GlusterFS

Important happenings for Gluster this month: GlusterFS-3.9rc1 is out for testing! Gluster 3.8.4 is released, users are advised to update: http://blog.gluster.org/2016/09/glusterfs-3-8-4-is-available-gluster-users-are-advised-to-update/ Gluster ... [More] Developer Summit: Next week, Gluster Developer Summit happens in Berlin from October 6 through 7th. Our schedule: https://www.gluster.org/events/schedule2016/ We will be recording scheduled talks, and posting them to our YouTube channel! Gluster-users: Amudhan […] [Less]

Even though the last release 3.8 was just two weeks ago, we're sticking to the release schedule and have 3.8.4 ready for all our current and future users. As with all updates, we advise users of previous versions to upgrade to the latest and greatest. ...

These days hyperconverged strategies are everywhere. But when you think about it, sharing the finite resources within a physical host requires an effective means of prioritisation and enforcement. Luckily, the Linux kernel already provides an ... [More] infrastructure for this in the shape of cgroups, and the interface to these controls is now simplified with systemd integration.So lets look at how you could use these capabilities to make Gluster a better neighbour in a collocated or hyperconverged  model. First some common systemd terms, we should to be familiar with; slice : a slice is a concept that systemd uses to group together resources into a hierarchy. Resource constraints can then be applied to the slice, which defines  how different slices may compete with each other for resources (e.g. weighting) how resources within a slice are controlled (e.g. cpu capping) unit : a systemd unit is a resource definition for controlling a specific system serviceNB. More information about control groups with systemd can be found here In this article, I'm keeping things simple by implementing a cpu cap on glusterfs processes. Hopefully, the two terms above are big clues, but conceptually it breaks down into two main steps; define a slice which implements a CPU limit ensure gluster's systemd unit(s) start within the correct slice. So let's look at how this is done.Defining a sliceSlice definitions can be found under /lib/systemd/system, but systemd provides a neat feature where /etc/systemd/system can be used provide local "tweaks". This override directory is where we'll place a slice definition. Create a file called glusterfs.slice, containing;[Slice]CPUQuota=200% CPUQuota is our means of applying a cpu limit on all resources running within the slice. A value of 200% defines a 2 cores/execution threads limit.Updating glusterdNext step is to give gluster a nudge so that it shows up in the right slice. If you're using RHEL7 or Centos7, cpu accounting may be off by default (you can check in /etc/systemd/system.conf). This is OK, it just means we have an extra parameter to define. Follow these steps to change the way glusterd is managed by systemd# cd /etc/systemd/system # mkdir glusterd.service.d# echo -e "[Service]\nCPUAccounting=true\nSlice=glusterfs.slice" > glusterd.service.d/override.conf glusterd is responsible for starting the brick and self heal processes, so by ensuring glusterd starts in our cpu limited slice, we capture all of glusterd's child processes too. Now the potentially bad news...this 'nudge' requires a stop/start of gluster services. If your doing this on a live system you'll need to consider quorum, self heal etc etc. However, with the settings above in place, you can get gluster into the right slice by;# systemctl daemon-reload# systemctl stop glusterd# killall glusterfsd && killall glusterfs# systemctl daemon-reload# systemctl start glusterdYou can see where gluster is within the control group hierarchy by looking at it's runtime settings# systemctl show glusterd | grep sliceSlice=glusterfs.sliceControlGroup=/glusterfs.slice/glusterd.serviceWants=glusterfs.sliceAfter=rpcbind.service glusterfs.slice systemd-journald.socket network.target basic.targetor use the systemd-cgls command to see the whole control group hierarchy ├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 19├─glusterfs.slice│ └─glusterd.service│   ├─ 867 /usr/sbin/glusterd -p /var/run/glusterd.pid --log-level INFO│   ├─1231 /usr/sbin/glusterfsd -s server-1 --volfile-id repl.server-1.bricks-brick-repl -p /var/lib/glusterd/vols/repl/run/server-1-bricks-brick-repl.pid  │   └─1305 /usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p /var/lib/glusterd/glustershd/run/glustershd.pid -l /var/log/glusterfs/glustershd.log ├─user.slice│ └─user-0.slice│   └─session-1.scope│     ├─2075 sshd: root@pts/0   │     ├─2078 -bash│     ├─2146 systemd-cgls│     └─2147 less└─system.slice At this point gluster is exactly where we want it! Time for some more systemd coolness ;) The resource constraints that are applied by the slice are dynamic, so if you need more cpu, you're one command away from getting it;# systemctl set-property glusterfs.slice CPUQuota=350%Try the 'systemd-cgtop' command to show the cpu usage across the complete control group hierarchy.Now if jumping straight into applying resource constraints to gluster is a little daunting, why not test this approach with a tool like 'stress'. Stress is designed to simply consume components of the system - cpu, memory, disk. Here's an example .service file which uses stress to consume 4 cores[Unit]Description=CPU soak task[Service]Type=simpleCPUAccounting=trueExecStart=/usr/bin/stress -c 4Slice=glusterfs.slice[Install]WantedBy=multi-user.targetNow you can tweak the service, and the slice with different thresholds before you move on to bigger things! Use stress to avoid stress :)And now the obligatory warning. Introducing any form of resource constraint may resort in unexpected outcomes especially in hyperconverged/collocated systems - so adequate testing is key.With that said...happy hacking :) [Less]

