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* Email: msimacek@redhat.com | * Email: msimacek@redhat.com | ||
* Email: mizdebsk@redhat.com | * Email: mizdebsk@redhat.com | ||
* Release notes owner: <!--- To be assigned by docs team [[User:FASAccountName| Release notes owner name]] <email address> --> | * Release notes owner: <!--- To be assigned by docs team [[User:FASAccountName| Release notes owner name]] <email address> -->[mailto:sclark@fedoraproject.org Simon Clark] ([[User:sclark|sclark]]) | ||
<!--- UNCOMMENT only for Changes with assigned Shepherd (by FESCo) | <!--- UNCOMMENT only for Changes with assigned Shepherd (by FESCo) | ||
* FESCo shepherd: [[User:FASAccountName| Shehperd name]] <email address> | * FESCo shepherd: [[User:FASAccountName| Shehperd name]] <email address> | ||
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CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development | CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development | ||
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* Tracker bug: | * Tracker bug: [https://bugzilla.redhat.com/show_bug.cgi?id=1474878 #1474878] | ||
== Detailed Description == | == Detailed Description == | ||
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* if the current environment contains JAVA_HOME variable (typically it doesn't), JVM executable is looked up there | * if the current environment contains JAVA_HOME variable (typically it doesn't), JVM executable is looked up there | ||
* if the configuration specifies JAVA_HOME (by default it doesn't), JVM is looked up there | * if the configuration specifies JAVA_HOME (by default it doesn't), JVM is looked up there | ||
* otherwise JVM executable is looked up on PATH, using `which java`. With default PATH setting on Fedora, this will be /usr/bin/java, which is a symlink managed by alternatives | * it tries to find JVM in java/jre subdirs of JVM_ROOT (by default /usr/lib/jvm). Those subdirs are managed by "jre"/"java_sdk" alternatives. This is the code path that is triggered by default. The /usr/lib/jvm alternative symlink is a slave of "java" configuration, so changing "java" alternatives will set it to different value or unset it, if the alternative provider doesn't specify the slave configuration. | ||
* otherwise JVM executable is looked up on PATH, using `which java`. With default PATH setting on Fedora, this will be /usr/bin/java, which is a symlink managed by "java" alternatives setting | |||
=== Disadvantages of the current behavior === | === Disadvantages of the current behavior === | ||
Let's say a user wants to change his java command to a different provider, | Let's say a user wants to change his java command to a different provider, | ||
because he needs to run an application that requires a different JDK | because he needs to run an application that requires a different JDK. He does this using | ||
alternatives (needs root), changing the provider of "java". | |||
alternatives (needs root), | This will not only change what /usr/bin/java points to, but because "jre" and "java_sdk" alternatives settings are defined as slave, | ||
it will also change the JVM system applications are run with. | |||
in the system installed from RPM, such application will be run with the | Now, when he runs any java application | ||
JVM | in the system installed from RPM, such application will be run with the JVM set in alternatives, | ||
not realize that the application is written in Java and the application may | not with the Fedora-supported one. | ||
The user might not realize that the application is written in Java and the application may | |||
not behave correctly if it's not compatible with given JVM (i.e. a legacy one). | not behave correctly if it's not compatible with given JVM (i.e. a legacy one). | ||
=== Proposed behavior === | === Proposed behavior === | ||
| Line 97: | Line 93: | ||
which is a symlink pointing to latest version of openjdk 8, provided by | which is a symlink pointing to latest version of openjdk 8, provided by | ||
java-1.8.0-openjdk package. | java-1.8.0-openjdk package. | ||
The system administrator would still be able | |||
to change the default system-wide JVM for applications in java.conf | to change the default system-wide JVM for applications in java.conf | ||
configuration file. Temporary changes of JVM would still be possible using | configuration file. Temporary changes of JVM would still be possible using | ||
| Line 106: | Line 102: | ||
== Benefit to Fedora == | == Benefit to Fedora == | ||
Users will be able to change their java command | Users (system administrators) will be able to change their java command without the risk of impacting system-wide applications installed from RPMs. | ||
without the risk of impacting system-wide applications installed from RPMs. | |||
<!-- What is the benefit to the platform? If this is a major capability update, what has changed? If this is a new functionality, what capabilities does it bring? Why will Fedora become a better distribution or project because of this proposal?--> | <!-- What is the benefit to the platform? If this is a major capability update, what has changed? If this is a new functionality, what capabilities does it bring? Why will Fedora become a better distribution or project because of this proposal?--> | ||
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[[Category: | [[Category:ChangeAcceptedF27]] | ||
<!-- When your change proposal page is completed and ready for review and announcement --> | <!-- When your change proposal page is completed and ready for review and announcement --> | ||
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Latest revision as of 19:55, 26 October 2017
Decouple system java setting from java command setting
Summary
By default, Java applications installed from RPMs are run with JVM found on PATH. We propose to run them with default system JVM, not considering PATH. Users will still be able to override the default using JAVA_HOME environment variable as before.
