state: reflect key Nomad data within internal store

agent/agent.go

@@ -3,7 +3,6 @@ package agent
 import (
 	"context"
 	"fmt"
-	"reflect"
 	"sync"
 	"time"
 
@@ -15,7 +14,8 @@ import (
 	"github.com/hashicorp/nomad-autoscaler/plugins/manager"
 	strategypkg "github.com/hashicorp/nomad-autoscaler/plugins/strategy"
 	targetpkg "github.com/hashicorp/nomad-autoscaler/plugins/target"
-	"github.com/hashicorp/nomad-autoscaler/policystorage"
+	"github.com/hashicorp/nomad-autoscaler/state"
+	"github.com/hashicorp/nomad-autoscaler/state/policy"
 	"github.com/hashicorp/nomad/api"
 )
 
@@ -42,7 +42,8 @@ func (a *Agent) Run(ctx context.Context) error {
 		return err
 	}
 
-	ps := policystorage.Nomad{Client: a.nomadClient}
+	stateHandler := state.NewHandler(ctx, a.logger, a.nomadClient)
+	stateHandler.Start()
 
 	// launch plugins
 	if err := a.setupPlugins(); err != nil {
@@ -63,34 +64,23 @@ Loop:
 	for {
 		select {
 		case <-ticker.C:
-			logger := a.logger.With("policy_storage", reflect.TypeOf(ps))
-			logger.Info("reading policies")
 
 			// read policies
-			policies, err := ps.List()
-			if err != nil {
-				logger.Error("failed to fetch policies", "error", err)
-				continue
-			}
-			logger.Info(fmt.Sprintf("found %d policies", len(policies)))
+			policies := stateHandler.PolicyState.List()
+			a.logger.Info(fmt.Sprintf("found %d policies", len(policies)))
 
 			// handle policies
 			for _, p := range policies {
 				wg.Add(1)
-				go func(ID string) {
+				go func(policy *policy.Policy) {
 					defer wg.Done()
 					select {
 					case <-ctx.Done():
 						return
 					default:
-						policy, err := ps.Get(ID)
-						if err != nil {
-							logger.Error("failed to fetch policy", "policy_id", ID, "error", err)
-							return
-						}
 						a.handlePolicy(policy)
 					}
-				}(p.ID)
+				}(p)
 			}
 			wg.Wait()
 		case <-ctx.Done():
@@ -163,7 +153,7 @@ func (a *Agent) generateNomadClient() error {
 	return nil
 }
 
-func (a *Agent) handlePolicy(p *policystorage.Policy) {
+func (a *Agent) handlePolicy(p *policy.Policy) {
 	logger := a.logger.With(
 		"policy_id", p.ID,
 		"source", p.Source,

