open-nomad/client/allocrunner/state/state.go

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package state
import (
"time"
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"github.com/hashicorp/nomad/nomad/structs"
)
// State captures the state of the allocation runner.
type State struct {
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// ClientStatus captures the overall state of the allocation
ClientStatus string
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// ClientDescription is an optional human readable description of the
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// allocations client state
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ClientDescription string
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// DeploymentStatus captures the status of the deployment
DeploymentStatus *structs.AllocDeploymentStatus
client: expose task state to client The interesting decision in this commit was to expose AR's state and not a fully materialized Allocation struct. AR.clientAlloc builds an Alloc that contains the task state, so I considered simply memoizing and exposing that method. However, that would lead to AR having two awkwardly similar methods: - Alloc() - which returns the server-sent alloc - ClientAlloc() - which returns the fully materialized client alloc Since ClientAlloc() could be memoized it would be just as cheap to call as Alloc(), so why not replace Alloc() entirely? Replacing Alloc() entirely would require Update() to immediately materialize the task states on server-sent Allocs as there may have been local task state changes since the server received an Alloc update. This quickly becomes difficult to reason about: should Update hooks use the TaskStates? Are state changes caused by TR Update hooks immediately reflected in the Alloc? Should AR persist its copy of the Alloc? If so, are its TaskStates canonical or the TaskStates on TR? So! Forget that. Let's separate the static Allocation from the dynamic AR & TR state! - AR.Alloc() is for static Allocation access (often for the Job) - AR.AllocState() is for the dynamic AR & TR runtime state (deployment status, task states, etc). If code needs to know the status of a task: AllocState() If code needs to know the names of tasks: Alloc() It should be very easy for a developer to reason about which method they should call and what they can do with the return values.
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// TaskStates is a snapshot of task states.
TaskStates map[string]*structs.TaskState
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}
// SetDeploymentStatus is a helper for updating the client-controlled
// DeploymentStatus fields: Healthy and Timestamp. The Canary and ModifyIndex
// fields should only be updated by the server.
func (s *State) SetDeploymentStatus(timestamp time.Time, healthy bool) {
if s.DeploymentStatus == nil {
s.DeploymentStatus = &structs.AllocDeploymentStatus{}
}
s.DeploymentStatus.Healthy = &healthy
s.DeploymentStatus.Timestamp = timestamp
}
// ClearDeploymentStatus is a helper to clear the client-controlled
// DeploymentStatus fields: Healthy and Timestamp. The Canary and ModifyIndex
// fields should only be updated by the server.
func (s *State) ClearDeploymentStatus() {
if s.DeploymentStatus == nil {
return
}
s.DeploymentStatus.Healthy = nil
s.DeploymentStatus.Timestamp = time.Time{}
}
client: expose task state to client The interesting decision in this commit was to expose AR's state and not a fully materialized Allocation struct. AR.clientAlloc builds an Alloc that contains the task state, so I considered simply memoizing and exposing that method. However, that would lead to AR having two awkwardly similar methods: - Alloc() - which returns the server-sent alloc - ClientAlloc() - which returns the fully materialized client alloc Since ClientAlloc() could be memoized it would be just as cheap to call as Alloc(), so why not replace Alloc() entirely? Replacing Alloc() entirely would require Update() to immediately materialize the task states on server-sent Allocs as there may have been local task state changes since the server received an Alloc update. This quickly becomes difficult to reason about: should Update hooks use the TaskStates? Are state changes caused by TR Update hooks immediately reflected in the Alloc? Should AR persist its copy of the Alloc? If so, are its TaskStates canonical or the TaskStates on TR? So! Forget that. Let's separate the static Allocation from the dynamic AR & TR state! - AR.Alloc() is for static Allocation access (often for the Job) - AR.AllocState() is for the dynamic AR & TR runtime state (deployment status, task states, etc). If code needs to know the status of a task: AllocState() If code needs to know the names of tasks: Alloc() It should be very easy for a developer to reason about which method they should call and what they can do with the return values.
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// Copy returns a deep copy of State.
func (s *State) Copy() *State {
taskStates := make(map[string]*structs.TaskState, len(s.TaskStates))
for k, v := range s.TaskStates {
taskStates[k] = v.Copy()
}
return &State{
ClientStatus: s.ClientStatus,
ClientDescription: s.ClientDescription,
DeploymentStatus: s.DeploymentStatus.Copy(),
TaskStates: taskStates,
}
}