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core_sched.go
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core_sched.go
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package nomad
import (
"fmt"
"math"
"time"
memdb "github.com/hashicorp/go-memdb"
"github.com/hashicorp/nomad/nomad/state"
"github.com/hashicorp/nomad/nomad/structs"
"github.com/hashicorp/nomad/scheduler"
)
var (
// maxIdsPerReap is the maximum number of evals and allocations to reap in a
// single Raft transaction. This is to ensure that the Raft message does not
// become too large.
maxIdsPerReap = (1024 * 256) / 36 // 0.25 MB of ids.
)
// CoreScheduler is a special "scheduler" that is registered
// as "_core". It is used to run various administrative work
// across the cluster.
type CoreScheduler struct {
srv *Server
snap *state.StateSnapshot
}
// NewCoreScheduler is used to return a new system scheduler instance
func NewCoreScheduler(srv *Server, snap *state.StateSnapshot) scheduler.Scheduler {
s := &CoreScheduler{
srv: srv,
snap: snap,
}
return s
}
// Process is used to implement the scheduler.Scheduler interface
func (c *CoreScheduler) Process(eval *structs.Evaluation) error {
switch eval.JobID {
case structs.CoreJobEvalGC:
return c.evalGC(eval)
case structs.CoreJobNodeGC:
return c.nodeGC(eval)
case structs.CoreJobJobGC:
return c.jobGC(eval)
case structs.CoreJobDeploymentGC:
return c.deploymentGC(eval)
case structs.CoreJobForceGC:
return c.forceGC(eval)
default:
return fmt.Errorf("core scheduler cannot handle job '%s'", eval.JobID)
}
}
// forceGC is used to garbage collect all eligible objects.
func (c *CoreScheduler) forceGC(eval *structs.Evaluation) error {
if err := c.jobGC(eval); err != nil {
return err
}
if err := c.evalGC(eval); err != nil {
return err
}
if err := c.deploymentGC(eval); err != nil {
return err
}
// Node GC must occur after the others to ensure the allocations are
// cleared.
return c.nodeGC(eval)
}
// jobGC is used to garbage collect eligible jobs.
func (c *CoreScheduler) jobGC(eval *structs.Evaluation) error {
// Get all the jobs eligible for garbage collection.
ws := memdb.NewWatchSet()
iter, err := c.snap.JobsByGC(ws, true)
if err != nil {
return err
}
var oldThreshold uint64
if eval.JobID == structs.CoreJobForceGC {
// The GC was forced, so set the threshold to its maximum so everything
// will GC.
oldThreshold = math.MaxUint64
c.srv.logger.Println("[DEBUG] sched.core: forced job GC")
} else {
// Get the time table to calculate GC cutoffs.
tt := c.srv.fsm.TimeTable()
cutoff := time.Now().UTC().Add(-1 * c.srv.config.JobGCThreshold)
oldThreshold = tt.NearestIndex(cutoff)
c.srv.logger.Printf("[DEBUG] sched.core: job GC: scanning before index %d (%v)",
oldThreshold, c.srv.config.JobGCThreshold)
}
// Collect the allocations, evaluations and jobs to GC
var gcAlloc, gcEval []string
var gcJob []*structs.Job
OUTER:
for i := iter.Next(); i != nil; i = iter.Next() {
job := i.(*structs.Job)
// Ignore new jobs.
if job.CreateIndex > oldThreshold {
continue
}
ws := memdb.NewWatchSet()
evals, err := c.snap.EvalsByJob(ws, job.Namespace, job.ID)
if err != nil {
c.srv.logger.Printf("[ERR] sched.core: failed to get evals for job %s: %v", job.ID, err)
continue
}
allEvalsGC := true
var jobAlloc, jobEval []string
for _, eval := range evals {
gc, allocs, err := c.gcEval(eval, oldThreshold, true)
if err != nil {
continue OUTER
}
if gc {
jobEval = append(jobEval, eval.ID)
jobAlloc = append(jobAlloc, allocs...)
} else {
allEvalsGC = false
break
}
}
// Job is eligible for garbage collection
if allEvalsGC {
gcJob = append(gcJob, job)
gcAlloc = append(gcAlloc, jobAlloc...)
gcEval = append(gcEval, jobEval...)
