Latest revision as of 23:26, 28 September 2023

Allow Removal of tzdata

Summary

Allow the removal of tzdata especially on containers in order to minimize size.

Owner

Name: Patsy Griffin (Franklin)
Email: patsy@redhat.com

Current status

Targeted release: Fedora Linux 39
Last updated: 2023-09-28
devel thread
FESCo issue: #3031
Tracker bug: #2233281
Release notes tracker: #1010

Detailed Description

This change will allow the removal of tzdata. When tzdata is removed, the system will default to UTC. In order to reduce overhead, many container installations now remove the data associated with tzdata but cannot fuly remove the package due to dependencies by other packages. This results in confusion regarding the expected timezone info.

In order for this to work, we need packages that use tzdata at run time to switch from Require'ing tzdata to Recommend'ing tzdata. These packages should also gracefully handle instances where tzdata has been removed. For example, this would require recognizing that tzdata is not present and providing an appropriate error, such as recommending that the user install tzdata.

Feedback

In June of 2021, we proposed creating a new tzdata sub-package that would only provide the UTC timezone. As part of the discussion around this proposal, it was recommended that we completely remove tzdata. We appreciated this input and welcome additional feedback.

Benefit to Fedora

This change will allow tzdata to be removed from containers without leaving inconsistent package remnants.

Scope

Proposal owners: No changes are needed to tzdata.

Other developers: Some packages need to change their spec files from Requires: tzdata to Recommends: tzdata. It would be beneficial if all packages switched in this way, but it is not required. Supporting optional tzdata installation for as many workloads as possible allows those workloads to minimize their container image size.

List of packages which need to be changed:

glibc (glibc-common)
gcc (libstdc++)

List of packages which would be beneficial to be changed:

python3.XX (3.9, 3.10, 3.11, 3.12)
python3-dateutil
python3-pytz
libical

Upon acceptance of the change request we will file bugs to fix each of these packages for Fedora 39.

Release engineering: No changes needed.

Policies and guidelines: N/A (not needed for this Change)

Trademark approval: N/A (not needed for this Change)

Alignment with Community Initiatives:

Upgrade/compatibility impact

If tzdata is already installed, then it continues to be installed on the system.

Following the Fedora Weak Dependencies Policy dnf will treat the Recommends on tzdata as if it were a Requires and tzdata will always be installed in a default system (https://docs.fedoraproject.org/en-US/packaging-guidelines/WeakDependencies/)

However, the recommends will allow tzdata to be correctly uninstalled in a container build file rather than having to use ‘rm -rf’ to delete the zone files to recover space.

How To Test

Language runtimes were installed and A/B tests carried out with tzdata present and tzdata removed. The intent of these tests was to ensure that the system can use the language frameworks without tzdata present and that when the data was required that meaningful errors were presented to the user.

Packages tested were C (glibc), C++ (libstdc++), Python (Python 3.11), using their time and date APIs. This testing led to the correction of the libstdc++ implementation as noted here: https://gcc.gnu.org/cgit/gcc/commit/?id=4abd5bc600193e821fbc41995a0b8d9ea42b42c3

Developers can test this by installing Rawhide and uninstalling tzdata and verifying their package operates as expected.

If tzdata cannot be uninstalled then we recommend filling a bug against the package that Requires: tzdata and having a discussion with the maintainer to make tzdata optional e.g. Recommends: tzdata.

User Experience

The user can remove tzdata to minimize the container size.

With tzdata removed the system is UTC only.

Dependencies

Fixing glibc, gcc, and python3.xx at a minimum to make tzdata Recommends instead of Requires.

Contingency Plan

Contingency mechanism: Back out the change. Don’t do it.
Contingency deadline: Can be backed out at the last minute since we are only dealing with conversions from Requires to Recommends.
Blocks release? No

Documentation

Document that the tzdata package may be removed if needed to reduce space on containers. With tzdata removed, the system will default to UTC.

