File Content Extraction 25.4
Filter SDK C++ Programming Guide

# Persist the Child Process

In out-of-process filtering, the parent process maintains a persistent connection with the child server after each file is filtered. While the connection is preserved in this way, subsequent filtering requests are processed more quickly because the server is already prepared to receive data.

You can restart the server at regular intervals by using a configuration setting.

## In the formats.ini File

To control whether Filter persists the server, use the `kvoopRefresh` parameter in the `[FilterSDK_Config]` section of the `formats.ini` file:

`kvoopRefresh=0` | When you set `kvoopRefresh` to `0` (zero), the connection to the server persists for as long as the parent process is running or until the server fails. This is the default when `kvoopRefresh` is not specified in `formats.ini`.
`kvoopRefresh=n` | When you set `kvoopRefresh` to `n` (where `n` is a positive number), the connection persists for `n` filter requests. After the `n`th request, the server is shut down and restarted before processing the next request. For example, if you set `kvoopRefresh` to `5`, the connection to the server persists for five filter requests. For the sixth request, the server is shut down and restarted.

When processing a file and an error or timeout occurs, the default out-of-process method does not attempt to process the file again because in most cases this only causes the same error or timeout. This behavior is not configurable. With the legacy out-of-process method, File Content Extraction attempts to process the file one more time, but you can configure the number of retry attempts by setting the `kvoopRetry` parameter in the `[FilterSDK_Config]` section of the `formats.ini` file.

`kvoopRetry=0` | The parent process does not resend the file to a new server.
`kvoopRetry=n` | The parent process resends the file to a new server `n` times (where `n` is a positive number, default `1`).

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Version 25.4 | Last updated October 2025

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Product: File Content Extraction 25.4

Topic Title: Persist the Child Process