How to get from dCache 5.2 to dCache 6.2
- bulk cache file cleanup on space pressure
- fifo/lifo capability of the flush queue
- TLS on p2p
- better support for distributed setups
- experimental internal message serialization format for better HPC support
- basic support for extended attributes
- full TLS support for all internal messages
- new telemetry service
- SciToken with XrootD
- Java 11
- systemd based packages
The dCache uses apache zookeeper for service discovery and coordination. Starting from version 6.2 the zookeeper 3.5.x is required. With this version jump, zookeeper supports TLS for communications between other zookeeper nodes as well as between zookeeper clients and server. This allows to make the whole dcache inter-component communication to be TLS protected, which is important for geo-distributed deployments over public networks.
The rpm packages with latest supported zookeeper server versions can be obtained from dcache.org yum repository:
[dcache-org-zk]
name=dCache.ORG zookeeper packages
baseurl=https://download.dcache.org/nexus/repository/zookeeper-rpms/el7/noarch
gpgcheck=0
enabled=1
Java 11 is the current LTS release of java runtime environment, that is required by dCache. In addition to language level changes for developers, the new JVM brings improvements for monitoring, integration with containers and debugging. For example, the JVM inspection tool Flight Recorder is now available as a part of openJDK, the java thread names can be shown by system tools, like top -H <pid>
and with new JVM options -XX:+PreserveFramePointer
the system profiler perf
can collect and display method invocation statistics and call graphs.
The all dCache releases are developed and tested with OpenJDK, which is license/subscription free. To use Oracle JVM you need
Java SE Subscriptions
.
The PostgreSQL DB is an essential part dCache. It powers the namespace, AKA Chimera, PinManager, Srm, space manger and billing.
The minimal PostgeSQL version number supported by dCache is 9.5, which allows dCache use new SQL syntax to improve the DB operation performance.
Starting from version 3.2.0 dcache domain processes can be managed as systemd services. However, this functionality was available for debian-based systems only.
As we have changed the grouping unit from
dcache.service
todcache.target
, debian based installations have to manually stop dcache.service before installing new package and use dcache.target in the future.
dCache uses systemd's generator functionality to create a service for each defined domain in the layout file. That's why, before starting the service all dynamic systemd units should be generated. As generator runs in a restricted environment, ensure that /usr/bin/java
points to a valid java11
binary.
systemctl daemon-reload
You need to regenerate dynamic units every time when new domains are added or removed as well as when systemd affected properties are modified. Those properties are:
- dcache.user
- dcache.java.options.extra
- dcache.restart.delay
- dcache.home
- dcache.java.library.path
To inspect all generated units of dcache.target the systemd list-dependencies
command can be used. For example:
systemctl list-dependencies dcache.target
dcache.target
● ├─[email protected]
● ├─[email protected]
● ├─[email protected]
● ├─[email protected]
● ├─[email protected]
● └─[email protected]
NOTE: by default, the log files are no longer created in /var/log/dcache and have to be accessed with through system journal, like
journalctl -u [email protected]
. To (partially) restore logfile functionality check thedcache.log.destination
option.
Command | Description |
---|---|
systemctl start/stop/status/enable dcache.target | Execute the command for all defined domains |
systemctl start/stop/status/enable [email protected] | Execute the command for a specified single domain |
journalctl -u [email protected] | Access the logs of a specified domain |
systemctl list-dependencies dcache.target | List all defined domains |
systemctl daemon-reload | Re-generate domain units |
systemctl daemon-reexec | Restart systemd daemon it it crashed config error |
To use the sysV-like dcache [start|stop|status]
commands disable systemd for dCache by adding
dcache.systemd.strict=false
in dcache.conf or in the layout files.
For more information check the install chapter in the dcache book.
The dCache pools stores the data in two places: a data file store and a complementary metadata store. The default metadata store was based on a pair of disk files for each data file. Over a decade a more effective BerkeleyDB-based metadata store was introduced and recommended for use in production. Now on, it becomes the default. To restore the old behavior add
pool.plugins.meta=org.dcache.pool.repository.meta.file.FileMetaDataRepository
into dcache.conf or layout files.
The BerkeleyDB-based metadata is enhanced with additional information which will be populated on pool start. Thus the very first start of the pools after upgrade to version 6.2 will take more time.
With introduction of dCache zones
, the zone become a keyword and can't be used as a pool tag.
The following properties have changed their default values:
property | new value |
---|---|
dcache.enable.authn.anonymous-fallback-on-failed-login | false |
pool.plugins.meta | org.dcache.pool.repository.meta.db.BerkeleyDBMetaDataRepository |
dcache.kafka.maximum-block | 60 |
The cms-tfc
plugin now needs to be of version 4.0.4 or higher.
Telememetry
is an optional service is added to collect statistics about running instances around the world. The telemetry cell has to be explicitly defined in a layout file as well as enabled:
[telemetryDomain]
[telemetryDomain/telemetry]
telemetry.cell.enable=true
telemetry.instance.site-name=dCache instance on \${host.name}
telemetry.instance.location.latitude=53.5772
telemetry.instance.location.longitude=9.8772
The dcache version, online capacity, site name and optional location will be sent to the stats.dcache.org collector.
The dCache.org kindly asks sites to enable telemetry service to let developers to see the deployments and version popularity.
Though we don't collect any personal information, please consult you site security officer before enabling the service.