On Fri, 21 Mar 2025 10:00:26 GMT, Aleksey Shipilev <sh...@openjdk.org> wrote:
> When jspawnhelper fails for whatever reason, but more prominently due to > [JDK-8325621](https://bugs.openjdk.org/browse/JDK-8325621), it will report > the errors into stdout, but not to the relevant `IOException`. So, if the > application is configured to only capture the exception logs (e.g. through > `java.util.logging`), we will miss any output from `jspawnhelper`, and user > would be left without a clue what have happened. We have seen customers > spending weeks trying to figure out what went wrong. > > It would be good to provide useful `IOException` when `jspawnhelper` fails. > We already have a precedent with vmError [printing helpful > suggestions](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/utilities/vmError.cpp#L422) > when VM fails, we can do a similar thing here. > > I am very open to bike-shedding about the actual message :) > > Additional testing: > - [x] Ad-hoc experiments with breaking jspawnhelper > - [x] macos-aarch64-server-fastdebug, `java/lang/Process > java/lang/ProcessBuilder` Easiest way to see what kind of exception is printed on jspawnhelper failure is to run `jdk/java/lang/ProcessBuilder/JspawnhelperProtocol.java`, and see this in its output: Command line: [... Djdk.lang.Process.launchMechanism=posix_spawn JspawnhelperProtocol simulateCrashInChild4 ] Recursively executing 'JspawnhelperProtocol simulateCrashInChild4' posix_spawn:0 java.io.IOException: Cannot run program "pwd": error=0, Failed to exec spawn helper: pid: 85166, exit value: 4 Possible reasons: - Spawn helper ran into JDK version or configuration problems - Spawn helper ran into unexpected internal error - Spawn helper was terminated by another process Possible solutions: - Restart JVM, especially after in-place JDK updates - Check system logs for JDK-related errors - Re-install JDK to fix permission/versioning problems - Switch to legacy launch mechanism with -Djdk.lang.Process.launchMechanism=VFORK at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1110) at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1044) at java.base/java.lang.Runtime.exec(Runtime.java:605) at java.base/java.lang.Runtime.exec(Runtime.java:470) at JspawnhelperProtocol.parentCode(JspawnhelperProtocol.java:56) at JspawnhelperProtocol.main(JspawnhelperProtocol.java:230) ------------- PR Comment: https://git.openjdk.org/jdk/pull/24149#issuecomment-2742889069
