Joyent's implementation of the Docker Remote API has some added features as well as omissions where the API conflicted with the needs of deploying containers across Triton data centers.
In containers you may see a
zsched process in addition to your other
processes. It owns the kernel threads that do work on behalf of your zone.
The PID of this process should always show up as 0, though some versions of
ps on Linux filter this out.
If you don't have
docker:noipmgmtd set in your internal_metadata, you will
have an additional process
ipmgmtd. This is the SmartOS daemon that manages
network interfaces and TCP/IP tunables. The default if you use sdc-docker is
that docker:noipmgmtd will be true when you're provisioning a regular LX docker
container, and false if you're provisioning a SmartOS container.
This is the log from the dockerinit process which sets up the container for your initial process and then exec()s it. This log exists only for debugging problems with the way the initial process has been setup.
If you run
df you will see several filesystems mounted in from
/native. These are bits from the SmartOS host mounted in to support the LX
This is the SmartOS kernel object filesystem. The contents of the filesystem are dynamic and reflect the current state of the system. See:
for more information.
This is the SmartOS contract file system which is the interface to the SmartOS contract subsystem.
for more information.
When a container exits the exit status as returned by sdc-docker will currently be different from that which would be returned by Docker Inc's docker. This is due to differences in the way we handle processes within zones. This is currently considered to be a deficiency and should be improved by DOCKER-41.
Actions performed against sdc-docker are slower, and sometimes much slower than those same actions performed against a local docker. This is something we are working on, and intend to keep improving over time.
In most cases Joyent has taken great efforts to be bug for bug compatible with Docker Inc's API implementation (see restart policies). Please see documentation for specific methods for any known divergence and file bugs as needed.
SDC Docker implements all the API methods necessary to build and deploy Docker containers in the cloud, though there are some missing docker API methods. Here's the list of API methods currently unimplemented as of this writing, but expect it to get shorter by the day:
docker networkis on our near-term roadmap, follow DOCKER-722, DOCKER-723, DOCKER-724, DOCKER-725 for updates.
docker eventswill not be implemented in the near future. This causes a trivial error when attempting to watch logs with
docker-compose. Users who intend to use
docker eventsfor container orchestration purposes should look at ContainerPilot’s automatic service registration, health checking, and configuration.
- There is no plan to implement
docker swarmas Triton is already working as a horizontally scalable cluster. There is no need for a set of compute node orchestration commands.
SDC Docker supports the integration with Docker Hub and third party registries through Docker's Registry v2 API (the deprecated v1 API is not supported).
In addition to the divergence in the use of these drivers, SDC Docker handles logging differently than Docker. With Docker, logs are only written to the host when the log driver is set to 'json-file'. With SDC Docker the logs are written to the host for every log driver except 'none'. These logs are captured because while the network-based log drivers are good for real-time log analysis, they can potentially lose messages due to conditions like remote host unavailablity and race conditions in startup/shutdown. The host logs are written to local storage by the zoneadmd process that manages the zone and therefore avoids these problems.
The storage for these log files will be within a container's quota but not visible from within the container itself. Operators will see these logs at /zones/:uuid/logs/stdio.log*. These will be rotated to another file in the same directory with a timestamp extension when they reach a max-size value. The max-size can be specified when using the json-file log driver. Otherwise the default (currently defaults to 50M) is set in the SDC configuration. This can be adjusted by an operator through the DEFAULT_MAX_LOG_SIZE property in the docker service's SAPI metadata.
For the user of SDC Docker, this additional log when using a log driver other than json-file is not of much use yet, but are important to know about as they do use space from the user's container. In the future, these logs will be automatically consumed and uploaded to Manta which will free this space and give users access to all their logs.
For the operator of SDC Docker these additional logs will require some cleanup process for long-lived containers when Manta support is not available.
Triton uses (and reserves) a number of custom container labels, to provide specific Triton features. These are:
triton.* namespace is reserved for Triton specific use cases, these label
names are currently defined:
triton.cns.disable(boolean): Can be set on a container to tell the CNS service to not serve records for this instance.
triton.cns.services(string): Comma-separated list of DNS-name strings for the CNS service.
triton.cns.reverse_ptr(string): DNS reverse pointer for this container. Used by the CNS service.
triton.network.public(string): Set on a container, used to specify the external network name the instance will use.
com.joyent.* namespace is reserved for Joyent/Triton specific use cases,
these label names are currently defined:
com.joyent.package(string): Set on a container, used to choose a specific package for the container. The value can be a package name like
g4-standard-1G, a UUID, or the first 8 characters of a UUID (short-UUID).
SDC Docker supports certain versions of Docker CLI and Compose clients. Check the supported versions and the individual command references to see which command options can be used with SDC Docker.