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Expose CircuitBreaker current condition (or state) to the metrics recorder interface and Prometheus. #25

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Expose CircuitBreaker current condition (or state) to the metrics recorder interface and Prometheus. #25

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b5e2dd3
WIP: expose a Recorder built from Prometheus' DefaultRegisterer
mickdwyer Mar 20, 2019
4d29958
WIP: create an unused circuit breaker state and close it on first use…
mickdwyer Mar 20, 2019
fcfae81
WIP: fix typo
mickdwyer Mar 20, 2019
57a6f52
WIP: fix typo
mickdwyer Mar 20, 2019
8978c16
WIP: rename the unused state to new
mickdwyer May 5, 2019
db7bf6a
WIP: use an itoa for the breaker state
mickdwyer May 5, 2019
2bf49fb
WIP: record the current circuit breaker state in the metrics recorder
mickdwyer May 5, 2019
c89af62
rename SetCircuitbreakerCurrentCondition to SetCircuitbreakerCurrentS…
mickdwyer May 7, 2019
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32 changes: 26 additions & 6 deletions circuitbreaker/circuitbreaker.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,14 +10,30 @@ import (
"github.com/slok/goresilience/metrics"
)

type state string
type state uint

const (
stateOpen state = "open"
stateHalfOpen state = "halfopen"
stateClosed state = "closed"
stateNew state = iota
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New state is the same as a closed state because a new circuitbreaker starts in a closed state. Do you have a use case where you need to know the difference between new and closed?

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@mickdwyer mickdwyer May 7, 2019 •
edited
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My choice to implement stateNew and the transition to stateClosed on first traversal provided a mechanism to ensure that the state of the breaker was recorded on first use.

Otherwise, I found that there are no state metrics recorded until the first state change occurs.

I might take a few moments to review how I'm using the circuitbreaker instance by my application.

stateOpen
stateHalfOpen
stateClosed
)

var stateStrings = []string {
"new",
"open",
"halfopen",
"closed",
}

func (st state) label () string {
return stateStrings[st]
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2 things:

  • Instead of label what do you think about implementing the Stringer interface?

  • This could panic if a state does not have an associated string in the array, although we control this it could lead to a runtime panic in a change. A better approach could be using a switch with a fallback string, would be safer.

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I'll have to read up on the Stringer interface but it feels a more natural fit.
I agree using a switch offers a more defensive implementation.

Will consider both when refactoring.

}

func (st state) condition () int {
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I think that we could remove the integer usage for state and use only the type and the string representation of it. It would simplify the usage and we remove code.

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I agree, will refactor accordingly. (Am I right in that you're happy with the use of iota?

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The iota is perfect

return int(st)
}

// Config is the configuration of the circuit breaker.
type Config struct {
// ErrorPercentThresholdToOpen is the error percent based on total execution requests
Expand Down Expand Up @@ -124,7 +140,7 @@ func NewMiddleware(cfg Config) goresilience.Middleware {

return func(next goresilience.Runner) goresilience.Runner {
return &circuitbreaker{
state: stateClosed,
state: stateNew,
recorder: newBucketWindow(cfg.MetricsSlidingWindowBucketQuantity, cfg.MetricsBucketDuration),
stateStarted: time.Now(),
cfg: cfg,
Expand Down Expand Up @@ -157,6 +173,9 @@ func (c *circuitbreaker) Run(ctx context.Context, f goresilience.Func) error {
func (c *circuitbreaker) preDecideState(metricsRec metrics.Recorder) {
state := c.getState()
switch state {
case stateNew:
// Close the breaker as this is the first time through and generate a statistic.
c.moveState(stateClosed, metricsRec)
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As stated before, the initial state of a circuit breaker is closed, so the above change of state: stateNew, and this moveState would not be required.

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True, although it's coupled to my comment above.

case stateOpen:
// Check if the circuit has been the required time in closed. If yes then
// we move to half open state.
Expand Down Expand Up @@ -223,7 +242,8 @@ func (c *circuitbreaker) moveState(state state, metricsRec metrics.Recorder) {

// Only change if the state changed.
if c.state != state {
metricsRec.IncCircuitbreakerState(string(state))
metricsRec.IncCircuitbreakerState(state.label())
metricsRec.SetCircuitbreakerCurrentState(state.condition())

