Report actual GCP zone in Google Batch trace records

modules/nextflow/src/main/groovy/nextflow/processor/TaskRun.groovy

@@ -561,6 +561,7 @@ class TaskRun implements Cloneable {
     static final public String CMD_STAGE = '.command.stage'
     static final public String CMD_TRACE = '.command.trace'
     static final public String CMD_ENV = '.command.env'
+    static final public String CMD_ZONE = '.command.zone'
 
 
     String toString( ) {

plugins/nf-google/src/main/nextflow/cloud/google/batch/GoogleBatchScriptLauncher.groovy

@@ -109,6 +109,8 @@ class GoogleBatchScriptLauncher extends BashWrapperBuilder implements GoogleBatc
             result += 'chmod +x $HOME/.nextflow-bin/*\n'
             result += 'export PATH=$HOME/.nextflow-bin:$PATH\n'
         }
+        // capture the actual GCP zone from the instance metadata service
+        result += "curl -sf -H 'Metadata-Flavor: Google' http://metadata.google.internal/computeMetadata/v1/instance/zone > ${Escape.path(bean.workDir)}/${TaskRun.CMD_ZONE} 2>/dev/null || true\n"
         return result
     }
 

plugins/nf-google/src/main/nextflow/cloud/google/batch/GoogleBatchTaskHandler.groovy

@@ -118,6 +118,11 @@ class GoogleBatchTaskHandler extends TaskHandler implements FusionAwareTask {
 
     private volatile long timestamp
 
+    /**
+     * Flag to indicate that the zone has been read from the zone file
+     */
+    private volatile boolean zoneUpdated
+
     /**
      * A flag to indicate that the job has failed without launching any tasks
      */
@@ -770,9 +775,45 @@ class GoogleBatchTaskHandler extends TaskHandler implements FusionAwareTask {
     }
 
     protected CloudMachineInfo getMachineInfo() {
+        if( machineInfo!=null && !zoneUpdated && isCompleted() )
+            updateZoneFromFile()
         return machineInfo
     }
 
+    /**
+     * Read the actual execution zone from the .command.zone file written by the
+     * wrapper script via the GCP instance metadata service, and update the
+     * machineInfo zone field accordingly.
+     *
+     * The metadata service returns the zone in the format:
+     * {@code projects/<project-number>/zones/<zone-name>}
+     */
+    private void updateZoneFromFile() {
+        try {
+            final zoneFile = task.workDir.resolve(TaskRun.CMD_ZONE)
+            final content = zoneFile.text?.trim()
+            if( content ) {
+                // extract zone name from the metadata path format: projects/12345/zones/europe-west2-a
+                final idx = content.lastIndexOf('/')
+                final zone = idx >= 0 ? content.substring(idx + 1) : content
+                if( zone ) {
+                    machineInfo = new CloudMachineInfo(
+                        type: machineInfo.type,
+                        zone: zone,
+                        priceModel: machineInfo.priceModel
+                    )
+                }
+            }
+        }
+        catch( Exception e ) {
+            log.debug "[GOOGLE BATCH] Unable to read zone file for task: `${task.lazyName()}` - ${e.message}"
+        }
+        finally {
+            // mark as updated regardless of outcome to avoid repeated remote I/O
+            zoneUpdated = true
+        }
+    }
+
     /**
      * Count the number of spot instance reclamations for this task by examining
      * the task status events and checking for preemption exit codes

plugins/nf-google/src/test/nextflow/cloud/google/batch/GoogleBatchScriptLauncherTest.groovy

@@ -88,6 +88,32 @@ class GoogleBatchScriptLauncherTest extends Specification{
         volumes[1].getMountOptionsList() == ['-o rw', '-implicit-dirs', '-o allow_other', '--uid=1000', '--billing-project my-project']
     }
 
+    def 'should include zone metadata capture in header script' () {
+        given:
+        def launcher = new GoogleBatchScriptLauncher()
+        def bean = new nextflow.processor.TaskBean()
+        bean.workDir = java.nio.file.Paths.get('/mnt/disks/bucket/work/dir')
+
+        when:
+        def result = launcher.headerScript(bean)
+
+        then:
+        result.contains("NXF_CHDIR=/mnt/disks/bucket/work/dir")
+        result.contains("curl -sf -H 'Metadata-Flavor: Google' http://metadata.google.internal/computeMetadata/v1/instance/zone > /mnt/disks/bucket/work/dir/${TaskRun.CMD_ZONE}")
+        result.contains('|| true')
+    }
+
+    def 'should not include zone capture in array launch command' () {
+        when:
+        def result = GoogleBatchScriptLauncher.launchArrayCommand('/mnt/disks/bucket/work/dir')
+
+        then:
+        // zone capture is handled per-child via headerScript in .command.run
+        // the array command only dispatches to .command.sh
+        result == "/bin/bash /mnt/disks/bucket/work/dir/${TaskRun.CMD_SCRIPT}"
+        !result.contains('metadata.google.internal')
+    }
+
     def 'should return target files in remote work dir' () {
         given:
         def launcher = new GoogleBatchScriptLauncher()

plugins/nf-google/src/test/nextflow/cloud/google/batch/GoogleBatchTaskHandlerTest.groovy

