On Tue, 14 Nov 2023 15:21:47 GMT, Severin Gehwolf <sgehw...@openjdk.org> wrote:
>> Please review this patch which adds a "jmodless" jlink mode to the JDK. >> Fundamentally this patch adds an option to use `jlink` even though your JDK >> install might not come with the packaged modules (directory `jmods`). This >> is particularly useful to further reduce the size of a jlinked runtime. >> After the removal of the concept of a JRE, a common distribution mechanism >> is still the full JDK with all modules and packaged modules. However, >> packaged modules can incur an additional size tax. For example in a >> container scenario it could be useful to have a base JDK container including >> all modules, but without also delivering the packaged modules. This comes at >> a size advantage of `~25%`. Such a base JDK container could then be used to >> `jlink` application specific runtimes, further reducing the size of the >> application runtime image (App + JDK runtime; as a single image *or* >> separate bundles, depending on the app being modularized). >> >> The basic design of this approach is to add a jlink plugin for tracking >> non-class and non-resource files of a JDK install. I.e. files which aren't >> present in the jimage (`lib/modules`). This enables producing a >> `JmodLessArchive` class which has all the info of what constitutes the final >> jlinked runtime. >> >> Basic usage example: >> >> $ diff -u <(./bin/java --list-modules --limit-modules java.se) >> <(../linux-x86_64-server-release/images/jdk/bin/java --list-modules >> --limit-modules java.se) >> $ diff -u <(./bin/java --list-modules --limit-modules java.se) >> <(../linux-x86_64-server-release/images/jdk/bin/java --list-modules >> --limit-modules jdk.jlink) >> $ ls ../linux-x86_64-server-release/images/jdk/jmods >> java.base.jmod java.net.http.jmod java.sql.rowset.jmod >> jdk.crypto.ec.jmod jdk.internal.opt.jmod >> jdk.jdi.jmod jdk.management.agent.jmod jdk.security.auth.jmod >> java.compiler.jmod java.prefs.jmod java.transaction.xa.jmod >> jdk.dynalink.jmod jdk.internal.vm.ci.jmod >> jdk.jdwp.agent.jmod jdk.management.jfr.jmod jdk.security.jgss.jmod >> java.datatransfer.jmod java.rmi.jmod java.xml.crypto.jmod >> jdk.editpad.jmod jdk.internal.vm.compiler.jmod >> jdk.jfr.jmod jdk.management.jmod jdk.unsupported.desktop.jmod >> java.desktop.jmod java.scripting.jmod java.xml.jmod >> jdk.hotspot.agent.jmod jdk.internal.vm.compiler.management.jmod >> jdk.jlink.jmod jdk.naming.dns.j... > > Severin Gehwolf has updated the pull request incrementally with four > additional commits since the last revision: > > - First pass at 'run-image' => 'run-time image' > - Remove 'Please double check!' phrase. > - Don't show --add-run-image-resources plugin in listing > - Rename resource file to jdk_internal_runimage Thanks. > How can the user know what plugins are applied to `image2`? i.e. what is the > jlink command to produce `image2` if running from `jdk22` with the packaged > modules present? The only way to know is by knowing the chain of `jlink` commands yielding up to the final image. Let `jlink'` be the jlink using packaged modules. Currently this can be at most two. In addition, the contents of `argfile` needs to be known. That doesn't seem to be very different to the status quo, though. See below. > Reading the changes, I'm not sure but I think it's not equivalent to: > > ``` > jdk22/bin/jlink --add-modules jdk.jlink --output image2 --vendor-bug.url > https://xyz.com/bugs --save-jlink-argfiles argfile --generate-jli-classes > jli_trace.txt --strip-debug --add-options "-Dcom.foo.XYZ=true" --add-options > "-Dcom.acme.name=BAR" > ``` Note that plugins like `--add-options` have been modified so that only the options passed at the current CLI will propagate to the final image. So in this case, `image1` would have property `com.foo.XYZ` set, but not `image2`. Incidentally, what you probably intended to use was `--add-options "-Dcom.foo.XYZ=true -Dcom.acme.name=BAR". Having said that, depending on the contents of `argfile`, those could be equivalent. In fact, they are with `--unlock-run-image`, and an empty `argfile`. `--unlock-run-image` avoids adding the marker file, which is the only difference when we extract the image. `--save-jlink-argfiles` brings a strange angle to this discussion, but it's conceivable to get a similarly different image, even