c.state = state
c.stateStarted = time.Now()
Expand Down
1 change: 1 addition & 0 deletions metrics/dummy.go
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Expand Up @@ -15,6 +15,7 @@ func (dummy) IncBulkheadQueued() {}
func (dummy) IncBulkheadProcessed() {}
func (dummy) IncBulkheadTimeout() {}
func (dummy) IncCircuitbreakerState(state string) {}
func (dummy) SetCircuitbreakerCurrentState(condition int) {}
func (dummy) IncChaosInjectedFailure(kind string) {}
func (dummy) SetConcurrencyLimitInflightExecutions(q int) {}
func (dummy) SetConcurrencyLimitExecutingExecutions(q int) {}
Expand Down
2 changes: 2 additions & 0 deletions metrics/metrics.go
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Expand Up @@ -22,6 +22,8 @@ type Recorder interface {
IncBulkheadTimeout()
// IncCircuitbreakerState increments the number of state change.
IncCircuitbreakerState(state string)
// SetCircuitbreakerCurrentState records the state of ciruit breaker.
SetCircuitbreakerCurrentState(condition int)
// IncChaosInjectedFailure increments the number of times injected failure.
IncChaosInjectedFailure(kind string)
// SetConcurrencyLimitInflightExecutions sets the number of queued and executions at a given moment.
Expand Down
19 changes: 18 additions & 1 deletion metrics/prometheus.go
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Expand Up @@ -7,7 +7,7 @@ import (
"github.com/prometheus/client_golang/prometheus"
)

var (
const (
promNamespace = "goresilience"

promCommandSubsystem = "command"
Expand All @@ -17,8 +17,11 @@ var (
promCBSubsystem = "circuitbreaker"
promChaosSubsystem = "chaos"
promConcurrencyLimitSubsystem = "concurrencylimit"

)

var DefaultPrometheusRecorder = NewPrometheusRecorder(prometheus.DefaultRegisterer)

type prometheusRec struct {
// Metrics.
cmdExecutionDuration *prometheus.HistogramVec
Expand All @@ -28,6 +31,7 @@ type prometheusRec struct {
bulkProcessed *prometheus.CounterVec
bulkTimeouts *prometheus.CounterVec
cbStateChanges *prometheus.CounterVec
cbCurrentState *prometheus.GaugeVec
chaosFailureInjections *prometheus.CounterVec
concurrencyLimitInflights *prometheus.GaugeVec
concurrencyLimitExecuting *prometheus.GaugeVec
Expand Down Expand Up @@ -59,6 +63,7 @@ func (p prometheusRec) WithID(id string) Recorder {
bulkProcessed: p.bulkProcessed,
bulkTimeouts: p.bulkTimeouts,
cbStateChanges: p.cbStateChanges,
cbCurrentState: p.cbCurrentState,
chaosFailureInjections: p.chaosFailureInjections,
concurrencyLimitInflights: p.concurrencyLimitInflights,
concurrencyLimitExecuting: p.concurrencyLimitExecuting,
Expand Down Expand Up @@ -122,6 +127,13 @@ func (p *prometheusRec) registerMetrics() {
Help: "Total number of state changes made by the circuit breaker runner.",
}, []string{"id", "state"})

p.cbCurrentState = prometheus.NewGaugeVec(prometheus.GaugeOpts{
Namespace: promNamespace,
Subsystem: promCBSubsystem,
Name: "current_state",
Help: "The current state of the circuit breaker runner.",
}, []string{"id"})

p.chaosFailureInjections = prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: promNamespace,
Subsystem: promChaosSubsystem,
Expand Down Expand Up @@ -172,6 +184,7 @@ func (p *prometheusRec) registerMetrics() {
p.bulkProcessed,
p.bulkTimeouts,
p.cbStateChanges,
p.cbCurrentState,
p.chaosFailureInjections,
p.concurrencyLimitInflights,
p.concurrencyLimitExecuting,
Expand Down Expand Up @@ -210,6 +223,10 @@ func (p prometheusRec) IncCircuitbreakerState(state string) {
p.cbStateChanges.WithLabelValues(p.id, state).Inc()
}

func (p prometheusRec) SetCircuitbreakerCurrentState(condition int) {
p.cbCurrentState.WithLabelValues(p.id).Set(float64(condition))
}

func (p prometheusRec) IncChaosInjectedFailure(kind string) {
p.chaosFailureInjections.WithLabelValues(p.id, kind).Inc()
}
Expand Down
15 changes: 15 additions & 0 deletions metrics/prometheus_test.go
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Expand Up @@ -138,6 +138,21 @@ func TestPrometheus(t *testing.T) {
`goresilience_circuitbreaker_state_changes_total{id="test2",state="close"} 1`,
},
},
{
name: "Recording circuitbreaker circuit breaker state should expose the state.",
recordMetrics: func(m metrics.Recorder) {
m1 := m.WithID("test")
m2 := m.WithID("test2")
m1.SetCircuitbreakerCurrentState(0) // new
m1.SetCircuitbreakerCurrentState(3) // open
m1.SetCircuitbreakerCurrentState(1) // close
m2.SetCircuitbreakerCurrentState(2) // half-open
},
expMetrics: []string{
`goresilience_circuitbreaker_current_state{id="test"} 1`,
`goresilience_circuitbreaker_current_state{id="test2"} 2`,
},
},
{
name: "Recording chaos metrics should expose the metrics.",
recordMetrics: func(m metrics.Recorder) {
Expand Down