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multidocker

package
v0.4.0 Latest Latest
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 Go to latest Published: Oct 11, 2026 License: AGPL-3.0 Imports: 29 Imported by: 0

Documentation

Overview

Package multidocker runs apps on several Docker hosts (notes-multi-host-docker-issue-72.md, issue #72 PR 7).

It is a router in front of one single-host Docker adapter per host: every operation on an app runs the existing Docker adapter's code against the app's host. What it adds is placement (R-256), the forwarding agent each host runs so Pando's proxy can reach an app on another host without routing around itself (O-45, design 06 §4), and capacity summed over hosts.

Like every adapter it does not authorize, audit or touch Pando's state (R-027). Where an app runs is recorded on the hosts themselves: the app's network and volumes carry its bundle label, and the adapter reads them back.

Index

Constants

View Source 
const (
	EnvAgentCert        = "PANDO_AGENT_CERT"
	EnvAgentKey         = "PANDO_AGENT_KEY"
	EnvAgentAuthorities = "PANDO_AGENT_AUTHORITIES"
	EnvAgentPool        = "PANDO_AGENT_NETWORK_POOL"
	EnvAgentListen      = "PANDO_AGENT_LISTEN"
)

Environment the agent reads its certificate, key and the authorities from. Set on its container by this adapter; the agent's key is on its own host only, and it is a server key: it cannot open a connection through any agent.

View Source 
const Kind = "docker-hosts"

Kind is the adapter's kind string.

Variables

This section is empty.

Functions

func Info 

func Info() api.KindInfo

Info describes this kind of adapter for the forms that configure one (api.KindInfo, R-261).

Types

type Adapter 

type Adapter struct {
	// contains filtered or unexported fields
}

Adapter runs workloads on several Docker hosts.

func New 

func New() *Adapter

New builds an unconfigured adapter.

func (*Adapter) Apply 

func (a *Adapter) Apply(ctx context.Context, p api.BundlePlan) (api.BundleHandle, error)

Apply places the bundle if it has no host (placement.go), makes sure the host's agent is running, and applies the plan there with the single-host adapter's code. The handle names the host.

func (*Adapter) ApplyEdge 

func (a *Adapter) ApplyEdge(ctx context.Context, p api.EdgePlan) error

The edge runs on the control host beside Pando's replicas, as on one host.

func (*Adapter) Capabilities 

func (a *Adapter) Capabilities(ctx context.Context) (api.RuntimeCapabilities, error)

Capabilities are the control host's, with what several hosts change (R-254).

func (*Adapter) Capacity 

func (a *Adapter) Capacity(ctx context.Context) (api.Capacity, error)

Capacity sums the hosts open to new apps, with each host's figures in Details and the roomiest one's free space as LargestFit (R-243).

func (*Adapter) Category 

func (a *Adapter) Category() api.Category

func (*Adapter) Configure 

func (a *Adapter) Configure(_ context.Context, raw json.RawMessage) error

Configure reads the host list and the credentials, makes one Docker client per host and issues Pando's client certificate for the agents, in memory. Nothing is contacted: a host that is down at start is reported by HealthCheck and Observe, not by refusing to configure.

func (*Adapter) CreateVolume 

func (a *Adapter) CreateVolume(ctx context.Context, req api.VolumeRequest) (api.VolumeHandle, error)

CreateVolume makes storage on the bundle's host, placing the bundle first if it has none: the volume is then what keeps it there.

func (*Adapter) Destroy 

func (a *Adapter) Destroy(ctx context.Context, ref api.BundleRef, opts api.DestroyOptions) error

Destroy tears the bundle down on its host. With its volumes kept, the host stays the app's home (R-204): a re-created app returns to its data.

func (*Adapter) DestroyVolume 

func (a *Adapter) DestroyVolume(ctx context.Context, vh api.VolumeHandle) error

func (*Adapter) EdgeVolumes 

func (a *Adapter) EdgeVolumes(ctx context.Context) ([]api.VolumeHandle, error)

func (*Adapter) Edges 

func (a *Adapter) Edges(ctx context.Context) ([]string, error)

func (*Adapter) Exec 

func (a *Adapter) Exec(ctx context.Context, ref api.WorkloadRef, req api.ExecRequest) (api.ExecSession, error)

func (*Adapter) HealthCheck 

func (a *Adapter) HealthCheck(ctx context.Context) error

HealthCheck asks every host. The adapter is healthy while the control host and at least one host open to new apps answer, and every answering host runs the same platform; a host that does not answer makes its own apps unobservable (Observe), not every app undeployable.

