Does camel use an implicit read lock for files?

Question

I'm consuming a file using Camel File component as follows:

<from uri="file:myDir?noop=true&amp;filter=myFilter&amp;scheduler=quartz2&amp;scheduler.cron={{schedule}}/>

The source location is read only. Camel File documentation says, it won't be using a read lock by default.

But, I'm getting a permission denied exception while running this code.

Endpoint[file://myFile?filter=myFilter&idempotent=true&noop=true&scheduler=quartz2&scheduler.cron={{mySchedule}} cannot begin processing file: GenericFile[myDir\myFile] due to: Access is denied. Caused by: [java.io.IOException - Access is denied]

Stack Trace java.io.IOException: Permission denied at java.io.UnixFileSystem.createFileExclusively(Native Method)[:1.8.0_66] at java.io.File.createNewFile(File.java:1012)[:1.8.0_66] at org.apache.camel.util.FileUtil.createNewFile(FileUtil.java:587)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.component.file.strategy.MarkerFileExclusiveReadLockStrategy.acquireExclusiveReadLock(MarkerFileExclusiveReadLockStrategy.java:71)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.component.file.strategy.GenericFileProcessStrategySupport.begin(GenericFileProcessStrategySupport.java:49)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.component.file.strategy.GenericFileRenameProcessStrategy.begin(GenericFileRenameProcessStrategy.java:35)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.component.file.GenericFileConsumer.processExchange(GenericFileConsumer.java:352)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.component.file.GenericFileConsumer.processBatch(GenericFileConsumer.java:211)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.component.file.GenericFileConsumer.poll(GenericFileConsumer.java:175)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.impl.ScheduledPollConsumer.doRun(ScheduledPollConsumer.java:174)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.impl.ScheduledPollConsumer.run(ScheduledPollConsumer.java:101)[org.apache.camel:camel-core:2.15.1.redhat-621090 com.googlecode.concurrentlinkedhashmap:concurrentlinkedhashmap-lru:1.4.2] at org.apache.camel.pollconsumer.quartz2.QuartzScheduledPollConsumerJob.execute(QuartzScheduledPollConsumerJob.java:59)[org.apache.camel:camel-quartz2:2.15.1.redhat-621090] at org.quartz.core.JobRunShell.run(JobRunShell.java:202)[org.quartz-scheduler:quartz:2.2.1] at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:573)[org.quartz-scheduler:quartz:2.2.1]

From the stack trace, it appears that, camel is trying to create a readLock and it is causing exception due to lack of of permission.

So, my questions are

• Why camel is using a lock, even if default value of read lock is none
• If this is expected behavior, how can I consume file from a read only location where I don't have write permission?

UPDATE

I tried setting readLockMarkingFile to false as suggested in one of the answer, but that did n't solve the problem. So, I explicitly set readLock to none. Now, it is working. Don't know, why readLock is not none by default as mentioned in documentation.

Answer 1

I have also encountered this problem, the documentation states that the default value of the parameter is none, but in fact markerFile is used. To resolve this, you must explicitly specify this parameter readLock=none(camel-version 2.20.2)

Answer 2

While this doesn't directly answer your question, I've used a trigger file (0 bytes) which the file watcher looks for. Your route would then work on the actual file to which the trigger is a companion. The trigger file is moved to a subdirectory /parent/.camel so it doesn't process again. Although we have noticed routes try to 'pick up' the actual file in a distributed environment where there is more than one server running the route.

Answer 3

The readLock-option only decides whether camel will try to acquire an exclusive read-lock on the file. There is another option called "readLockMarkerFile" which defaults to true, set that option to false and you should be fine.

<from uri="file:myDir?noop=true&amp;filter=myFilter&amp;scheduler=quartz2&amp;scheduler.cron={{schedule}}&amp;readLockMarkerFile=false/>