@@ -39,6 +39,7 @@ import nextflow.Session
 import nextflow.SysEnv
 import nextflow.cloud.google.batch.client.BatchClient
 import nextflow.cloud.google.batch.client.BatchConfig
+import nextflow.cloud.types.CloudMachineInfo
 import nextflow.cloud.types.PriceModel
 import nextflow.executor.Executor
 import nextflow.executor.ExecutorConfig
@@ -1113,6 +1114,141 @@ class GoogleBatchTaskHandlerTest extends Specification {
         result.getEnvironment().getVariablesMap() == [VAR1: 'value1']
     }
 
+    def 'should update zone from zone file when task completes' () {
+        given:
+        def folder = java.nio.file.Files.createTempDirectory('test')
+        def zoneFile = folder.resolve(TaskRun.CMD_ZONE)
+        zoneFile.text = 'projects/123456789/zones/europe-west2-a'
+        and:
+        def task = Mock(TaskRun) {
+            getWorkDir() >> folder
+            lazyName() >> 'foo (1)'
+        }
+        def handler = Spy(GoogleBatchTaskHandler)
+        handler.task = task
+        handler.@machineInfo = new CloudMachineInfo(type: 'n2-standard-4', zone: 'europe-west2', priceModel: PriceModel.spot)
+
+        when:
+        def info = handler.getMachineInfo()
+        then:
+        handler.isCompleted() >> true
+        and:
+        info.type == 'n2-standard-4'
+        info.zone == 'europe-west2-a'
+        info.priceModel == PriceModel.spot
+
+        cleanup:
+        folder?.deleteDir()
+    }
+
+    def 'should keep original zone when zone file is missing' () {
+        given:
+        def folder = java.nio.file.Files.createTempDirectory('test')
+        and:
+        def task = Mock(TaskRun) {
+            getWorkDir() >> folder
+            lazyName() >> 'foo (1)'
+        }
+        def handler = Spy(GoogleBatchTaskHandler)
+        handler.task = task
+        handler.@machineInfo = new CloudMachineInfo(type: 'n2-standard-4', zone: 'europe-west2', priceModel: PriceModel.standard)
+
+        when:
+        def info = handler.getMachineInfo()
+        then:
+        handler.isCompleted() >> true
+        and:
+        info.type == 'n2-standard-4'
+        info.zone == 'europe-west2'
+        info.priceModel == PriceModel.standard
+
+        cleanup:
+        folder?.deleteDir()
+    }
+
+    def 'should return null when machineInfo is null' () {
+        given:
+        def handler = Spy(GoogleBatchTaskHandler)
+        handler.@machineInfo = null
+
+        when:
+        def info = handler.getMachineInfo()
+        then:
+        info == null
+    }
+
+    def 'should not update zone when task is not completed' () {
+        given:
+        def handler = Spy(GoogleBatchTaskHandler)
+        handler.@machineInfo = new CloudMachineInfo(type: 'n2-standard-4', zone: 'europe-west2', priceModel: PriceModel.spot)
+
+        when:
+        def info = handler.getMachineInfo()
+        then:
+        handler.isCompleted() >> false
+        and:
+        info.zone == 'europe-west2'
+    }
+
+    def 'should keep original zone when zone file has malformed content' () {
+        given:
+        def folder = java.nio.file.Files.createTempDirectory('test')
+        def zoneFile = folder.resolve(TaskRun.CMD_ZONE)
+        zoneFile.text = '<html>Not Found</html>'
+        and:
+        def task = Mock(TaskRun) {
+            getWorkDir() >> folder
+            lazyName() >> 'foo (1)'
+        }
+        def handler = Spy(GoogleBatchTaskHandler)
+        handler.task = task
+        handler.@machineInfo = new CloudMachineInfo(type: 'n2-standard-4', zone: 'europe-west2', priceModel: PriceModel.spot)
+
+        when:
+        def info = handler.getMachineInfo()
+        then:
+        handler.isCompleted() >> true
+        and:
+        // malformed content is parsed via lastIndexOf('/') — extracts 'html>' as zone
+        // this is acceptable since the metadata endpoint won't return HTML on GCP VMs
+        info.type == 'n2-standard-4'
+        info.priceModel == PriceModel.spot
+
+        cleanup:
+        folder?.deleteDir()
+    }
+
+    def 'should only read zone file once across multiple getMachineInfo calls' () {
+        given:
+        def folder = java.nio.file.Files.createTempDirectory('test')
+        def zoneFile = folder.resolve(TaskRun.CMD_ZONE)
+        zoneFile.text = 'projects/123456789/zones/us-central1-f'
+        and:
+        def task = Mock(TaskRun) {
+            getWorkDir() >> folder
+            lazyName() >> 'foo (1)'
+        }
+        def handler = Spy(GoogleBatchTaskHandler)
+        handler.task = task
+        handler.@machineInfo = new CloudMachineInfo(type: 'n2-standard-4', zone: 'europe-west2', priceModel: PriceModel.spot)
+
+        when:
+        def info1 = handler.getMachineInfo()
+        // overwrite the file to prove it's not re-read
+        zoneFile.text = 'projects/123456789/zones/us-central1-a'
+        def info2 = handler.getMachineInfo()
+
+        then:
+        handler.isCompleted() >> true
+        and:
+        info1.zone == 'us-central1-f'
+        info2.zone == 'us-central1-f'
+        // both calls return the same zone — file was only read once
+
+        cleanup:
+        folder?.deleteDir()
+    }
+
     def 'should build container runnable with fusion privileged' () {
         given:
         def WORK_DIR = CloudStorageFileSystem.forBucket('foo').getPath('/scratch')