Fix reloading of the configuration from HTTP(S)

[ppkarwasz]

The HttpWatcher didn't propagate the observed last modification time back to the configuration.
As a result, each new Configuration had the same last modification date as the first one and the reconfiguration process looped.

Closes #2937

[ppkarwasz]

In general I took the liberty of bumping some status logger messages to INFO.
IMHO the INFO level should be used for important events like:

• The start and stop of configurations,
• The start and stop of logger contexts,
• Whenever Watcher#isModified returns true, which triggers a reconfiguration.

The overall effect should be the following:

2024-09-10T17:57:04.161594820Z main INFO Starting configuration XmlConfiguration[location=http://localhost:8000/log4j2-file.xml, lastModified=2024-09-10T13:34:24Z]...
2024-09-10T17:57:04.161688451Z main INFO Start watching for changes to http://localhost:8000/log4j2-file.xml every 5 seconds
2024-09-10T17:57:04.162631305Z main INFO Configuration XmlConfiguration[location=http://localhost:8000/log4j2-file.xml, lastModified=2024-09-10T13:34:24Z] started.
2024-09-10T17:57:04.162821558Z main INFO Stopping configuration org.apache.logging.log4j.core.config.DefaultConfiguration@23d2a7e8...
2024-09-10T17:57:04.163001700Z main INFO Configuration org.apache.logging.log4j.core.config.DefaultConfiguration@23d2a7e8 stopped.
2024-09-10T17:57:49.186202317Z Log4j2-TF-2-Scheduled-1 INFO HTTP resource at http://localhost:8000/log4j2-file.xml was modified on 2024-09-10T17:57:44Z
2024-09-10T17:57:49.186810805Z Log4j2-TF-2-Scheduled-1 INFO Configuration source at http://localhost:8000/log4j2-file.xml was modified on 2024-09-10T17:57:44Z, previous modification was on 2024-09-10T13:34:24Z
2024-09-10T17:57:49.191685641Z Log4j2-TF-1-ConfigurationFileWatcher-2 INFO Starting configuration XmlConfiguration[location=http://localhost:8000/log4j2-file.xml, lastModified=2024-09-10T17:57:44Z]...
2024-09-10T17:57:49.191751282Z Log4j2-TF-1-ConfigurationFileWatcher-2 INFO Start watching for changes to http://localhost:8000/log4j2-file.xml every 5 seconds
2024-09-10T17:57:49.191891764Z Log4j2-TF-1-ConfigurationFileWatcher-2 INFO Configuration XmlConfiguration[location=http://localhost:8000/log4j2-file.xml, lastModified=2024-09-10T17:57:44Z] started.
2024-09-10T17:57:49.191969215Z Log4j2-TF-1-ConfigurationFileWatcher-2 INFO Stopping configuration XmlConfiguration[location=http://localhost:8000/log4j2-file.xml, lastModified=2024-09-10T13:34:24Z]...
2024-09-10T17:57:49.192266340Z Log4j2-TF-1-ConfigurationFileWatcher-2 INFO Configuration XmlConfiguration[location=http://localhost:8000/log4j2-file.xml, lastModified=2024-09-10T13:34:24Z] stopped.

[ppkarwasz]

Accidentally I had to rewrite HttpThreadContextMapTest. I believe it exploited the fact that its JSON configuration was reloaded every monitor interval. I'll double check that.

Since HttpThreadContextMapTest used Jetty, I rewrote also UrlConfigurationFactoryTest and removed Jetty from the dependencies of log4j-core-test (fixes #2813).

[ppkarwasz]

@vy, could you take a look at this?

[ppkarwasz]

Regarding the Source and ConfigurationSource change I added nullability annotations to both.

ConfigurationSource is basically a triple (Source, byte[] and a long timestamp). The source and data fields can be null, but not at the same time. All the ConfigurationSource#getUri() and similar methods are delegated to Source#getUri(), unless the source field is null.

If we look at the Source class, the uri and location fields can not be null, since each constructor throws something if this happens. The only constructor that does not throw if uri or location are null is the one that takes ConfigurationSource as parameter. I would propose to deprecate that constructor in the next minor release, since it introduces an artificial cyclical dependency between Source and ConfigurationSource.

I have modified the 2 call sites that use the Source(ConfigurationSource) constructor to use more appropriate ones.

[github-actions]

Job	Requested goals	Build Tool Version	Build Outcome	Build Scan®
build-ubuntu-latest	clean install	3.9.8	✅

Generated by gradle/develocity-actions

[ppkarwasz]

While merging #2963, which was based on this PR, I accidentally merged part of these modifications.

It is fixed now, but a force-push was necessary, sorry.

[vy]

Can you double-check that I didn't modify the behavior of ConfigurationSource?

New canonical ctor and its usage LGTM, thanks!

I've dropped some more remarks.