Race condition on initial Karaf start corrupts config file

[olfuerniss]

And the result are a lot of "Key [] must not be an empty string" errors in the log like this for nearly all cfg files:

2026-08-17T14:30:54,225 | ERROR | fileinstall-/home/bb/Documents/dev/karaf-5.1.0-SNAPSHOT/etc | fileinstall                      | 11 - org.apache.felix.fileinstall - 3.7.4 | Failed to install artifact: /home/bb/Documents/dev/karaf-5.1.0-SNAPSHOT/etc/jmx.acl.osgi.compendium.cm.cfg

java.lang.IllegalArgumentException: Key [] must not be an empty string
	at org.apache.felix.cm.impl.CaseInsensitiveDictionary.checkKey(CaseInsensitiveDictionary.java:269)
	at org.apache.felix.cm.impl.CaseInsensitiveDictionary.<init>(CaseInsensitiveDictionary.java:73)
	at org.apache.felix.cm.impl.persistence.CachingPersistenceManagerProxy.cache(CachingPersistenceManagerProxy.java:171)
	at org.apache.felix.cm.impl.persistence.CachingPersistenceManagerProxy.getDictionaries(CachingPersistenceManagerProxy.java:209)
	at org.apache.felix.cm.impl.ConfigurationManager.listConfigurations(ConfigurationManager.java:534)
	at org.apache.felix.cm.impl.ConfigurationAdminImpl.listConfigurations(ConfigurationAdminImpl.java:190)
	at org.apache.felix.fileinstall.internal.ConfigInstaller.findExistingConfiguration(ConfigInstaller.java:506)
	at org.apache.felix.fileinstall.internal.ConfigInstaller.getConfiguration(ConfigInstaller.java:476)
	at org.apache.felix.fileinstall.internal.ConfigInstaller.setConfig(ConfigInstaller.java:386)
	at org.apache.felix.fileinstall.internal.ConfigInstaller.install(ConfigInstaller.java:192)
	at org.apache.felix.fileinstall.internal.DirectoryWatcher.install(DirectoryWatcher.java:950)
	at org.apache.felix.fileinstall.internal.DirectoryWatcher.install(DirectoryWatcher.java:884)
	at org.apache.felix.fileinstall.internal.DirectoryWatcher.doProcess(DirectoryWatcher.java:489)
	at org.apache.felix.fileinstall.internal.DirectoryWatcher.process(DirectoryWatcher.java:365)
	at org.apache.felix.fileinstall.internal.DirectoryWatcher.run(DirectoryWatcher.java:316)

In our custom Karaf it happens only from time to time and is hard to reproduce. @grgrzybek (Grzegorz Grzybek) had a similar issue in ticket https://issues.apache.org/jira/browse/KARAF-7389. Unfortunately, he only fixed it for the case where the cfg file didn't exist yet. In our case, the cfg file already exists and is being updated. This leads to a race condition, and the cfg file becomes corrupt.

For us, only ONE cfg-file gets updated on the initial start of our custom Karaf and that is [karaf]/etc/org.apache.felix.eventadmin.impl.EventAdmin.cfg. This update happens due to the fact that we add Karaf-Decanter ('decanter-collector-log') to our boot features.

The default [karaf]/etc/org.apache.felix.eventadmin.impl.EventAdmin.cfg looks like this

################################################################################
#
#    Licensed to the Apache Software Foundation (ASF) under one or more
#    contributor license agreements.  See the NOTICE file distributed with
#    this work for additional information regarding copyright ownership.
#    The ASF licenses this file to You under the Apache License, Version 2.0
#    (the "License"); you may not use this file except in compliance with
#    the License.  You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.
#
################################################################################

org.apache.felix.eventadmin.AddTimestamp=true
org.apache.felix.eventadmin.AddSubject=true

The Karaf-Decanter extends the config file [karaf]/etc/org.apache.felix.eventadmin.impl.EventAdmin.cfg by 3 additional EventAdmin settings:

<features name="karaf-decanter-${project.version}" xmlns="http://karaf.apache.org/xmlns/features/v1.4.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://karaf.apache.org/xmlns/features/v1.4.0 http://karaf.apache.org/xmlns/features/v1.4.0">

    <feature name="decanter-common" version="${project.version}" description="Karaf Decanter API">
        <config name="org.apache.felix.eventadmin.impl.EventAdmin" append="true">
org.apache.felix.eventadmin.ThreadPoolSize=40
org.apache.felix.eventadmin.Timeout=0
org.apache.felix.eventadmin.IgnoreTimeout=org.apache.karaf.decanter.
        </config>
        <feature>eventadmin</feature>
      ....

When it comes to a race condition [karaf]/etc/org.apache.felix.eventadmin.impl.EventAdmin.cfg is corrupt and looks for example like this:

org.apache.felix.eventadmin.ThreadPoolSize = 40
org.apache.felix.eventadmin.Timeout = 0
org.apache.felix.eventadmin.IgnoreTimeout = org.apache.karaf.decanter.
=true
org.apache.felix.eventadmin.AddSubject=true

When everything is fine (most of the time), it looks like this:

################################################################################
#
#    Licensed to the Apache Software Foundation (ASF) under one or more
#    contributor license agreements.  See the NOTICE file distributed with
#    this work for additional information regarding copyright ownership.
#    The ASF licenses this file to You under the Apache License, Version 2.0
#    (the "License"); you may not use this file except in compliance with
#    the License.  You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.
#
################################################################################

org.apache.felix.eventadmin.AddTimestamp=true
org.apache.felix.eventadmin.AddSubject=true
org.apache.felix.eventadmin.Timeout = 0
org.apache.felix.eventadmin.ThreadPoolSize = 40
org.apache.felix.eventadmin.IgnoreTimeout = org.apache.karaf.decanter.

P.S. In our custom Karaf we can workaround a potential race condition, by providing a [karaf]/etc/org.apache.felix.eventadmin.impl.EventAdmin.cfg that already contains all settings so that no update of the file must be done.