go.sum

@@ -80,7 +80,6 @@ github.com/json-iterator/go v1.1.9/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/u
 github.com/julienschmidt/httprouter v1.2.0/go.mod h1:SYymIcj16QtmaHHD7aYtjjsJG7VTCxuUUipMqKk8s4w=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
-github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pretty v0.2.0 h1:s5hAObm+yFO5uHYt5dYjxi2rXrsnmRpJx4OYvIWUaQs=
 github.com/kr/pretty v0.2.0/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
@@ -89,14 +88,11 @@ github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kylelemons/godebug v0.0.0-20170820004349-d65d576e9348 h1:MtvEpTB6LX3vkb4ax0b5D2DHbNAUsen0Gx5wZoq3lV4=
 github.com/kylelemons/godebug v0.0.0-20170820004349-d65d576e9348/go.mod h1:B69LEHPfb2qLo0BaaOLcbitczOKLWTsrBG9LczfCD4k=
-github.com/mattn/go-colorable v0.0.9 h1:UVL0vNpWh04HeJXV0KLcaT7r06gOH2l4OW6ddYRUIY4=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-colorable v0.1.4 h1:snbPLB8fVfU9iwbbo30TPtbLRzwWu6aJS6Xh4eaaviA=
 github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
-github.com/mattn/go-isatty v0.0.3 h1:ns/ykhmWi7G9O+8a448SecJU3nSMBXJfqQkl0upE1jI=
 github.com/mattn/go-isatty v0.0.3/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
 github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
-github.com/mattn/go-isatty v0.0.10 h1:qxFzApOv4WsAL965uUPIsXzAKCZxN2p9UqdhFS4ZW10=
 github.com/mattn/go-isatty v0.0.10/go.mod h1:qgIWMr58cqv1PHHyhnkY9lrL7etaEgOFcMEpPG5Rm84=
 github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOAqxQCu2WE=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
@@ -108,11 +104,9 @@ github.com/mitchellh/copystructure v1.0.0 h1:Laisrj+bAB6b/yJwB5Bt3ITZhGJdqmxquMK
 github.com/mitchellh/copystructure v1.0.0/go.mod h1:SNtv71yrdKgLRyLFxmLdkAbkKEFWgYaq1OVrnRcwhnw=
 github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
-github.com/mitchellh/go-testing-interface v0.0.0-20171004221916-a61a99592b77 h1:7GoSOOW2jpsfkntVKaS2rAr1TJqfcxotyaUcuxoZSzg=
 github.com/mitchellh/go-testing-interface v0.0.0-20171004221916-a61a99592b77/go.mod h1:kRemZodwjscx+RGhAo8eIhFbs2+BFgRtFPeD/KE+zxI=
 github.com/mitchellh/go-testing-interface v1.0.0 h1:fzU/JVNcaqHQEcVFAKeR41fkiLdIPrefOvVG1VZ96U0=
 github.com/mitchellh/go-testing-interface v1.0.0/go.mod h1:kRemZodwjscx+RGhAo8eIhFbs2+BFgRtFPeD/KE+zxI=
-github.com/mitchellh/go-wordwrap v0.0.0-20150314170334-ad45545899c7 h1:DpOJ2HYzCv8LZP15IdmG+YdwD2luVPHITV96TkirNBM=
 github.com/mitchellh/go-wordwrap v0.0.0-20150314170334-ad45545899c7/go.mod h1:ZXFpozHsX6DPmq2I0TCekCxypsnAUbP2oI0UX1GXzOo=
 github.com/mitchellh/go-wordwrap v1.0.0 h1:6GlHJ/LTGMrIJbwgdqdl2eEH8o+Exx/0m8ir9Gns0u4=
 github.com/mitchellh/go-wordwrap v1.0.0/go.mod h1:ZXFpozHsX6DPmq2I0TCekCxypsnAUbP2oI0UX1GXzOo=
@@ -149,59 +143,46 @@ github.com/prometheus/procfs v0.0.8/go.mod h1:7Qr8sr6344vo1JqZ6HhLceV9o3AJ1Ff+Gx
 github.com/sergi/go-diff v1.0.0 h1:Kpca3qRNrduNnOQeazBd0ysaKrUJiIuISHxogkT9RPQ=
 github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAmXWZgo=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
-github.com/sirupsen/logrus v1.4.2 h1:SPIRibHv4MatM3XXNO2BJeFLZwZ2LvZgfQ5+UNI2im4=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
 github.com/spf13/pflag v1.0.2/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
-github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-github.com/vmihailenco/msgpack v3.3.3+incompatible h1:wapg9xDUZDzGCNFlwc5SqI1rvcciqcxEHac4CYj89xI=
 github.com/vmihailenco/msgpack v3.3.3+incompatible/go.mod h1:fy3FlTQTDXWkZ7Bh6AcGMlsjHatGryHQYUTf1ShIgkk=
-github.com/zclconf/go-cty v1.2.0 h1:sPHsy7ADcIZQP3vILvTjrh74ZA175TFP5vqiNK1UmlI=
 github.com/zclconf/go-cty v1.2.0/go.mod h1:hOPWgoHbaTUnI5k4D2ld+GRpFJSCe6bCM7m1q/N4PQ8=
 github.com/zclconf/go-cty v1.3.1 h1:QIOZl+CKKdkv4l2w3lG23nNzXgLoxsWLSEdg1MlX4p0=
 github.com/zclconf/go-cty v1.3.1/go.mod h1:YO23e2L18AG+ZYQfSobnY4G65nvwvprPCxBHkufUH1k=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734 h1:p/H982KKEjUnLJkM3tt/LemDnOc1GiZL5FCVlORJ5zo=
 golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/net v0.0.0-20180811021610-c39426892332/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/net v0.0.0-20180826012351-8a410e7b638d h1:g9qWBGx4puODJTMVyoPrpoxPFgVGd+z1DZwjfRu4d0I=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20181114220301-adae6a3d119a/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3 h1:0GoQqolDA55aaLxZyTzK/Y2ePZzZTUrRacwib7cNsYQ=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190613194153-d28f0bde5980 h1:dfGZHvZk057jK2MCeWus/TowKpJ8y4AmooUzdBSR9GU=
 golang.org/x/net v0.0.0-20190613194153-d28f0bde5980/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 h1:YUO/7uOKsKeq9UokNS62b8FYywz3ker1l1vDZRCRefw=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc h1:MeuS1UDyZyFH++6vVy44PuufTeFF0d0nfI6XB87YGSk=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190129075346-302c3dd5f1cc h1:WiYx1rIFmx8c0mXAFtv5D/mHyKe1+jmuP7PViuwqwuQ=
 golang.org/x/sys v0.0.0-20190129075346-302c3dd5f1cc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190422165155-953cdadca894/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20190502175342-a43fa875dd82 h1:vsphBvatvfbhlb4PO1BYSr9dzugGxJ/SQHoNufZJq1w=
 golang.org/x/sys v0.0.0-20190502175342-a43fa875dd82/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200122134326-e047566fdf82 h1:ywK/j/KkyTHcdyYSZNXGjMwgmDSfjglYZ3vStQ/gSCU=
 golang.org/x/sys v0.0.0-20200122134326-e047566fdf82/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9 h1:1/DFK4b7JH8DmkqhUk48onnSfrPzImPoVxuomtbT2nk=
 golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
@@ -221,7 +202,6 @@ gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.2.5 h1:ymVxjfMaHvXD8RqPRmzHHsB3VvucivSkIAvJFDI5O3c=
 gopkg.in/yaml.v2 v2.2.5/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

