destination path normalization

The destination paths are normalized and any forward slash or backward slash is automatically converted to the path delimiter used by the operating system hosting the STPPlus application.

For example if you have the following configuration on a Linux system, the destination path is `/staging/john/SRV_123.PDF`:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, m/users/(.+)/SRV_.+\.PDF/, \staging\{1}\

While with the following example on Windows the destination path is `C:\staging\john/SRV_123.PDF`:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, m/C:\\users\\(.+)/SRV_.+\.PDF/, c:/staging/{1}/

## 13.6.7. Advanced Regular Expressions

Using the matching_expressions configuration, you can create a destination path using multiple data sources, not only the path of the handled file.

At the same time, you can transform the values to uppercase or lowercase.

As an example, suppose we handle ZIP archives copied to /inbox/AcmeCo-reports.zip containing files /sales.csv and /returns.csv. The system is configured to automatically extract the files to the /storage/received/ path. Upon normal operation, this would result in /received/sales.csv and /storage/received/returns.pdf.

However, if you want to have these files extracted as /received/sales-AcmeCo.csv and /received/returns-AcmeCo.pdf, you can use the following configuration::

    matching_expressions:
        source_path, m//inbox/(\d{6})-.+.zip/i

    dispatch_rules:
        rename, m/.+/(.+\)\.([a-z])/i, /received/{1}-{source_path.1}.{2}

Using character case transform operations, you could have the files extracted as /received/sales-ACMECO.csv and /received/returns-ACMECO.pdf with the following configuration:

    matching_expressions:
        source_path, m//inbox/(\d{6})-.+.zip/i

    dispatch_rules:
        rename, m/.+/(.+\)\.([a-z])/i, /received/{1}-{source_path.1_upper}.{2}

## 13.6.8. Triggering the Dispatch Rule

For the dispatch_rules configuration option you can specify multiple rules, one per line.

Multiple rules are checked in the order of their definition.

The dispatch will stop after the first rule which matches the current file path.

When none of the configured path matching expression could match the path associated with the handled event, the fallback rule is used.

When no fallback rule is defined and none of the configured expression matches the path no action is taken by the event handler.

## 13.6.9. Events with multiple paths

Some events emitted by SFTPPlus have associated multiple paths.

You can still use the file dispatcher together with those events.

The actions are executed for each of the associated files.

The event handling operation is aborted when failing to perform the configured action for one of the associated files. In this case the remaining files are not actioned.

## 13.6.10. File Overwrite Prevention

The file dispatcher will not overwrite existing file and the whole dispatch process will fail if one of the configured destinations already contains a file with the same name.

## 13.6.11. Handling of temporary / transient files

It is common to have an external client or process pushing a file using a temporary name and rename to the final name once the transfer is complete.

In this case, you can use the dispatch_delay option to configure the file dispatcher to execute the dispatching with a delay. This will allow the file to be created with a final name.

## 13.6.12. Retry on errors

The file dispatcher can be configured to retry the operation on error.

It can wait a configurable number of seconds before retrying.

## 13.6.13. Automatically creating destination folders

The default behaviour of the file dispatcher event handler is to fail when the destination does not exist.

The create_destination_folder configuration option can be used to automatically create the destination.

To create the parent for the destination folder, set the event handler as the following example. To prevent accidental configurations, the event handler will still fail if the path to the parent folder does not exist:

    [event-handlers/f040be6a-e158]
    create_destination_folder = parent

## 13.6.14. Copy Action

The copy action will create copies of the source file in each of the configured destinations.

If for any reason the file fails to be successfully copied to any of the destination, the process of copying to the remaining destination is aborted.

For example, to have a file named RPT_123.xml copied to both `/data/teams/invoicing/RPT_123.xml` and `/data/teams/ops/RPT_123.xml`, use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        copy, */rpt_*.xml, /srv/teams/invoicing, /srv/teams/ops

## 13.6.15. Move Action

The move action will create copies of the the source file in each of the configured destinations.

Once the file is copied to all the destinations, it will delete the source file. This is the reason why it is named move.

If for any reason the file fails to be successfully copied to any of the destination, the source file is not removed.

