Docker can be used to simplify the deployment and management of Alluxio servers. Using the alluxio/{{site.ALLUXIO_DOCKER_IMAGE}} Docker image available on Dockerhub, you can go from zero to a running Alluxio cluster with a couple of docker run commands. This document provides a tutorial for running Dockerized Alluxio on a single node with local disk as the under storage. We'll also discuss more advanced topics and how to troubleshoot.
Prerequisites
A machine with Docker installed.
Ports 19998, 19999, 29998, 29999, and 30000 available
If you don't have access to a machine with Docker installed, you can provision a small AWS EC2 instance (e.g. t2.small) to follow along with the tutorial. When provisioning the instance, set the security group so that the following ports are open to your IP address and the CIDR range of the Alluxio clients (e.g. remote Spark clusters):
19998 for the CIDR range of your Alluxio servers and clients: Allow the clients and workers to communicate with Alluxio Master RPC processes.
19999 for the IP address of your browser: Allow you to access the Alluxio master web UI.
29999 for the CIDR range of your Alluxio and clients: Allow the clients to communicate with Alluxio Worker RPC processes.
30000 for the IP address of your browser: Allow you to access the Alluxio worker web UI.
To set up Docker after provisioning the instance, which will be referred to as the Docker Host, run
$ sudo yum install -y docker# Create docker group$ sudo groupadd docker# Add the current user to the docker group$ sudo usermod -a -G docker $(id-u-n)# Start docker service$ sudo service docker start# Log out and log back in again to pick up the group changes$ exit
Prepare Docker Volume to Persist Data
By default, all files created inside a container are stored on a writable container layer. The data doesn’t persist when that container no longer exists. Docker volumes are the preferred way to save data outside the containers. The following two types of Docker volumes are used the most:
Host Volume: You manage where in the Docker host's file system to store and share the containers' data. To create a host volume, include the following when launching your containers:
$ docker run -v /path/on/host:/path/in/container ...
The file or directory is referenced by its full path on the Docker host. It can exist on the Docker host already, or it will be created automatically if it does not yet exist.
Named Volume: Docker manage where they are located. It should be referred to by specific names. To create a named volume, first run:
$ docker volume create volumeName
Then include the following when launching your containers:
$ docker run -v volumeName:/path/in/container ...
Either host volume or named volume can be used for Alluxio containers. For purpose of test, the host volume is recommended, since it is the easiest type of volume to use and very performant. More importantly, you know where to refer to the data in the host file system, and you can manipulate the files directly and easily outside the containers.
For example, we will use the host volume and mount the host directory /tmp/alluxio_ufs to the container location /opt/alluxio/underFSStorage, which is the default setting for the Alluxio UFS root mount point in the Alluxio docker image:
$ mkdir -p /tmp/alluxio_ufs$ docker run -v /tmp/alluxio_ufs:/opt/alluxio/underFSStorage ...
Of course, you can choose to mount a different path instead of /tmp/alluxio_ufs. From version 2.1 on, Alluxio Docker image runs as user alluxio by default. It has UID 1000 and GID 1000. Please make sure the host volume is writable by the user the Docker image is run as.
Launch Alluxio Containers for Master and Worker
The Alluxio clients (local or remote) need to communicate with both Alluxio master and workers. Therefore, it is important to make sure clients can reach both of the following services:
Master RPC on port 19998
Worker RPC on port 29999
Within the Alluxio cluster, please also make sure the master and worker containers can reach each other on the ports defined in General requirements.
We are going to launch Alluxio master and worker containers on the same Docker host machine. In order to make sure this works for either local or remote clients, we have to set up the Docker network and expose the required ports correctly.
There are two ways to launch Alluxio Docker containers on the Docker host:
Host network shares ip-address and networking namespace between the container and the Docker host. User-defined bridge network allows containers connected to communicate, while providing isolation from containers not connected to that bridge network. It is recommended to use host network, option 1, for testing.
The argument --net=host tells Docker to use the host network. Under this setup, the containers are directly using the host's network adapter. All containers will have the same hostname and IP address as the Docker host, and all the host's ports are directly mapped to containers. Therefore, all the required container ports 19999, 19998, 29999, 30000 are available for the clients via the Docker host. You can find more details about this setting here.
The argument -e ALLUXIO_JAVA_OPTS="-Dalluxio.worker.ramdisk.size=1G -Dalluxio.master.hostname=localhost" allocates the worker's memory capacity and binds the master address. When using the host network driver, the master can't be referenced to by the master container name alluxio-master or it will throw "No Alluxio worker available" error. Instead, it should be referenced to by the host IP address. The substitution localhost uses the docker host's name instead.
The argument --shm-size=1G will allocate a 1G tmpfs for the worker to store Alluxio data.
