Process limits

Some tools run external programs such as LibreOffice, Tesseract or Ghostscript. For each program you can set:

Session limit: how many copies run at once. Extra jobs wait in a queue.
Timeout: how many minutes one run may take before it is stopped and returns an error.

Change them under Settings → Server → Advanced → Process Executor Limits, or under processExecutor in settings.yml. A value of 0 or less uses the default. Restart Stirling PDF after editing the file.

Session limits#

Setting	Default	Used for
`libreOfficeSessionLimit`	`1`	Office documents to and from PDF
`tesseractSessionLimit`	`1`	OCR with Tesseract
`ocrMyPdfSessionLimit`	`2`	OCR with OCRmyPDF
`pdfToHtmlSessionLimit`	`1`	PDF to HTML and Markdown
`ghostscriptSessionLimit`	`8`	Compression, repair and other Ghostscript tools
`qpdfSessionLimit`	`4` in `settings.yml`, `2` if unset	PDF/A conversion, repair and compression
`imageMagickSessionLimit`	`4`	Line-art conversion in Compress
`pythonOpenCvSessionLimit`	`8`	Image processing, such as scan extraction
`weasyPrintSessionLimit`	`16`	HTML to PDF
`calibreSessionLimit`	`1`	E-book conversion
`installAppSessionLimit`	`1`	Internal install tasks

Raise limits on a large server with many users. Lower them on a small one: each copy uses its own memory and CPU, and LibreOffice is especially memory-hungry. For more LibreOffice capacity, see LibreOffice parallel processing.

Timeouts#

All timeouts are in minutes and default to 30, except pdfToHtmltimeoutMinutes (20) and installApptimeoutMinutes (60). The keys in settings.yml are:

libreOfficetimeoutMinutes, pdfToHtmltimeoutMinutes, pythonOpenCvtimeoutMinutes, weasyPrinttimeoutMinutes, installApptimeoutMinutes, calibretimeoutMinutes, imageMagickTimeoutMinutes, tesseractTimeoutMinutes, qpdfTimeoutMinutes, ghostscriptTimeoutMinutes and ocrMyPdfTimeoutMinutes.

Frequent timeouts usually mean the server is short of CPU or memory.

Example#

A small, low-memory server:

yaml

processExecutor:
  sessionLimit:
    libreOfficeSessionLimit: 1
    tesseractSessionLimit: 1
    ghostscriptSessionLimit: 2
    imageMagickSessionLimit: 2
    pythonOpenCvSessionLimit: 2
    weasyPrintSessionLimit: 4
    qpdfSessionLimit: 1
    ocrMyPdfSessionLimit: 1
  timeoutMinutes:
    libreOfficetimeoutMinutes: 10
    tesseractTimeoutMinutes: 15

bash

PROCESSEXECUTOR_SESSIONLIMIT_LIBREOFFICESESSIONLIMIT=1
PROCESSEXECUTOR_SESSIONLIMIT_TESSERACTSESSIONLIMIT=1
PROCESSEXECUTOR_SESSIONLIMIT_GHOSTSCRIPTSESSIONLIMIT=2
PROCESSEXECUTOR_SESSIONLIMIT_IMAGEMAGICKSESSIONLIMIT=2
PROCESSEXECUTOR_SESSIONLIMIT_PYTHONOPENCVSESSIONLIMIT=2
PROCESSEXECUTOR_SESSIONLIMIT_WEASYPRINTSESSIONLIMIT=4
PROCESSEXECUTOR_SESSIONLIMIT_QPDFSESSIONLIMIT=1
PROCESSEXECUTOR_SESSIONLIMIT_OCRMYPDFSESSIONLIMIT=1
PROCESSEXECUTOR_TIMEOUTMINUTES_LIBREOFFICETIMEOUTMINUTES=10
PROCESSEXECUTOR_TIMEOUTMINUTES_TESSERACTTIMEOUTMINUTES=15

yaml

services:
  stirling-pdf:
    environment:
      PROCESSEXECUTOR_SESSIONLIMIT_LIBREOFFICESESSIONLIMIT: 1
      PROCESSEXECUTOR_SESSIONLIMIT_TESSERACTSESSIONLIMIT: 1
      PROCESSEXECUTOR_SESSIONLIMIT_GHOSTSCRIPTSESSIONLIMIT: 2
      PROCESSEXECUTOR_SESSIONLIMIT_IMAGEMAGICKSESSIONLIMIT: 2
      PROCESSEXECUTOR_SESSIONLIMIT_PYTHONOPENCVSESSIONLIMIT: 2
      PROCESSEXECUTOR_SESSIONLIMIT_WEASYPRINTSESSIONLIMIT: 4
      PROCESSEXECUTOR_SESSIONLIMIT_QPDFSESSIONLIMIT: 1
      PROCESSEXECUTOR_SESSIONLIMIT_OCRMYPDFSESSIONLIMIT: 1
      PROCESSEXECUTOR_TIMEOUTMINUTES_LIBREOFFICETIMEOUTMINUTES: 10
      PROCESSEXECUTOR_TIMEOUTMINUTES_TESSERACTTIMEOUTMINUTES: 15

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