func (*Adapter) ImportImage 

func (a *Adapter) ImportImage(context.Context, io.Reader) (string, error)

ImportImage is not offered (ImageDelivery is registry only).

func (*Adapter) InUse 

func (a *Adapter) InUse(ctx context.Context) (api.InUse, error)

InUse sums every host, at once: each takes about a second.

func (*Adapter) Kind 

func (a *Adapter) Kind() string

func (*Adapter) LargestFitFor 

func (a *Adapter) LargestFitFor(ctx context.Context, bundleID string) (*api.Fit, error)

LargestFitFor is the roomiest place this bundle may go, for the planner (R-242 per host). A bundle already on a host may go only there, and what it holds there counts as free. A new one may go to any host open to new apps that answers. Nil when its host does not answer: Observe reports that, and the planner checks the totals alone.

func (*Adapter) Logs 

func (a *Adapter) Logs(ctx context.Context, ref api.WorkloadRef, opts api.LogOptions) (io.ReadCloser, error)

func (*Adapter) Observe 

func (a *Adapter) Observe(ctx context.Context, ref api.BundleRef) (api.ObservedBundle, error)

Observe reports the bundle on its host. An app whose host does not answer is an error, which the reconciler records as unobservable — never as failed (R-151, design 05 §2) — and never as absent, which would have the reconciler create it again on another host (O-46).

func (*Adapter) ObserveEdge 

func (a *Adapter) ObserveEdge(ctx context.Context, name string) (api.EdgeState, error)

func (*Adapter) PullImage 

func (a *Adapter) PullImage(ctx context.Context, ref string) error

func (*Adapter) ReclaimNetworks 

func (a *Adapter) ReclaimNetworks(ctx context.Context, owns func(string) bool) (int, error)

ReclaimNetworks removes each host's app networks nothing is attached to.

func (*Adapter) RejoinNetworks 

func (a *Adapter) RejoinNetworks(ctx context.Context, owns func(string) bool) (int, error)

RejoinNetworks keeps each host's agent running and joined to that host's app networks, and refreshes the placement map. Called at start and every fifteen seconds on every replica (cmd/pando); Pando's own replicas join no app network on this runtime.

func (*Adapter) RemoveEdge 

func (a *Adapter) RemoveEdge(ctx context.Context, name string) error

func (*Adapter) RemoveHelpers 

func (a *Adapter) RemoveHelpers(ctx context.Context) error

func (*Adapter) RestoreVolume 

func (a *Adapter) RestoreVolume(ctx context.Context, vh api.VolumeHandle, src io.Reader) error

func (*Adapter) Self 

func (a *Adapter) Self(ctx context.Context) (api.SelfWorkload, error)

Self-upgrade replaces Pando's container on the control host, as on one host (R-359); core allows it only with a single replica.

func (*Adapter) SnapshotVolume 

func (a *Adapter) SnapshotVolume(ctx context.Context, vh api.VolumeHandle, dst io.Writer) error

func (*Adapter) StartHelper 

func (a *Adapter) StartHelper(ctx context.Context, spec api.HelperSpec) (string, error)

func (*Adapter) Stop 

func (a *Adapter) Stop(ctx context.Context, ref api.BundleRef) error

func (*Adapter) Trial 

func (a *Adapter) Trial(ctx context.Context, req api.TrialRequest) (api.TrialResult, error)

Trial runs on the control host [P]: it is thrown away, so it needs no placement.

func (*Adapter) Upstream 

func (a *Adapter) Upstream(ctx context.Context, ref api.WorkloadRef, port int) (api.Upstream, error)

Upstream is the workload's container name on its host, as one host's adapter answers, and a Dial through that host's agent (O-45). The proxy decides the request before it calls Dial; the agent only carries it.

Answered from the placement map, which is in memory: this runs on every proxied request.

func (*Adapter) Usage 

func (a *Adapter) Usage(ctx context.Context, ref api.BundleRef) (api.BundleUsage, error)

func (*Adapter) WatchBundles 

func (a *Adapter) WatchBundles(ctx context.Context, sink func(api.BundleEvent)) error

WatchBundles follows every host's event stream at once, one stream per host (O-52), and reports what happened without acting on it (R-148).