The argument -v /tmp/alluxio_ufs:/opt/alluxio/underFSStorage tells Docker to use the host volume and persist the Alluxio UFS root data in the host directory /tmp/alluxio_ufs, as explained above in the Docker volume section.
Using User-Defined Network
Using host network is simple, but it has disadvantages. For example
The Services running inside the container could potentially conflict with other services in other containers which run on the same port.
Containers can access to the host's full network stack and bring up potential security risks.
The better way is using the user-defined network, but we need to explicitly expose the required ports so that the external clients can reach out the containers' services:
The argument --net=alluxio_network tells Docker to use the user-defined bridge network alluxio_network. All containers will use their own container IDs as their hostname, and each of them has a different IP address within the network's subnet. Containers connected to the same user-defined bridge network effectively expose all ports to each other, unless firewall policies are defined. You can find more details about the bridge network driver here.
Only the specified ports (-p option) are exposed to the outside network, where the client may be run. The command -p <host-port>:<container-port> maps the container port to a host port. Therefore, you must explicitly expose the two ports 19999 and 19998 for the master container and the port 29999 and 30000 for the worker container. Otherwise, the clients can't communicate with the master and worker.
You can refer to the master either by the container name (alluxio-master for master container and alluxio-worker for worker container) or by the Docker host's IP address $(hostname -i), if all the communication is within the docker network (e.g., no external client outside the docker network). Otherwise, you must specify the master and worker's docker host IP that client can reach out (e.g., by -Dalluxio.worker.hostname=$(hostname -i)). This is required for the external communication between master/worker and clients outside the docker network. Otherwise, clients can't connect to worker, since they do not recognize the worker's container Id. It will throw error like below:
Target: 5a1a840d2a98:29999, Error: alluxio.exception.status.UnavailableException: Unable to resolve host 5a1a840d2a98
Verify the Cluster
To verify that the services came up, check docker ps. You should see something like
$ docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES1fef7c714d25 alluxio/{{site.ALLUXIO_DOCKER_IMAGE}} "/entrypoint.sh work…" 39 seconds ago Up 38 seconds alluxio-worker27f92f702ac2 alluxio/{{site.ALLUXIO_DOCKER_IMAGE}} "/entrypoint.sh mast…" 44 seconds ago Up 43 seconds 0.0.0.0:19999->19999/tcp alluxio-master
If you don't see the containers, run docker logs on their container ids to see what happened. The container ids were printed by the docker run command, and can also be found in docker ps -a.
Visit instance-hostname:19999 to view the Alluxio web UI. You should see one worker connected and providing 1024MB of space.
To run tests, enter the worker container
$ docker exec -it alluxio-worker /bin/bash
Run the tests
$ cd /opt/alluxio$ ./bin/alluxio runTests
To test the remote client access, for example, from the Spark cluster (python 3)
textFile_alluxio_path ="alluxio://{docker_host-ip}:19998/path_to_the_file"textFile_RDD = sc.textFile (textFile_alluxio_path)for line in textFile_RDD.collect(): print (line)
Congratulations, you've deployed a basic Dockerized Alluxio cluster! Read on to learn more about how to manage the cluster and make is production-ready.
Advanced Setup
Launch Alluxio with Java 11
Starting from v2.9.0, Alluxio processes can be launched with Java 11 inside Docker containers by pulling the alluxio/alluxio-jdk11 image from Dockerhub.
To use java 11 image, replace alluxio/alluxio with alluxio/alluxio-jdk11 in the command launching Alluxio Docker container.
Launch Alluxio with the development image
Starting from v2.6.2, a new docker image, alluxio-dev, is available in Dockerhub for development usage. Unlike the default alluxio/alluxio image that only contains packages needed for Alluxio service to run, this alluxio-dev image installs more development tools, including gcc, make, async-profiler, etc., making it easier for users to deploy more services in the container along with Alluxio.
To use the development image, simply replace alluxio/alluxio with alluxio/alluxio-dev in the container launching process.
Set server configuration
Configuration changes require stopping the Alluxio Docker images, then re-launching them with the new configuration.
To set an Alluxio configuration property, add it to the Alluxio java options environment variable with
If a property value contains spaces, you must escape it using single quotes.
-e ALLUXIO_JAVA_OPTS="-Dalluxio.property1=value1 -Dalluxio.property2='value2 with spaces'"
Alluxio environment variables will be copied to conf/alluxio-env.sh when the image starts. If you are not seeing a property take effect, make sure the property in conf/alluxio-env.sh within the container is spelled correctly. You can check the contents with
A lone Alluxio master is a single point of failure. To guard against this, a production cluster should run multiple Alluxio masters in High Availability mode.
There are two ways to enable HA mode in Alluxio, either with internal leader election and embedded journal, or external Zookeeper and a shared journal storage. Please read running Alluxio with HA for more details. It is recommended to use the second option for production use case.
