saltstack / saltstack/salt

[BUG] file.append can be extremely slow with just tens of lines

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bug severity-low
Dominant language
Python
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Avg merge
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Merged PRs (30d)
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Description

Description
The below simple setup has 50% chance to take 10+ seconds when applying several times. The time increases exponentially with the number of lines in the file.

Setup

# test.sls
/tmp/test.txt:
    file.append:
        - source: salt://test.txt
# test.txt
{%-  for ip in range(25) -%}
a
{%  endfor -%}
{{ 2 | random_hash }}

Steps to Reproduce the behavior
for i in {1..10}; do salt-call --log-level=debug state.apply test; done

Expected behavior
The command should be finished within tens of ms.

Versions Report

v2019.2.3. Saw similar on v2018.3.2 as well before upgrading to v2019.2.3.

salt --versions-report (Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)
Salt Version:
           Salt: 2019.2.3

Dependency Versions:
           cffi: 1.14.0
       cherrypy: Not Installed
       dateutil: 2.4.2
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.8
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: 0.21.1
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.6.2
   mysql-python: Not Installed
      pycparser: 2.20
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.12 (default, Oct  8 2019, 14:14:10)
   python-gnupg: Not Installed
         PyYAML: 3.11
          PyZMQ: 15.2.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.1.4

System Versions:
           dist: Ubuntu 16.04 xenial
         locale: UTF-8
        machine: x86_64
        release: 4.15.0-96-generic
         system: Linux
        version: Ubuntu 16.04 xenial

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the test.sls and test.txt reproducer, then run the provided salt-call loop with debug logging on Salt 2019.2.3 or a comparable environment. Trace the file.append execution and templated source handling to identify the scaling delay; done means repeated applies complete within tens of milliseconds for the sample input without changing its result.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
infrastructure, performance
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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