[
https://issues.apache.org/jira/browse/FLINK-23022?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17368252#comment-17368252
]
Arvid Heise edited comment on FLINK-23022 at 6/23/21, 2:52 PM:
---------------------------------------------------------------
Imho is the ticket correct and we should fix documentation or even the
{{PluginClassLoader}}.
{noformat}
"A (semicolon-separated) list of patterns that specifies which classes should
always be"
+ " resolved through the plugin parent ClassLoader first. A pattern is
a simple prefix that is checked "
+ " against the fully qualified class name. This setting should
generally not be modified. To add another "
+ " pattern we recommend to use
\"plugin.classloader.parent-first-patterns.additional\" instead."{noformat}
This is more or less c&p from user classloader. However, in
{{PluginClassLoader}}, it's actually different: it gives a list of classes that
can be accessed from inside the plugins when resolution within the plugin class
loader failed. It's a poor man's solution for a proper SPI system and has some
flaws.
Ideally, we would have some {{@SPI}} annotation on all white-listed classes.
The plugin system would collect them on start and then the
{{PluginClassLoader#loadClass}} should work like this
{noformat}
if (className in spiClasses) {
resolve from flinkClassLoader
} else {
resolve from pluginClassLoader
}{noformat}
This would avoid having flink classes being shaded into the plugin from being
used and avoid access to anything internal.
At some point I was thinking if we should just assume
{{@SPI=@Public+@PublicEvolving+@Experimental}}. WDYT? [~chesnay]
was (Author: arvid):
Imho is the ticket correct and we should fix documentation or even the
{{PluginClassLoader}}.
{noformat}
"A (semicolon-separated) list of patterns that specifies which classes should
always be"
+ " resolved through the plugin parent ClassLoader first. A pattern is
a simple prefix that is checked "
+ " against the fully qualified class name. This setting should
generally not be modified. To add another "
+ " pattern we recommend to use
\"plugin.classloader.parent-first-patterns.additional\" instead."{noformat}
This is more or less c&p from user classloader. However, in
{{PluginClassLoader}}, it's actually different: it gives a list of classes that
can be accessed from inside the plugins. It's a poor man's solution for a
proper SPI system.
Ideally, we would have some {{@SPI}} annotation on all white-listed classes.
The plugin system would collect them on start and then the
{{PluginClassLoader#loadClass}} should work like this
{noformat}
if (className in spiClasses) {
resolve from flinkClassLoader
} else {
resolve from pluginClassLoader
}{noformat}
This would avoid having flink classes being shaded into the plugin from being
used and avoid access to anything internal.
At some point I was thinking if we should just assume
{{@SPI=@Public+@PublicEvolving+@Experimental}}. WDYT? [~chesnay]
> Plugin classloader settings do not work as described
> ----------------------------------------------------
>
> Key: FLINK-23022
> URL: https://issues.apache.org/jira/browse/FLINK-23022
> Project: Flink
> Issue Type: Bug
> Components: API / Core
> Reporter: Dawid Wysakowicz
> Priority: Major
>
> The options {{plugin.classloader.parent-first-patterns}} are documented as
> all patterns that are put there should be loaded from the Flink classloader
> instead of the plugin classloader.
> However, the way they work is that they define a set of patterns allowed to
> be pulled from the parent classloader. The plugin classloader takes
> precedence in all cases. And a class can be loaded from the parent
> classloader only if it matches the pattern in one of the aforementioned
> options.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