with --keep-packaged-modules. Consider: echo '--add-options=-XX:+UseParallelGC' > argfile ./jdk22/bin/jlink --save-jlink-argfiles argfile --strip-debug --add-modules jdk.jlink --keep-packaged-modules ./image_a/jmods --output image_a ./image_a/bin/jlink --add-modules java.base --output image_b It's not very apparent that `image_b` will have `-XX:+UseParallelGC`. So you need some sort of track record what you've used previously already in order to know how `image_b` got produced (short of `--save-opts`)? > I think this behavior should be documented. Makes a lot of sense. Where? In the CSR? > > Note that plugins like `--add-options` have been modified so that only the > > options passed at the current CLI will propagate to the final image. So in > > this case, `image1` would have property `com.foo.XYZ` set, but not > > `image2`. Incidentally, what you probably intended to use was > > `--add-options "-Dcom.foo.XYZ=true -Dcom.acme.name=BAR". > > Having said that, depending on the contents of `argfile`, those could be > > equivalent. In fact, they are with `--unlock-run-image`, and an empty > > `argfile`. `--unlock-run-image` avoids adding the marker file, which is the > > only difference when we extract the image. > > `--save-jlink-argfiles` brings a strange angle to this discussion, but it's > > conceivable to get a similarly different image, even with > > --keep-packaged-modules. > > Right. This example intends to show that the behavior is not straight-forward > for users to follow and also subject to the implementation of each of the > plugins. I think we need an easy-to-understand model for developers to > understand. Some possible options: > > Option 1: all plugins applied in `image1` are _auto-applied_ to `image2` by > default Option 1 seems most appealing. I can massage `--add-options` to concatenate. The exception of the rule seems `--system-modules` for obvious reasons. > Option 2: all plugins applied in `image1` are _not applied_ to `image2` by > default > > When there is an exception, it should be documented clearly by the plugin > (possibly in the output from `--list-plugins`). I also think option 1 may be > more useful to the developers. I'm not sure how many plugins can undo the > transformation done in `image1` when creating `image2`. > > For example, with option 1, > > ``` > $ jdk22/bin/jlink --add-modules jdk.compiler,jdk.jlink --output image1 > --vendor-bug.url https://xyz.com/bugs --save-jlink-argfiles argfile > --generate-jli-classes jli_trace.txt --strip-debug --add-options > "-Dcom.foo.XYZ=true" > > $ image1/bin/jlink --add-modules jdk.jlink --output image2 --add-options > "-Dcom.acme.name=BAR" > # equivalent to: > $ jdk22/bin/jlink --add-modules jdk.jlink --output image2 --vendor-bug.url > https://xyz.com/bugs --save-jlink-argfiles argfile --generate-jli-classes > jli_trace.txt --strip-debug --add-options "-Dcom.foo.XYZ=true > -Dcom.acme.name=BAR" > > $ image1/bin/jlink --add-modules java.base --output image3 --vendor-bug.url > https://com.acme/bugs > # equivalent to: > $ jdk22/bin/jlink --add-modules java.base --output image3 > --generate-jli-classes jli_trace.txt --strip-debug --add-options > "-Dcom.foo.XYZ=true" --vendor-bug.url https://com.acme/bugs > ``` > > Discussion points are: > > * `--save-jlink-argfiles` is only applicable when `jdk.jlink` is added to > the custom module. I think this one is not an issue. For the runtime image link that's a requirement: `jdk.jlink` part of the image that is being used to create the image to perform the runtime image link. But I agree that this use-case seems rather expert. > * `--add-options` concatenates the options? Sure, that can be done. > * `-vendor-bug.url https://xyz.com/bugs --vendor-bug.url > https://com.acme/bugs` last one wins? Yes. That's also how it works if the build got configured with specific vendor and then a jlink is being performed using packaged modules. > We need to go through each plugin and decide on its behavior. OK. I'll add documentation to the `--list-plugins` help should there be deviations. > I'm also pondering how the Plugin API should support this run-time image > based linking. It could, but doesn't need to IMO. OTOH, `transform()` could grow an argument to indicate packaged-modules vs runtime image link. ------------- PR Comment: https://git.openjdk.org/jdk/pull/14787#issuecomment-1815011717
