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timeit.go
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timeit.go
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package skbtrace
import (
"errors"
"fmt"
"time"
)
const (
aggrCleanupInterval = 5 * time.Second
)
const (
TUSecond = "sec"
TUMillisecond = "ms"
TUMicrosecond = "us"
TUNanosecond = "ns"
)
var timeUnitDivisors = map[string]time.Duration{
TUSecond: time.Second,
TUMillisecond: time.Millisecond,
TUMicrosecond: time.Microsecond,
TUNanosecond: 1,
}
type TimeSpec struct {
// Name of the probe this probe is refers to
Probe string
// Lists of filters applied to this probe
FilterOptions
// List of keys used to map requests
Keys []string
// Hints for this probe
Hints []string
}
// TimeCommonOptions are shared between time options requests.
type TimeCommonOptions struct {
CommonOptions
// Specification of the probe in which start time is collected.
FromSpec TimeSpec
// Specification of the probe in which time delta is computed.
// If filters or keys are omitted in ToSpec, they are derived from FromSpec.
ToSpec TimeSpec
}
// Options for BuildTimeAggregate.
type TimeAggregateOptions struct {
TimeCommonOptions
AggregateCommonOptions
// Aggregate Func for time and divisor for adjusting from nanoseconds
Func AggrFunc
// ToEventCount is a number of to probe firings before we start
// measuring time delta. Useful for measuring longer handshakes
// such as TLS handshake for each 2nd ACK is of interest
ToEventCount int
}
// Options for BuildTimeOutlierDump.
type TimeOutlierDumpOptions struct {
TimeCommonOptions
// OutlierThreshold allows to dump events which time exceed specified threshold
OutlierThreshold time.Duration
// Specifies if exit() should be called on first outlier
Exit bool
CommonDumpOptions
}
// Options for BuildDuplicateEvent.
type DuplicateEventOptions struct {
CommonOptions
// Specification of the probe
Spec TimeSpec
// Specifies if exit() should be called on first duplicate
Exit bool
CommonDumpOptions
}
// timeBuilderHelper is a function which injects statements into a probe
// block (and sometimes replaces it with nested block). Combining these
// functions allows to flexible build all options that timeit provides.
type timeBuilderHelper func(b *Builder, ctx *timeProbeContext) error
type timeProbeContext struct {
filters [][]*ProcessedFilter
probeName string
probeBlock *Block
outerBlock *Block
block *Block
keys []*fieldAliasRef
// For sharing between builder helpers
keysExprs []Expression
}
func combineTimeHelpers(helpers ...timeBuilderHelper) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
for _, helper := range helpers {
err := helper(b, ctx)
if err != nil {
return err
}
}
return nil
}
}
func newTimeMeasurePrepare(convMask uint) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
keyBlock, exprs, err := b.getBlockWithKeys(ctx.block, ctx.keys, convMask)
if err != nil {
return err
}
ctx.block = keyBlock
ctx.keysExprs = exprs
return nil
}
}
func timeMeasureStartImpl(b *Builder, ctx *timeProbeContext) error {
ctx.block.Addf("@start_time[%s] = nsecs", ExprJoin(ctx.keysExprs))
return nil
}
func newTimeMeasureStart(convMask uint) timeBuilderHelper {
return combineTimeHelpers(newTimeMeasurePrepare(convMask), timeMeasureStartImpl)
}
func timeMeasureStartFetchImpl(b *Builder, ctx *timeProbeContext) error {
ctx.block.Addf("$st = @start_time[%s]", ExprJoin(ctx.keysExprs))
ctx.block = ctx.block.AddIfBlock(Expr("$st > 0"))
return nil
}
func timeMeasureDeltaImpl(b *Builder, ctx *timeProbeContext) error {
ctx.block.Add(Stmt("$dt = (nsecs - $st)"))
return nil
}
func newTimeMeasureDelta(convMask uint) timeBuilderHelper {
return combineTimeHelpers(newTimeMeasurePrepare(convMask), timeMeasureStartFetchImpl, timeMeasureDeltaImpl)
}
func getTimeUnitDivisor(timeUnit string) (int64, error) {
divisor, ok := timeUnitDivisors[timeUnit]
