core

Documentation

Overview

package core defines pandora engine extension points. Core interfaces implementations MAY be used for custom engine creation and using as a library, or MAY be registered in pandora plugin system (look at core/plugin package), for creating engine from abstract config.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in that package doc are to be interpreted as described in https://www.ietf.org/rfc/rfc2119.txt

Index

• type Aggregator
• type AggregatorDeps
• type Ammo
• type BorrowedSample
• type DataSink
• type DataSource
• type Gun
• type GunDeps
• type Provider
• type ProviderDeps
• type ResettableAmmo
• type Sample
• type Schedule

Types

type Aggregator

type Aggregator interface {
	// Run starts aggregator routine of handling Samples. Blocks until fail or context cancel.
	// Run MUST be called only once. Run SHOULD be called before Report calls, but MAY NOT because
	// of goroutine races.
	// In case of ctx cancel, SHOULD return nil, but MAY ctx.Err(), or error caused ctx.Err()
	// in terms of github.com/pkg/errors.Cause.
	// In case of any dropped Sample (unhandled because of Sample queue overflow) Run SHOULD return
	// error describing how many samples were dropped.
	Run(ctx context.Context, deps AggregatorDeps) error
	// Report reports sample to aggregator. SHOULD be lightweight and not blocking,
	// so Instance can Shoot as soon as possible.
	// That means, that Sample encode and reporting SHOULD NOT be done in caller goroutine,
	// but SHOULD in Aggregator Run goroutine.
	// If Aggregator can't handle Reported Sample without blocking, it SHOULD just drop it.
	// Reported Samples MAY just be dropped, after context cancel.
	// Reported Sample MAY be reused for efficiency, so caller MUST NOT retain reference to Sample.
	// Report MAY be called before Aggregator Run. Report MAY be called after Run finish, in case of
	// Pool Run cancel.
	// Aggregator SHOULD Return Sample if it implements BorrowedSample.
	Report(s Sample)
}

Aggregator is routine that aggregates Samples from all Pool Instances. Usually aggregator is shooting result reporter, that writes Reported Samples to DataSink in machine readable format for future analysis. An Aggregator MUST be goroutine safe. GunDeps are passed to Gun before Instance Run.

type AggregatorDeps

type AggregatorDeps struct {
	Log *zap.Logger
}

AggregatorDeps are passed to Aggregator in Run. WARN: another fields could be added in next MINOR versions. That is NOT considered as a breaking compatibility change.

type Ammo

type Ammo interface{}

Ammo is data required for one shot. SHOULD contains something that differs from one shot to another. Something like requested recourse indetificator, query params, meta information helpful for future shooting analysis. Information common for all shoots SHOULD be passed via Provider configuration.

type BorrowedSample

type BorrowedSample interface {
	Sample
	Return()
}

BorrowedSample is Sample that was borrowed from pool, and SHOULD be returned by Aggregator, after it will handle Sample.

type DataSink

type DataSink interface {
	// OpenSink opens sink for writing. OpenSink MUST NOT be called more than once.
	// Returned wc SHOULD have low latency and good enough throughput for Write.
	// wc MAY be afero.File but SHOULD NOT be TCP connection for example.
	// DataSink MAY upload Wrote data somewhere but SHOULD do it on wc Close or in background
	// goroutine.
	// wc Writes SHOULD be buffered for better performance if it doesn't implement io.ByteWriter.
	// That usually means that short Writes are efficient enough. It is implemented by *bytes.Buffer
	// and *bufio.Writer, for example. wc Writes MAY be buffered regardless.
	OpenSink() (wc io.WriteCloser, err error)
}

DataSink is abstract ready to open sink of data.

Examples: Dummy os.Stdout wrapper. File DataSink that contains filename and afero.Fs, and returns afero.File on OpenSource. HTTP DataSink caches Written data to temporary file on wc Writes, and POST it using contained URL and headers on wc Close.

type DataSource

type DataSource interface {
	// OpenSource opens source for read. OpenSource MUST NOT be called more than once.
	// Returned rc SHOULD have low latency and good enough throughput for Read.
	// rc MAY be afero.File but SHOULD NOT be TCP connection for example.
	// DataSource MAY be some remote resource, but OpenSource SHOULD download all necessary data to
	// local temporary file and return it as rc.
	// Rule of thumb: returned rc SHOULD be afero.File or wrapped *bytes.Buffer.
	// Returned rc SHOULD cleanup all created temporary resources on Close.
	// rc owner SHOULD NOT try cast it to concrete types. For example, rc can be
	// wrapped temporary *os.File, that will be deleted on Close, so it can't be casted to *os.File,
	// because has type of wrapper, but can be used as afero.File.
	// rc Reads SHOULD be buffered for better performance if it doesn't implement io.ByteReader.
	// That usually means that short Reads are efficient enough. It is implemented by *bytes.Buffer
	// and *bufio.Reader, for example. rc Reads MAY be buffered regardless.
	OpenSource() (rc io.ReadCloser, err error)
}