}
}
// Fast-path the nothing case
if len(gcEval) == 0 && len(gcAlloc) == 0 && len(gcJob) == 0 {
return nil
}
c.srv.logger.Printf("[DEBUG] sched.core: job GC: %d jobs, %d evaluations, %d allocs eligible",
len(gcJob), len(gcEval), len(gcAlloc))
// Reap the evals and allocs
if err := c.evalReap(gcEval, gcAlloc); err != nil {
return err
}
// Call to the leader to deregister the jobs.
for _, job := range gcJob {
req := structs.JobDeregisterRequest{
JobID: job.ID,
Purge: true,
WriteRequest: structs.WriteRequest{
Region: c.srv.config.Region,
Namespace: job.Namespace,
},
}
var resp structs.JobDeregisterResponse
if err := c.srv.RPC("Job.Deregister", &req, &resp); err != nil {
c.srv.logger.Printf("[ERR] sched.core: job deregister failed: %v", err)
return err
}
}
return nil
}
// evalGC is used to garbage collect old evaluations
func (c *CoreScheduler) evalGC(eval *structs.Evaluation) error {
// Iterate over the evaluations
ws := memdb.NewWatchSet()
iter, err := c.snap.Evals(ws)
if err != nil {
return err
}
var oldThreshold uint64
if eval.JobID == structs.CoreJobForceGC {
// The GC was forced, so set the threshold to its maximum so everything
// will GC.
oldThreshold = math.MaxUint64
c.srv.logger.Println("[DEBUG] sched.core: forced eval GC")
} else {
// Compute the old threshold limit for GC using the FSM
// time table. This is a rough mapping of a time to the
// Raft index it belongs to.
tt := c.srv.fsm.TimeTable()
cutoff := time.Now().UTC().Add(-1 * c.srv.config.EvalGCThreshold)
oldThreshold = tt.NearestIndex(cutoff)
c.srv.logger.Printf("[DEBUG] sched.core: eval GC: scanning before index %d (%v)",
oldThreshold, c.srv.config.EvalGCThreshold)
}
// Collect the allocations and evaluations to GC
var gcAlloc, gcEval []string
for raw := iter.Next(); raw != nil; raw = iter.Next() {
eval := raw.(*structs.Evaluation)
// The Evaluation GC should not handle batch jobs since those need to be
// garbage collected in one shot
gc, allocs, err := c.gcEval(eval, oldThreshold, false)
if err != nil {
return err
}
if gc {
gcEval = append(gcEval, eval.ID)
}
gcAlloc = append(gcAlloc, allocs...)
}
// Fast-path the nothing case
if len(gcEval) == 0 && len(gcAlloc) == 0 {
return nil
}
c.srv.logger.Printf("[DEBUG] sched.core: eval GC: %d evaluations, %d allocs eligible",
len(gcEval), len(gcAlloc))
return c.evalReap(gcEval, gcAlloc)
}
// gcEval returns whether the eval should be garbage collected given a raft
// threshold index. The eval disqualifies for garbage collection if it or its
// allocs are not older than the threshold. If the eval should be garbage
// collected, the associated alloc ids that should also be removed are also
// returned
func (c *CoreScheduler) gcEval(eval *structs.Evaluation, thresholdIndex uint64, allowBatch bool) (
bool, []string, error) {
// Ignore non-terminal and new evaluations
if !eval.TerminalStatus() || eval.ModifyIndex > thresholdIndex {
return false, nil, nil
}
// Create a watchset
ws := memdb.NewWatchSet()
// If the eval is from a running "batch" job we don't want to garbage
// collect its allocations. If there is a long running batch job and its
// terminal allocations get GC'd the scheduler would re-run the
// allocations.
if eval.Type == structs.JobTypeBatch {
// Check if the job is running
job, err := c.snap.JobByID(ws, eval.Namespace, eval.JobID)
if err != nil {
return false, nil, err
}
// Can collect if:
// Job doesn't exist
// Job is Stopped and dead
// allowBatch and the job is dead
collect := false
if job == nil {
collect = true
} else if job.Status != structs.JobStatusDead {
collect = false
} else if job.Stop {
collect = true
} else if allowBatch {
collect = true
}
// We don't want to gc anything related to a job which is not dead
// If the batch job doesn't exist we can GC it regardless of allowBatch
if !collect {
return false, nil, nil
}
}
// Get the allocations by eval
allocs, err := c.snap.AllocsByEval(ws, eval.ID)
if err != nil {
c.srv.logger.Printf("[ERR] sched.core: failed to get allocs for eval %s: %v",
eval.ID, err)
return false, nil, err
}
// Scan the allocations to ensure they are terminal and old
gcEval := true
var gcAllocIDs []string
for _, alloc := range allocs {
if !alloc.TerminalStatus() || alloc.ModifyIndex > thresholdIndex {
// Can't GC the evaluation since not all of the allocations are
// terminal
gcEval = false
} else {
// The allocation is eligible to be GC'd
gcAllocIDs = append(gcAllocIDs, alloc.ID)
}
}
return gcEval, gcAllocIDs, nil
}
// evalReap contacts the leader and issues a reap on the passed evals and
// allocs.