helper/blocking/blocking.go

@@ -0,0 +1,14 @@
+package blocking
+
+// IndexHasChanged is used to check whether a returned blocking query has an
+// updated index, compared to a tracked value.
+func IndexHasChanged(new, old uint64) bool { return new > old }
+
+// FindMaxFound is used to determine which value passed is the greatest. This
+// is used to track the most recently found highest index value.
+func FindMaxFound(new, old uint64) uint64 {
+	if new <= old {
+		return old
+	}
+	return new
+}

helper/blocking/blocking_test.go

@@ -0,0 +1,70 @@
+package blocking
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_indexHasChange(t *testing.T) {
+	testCases := []struct {
+		newValue       uint64
+		oldValue       uint64
+		expectedReturn bool
+	}{
+		{
+			newValue:       13,
+			oldValue:       7,
+			expectedReturn: true,
+		},
+		{
+			newValue:       13696,
+			oldValue:       13696,
+			expectedReturn: false,
+		},
+		{
+			newValue:       7,
+			oldValue:       13,
+			expectedReturn: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		res := IndexHasChanged(tc.newValue, tc.oldValue)
+		assert.Equal(t, tc.expectedReturn, res)
+	}
+}
+
+func Test_findMaxFound(t *testing.T) {
+	testCases := []struct {
+		newValue       uint64
+		oldValue       uint64
+		expectedReturn uint64
+	}{
+		{
+			newValue:       13,
+			oldValue:       7,
+			expectedReturn: 13,
+		},
+		{
+			newValue:       13696,
+			oldValue:       13696,
+			expectedReturn: 13696,
+		},
+		{
+			newValue:       7,
+			oldValue:       13,
+			expectedReturn: 13,
+		},
+		{
+			newValue:       1,
+			oldValue:       0,
+			expectedReturn: 1,
+		},
+	}
+
+	for _, tc := range testCases {
+		res := FindMaxFound(tc.newValue, tc.oldValue)
+		assert.Equal(t, tc.expectedReturn, res)
+	}
+}

state/handler.go

@@ -0,0 +1,85 @@
+package state
+
+import (
+	"context"
+	"sync"
+
+	hclog "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/nomad-autoscaler/state/policy"
+	"github.com/hashicorp/nomad-autoscaler/state/policy/source"
+	nomadSource "github.com/hashicorp/nomad-autoscaler/state/policy/source/nomad"
+	"github.com/hashicorp/nomad-autoscaler/state/status"
+	"github.com/hashicorp/nomad/api"
+)
+
+// Handler manages the internal state storage for the Autoscaler agent and
+// should be used to ensure required information from Nomad (our source of
+// truth) is stored locally. This reduces pressure on the Nomad API and allows
+// for faster lookups.
+type Handler struct {
+
+	// ctx is the context passed by the controlling agent in order to propagate
+	// shutdown.
+	//
+	// TODO(jrasell) we should figure out how to shutdown blocking queries
+	//  based on this.
+	ctx context.Context
+
+	log   hclog.Logger
+	nomad *api.Client
+
+	// PolicyState is the interface for interacting with the internal policy
+	// state. It is public as the agent needs to be able to list policies.
+	PolicyState policy.State
+
+	// policyUpdateChan is the channel where policy.Watcher process should send
+	// any updates to scaling policies. The state handler is responsible for
+	// listening to this, and processing any items on the channel.
+	policyUpdateChan chan *api.ScalingPolicy
+
+	// policySource
+	policySource source.PolicySource
+
+	// statusState is the interface for interacting with the internal job scale
+	// status state.
+	statusState status.State
+
+	// statusWatcherHandlerLock is the mutex which should be used when
+	// manipulating the statusWatcherHandlers map.
+	statusWatcherHandlerLock sync.RWMutex
+
+	// statusWatcherHandlers is a mapping on our job scaling status blocking
+	// query handlers. Each job which is running and configured with at least
+	// one scaling policy should have an associated watcher. The map is keyed
+	// by the JobID.
+	statusWatcherHandlers map[string]*status.Watcher
+}
+
+// NewHandler is used to build a new state Handler object for use in managing
+// the Autoscaler internal state.
+func NewHandler(ctx context.Context, log hclog.Logger, nomad *api.Client) *Handler {
+	h := Handler{
+		ctx:                   ctx,
+		log:                   log.Named("state_handler"),
+		nomad:                 nomad,
+		PolicyState:           policy.NewStateBackend(),
+		policyUpdateChan:      make(chan *api.ScalingPolicy, 10),
+		statusWatcherHandlers: make(map[string]*status.Watcher),
+		statusState:           status.NewStateBackend(),
+	}
+
+	h.policySource = nomadSource.NewNomadPolicySource(h.log, h.nomad)
+
+	return &h
+}
+
+// Start starts the initially required state handling processes.
+func (h *Handler) Start() {
+
+	// Start the policy update handler before anything else.
+	go h.policyUpdateHandler()
+
+	// The policy source runs as a single process per Autoscaler agent, start
+	// it now.
+	go h.policySource.Start(h.policyUpdateChan)
+}