mirror of
https://source.quilibrium.com/quilibrium/ceremonyclient.git
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301 lines
9.3 KiB
Go
301 lines
9.3 KiB
Go
// Copyright 2023 The LevelDB-Go and Pebble Authors. All rights reserved. Use
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// of this source code is governed by a BSD-style license that can be found in
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// the LICENSE file.
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package errorfs
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import (
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"encoding/binary"
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"fmt"
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"go/token"
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"hash/maphash"
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"math/rand"
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"path/filepath"
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"strconv"
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"sync"
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"github.com/cockroachdb/errors"
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"github.com/cockroachdb/pebble/internal/dsl"
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)
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// Predicate encodes conditional logic that determines whether to inject an
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// error.
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type Predicate = dsl.Predicate[Op]
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// PathMatch returns a predicate that returns true if an operation's file path
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// matches the provided pattern according to filepath.Match.
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func PathMatch(pattern string) Predicate {
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return &pathMatch{pattern: pattern}
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}
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type pathMatch struct {
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pattern string
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}
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func (pm *pathMatch) String() string {
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return fmt.Sprintf("(PathMatch %q)", pm.pattern)
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}
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func (pm *pathMatch) Evaluate(op Op) bool {
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matched, err := filepath.Match(pm.pattern, op.Path)
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if err != nil {
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// Only possible error is ErrBadPattern, indicating an issue with
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// the test itself.
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panic(err)
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}
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return matched
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}
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var (
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// Reads is a predicate that returns true iff an operation is a read
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// operation.
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Reads Predicate = opKindPred{kind: OpIsRead}
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// Writes is a predicate that returns true iff an operation is a write
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// operation.
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Writes Predicate = opKindPred{kind: OpIsWrite}
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)
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type opFileReadAt struct {
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// offset configures the predicate to evaluate to true only if the
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// operation's offset exactly matches offset.
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offset int64
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}
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func (o *opFileReadAt) String() string {
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return fmt.Sprintf("(FileReadAt %d)", o.offset)
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}
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func (o *opFileReadAt) Evaluate(op Op) bool {
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return op.Kind == OpFileReadAt && o.offset == op.Offset
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}
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type opKindPred struct {
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kind OpReadWrite
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}
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func (p opKindPred) String() string { return p.kind.String() }
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func (p opKindPred) Evaluate(op Op) bool { return p.kind == op.Kind.ReadOrWrite() }
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// Randomly constructs a new predicate that pseudorandomly evaluates to true
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// with probability p using randomness determinstically derived from seed.
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//
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// The predicate is deterministic with respect to file paths: its behavior for a
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// particular file is deterministic regardless of intervening evaluations for
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// operations on other files. This can be used to ensure determinism despite
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// nondeterministic concurrency if the concurrency is constrained to separate
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// files.
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func Randomly(p float64, seed int64) Predicate {
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rs := &randomSeed{p: p, rootSeed: seed}
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rs.mu.perFilePrng = make(map[string]*rand.Rand)
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return rs
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}
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type randomSeed struct {
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// p defines the probability of an error being injected.
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p float64
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rootSeed int64
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mu struct {
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sync.Mutex
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h maphash.Hash
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perFilePrng map[string]*rand.Rand
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}
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}
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func (rs *randomSeed) String() string {
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if rs.rootSeed == 0 {
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return fmt.Sprintf("(Randomly %.2f)", rs.p)
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}
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return fmt.Sprintf("(Randomly %.2f %d)", rs.p, rs.rootSeed)
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}
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func (rs *randomSeed) Evaluate(op Op) bool {
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rs.mu.Lock()
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defer rs.mu.Unlock()
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prng, ok := rs.mu.perFilePrng[op.Path]
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if !ok {
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// This is the first time an operation has been performed on the file at
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// this path. Initialize the per-file prng by computing a deterministic
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// hash of the path.
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rs.mu.h.Reset()
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var b [8]byte
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binary.LittleEndian.PutUint64(b[:], uint64(rs.rootSeed))
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if _, err := rs.mu.h.Write(b[:]); err != nil {
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panic(err)
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}
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if _, err := rs.mu.h.WriteString(op.Path); err != nil {
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panic(err)
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}
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seed := rs.mu.h.Sum64()
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prng = rand.New(rand.NewSource(int64(seed)))
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rs.mu.perFilePrng[op.Path] = prng
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}
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return prng.Float64() < rs.p
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}
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// ParseDSL parses the provided string using the default DSL parser.
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func ParseDSL(s string) (Injector, error) {
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return defaultParser.Parse(s)
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}
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var defaultParser = NewParser()
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// NewParser constructs a new parser for an encoding of a lisp-like DSL
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// describing error injectors.
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//
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// Errors:
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// - ErrInjected is the only error currently supported by the DSL.
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//
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// Injectors:
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// - <ERROR>: An error by itself is an injector that injects an error every
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// time.
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// - (<ERROR> <PREDICATE>) is an injector that injects an error only when
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// the operation satisfies the predicate.
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//
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// Predicates:
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// - Reads is a constant predicate that evalutes to true iff the operation is a
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// read operation (eg, Open, Read, ReadAt, Stat)
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// - Writes is a constant predicate that evaluates to true iff the operation is
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// a write operation (eg, Create, Rename, Write, WriteAt, etc).
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// - (PathMatch <STRING>) is a predicate that evalutes to true iff the
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// operation's file path matches the provided shell pattern.