For example, to have a file named RPT_123.xml copied to both `/data/teams/invoicing/RPT_123.xml` and `/data/teams/ops/RPT_123.xml` and then removed from the source, use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move, */rpt_*.xml, /srv/teams/invoicing, /srv/teams/ops

## 13.6.16. Move With Timestamp Action

The move-with-timestamp is similar to the move action but files are created in the destination with a timestamp inserted at the end of the filename but before the file extension.

When the file has no extension, the timestamp is suffixed.

This action is useful to dispatch files and mitigate the risk of overwriting existing files.

The timestamp has a sub-seconds resolution. The resolution is depended on the host operating system.

Besides the sub-second resolution, the timestamp includes a random number so that even when you have multiple files generated in the same sub-second, they will still have different timestamps.

For example, to have a file named RPT_123.xml copied to both `/data/teams/invoicing/RPT_123.2013-02-24-16-50-43-983422-042.xml` and `/data/teams/ops/RPT_123.2013-02-24-16-50-43-983422-042.xml` and then removed from the source, use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        move-with-timestamp, */rpt_*.xml, /srv/teams/invoicing, /srv/teams/ops

## 13.6.17. Rename Action

The rename action does a rename of source path to destination path.

The rename is done on the full path. You can use it to move a file from one path to another.

It is called renamed, since it can only be used with a single destination. This is done in order to differentiate it from our other move actions, which are performed on multiple destinations.

As long as the source and destination are on the same filesystem, the operation will be atomic and instant.

The operation will fail if the destination already exists.

For example, to have a file named `RPT_123.xml` pushed to `/inbox/reports` folder, renamed to `/data/teams/ops/RPT_123.xml`, use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        rename, /inbox/reports/rpt_*.xml, /srv/teams/ops

## 13.6.18. Rename with Unix Timestamp Prefix Action

The rename-prepend-unixtime action does a rename of source path to destination path.

The renaming is done with prepending the Unix timestamp (with milliseconds) to the source filename.

For example, to have a file named `RPT_123.xml` pushed to `/inbox/reports` folder, renamed to `/data/teams/ops/0031550404.009876-RPT_123.xml`, use the following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        rename-prepend-unixtime, /inbox/reports/rpt_*.xml, /srv/teams/ops

## 13.6.19. Delete Action

The delete action will delete the source path. It does not require any configured destinations.

## 13.6.20. Ignore Operation Action

The ignore action will not perform any action on the path. It does not require any configured destinations.

This action can be used to implement exceptions from a more generic rule that might be configured in the same event handler.

For example, to have any XML file moved to another directory, with the exception of XML files starting with test- you can use something similar to following configuration:

    [event-handlers/f040be6a-e158]
    dispatch_rules =
        ignore, /import/test-*.xml
        move, /inbox/*.xml, /srv/db-app/import

## 13.6.21. Execute Action

The execute action allows you to call an external executable or script and pass a set of arguments that most often will include the source file path.

This action is useful to reuse the file name matching selection present in the dispatch files and integrate it with custom external actions.

It is configured as a comma separated list of values, to make it easy to handle spaces in the executable source path or the targeted file.

The first value is the path to the executable or script that is invoked for the configured file pattern.

The remaining values are arguments used when calling the executable. Remember to add commas between arguments.

For example, we move a local file to an S3 bucket using the AWS CLI. It assumes that you are running SFTPPlus in an EC2 for which the S3 bucket role was enabled at the instance level:

    [event-handlers/f040be6a-e158]
    target = 40017
    executable_timeout: 60
    dispatch_rules =
        execute, *.csv, /bin/aws, s3, move, {data.real_path}, https://test-bucket/{data.file_name}, --acl=private

It expects the execute command to finalize after executable_timeout seconds and to exit with code 0.

Any other exit code is considered an error and it will retry to process the file based on the configured retry rules.

The following environment variables are set when calling the external executable:

- SOURCE_PATH - path to the file that is dispatched

- ARGUMENTS - space separated list of configured arguments for the dispatcher

13.5. Auditing the encryption used for FTPS, SFTP, SCP and HTTPS connections
13.7. Deploying file transfers with Docker containers