Release Notes

@@ Line 1: / Line 1: @@
-{{admon/important | Comments and Explanations | The page source contains comments providing guidance to fill out each section. They are invisible when viewing this page. To read it, choose the "view source" link.<br/> '''Copy the source to a ''new page'' before making changes!  DO NOT EDIT THIS TEMPLATE FOR YOUR CHANGE PROPOSAL.'''}}
-{{admon/tip | Guidance | For details on how to fill out this form, see the [https://docs.fedoraproject.org/en-US/program_management/changes_guide/ documentation].}}
-{{admon/tip | Report issues | To report an issue with this template, file an issue in the [https://pagure.io/fedora-pgm/pgm_docs pgm_docs repo].}}
 <!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
@@ Line 9: / Line 4: @@
 = Allow Removal of tzdata <!-- The name of your change proposal --> =
-{{Change_Proposal_Banner}}
 == Summary ==
@@ Line 28: / Line 22: @@
 == Current status ==
-[[Category:ChangePageIncomplete]]
+[[Category:ChangeAcceptedF39]]
 <!-- When your change proposal page is completed and ready for review and announcement -->
 <!-- remove Category:ChangePageIncomplete and change it to Category:ChangeReadyForWrangler -->
@@ Line 45: / Line 39: @@
 ON_QA -> change is fully code complete
 -->
-* [<will be assigned by the Wrangler> devel thread]
+* [https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/CRUWIEHISRLYQ5ZLPFSAFJPRTDQQLBO2/ devel thread]
-* FESCo issue: <will be assigned by the Wrangler>
+* FESCo issue: [https://pagure.io/fesco/issue/3031 #3031]
-* Tracker bug: <will be assigned by the Wrangler>
+* Tracker bug: [https://bugzilla.redhat.com/show_bug.cgi?id=2233281 #2233281]
-* Release notes tracker: <will be assigned by the Wrangler>
+* Release notes tracker: [https://pagure.io/fedora-docs/release-notes/issue/1010 #1010]
 == Detailed Description ==
 This change will allow the removal of tzdata.  When tzdata is removed, the system will default to UTC. In order to reduce overhead, many container installations now remove the data associated with tzdata but cannot fuly remove the package due to dependencies by other packages.  This results in confusion regarding the expected timezone info.
-In order for this to work, we need packages that use tzdata at run time to switch from Require'ing tzdata to Recommend'ing tzdata.  These packages should also gracefully handle instances where tzdata has been resolved.  For example, this would require recognizing that tzdata is not present and providing an appropriate error, such as recommending that the user install tzdata.
+In order for this to work, we need packages that use tzdata at run time to switch from Require'ing tzdata to Recommend'ing tzdata.  These packages should also gracefully handle instances where tzdata has been removed.  For example, this would require recognizing that tzdata is not present and providing an appropriate error, such as recommending that the user install tzdata.
 == Feedback ==
@@ Line 93: / Line 87: @@
 <!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
-* Other developers: Some packages need to change their spec files from Requires: tzdata to Recommend: tzdata.  They will also need to provide appropriate errors/responses when tzdata is not available at run time.
+* Other developers: Some packages need to change their spec files from `Requires: tzdata` to `Recommends: tzdata`. It would be beneficial if all packages switched in this way, but it is not required. Supporting optional tzdata installation for as many workloads as possible allows those workloads to minimize their container image size.
+List of packages which need to be changed:
+* glibc (glibc-common)
+* gcc (libstdc++)
+List of packages which would be beneficial to be changed:
+* python3.XX (3.9, 3.10, 3.11, 3.12)
+* python3-dateutil
+* python3-pytz
+* libical
+Upon acceptance of the change request we will file bugs to fix each of these packages for Fedora 39.
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- What work do other developers have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
 * Release engineering: No changes needed.
-[https://pagure.io/releng/issues #Releng issue number] <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+ <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- Does this feature require coordination with release engineering (e.g. changes to installer image generation or update package delivery)?  Is a mass rebuild required?  include a link to the releng issue.
 The issue is required to be filed prior to feature submission, to ensure that someone is on board to do any process development work and testing and that all changes make it into the pipeline; a bullet point in a change is not sufficient communication -->
@@ Line 112: / Line 116: @@
 == Upgrade/compatibility impact ==
+If tzdata is already installed, then it continues to be installed on the system.
+Following the Fedora Weak Dependencies Policy dnf will treat the Recommends on tzdata as if it were a Requires and tzdata will always be installed in a default system (https://docs.fedoraproject.org/en-US/packaging-guidelines/WeakDependencies/)
+However, the recommends will allow tzdata to be correctly uninstalled in a container build file rather than having to use ‘rm -rf’ to delete the zone files to recover space.
 <!-- What happens to systems that have had a previous versions of Fedora installed and are updated to the version containing this change? Will anything require manual configuration or data migration? Will any existing functionality be no longer supported? -->
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+== How To Test ==
+Language runtimes were installed and A/B tests carried out with tzdata present and tzdata removed. The intent of these tests was to ensure that the system can use the language frameworks without tzdata present and that when the data was required that meaningful errors were presented to the user.
+Packages tested were C (glibc), C++ (libstdc++), Python (Python 3.11), using their time and date APIs. This testing led to the correction of the libstdc++ implementation as noted here:
+https://gcc.gnu.org/cgit/gcc/commit/?id=4abd5bc600193e821fbc41995a0b8d9ea42b42c3
+Developers can test this by installing Rawhide and uninstalling tzdata and verifying their package operates as expected.
+If tzdata cannot be uninstalled then we recommend filling a bug against the package that Requires: tzdata and having a discussion with the maintainer to make tzdata optional e.g. Recommends: tzdata.
-== How To Test ==
 <!-- This does not need to be a full-fledged document. Describe the dimensions of tests that this change implementation is expected to pass when it is done.  If it needs to be tested with different hardware or software configurations, indicate them.  The more specific you can be, the better the community testing can be.
@@ Line 134: / Line 153: @@
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+== User Experience ==
+The user can remove tzdata to minimize the container size.
+With tzdata removed the system is UTC only.
-== User Experience ==
 <!-- If this change proposal is noticeable by users, how will their experiences change as a result?
@@ Line 148: / Line 171: @@
 == Dependencies ==
+Fixing glibc, gcc, and python3.xx at a minimum to make tzdata Recommends instead of Requires.
 <!-- What other packages (RPMs) depend on this package?  Are there changes outside the developers' control on which completion of this change depends?  In other words, completion of another change owned by someone else and might cause you to not be able to finish on time or that you would need to coordinate?  Other upstream projects like the kernel (if this is not a kernel change)? -->
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 == Contingency Plan ==
 <!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
-* Contingency mechanism: (What to do?  Who will do it?) N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Contingency mechanism: Back out the change. Don’t do it.
+  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->
-* Contingency deadline: N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Contingency deadline:  Can be backed out at the last minute since we are only dealing with conversions from Requires to Recommends.   <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- Does finishing this feature block the release, or can we ship with the feature in incomplete state? -->
-* Blocks release? N/A (not a System Wide Change), Yes/No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Blocks release? No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 == Documentation ==
@@ Line 167: / Line 191: @@
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
+Document that the tzdata package may be removed if needed to reduce space on containers.  With tzdata removed, the system will default to UTC.
 == Release Notes ==

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