The goal of albatross is robust deployment of MirageOS
unikernels using Solo5. Resources managed
by albatross are network interfaces of kind
tap, which are connected to
already existing bridges, block devices, memory, and CPU. Each unikernel is
taskset) to a specific core.
Albatross allows remote management. To deploy or destroy a unikernel, no shell
access is necessary. The remote channel is a mutually authenticated (with X.509
certificates) TLS connection. Console output of the unikernels is stored in
memory in a ring buffer, and accessible remotely. Monitoring data (CPU and
memory usage) of the unikernels can be collected as well, and pushed into an
Influx time series database.
Albatross consists of multiple processes, each running with the least
privileges. Albatross can be run next to other orchestration systems; it does
not assume to be the single instance on a dom0 which creates and destroys
virtual machines. Resource policies can be dynamically configured for each
administrative domain (similar to DNS, a hierarchical naming scheme), and are
checked statically (to decrease while going down the tree)
and dynamically when a new unikernel is to be deployed.
When a unikernel is deployed, albatross tries its best to keep it
running, even when the physical hardware reboots, or albatross is restarted.
When the unikernel exits, depending on configuration and its exit code, it is
re-started. The current set of running unikernels is persisted on disk, though
there is no dependency or order for restarting them.
The scope of albatross is to provide a minimal orchestration system that avoids
the need for shell access on the dom0. This leads to mostly immutable - or only
mutable via albatross - infrastructure. Further dissemination of albatross into
virtual machines, and a communication interface for deploying and destroying
unikernels, is being researched on.
Albatross consists of a set of binaries. Several daemons, which communicate in a
request-response style over Unix domain sockets, are run in the host system:
albatrossd: privileged to create and destroy unikernels
albatross-console: reads the console output of unikernels
albatross-stats: statistics gathering (rusage, ifstat, BHyve debug counters)
albatross-tls-inetd: remote deployment via TLS and inetd (an alternative is
albatross-influx: statistic reporting from
The main daemon is the privileged
albatrossd, which supervises unikernels. It opens
a listening Unix domain socket, reads the persisted unikernel configuration,
starts these unikernels, and awaits commands. Access can be regulated by Unix
file permissions -- only those users who can write to that socket can send
Albatross-console does not keep any persistent state, but a ring buffer of console
output from each unikernel. These messages can be retrieved by a client as a
stream of messages (history, and whenever a new line is output, it is sent to
the interested client). Each unikernel output can only be read by a single
client, to avoid amplification of traffic if lots of clients are connected.
Albatrossd sends a message to
albatross-console whenever a new unikernel is started,
albatross-console opens and reads the fifo which the unikernel will
write their standard output to.
Albatross-stats periodically gathers statistics (memory, CPU, network, hypervisor)
from all running unikernels.
Albatross-tls-inetd is executed via inetd (socket activation) and proxies
requests from remote clients to the respective daemons described above. It
enforces client authentication, and uses the common names of the client
certificate chain as the administrative domain. The policies are embedded in CA
certificates, and the command is embedded in the leaf certificate. The
albatross-tls-endpoint is an alternative which listens on a TCP port and
executes an asynchronous task for each incoming request.
The following command-line applications for local and remote management are provided:
albatross-client-local: sends a command locally to the Unix domain sockets
albatross-client-remote-tls: connects to a remote TLS endpoint and sends a command
albatross-provision-request: creates a certificate signing request containing a command
albatross-provision-ca: certificate authority operations: sign, generate, and revoke (NYI)
albatross-client-bistro: command line utility to execute a command remotely: request, sign, remote (do not use in production, requires CA key locally)
To install Albatross, run
opam install albatross.
Init scripts for FreeBSD are provided in the
subdirectory, and a script to create a FreeBSD package
For Linux, systemd service scripts are available in
NetworkManager-wait-online.service from the
Wants= directive in albatross.service if you don't need it.
It may help to read the outdated blog article
for the motivation behind albatross and an overview of its functionality.
os = "linux"