if !ok {
return 0, fmt.Errorf("unknown divisor '%s'", timeUnit)
}
return int64(divisor), nil
}
func newEventCounter(toEventCount int) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
if toEventCount >= 2 {
ctx.block.Addf("@event_count[%s] += 1", ExprJoin(ctx.keysExprs))
ctx.block = ctx.block.AddIfBlock(Exprf("@event_count[%s] >= %d",
ExprJoin(ctx.keysExprs), toEventCount))
ctx.block.Addf("delete(@event_count[%s])", ExprJoin(ctx.keysExprs))
}
return nil
}
}
func newAggregateTimeDelta(aggrFunc AggrFunc, timeUnit string) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
divisor, err := getTimeUnitDivisor(timeUnit)
if err != nil {
return err
}
ctx.block.Addf("@ = %s($dt / %d)", aggrFunc, divisor)
return nil
}
}
func newOutlierCondition(threshold time.Duration) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
ctx.block = ctx.block.AddIfBlock(Exprf("$dt > %d", threshold.Nanoseconds()))
return nil
}
}
func newDumper(opt *CommonOptions, dumpOpt CommonDumpOptions, exit bool) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
divisor, err := getTimeUnitDivisor(opt.TimeUnit)
if err != nil {
return err
}
ctx.block.Addf(`printf("TIME: %%d %s\n", $dt / %d)`, opt.TimeUnit, divisor)
err = b.addDumpRowsStatements(ctx.block, dumpOpt)
if err != nil {
return err
}
if exit {
ctx.block.Add(Stmt("exit()"))
}
return nil
}
}
func newEventCount(event string) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
ctx.block.Addf(`@["%s:filtered"] = count()`, event)
ctx.probeBlock.Addf(`@["%s"] = count()`, event)
return nil
}
}
func newDuplicateEvent() timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
ctx.block.Addf("$st = @start_time[%s]", ExprJoin(ctx.keysExprs))
outerBlock := ctx.block
ctx.block = ctx.block.AddIfBlock(Expr("$st == 0"))
timeMeasureStartImpl(b, ctx)
ctx.block = outerBlock.AddBlock("else")
ctx.block.Add(Stmt(`printf("DUPLICATE EVENT ")`))
return timeMeasureDeltaImpl(b, ctx)
}
}
func newAggrCleanup(aggrVar string) timeBuilderHelper {
return func(b *Builder, ctx *timeProbeContext) error {
if len(ctx.keysExprs) == 0 {
return errors.New("internal error: aggregate cleanup called before time measurement")
}
ctx.block.Addf("delete(%s[%s])", aggrVar, ExprJoin(ctx.keysExprs))
return nil
}
}
// BuildTimeAggregate is a default time mode builder: measures time deltas, puts them
// into aggregation and periodically dumps aggregation contents.
func (b *Builder) BuildTimeAggregate(opt TimeAggregateOptions) (*Program, error) {
prog, err := b.buildTimeTrace(
&opt.TimeCommonOptions, nil,
newTimeMeasureStart(ConverterHiddenKey),
combineTimeHelpers(
newEventCounter(opt.ToEventCount),
newTimeMeasureDelta(ConverterHiddenKey),
newAggregateTimeDelta(opt.Func, opt.TimeUnit),
newAggrCleanup("@start_time")))
if err != nil {
return nil, err
}
aggrs := []string{"@start_time"}
if opt.ToEventCount >= 2 {
aggrs = append(aggrs, "@event_count")
}
prog.addAggrDumpBlock(opt.Interval, opt.Truncate)
prog.addAggrCleanupBlock(aggrs...)
return prog, err
}
// BuildTimeOutlierDump builds trace script which mearures time delta,
// but instead of putting it into an aggregation, it dumps objects that
// reveal such behaviour, i.e. tcp packet which causes troublingly long handshake.
func (b *Builder) BuildTimeOutlierDump(opt TimeOutlierDumpOptions) (*Program, error) {
prog, err := b.buildTimeTrace(
&opt.TimeCommonOptions, opt.FieldGroupRows,
newTimeMeasureStart(ConverterHiddenKey),
combineTimeHelpers(
newTimeMeasureDelta(ConverterHiddenKey),
newOutlierCondition(opt.OutlierThreshold),
newDumper(&opt.CommonOptions, opt.CommonDumpOptions, opt.Exit)))
if err != nil {
return nil, err
}
prog.addAggrCleanupBlock("@start_time")
return prog, err
}
// BuildTimeEventCount builds a program which counts number of times from and to
// probes are hit. Useful when other time probes do not reveal anything useful
// because filter is incorrect.