Owner
- Name: Michael Simacek
- Name: Mikolaj Izdebski
- Email: msimacek@redhat.com
- Email: mizdebsk@redhat.com
- Release notes owner: Simon Clark (sclark)
Current status
Detailed Description
Java applications are not directly executable and thus they typically ship a launcher script that performs the lookup of the JVM executable used to run the application and setups its environment. In Fedora, applications packaged as RPMs ship launcher scripts (most commonly generated using %jpackage_script macro) that delegate the setup to helper routines provided by javapackages-tools.
Currently (Fedora 26), the lookup of a JVM by javapackages-tools works as follows:
- it reads java.conf configuration file from config paths (default /etc/java/java.conf)
- if the current environment contains JAVA_HOME variable (typically it doesn't), JVM executable is looked up there
- if the configuration specifies JAVA_HOME (by default it doesn't), JVM is looked up there
- it tries to find JVM in java/jre subdirs of JVM_ROOT (by default /usr/lib/jvm). Those subdirs are managed by "jre"/"java_sdk" alternatives. This is the code path that is triggered by default. The /usr/lib/jvm alternative symlink is a slave of "java" configuration, so changing "java" alternatives will set it to different value or unset it, if the alternative provider doesn't specify the slave configuration.
- otherwise JVM executable is looked up on PATH, using
which java. With default PATH setting on Fedora, this will be /usr/bin/java, which is a symlink managed by "java" alternatives setting
Disadvantages of the current behavior
Let's say a user wants to change his java command to a different provider, because he needs to run an application that requires a different JDK. He does this using alternatives (needs root), changing the provider of "java". This will not only change what /usr/bin/java points to, but because "jre" and "java_sdk" alternatives settings are defined as slave, it will also change the JVM system applications are run with. Now, when he runs any java application in the system installed from RPM, such application will be run with the JVM set in alternatives, not with the Fedora-supported one. The user might not realize that the application is written in Java and the application may not behave correctly if it's not compatible with given JVM (i.e. a legacy one).
Proposed behavior
If JAVA_HOME is not set (neither in the environment, nor in configuration), it is set to a default value that points to the currently supported default Java implementation. The default would be stored in javapackages-tools (the package providing the lookup functions). For Fedora 27, this would be /usr/lib/jvm/java-1.8.0-openjdk, which is a symlink pointing to latest version of openjdk 8, provided by java-1.8.0-openjdk package. The system administrator would still be able to change the default system-wide JVM for applications in java.conf configuration file. Temporary changes of JVM would still be possible using JAVA_HOME environment variable.
The change would be implemented by altering the lookup functions in javapackages-tools and updating the package in Fedora. Note that we (the change owners) are both upstream and Fedora maintainers of javapackages-tools.
Benefit to Fedora
Users (system administrators) will be able to change their java command without the risk of impacting system-wide applications installed from RPMs.
Scope
- Proposal owners:
- Adjust javapackages-tools to provide default Java setting in /etc/java/java.conf
- Other developers: N/A (not a System Wide Change)
- Release engineering: [1] (a check of an impact with Release Engeneering is needed)
- List of deliverables: N/A (not a System Wide Change)
- Policies and guidelines: N/A (not a System Wide Change)
- Trademark approval: N/A (not needed for this Change)
Upgrade/compatibility impact
N/A (not a System Wide Change)
How To Test
N/A (not a System Wide Change)
User Experience
N/A (not a System Wide Change)
Dependencies
N/A (not a System Wide Change)
Contingency Plan
- Contingency mechanism: revert to using single alternatives provider
- Contingency deadline: N/A (not a System Wide Change)
- Blocks release? No
Documentation
N/A (not a System Wide Change)