Demo video is included in the end, or you can directly watch it on Youtube Gluster Eventing is the new feature as part of Gluster.Next initiatives, it provides close to realtime notification and alerts for the Gluster cluster state changes. ... [More] Websockets APIs to consume events will be added later. Now we emit events via another popular mechanism called "Webhooks".(Many popular products provide notifications via Webhooks Github, Atlassian, Dropbox, and many more) Webhooks are similar to callbacks(over HTTP), on event Gluster will call the Webhook URL(via POST) which is configured. Webhook is a web server which listens on a URL, this can be deployed outside of the Cluster. Gluster nodes should be able to access this Webhook server on the configured port. We will discuss about adding/testing webhook later. Example Webhook written in python, from flask import Flask, request app = Flask(__name__) @app.route("/listen", methods=["POST"]) def events_listener(): gluster_event = request.json if gluster_event is None: # No event to process, may be test call return "OK" # Process gluster_event # { # "nodeid": NODEID, # "ts": EVENT_TIMESTAMP, # "event": EVENT_TYPE, # "message": EVENT_DATA # } return "OK" app.run(host="0.0.0.0", port=9000) Eventing feature is not yet available in any of the releases, patch is under review in upstream master(http://review.gluster.org/14248). If anybody interested in trying it out can cherrypick the patch from review.gluster.org git clone http://review.gluster.org/glusterfs cd glusterfs git fetch http://review.gluster.org/glusterfs refs/changes/48/14248/5 git checkout FETCH_HEAD git checkout -b ./autogen.sh ./configure make make install Start the Eventing using, gluster-eventing start Other commands available are stop, restart, reload and status. gluster-eventing --help for more details. Now Gluster can send out notifications via Webhooks. Setup a web server listening to a POST request and register that URL to Gluster Eventing. Thats all. gluster-eventing webhook-add For example, if my webserver is running at http://192.168.122.188:9000/listen then register using, gluster-eventing webhook-add ``http://192.168.122.188:9000/listen`` We can also test if web server is accessible from all Gluster nodes using webhook-test subcommand. gluster-eventing webhook-test http://192.168.122.188:9000/listen With the initial patch only basic events are covered, I will add more events once this patch gets merged. Following events are available now. Volume Create Volume Delete Volume Start Volume Stop Peer Attach Peer Detach Created a small demo to show this eventing feature, it uses Web server which is included with the patch for Testing.(laptop hostname is sonne) /usr/share/glusterfs/scripts/eventsdash.py --port 8080 Login to Gluster node and start the eventing, gluster-eventing start gluster-eventing webhook-add http://sonne:8080/listen And then login to VM and run Gluster commands to probe/detach peer, volume create, start etc and Observe the realtime notifications for the same where eventsdash is running. Example, ssh root@fvm1 gluster peer attach fvm2 gluster volume create gv1 fvm1:/bricks/b1 fvm2:/bricks/b2 force gluster volume start gv1 gluster volume stop gv1 gluster volume delete gv1 gluster peer detach fvm2 Demo also includes a Web UI which refreshes its UI automatically when something changes in Cluster.(I am still fine tuning this UI, not yet available with the patch. But soon will be available as seperate repo in my github) FAQ: Will this feature available in 3.8 release? Sadly No. I couldn't get this merged before 3.8 feature freeze :( Is it possible to create a simple Gluster dashboard outside the cluster? It is possible, along with the events we also need REST APIs to get more information from cluster or to perform any action in cluster. (WIP REST APIs are available here) Is it possible to filter only alerts or critical notifications? Thanks Kotresh for the suggestion. Yes it is possible to add event_type and event_group information to the dict so that it can be filtered easily.(Not yet available now, but will add this feature once this patch gets merged in Master) Is documentation available to know more about eventing design and internals? Design spec available here (which discusses about Websockets, currently we don't have Websockets support). Usage documentation is available in the commit message of the patch(http://review.gluster.org/14248). Comments and Suggestions Welcome. [Less]

Recently I got a chance to consolidate the Demo videos which covers how GlusterFS can be used in Docker, kubernetes and Openshift. I have placed everything in single channel for better tracking. The demo videos are analogous to previously published blog entries in this space. Here is a brief description… Continue reading

Tiering is a powerful feature in Gluster. It divides the available storage into two parts: the hot tier populated by small fast storage devices like SSDs or a RAMDisk, and the cold tier populated by large slow devices like mechanical HDDs. By placing most recently accessed files in the hot , Gluster can quickly process […]

Now that we know how to create GlusterFS snapshots, it will be handy to know, how to delete them as well. Right now I have a cluster with two volumes at my disposal. As can be seen below, each volume has 1 brick.# gluster volume infoVolume Name: test_v...

In previous blog, I explained a method ( oci-systemd-hook) to run systemd gluster containers using oci-system-hook in a locked down mode. Today we will discuss about how to run gluster systemd containers without ‘privilege’ mode !! Awesome .. Isnt it ? I owe this blog to few people latest being… Continue reading

Important happenings for Gluster this month:  3.7.14 released 3.8.3 released CFP for Gluster Developer Summit open until August 31st gluster-users: [Gluster-users] release-3.6 end of life ... [More] http://www.gluster.org/pipermail/gluster-users/2016-August/028078.html – Joe requests a review of the 3.6 EOL proposal [Gluster-users] The out-of-order GlusterFS 3.8.3 release addresses a usability regression http://www.gluster.org/pipermail/gluster-users/2016-August/028155.html Niels de Vos announces 3.8.3 [Gluster-users] GlusterFS-3.7.14 released […] [Less]

In previous blog posts we discussed, how to use GlusterFS as a persistent storage in Kubernetes and Openshift. In nutshell, the GlusterFS can be deployed/used in a kubernetes/openshift environment as : *) Contenarized GlusterFS ( Pod ) *) GlusterFS as Openshift service and Endpoint (Service and Endpoint). *) GlusterFS volume… Continue reading