func (b *Builder) BuildTimeEventCount(opt TimeCommonOptions) (*Program, error) {
return b.buildTimeTrace(
&opt, nil,
newEventCount("from"),
newEventCount("to"))
}
// BuildDuplicateEvent builds a program which attaches to a single probe, but
// fires only when the probe hits same set of keys second time. Useful for
// tracking retransmits or measure port reuse time.
func (b *Builder) BuildDuplicateEvent(opt DuplicateEventOptions) (*Program, error) {
prog := NewProgram()
builder := combineTimeHelpers(
newTimeMeasurePrepare(ConverterHiddenKey),
newDuplicateEvent(),
newDumper(&opt.CommonOptions, opt.CommonDumpOptions, opt.Exit))
_, err := b.buildTimeProbe(prog, nil,
opt.Spec, opt.FieldGroupRows, &opt.CommonOptions, builder)
if err != nil {
return nil, newProbeBuildError(opt.Spec.Probe, err)
}
prog.addAggrCleanupBlock("@start_time")
return prog, err
}
func (b *Builder) buildTimeTrace(
opt *TimeCommonOptions, rows []string,
fromBuilder timeBuilderHelper,
toBuilder timeBuilderHelper,
) (*Program, error) {
prog := NewProgram()
prog.addCommonBlock(&opt.CommonOptions)
fromCtx, err := b.buildTimeProbe(prog, nil,
opt.FromSpec, rows, &opt.CommonOptions, fromBuilder)
if err != nil {
return nil, newProbeBuildError(fmt.Sprintf("%s (from)", opt.FromSpec.Probe), err)
}
_, err = b.buildTimeProbe(prog, fromCtx,
opt.ToSpec, rows, &opt.CommonOptions, toBuilder)
if err != nil {
return nil, newProbeBuildError(fmt.Sprintf("%s (to)", opt.ToSpec.Probe), err)
}
return prog, nil
}
func (b *Builder) buildTimeProbe(
prog *Program, ctxBase *timeProbeContext,
spec TimeSpec, rows []string, opt *CommonOptions,
builder timeBuilderHelper,
) (ctx *timeProbeContext, err error) {
// Build time probe. For "from probe" we build it initially meaning
// that all values must be computed from scratch. For "to" probe we
// can reuse probe, keys and filters if they are the same as in "from".
ctx = &timeProbeContext{probeName: spec.Probe}
if ctxBase == nil {
ctxBase = &timeProbeContext{}
}
var boSet builderObjectSet
getBoSet := func() builderObjectSet {
if boSet == nil {
boSet = b.newBuildObjectSet(ctx.filters, rows, append(opt.Hints, spec.Hints...))
}
return boSet
}
var sharedFilters bool
if len(spec.Filters) > 0 || len(spec.RawFilters) > 0 {
ctx.filters, err = b.prepareFilters(spec.FilterOptions)
if err != nil {
return
}
err = b.resolveWeakAliasRefs(b.getFilterWeakRefs(ctx.filters), getBoSet())
if err != nil {
return
}
} else {
ctx.filters = ctxBase.filters
sharedFilters = true
}
if spec.Probe != ctxBase.probeName || ctxBase.probeBlock == nil {
ctx.probeBlock, ctx.outerBlock, err = b.addProbeBlock(prog, spec.Probe, false, ctx.filters)
} else {
ctx.probeBlock = ctxBase.probeBlock
if !sharedFilters {
ctx.outerBlock, err = b.wrapFilters(ctx.probeBlock, ctx.filters)
} else {
// Both filter and probe name are matching meaning that we can
// reuse outer block from the previous probe
ctx.outerBlock = ctxBase.outerBlock
}
}
if err != nil {
return
}
ctx.block = ctx.outerBlock
if len(spec.Keys) > 0 {
ctx.keys, err = b.prepareKeys(spec.Keys)
if err != nil {
return
}
err = b.resolveWeakAliasRefs(b.getFieldWeakRefs(ctx.keys), getBoSet())
if err != nil {
return
}
} else if ctxBase.keys != nil {
ctx.keys = ctxBase.keys
} else {
err = errors.New("no keys supplied for time probe")
return
}
err = builder(b, ctx)
return
}