func (c *CoreScheduler) evalReap(evals, allocs []string) error {
// Call to the leader to issue the reap
for _, req := range c.partitionEvalReap(evals, allocs) {
var resp structs.GenericResponse
if err := c.srv.RPC("Eval.Reap", req, &resp); err != nil {
c.srv.logger.Printf("[ERR] sched.core: eval reap failed: %v", err)
return err
}
}
return nil
}
// partitionEvalReap returns a list of EvalDeleteRequest to make, ensuring a single
// request does not contain too many allocations and evaluations. This is
// necessary to ensure that the Raft transaction does not become too large.
func (c *CoreScheduler) partitionEvalReap(evals, allocs []string) []*structs.EvalDeleteRequest {
var requests []*structs.EvalDeleteRequest
submittedEvals, submittedAllocs := 0, 0
for submittedEvals != len(evals) || submittedAllocs != len(allocs) {
req := &structs.EvalDeleteRequest{
WriteRequest: structs.WriteRequest{
Region: c.srv.config.Region,
},
}
requests = append(requests, req)
available := maxIdsPerReap
// Add the allocs first
if remaining := len(allocs) - submittedAllocs; remaining > 0 {
if remaining <= available {
req.Allocs = allocs[submittedAllocs:]
available -= remaining
submittedAllocs += remaining
} else {
req.Allocs = allocs[submittedAllocs : submittedAllocs+available]
submittedAllocs += available
// Exhausted space so skip adding evals
continue
}
}
// Add the evals
if remaining := len(evals) - submittedEvals; remaining > 0 {
if remaining <= available {
req.Evals = evals[submittedEvals:]
submittedEvals += remaining
} else {
req.Evals = evals[submittedEvals : submittedEvals+available]
submittedEvals += available
}
}
}
return requests
}
// nodeGC is used to garbage collect old nodes
func (c *CoreScheduler) nodeGC(eval *structs.Evaluation) error {
// Iterate over the evaluations
ws := memdb.NewWatchSet()
iter, err := c.snap.Nodes(ws)
if err != nil {
return err
}
var oldThreshold uint64
if eval.JobID == structs.CoreJobForceGC {
// The GC was forced, so set the threshold to its maximum so everything
// will GC.
oldThreshold = math.MaxUint64
c.srv.logger.Println("[DEBUG] sched.core: forced node GC")
} else {
// Compute the old threshold limit for GC using the FSM
// time table. This is a rough mapping of a time to the
// Raft index it belongs to.
tt := c.srv.fsm.TimeTable()
cutoff := time.Now().UTC().Add(-1 * c.srv.config.NodeGCThreshold)
oldThreshold = tt.NearestIndex(cutoff)
c.srv.logger.Printf("[DEBUG] sched.core: node GC: scanning before index %d (%v)",
oldThreshold, c.srv.config.NodeGCThreshold)
}
// Collect the nodes to GC
var gcNode []string
OUTER:
for {
raw := iter.Next()
if raw == nil {
break
}
node := raw.(*structs.Node)
// Ignore non-terminal and new nodes
if !node.TerminalStatus() || node.ModifyIndex > oldThreshold {
continue
}
// Get the allocations by node
ws := memdb.NewWatchSet()
allocs, err := c.snap.AllocsByNode(ws, node.ID)
if err != nil {
c.srv.logger.Printf("[ERR] sched.core: failed to get allocs for node %s: %v",
eval.ID, err)
continue
}
// If there are any non-terminal allocations, skip the node. If the node
// is terminal and the allocations are not, the scheduler may not have
// run yet to transition the allocs on the node to terminal. We delay
// GC'ing until this happens.
