Bug :: Multisite :: Sub-Directory Install :: Cache Clearing

[jaswrks]

Overview

Clearing the cache from the main site when there are child blogs in sub-directories, results in all child blogs being cleared from the cache, not just the main site as would be expected. In short, this results in what is essentially a full wipe of the cache, when in fact I just want to clear the cache for the main site.

Steps to Reproduce

• Setup MS network w/ sub-directories.
• Create sites example.com/child1 and example.com/child2
• Enable user-specific caching for easier testing.
• Hit the front page of the main site and let it cache you; i.e., example.com/
• Hit the front page of each of the child sites as well; i.e., example.com/child1 and example.com/child2
• Clear the cache from the dashboard of the main site.

Expected Behavior

That only the cache for the main site would be cleared.

Observed Behavior

All child blog sub-directories are cleared as well. It's a full wipe when it should just clear the main site. This happens due to the fact that child blogs are stored in sub-directories; i.e., they are not associated with their own host.

[jaswrks]

Noting that the HTML Compressor cache is immune to this. It only impacts ZenCache itself. Files cached by the HTML Compressor are stored in nested directories that work around this issue.

[jaswrks]

This also has the potential to cause performance issues whenever the cached is cleared from the main site in a sub-directory network. ALL of the child blogs are being scanned, instead of just the main site.

[raamdev]

@jaswsinc Thanks for the detailed bug report! My feeling is that the priority for this bug can slip to the following release; I see this as confusing and potentially harmful (for performance reasons), but nothing catastrophic.

If you've already started working on this and you feel it's a relatively easy fix, I certainly wouldn't mind getting it into the next release, but if not I wanted to share my thoughts on priority. :-)

[jaswrks]

Changes to Branched Cache Structure

Legend: [URL] = [cache path]

---

• Old way: http://wp-multisite.com/child1/ = http/wp-multisite-com/child1.html
• New way: http://wp-multisite.com/child1/ = http/wp-multisite-com-child1/child1/index.html

---

If the installation is in a sub-directory:

• Old way: http://wp-multisite.com/base/child1/ = http/wp-multisite-com/base/child1.html
• New way: http://wp-multisite.com/base/child1/ = http/wp-multisite-com-base-child1/base/child1/index.html

---

Summary

If there is a multisite base directory and/or child sub-directory, that collective path becomes a suffix of the host fragment used in cache path generation. This way each child blog has a host-based root--which makes clearing the cache much more logical and it improves performance considerably in a MS network that runs from a sub-directory base and/or uses a sub-directory structure for child blogs.

In addition, each multisite base directory and/or child sub-directory gets it's own /index in order to resolve the issues documented in: #536 & #409

[jaswrks]

Another example of the new behavior:

<!-- ZenCache HTML Compressor took 0.05899 seconds (overall). -->
<!-- ZenCache file path: /cache/zencache/cache/http/wordpress-vm-child1/child1/index.u/1.html -->
<!-- ZenCache file built for (http://wordpress.vm/child1/; user token: 1) in 0.38910 seconds, on: Aug 5th, 2015 @ 10:05 pm UTC. -->
<!-- This ZenCache file will auto-expire (and be rebuilt) on: Aug 12th, 2015 @ 10:05 pm UTC (based on your configured expiration time). -->

[jaswrks]

From the main site:

<!-- ZenCache HTML Compressor took 1.61151 seconds (overall). -->
<!-- ZenCache file path: /cache/zencache/cache/http/wordpress-vm/index.u/1.html -->
<!-- ZenCache file built for (http://wordpress.vm/; user token: 1) in 1.98672 seconds, on: Aug 5th, 2015 @ 10:05 pm UTC. -->
<!-- This ZenCache file will auto-expire (and be rebuilt) on: Aug 12th, 2015 @ 10:05 pm UTC (based on your configured expiration time). -->

[raamdev]

Next Pro Release Changelog:

• Multisite Bug Fix: Fixed a bug where clearing the cache from the main site of a multisite network, when there are child blogs in sub-directories, resulted in all child blogs being cleared from the cache, not just the main site as would be expected. This has been resolved and only the main site is cleared when clicking the Clear Cache button. Note that the Wipe Cache button can still be used to clear the cache for all sites in a Multisite Network. Props @jaswsinc. See Issue #540.

[raamdev]

ZenCache Pro v150821 has been released and includes changes from this GitHub Issue.

See the ZenCache Pro v150821 announcement for further details.

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This issue will now be locked to further updates. If you have something to add related to this GitHub Issue, please open a new GitHub Issue and reference this one (#540).