A host whose stream drops is reconnected here, with backoff, while every other host's stream carries on: one host restarting its daemon must not make the reconciler look at every app on every host. When a host's stream opens again after a gap, BundleEventMissed says that something on it may have been missed. BundleEventWatching is sent once every host's first attempt has opened or failed — a host that is down at the start is caught up with BundleEventMissed when it comes back. It returns only when ctx ends.

type Config 

type Config struct {
	// Hosts are the Docker hosts, in order. Exactly one is the control host:
	// the one Pando's replicas, the edge, BuildKit and the registry run on
	// (O-47). A JSON list, or a string holding one, which is how a form's
	// text area sends it.
	Hosts json.RawMessage `json:"hosts"`

	// NetworkPool, NetworkBlockBits and OCIRuntime are the single-host Docker
	// adapter's settings of the same names, applied on every host. Each host
	// carves its own app networks from the same range: a bridge network
	// exists on one host only.
	NetworkPool      string `json:"network_pool,omitempty"`
	NetworkBlockBits int    `json:"network_block_bits,omitempty"`
	OCIRuntime       string `json:"oci_runtime,omitempty"`

	// AgentImage is the image each host's forwarding agent and each
	// restricted app's egress gateway run: an image of Pando that every host
	// can pull. Empty is the image Pando's own container on the control host
	// was started from.
	AgentImage string `json:"agent_image,omitempty"`

	// AgentPort is the host port each agent publishes. Zero is 7443.
	AgentPort int `json:"agent_port,omitempty"`

	// Credentials arrive from the encrypted adapter_credentials store and
	// are held in memory only (R-190).
	Credentials Credentials `json:"credentials"`
}

Config is the adapter's configuration.

type Credentials 

type Credentials struct {
	// AgentAuthority is the agents' certificate authority as PEM, each
	// certificate followed by its key, the one that issues first. Generated
	// by `pando host-agent new-authority`. Pando issues its own client
	// certificate and each agent's server certificate from it.
	AgentAuthority string `json:"agent_authority"`

	// DockerTLS is the client certificate, its key and the CA that signed the
	// daemons' certificates, as PEM, for hosts reached over tcp://.
	DockerTLS string `json:"docker_tls,omitempty"`

	// SSHKey is the private key for hosts reached over ssh://.
	SSHKey string `json:"ssh_key,omitempty"`
}

Credentials are the adapter's secrets.

type HostConfig 

type HostConfig struct {
	// Name is how the host is known in placement, the console, errors and
	// the agent's certificate: lower-case letters, digits and dashes.
	Name string `json:"name"`

	// Endpoint is the Docker API: unix:///var/run/docker.sock (the control
	// host, usually), tcp://host:2376 with docker_tls, or ssh://user@host
	// with ssh_key. Empty is the environment, as the single-host adapter.
	Endpoint string `json:"endpoint,omitempty"`

	// SSHHostKey is the host's SSH public key, as in known_hosts or
	// authorized_keys, for an ssh:// endpoint. Required: an unverified SSH
	// host key would hand the root-equivalent Docker credential to whoever
	// answers.
	SSHHostKey string `json:"ssh_host_key,omitempty"`

	// AgentAddress is where Pando's proxy reaches this host's agent, as
	// host:port. Empty is the endpoint's host and the agent port.
	AgentAddress string `json:"agent_address,omitempty"`

	// Control marks the control host.
	Control bool `json:"control,omitempty"`

	// NoPlacement keeps new apps off the host; apps already on it stay
	// (R-256). It is how a host is emptied before it is removed.
	NoPlacement bool `json:"no_placement,omitempty"`

	// TotalCPUMillis and TotalMemoryBytes tell Pando how much of the host it
	// may use, as on one host. Empty asks the daemon.
	TotalCPUMillis   int   `json:"total_cpu_millis,omitempty"`
	TotalMemoryBytes int64 `json:"total_memory_bytes,omitempty"`
	TotalDiskBytes   int64 `json:"total_disk_bytes,omitempty"`
}

HostConfig is one Docker host.

Source Files

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