DataSource is abstract, ready to only open, source of data. Returned source MUST implement io.ReadCloser at least, but can implement more wide interface, and this interface methods MAY be used. For example, returned source can be afero.File, and can be seeked in such case. Examples: Dummy os.Stdin wrapper. File DataSource that contains filename and afero.Fs, and returns afero.File on OpenSource. HTTP DataSource that contains URL and headers used on OpenSource to download content to file, and return afero.File, that will be deleted on rc Close. String DataSource returns just wrapped *bytes.Buffer with string content.

type Gun

type Gun interface {
	// Bind passes dependencies required for shooting. MUST be called once before any Shoot call.
	Bind(aggr Aggregator, deps GunDeps) error
	// Shoot makes one shoot. Shoot means some abstract load operation: web service or database
	// request, for example.
	// During shoot Gun SHOULD Acquire one or more Samples and Report them to bound Aggregator.
	// Shoot error that MAY mean service under load fail SHOULD be reported to Aggregator in sample
	// and SHOULD be logged to deps.Log at zap.WarnLevel.
	// For example, HTTP request fail SHOULD be Reported and logged,.
	// In case of error, that SHOULD cancel shooting for all Instances Shoot MUST panic using error
	// value describing the problem. That could be configuration error, unsupported Ammo type,
	// situation when service under load doesn't support required protocol,
	Shoot(ammo Ammo)
}

Gun represents logic of making shoots sequentially. A Gun is owned by only Instance that uses it for shooting in cycle: Acquire Ammo from Provider -> wait for next shoot schedule event -> Shoot with Gun. Guns that also implements io.Closer will be Closed after Instance finish. Rule of thumb: Guns that create resources which SHOULD be closed after Instance finish, SHOULD implement io.Closer. Example: Gun that makes HTTP requests through keep alive connection SHOULD close it in Close.

type GunDeps

type GunDeps struct {
	// Ctx is canceled on shoot cancel or finish.
	Ctx context.Context
	// Log fields already contains Id's of Pool and Instance.
	Log *zap.Logger
	// Unique of Gun owning Instance. MAY be used for tagging Samples.
	// Pool set's ids to Instances from 0, incrementing it after Instance Run.
	// There is a race between Instances for Ammo Acquire, so it's not guaranteed, that
	// Instance with lower InstanceId gets it's Ammo earlier.
	InstanceID int
}

GunDeps are passed to Gun before Instance Run. WARN: another fields could be added in next MINOR versions. That is NOT considered as a breaking compatibility change.

type Provider

type Provider interface {
	// Run starts provider routine of ammo  generation.
	// Blocks until ammo finish, error or context cancel.
	// Run MUST be called only once. Run SHOULD be called before Acquire or Release calls, but
	// MAY NOT because of goroutine races.
	// In case of ctx cancel, SHOULD return nil, but MAY ctx.Err(), or error caused ctx.Err()
	// in terms of github.com/pkg/errors.Cause.
	Run(ctx context.Context, deps ProviderDeps) error
	// Acquire acquires ammo for shoot. Acquire SHOULD be lightweight, so Instance can Shoot as
	// soon as possible. That means ammo format parsing SHOULD be done in Provider Run goroutine,
	// but acquire just takes ammo from ready queue.
	// Ok false means that shooting MUST be stopped because ammo finished or shooting is canceled.
	// Acquire MAY be called before Run, but SHOULD block until Run is called.
	Acquire() (ammo Ammo, ok bool)
	// Release notifies that ammo usage is finished, and it can be reused.
	// Instance MUST NOT retain references to released ammo.
	Release(ammo Ammo)
}

Provider is routine that generates ammo for Instance shoots. A Provider MUST be goroutine safe.

type ProviderDeps

type ProviderDeps struct {
	Log *zap.Logger
}

ProviderDeps are passed to Provider in Run. WARN: another fields could be added in next MINOR versions. That is NOT considered as a breaking compatibility change.

type ResettableAmmo

type ResettableAmmo interface {
	Ammo
	Reset()
}

ResettableAmmo is ammo that can be efficiently reset before reuse. Generic Provider (Provider that accepts undefined type of Ammo) SHOULD Reset Ammo before reuse if it implements ResettableAmmo. Ammo that is not going to be used with generic Providers don't need to implement ResettableAmmo.

type Sample

type Sample interface{}

Sample is data containing shoot report. Return code, timings, shoot meta information.

type Schedule

type Schedule interface {
	// Start starts schedule at passed time.
	// Start SHOULD be called once, before any Next call.
	// Start MUST NOT be called more than once or after Next call.
	// If Start was not called, Schedule MUST be started on first Next call.
	Start(startAt time.Time)

	// Next withdraw one operation token and returns next operation time and
	// ok equal true, when Schedule is not finished.
	// If there is no operation tokens left, Next returns Schedule finish time and ok equals false.
	// If Next called first time and Start was not called, Schedule MUST start and return tx
	// equal to start time.
	// Returned ts values MUST increase monotonically. That is, ts returned on next Next call MUST
	// be greater or equal than returned on previous.
	Next() (ts time.Time, ok bool)

	// Left returns n >= 0 number operation token left, if it is known exactly.
	// Returns n < 0, if number of operation tokens is unknown.
	// Left MAY be called before Start.
	Left() int
}

Schedule represents operation schedule. Schedule MUST be goroutine safe.