Internal Leader Election
Alluxio uses internal leader election by default.
Provide the master embedded journal addresses and set the hostname of the current master:
You can find more on ZooKeeper and shared journal configuration here.
Relaunch Alluxio Servers
When relaunching Alluxio master docker containers, use the --no-format flag to avoid re-formatting the journal. The journal should only be formatted the first time the image is run. Formatting the journal deletes all Alluxio metadata, and starts the cluster in a fresh state. You can find more details about the Alluxio journal here.
The same applies to Alluxio worker docker containers, use the --no-format flag to avoid re-formatting the worker storage. Formatting the worker storage deletes all the cached blocks. You can find more details about the worker storage here.
Enable POSIX API access
Alluxio POSIX access is implemented via FUSE. There are two options to enable POSIX accesses to Alluxio in a docker environment. [POSIX API docs]({{ '/en/api/POSIX-API.html' | relative_url }}#fuse-on-worker-process) provides more details about how to configure Alluxio POSIX API.
Option1: Run a standalone Alluxio FUSE container, or
Option2: Enable FUSE support when running a worker container.
First make sure a directory with the right permissions exists on the host to bind-mount in the Alluxio FUSE container:
For example, the following commands run the alluxio-fuse container as a long-running client that presents Alluxio file system through a POSIX interface on the Docker host:
Run the Alluxio FUSE service to create a FUSE mount in the host bind-mounted directory:
-v /tmp/mnt:/mnt:rshared binds path /mnt/alluxio-fuse the default directory to Alluxio through fuse inside the container, to a mount accessible at /tmp/mnt/alluxio-fuse on host. To change this path to /foo/bar/alluxio-fuse on host file system, replace /tmp/mnt with /foo/bar.
--cap-add SYS_ADMIN launches the container with SYS_ADMIN capability.
--device /dev/fuse shares host device /dev/fuse with the container.
FUSE on worker
When running a worker container, specifying FUSE enabled:
-v /tmp/mnt:/mnt:rshared binds path /mnt/alluxio-fuse the default directory to Alluxio through fuse inside the container, to a mount accessible at /tmp/mnt/alluxio-fuse on host. To change this path to /foo/bar/alluxio-fuse on host file system, replace /tmp/mnt with /foo/bar.
--cap-add SYS_ADMIN launches the container with SYS_ADMIN capability.
--device /dev/fuse shares host device /dev/fuse with the container.
Property alluxio.worker.fuse.enabled=true enables FUSE support on this worker. The default fuse mount point is /mnt/alluxio-fuse in the worker container which will be created at runtime if not exist. See Fuse on worker process for more details about how to modify the mount configuration.
Once this container is launched successfully, one can access Alluxio via host path /tmp/mnt/alluxio-fuse. This is because local path /mnt in worker container is mapped to host path /tmp/mnt, and mount point of Alluxio service is /mnt/alluxio-fuse, mapped to host path /tmp/mnt/alluxio-fuse.
See Properties List for more configuration options for Alluxio proxy server.
Performance Optimization
Enable short-circuit reads and writes
If your application pods will run on the same host as your Alluxio worker pods, performance can be greatly improved by enabling short-circuit reads and writes. This allows applications to read from and write to their local Alluxio worker without going over the loopback network. In dockerized environments, there are two ways to enable short-circuit reads and writes in Alluxio.
Using shared volumes is slightly easier and may yield higher performance, but may result in inaccurate resource accounting. Using domain sockets is recommended for production deployment.
Domain socket
On worker host machines, create a directory for the shared domain socket.
$ mkdir /tmp/domain$ chmod a+w /tmp/domain
When starting both workers and clients, run their docker containers with -v /tmp/domain:/opt/domain to share the domain socket directory. Also set domain socket properties by passing alluxio.worker.data.server.domain.socket.address=/opt/domain and alluxio.worker.data.server.domain.socket.as.uuid=true when launching worker containers.
When starting both workers and clients, run their docker containers with the worker storage as shared volumes across host, worker and client pods. With default Alluxio setting on docker, MEM is the main storage on host path /dev/shm. In this case, pass -v /dev/shm:/dev/shm when running both containers so both worker and clients can access this path directly.
To run application containers, also pass alluxio.user.hostname=<host ip>.
Troubleshooting
If the Alluxio servers are not able to be launched, remove the -d when running the docker run command so that the processes can be launched in the foreground and the console output can provide some helpful information.
If the Alluxio servers are launched, their logs can be accessed by running docker logs $container_id. Usually the logs will give a good indication of what is wrong. If they are not enough to diagnose your issue, you can get help on the user mailing list or github issues.
Logging can also have a performance impact if sufficiently verbose. You can disable or redirect logging to mitigate this problem.
FAQ
AvailableProcessors: returns 0 in docker container
When you execute alluxio ls in the alluxio master container and got the following error.