for _, alloc := range allocs {
if !alloc.TerminalStatus() {
continue OUTER
}
}
// Node is eligible for garbage collection
gcNode = append(gcNode, node.ID)
}
// Fast-path the nothing case
if len(gcNode) == 0 {
return nil
}
c.srv.logger.Printf("[DEBUG] sched.core: node GC: %d nodes eligible", len(gcNode))
// Call to the leader to issue the reap
for _, nodeID := range gcNode {
req := structs.NodeDeregisterRequest{
NodeID: nodeID,
WriteRequest: structs.WriteRequest{
Region: c.srv.config.Region,
},
}
var resp structs.NodeUpdateResponse
if err := c.srv.RPC("Node.Deregister", &req, &resp); err != nil {
c.srv.logger.Printf("[ERR] sched.core: node '%s' reap failed: %v", nodeID, err)
return err
}
}
return nil
}
// deploymentGC is used to garbage collect old deployments
func (c *CoreScheduler) deploymentGC(eval *structs.Evaluation) error {
// Iterate over the deployments
ws := memdb.NewWatchSet()
iter, err := c.snap.Deployments(ws)
if err != nil {
return err
}
var oldThreshold uint64
if eval.JobID == structs.CoreJobForceGC {
// The GC was forced, so set the threshold to its maximum so everything
// will GC.
oldThreshold = math.MaxUint64
c.srv.logger.Println("[DEBUG] sched.core: forced deployment GC")
} else {
// Compute the old threshold limit for GC using the FSM
// time table. This is a rough mapping of a time to the
// Raft index it belongs to.
tt := c.srv.fsm.TimeTable()
cutoff := time.Now().UTC().Add(-1 * c.srv.config.DeploymentGCThreshold)
oldThreshold = tt.NearestIndex(cutoff)
c.srv.logger.Printf("[DEBUG] sched.core: deployment GC: scanning before index %d (%v)",
oldThreshold, c.srv.config.DeploymentGCThreshold)
}
// Collect the deployments to GC
var gcDeployment []string
OUTER:
for {
raw := iter.Next()
if raw == nil {
break
}
deploy := raw.(*structs.Deployment)
// Ignore non-terminal and new deployments
if deploy.Active() || deploy.ModifyIndex > oldThreshold {
continue
}
// Ensure there are no allocs referencing this deployment.
allocs, err := c.snap.AllocsByDeployment(ws, deploy.ID)
if err != nil {
c.srv.logger.Printf("[ERR] sched.core: failed to get allocs for deployment %s: %v",
deploy.ID, err)
continue
}
// Ensure there is no allocation referencing the deployment.
for _, alloc := range allocs {
if !alloc.TerminalStatus() {
continue OUTER
}
}
// Deployment is eligible for garbage collection
gcDeployment = append(gcDeployment, deploy.ID)
}
// Fast-path the nothing case
if len(gcDeployment) == 0 {
return nil
}
c.srv.logger.Printf("[DEBUG] sched.core: deployment GC: %d deployments eligible", len(gcDeployment))
return c.deploymentReap(gcDeployment)
}
// deploymentReap contacts the leader and issues a reap on the passed
// deployments.
func (c *CoreScheduler) deploymentReap(deployments []string) error {
// Call to the leader to issue the reap
for _, req := range c.partitionDeploymentReap(deployments) {
var resp structs.GenericResponse
if err := c.srv.RPC("Deployment.Reap", req, &resp); err != nil {
c.srv.logger.Printf("[ERR] sched.core: deployment reap failed: %v", err)
return err
}
}
return nil
}
// partitionDeploymentReap returns a list of DeploymentDeleteRequest to make,
// ensuring a single request does not contain too many deployments. This is
// necessary to ensure that the Raft transaction does not become too large.
func (c *CoreScheduler) partitionDeploymentReap(deployments []string) []*structs.DeploymentDeleteRequest {
var requests []*structs.DeploymentDeleteRequest
submittedDeployments := 0
for submittedDeployments != len(deployments) {
req := &structs.DeploymentDeleteRequest{
WriteRequest: structs.WriteRequest{
Region: c.srv.config.Region,
},
}
requests = append(requests, req)
available := maxIdsPerReap
if remaining := len(deployments) - submittedDeployments; remaining > 0 {
if remaining <= available {
req.Deployments = deployments[submittedDeployments:]
submittedDeployments += remaining
} else {
req.Deployments = deployments[submittedDeployments : submittedDeployments+available]
submittedDeployments += available
}
}
}
return requests
}