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// - (OnIndex <INTEGER>) is a predicate that evaluates to true only on the n-th
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// invocation.
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// - (And <PREDICATE> [PREDICATE]...) is a predicate that evaluates to true
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// iff all the provided predicates evaluate to true. And short circuits on
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// the first predicate to evaluate to false.
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// - (Or <PREDICATE> [PREDICATE]...) is a predicate that evaluates to true iff
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// at least one of the provided predicates evaluates to true. Or short
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// circuits on the first predicate to evaluate to true.
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// - (Not <PREDICATE>) is a predicate that evaluates to true iff its provided
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// predicates evaluates to false.
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// - (Randomly <FLOAT> [INTEGER]) is a predicate that pseudorandomly evaluates
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// to true. The probability of evaluating to true is determined by the
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// required float argument (must be ≤1). The optional second parameter is a
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// pseudorandom seed, for adjusting the deterministic randomness.
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// - Operation-specific:
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// (OpFileReadAt <INTEGER>) is a predicate that evaluates to true iff
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// an operation is a file ReadAt call with an offset that's exactly equal.
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//
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// Example: (ErrInjected (And (PathMatch "*.sst") (OnIndex 5))) is a rule set
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// that will inject an error on the 5-th I/O operation involving an sstable.
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func NewParser() *Parser {
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p := &Parser{
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predicates: dsl.NewPredicateParser[Op](),
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injectors: dsl.NewParser[Injector](),
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}
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p.predicates.DefineConstant("Reads", func() dsl.Predicate[Op] { return Reads })
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p.predicates.DefineConstant("Writes", func() dsl.Predicate[Op] { return Writes })
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p.predicates.DefineFunc("PathMatch",
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func(p *dsl.Parser[dsl.Predicate[Op]], s *dsl.Scanner) dsl.Predicate[Op] {
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pattern := s.ConsumeString()
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s.Consume(token.RPAREN)
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return PathMatch(pattern)
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})
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p.predicates.DefineFunc("OpFileReadAt",
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func(p *dsl.Parser[dsl.Predicate[Op]], s *dsl.Scanner) dsl.Predicate[Op] {
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return parseFileReadAtOp(s)
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})
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p.predicates.DefineFunc("Randomly",
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func(p *dsl.Parser[dsl.Predicate[Op]], s *dsl.Scanner) dsl.Predicate[Op] {
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return parseRandomly(s)
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})
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p.AddError(ErrInjected)
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return p
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}
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// A Parser parses the error-injecting DSL. It may be extended to include
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// additional errors through AddError.
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type Parser struct {
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predicates *dsl.Parser[dsl.Predicate[Op]]
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injectors *dsl.Parser[Injector]
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}
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// Parse parses the error injection DSL, returning the parsed injector.
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func (p *Parser) Parse(s string) (Injector, error) {
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return p.injectors.Parse(s)
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}
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// AddError defines a new error that may be used within the DSL parsed by
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// Parse and will inject the provided error.
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func (p *Parser) AddError(le LabelledError) {
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// Define the error both as a constant that unconditionally injects the
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// error, and as a function that injects the error only if the provided
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// predicate evaluates to true.
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p.injectors.DefineConstant(le.Label, func() Injector { return le })
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p.injectors.DefineFunc(le.Label,
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func(_ *dsl.Parser[Injector], s *dsl.Scanner) Injector {
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pred := p.predicates.ParseFromPos(s, s.Scan())
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s.Consume(token.RPAREN)
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return le.If(pred)
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})
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}
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// LabelledError is an error that also implements Injector, unconditionally
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// injecting itself. It implements String() by returning its label. It
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// implements Error() by returning its underlying error.
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type LabelledError struct {
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error
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Label string
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predicate Predicate
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}
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// String implements fmt.Stringer.
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func (le LabelledError) String() string {
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if le.predicate == nil {
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return le.Label
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}
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return fmt.Sprintf("(%s %s)", le.Label, le.predicate.String())
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}
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// MaybeError implements Injector.
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func (le LabelledError) MaybeError(op Op) error {
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if le.predicate == nil || le.predicate.Evaluate(op) {
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return le
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}
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return nil
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}
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// If returns an Injector that returns the receiver error if the provided
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// predicate evalutes to true.
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func (le LabelledError) If(p Predicate) Injector {
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le.predicate = p
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return le
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}
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func parseFileReadAtOp(s *dsl.Scanner) *opFileReadAt {
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lit := s.Consume(token.INT).Lit
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off, err := strconv.ParseInt(lit, 10, 64)
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if err != nil {
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panic(err)
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}
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s.Consume(token.RPAREN)
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return &opFileReadAt{offset: off}
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}
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func parseRandomly(s *dsl.Scanner) Predicate {
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lit := s.Consume(token.FLOAT).Lit
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p, err := strconv.ParseFloat(lit, 64)
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if err != nil {
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panic(err)
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} else if p > 1.0 {
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// NB: It's not possible for p to be less than zero because we don't
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// try to parse the '-' token.
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panic(errors.Newf("errorfs: Randomly proability p must be within p ≤ 1.0"))
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}
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var seed int64
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tok := s.Scan()
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switch tok.Kind {
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case token.RPAREN:
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case token.INT:
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seed, err = strconv.ParseInt(tok.Lit, 10, 64)
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if err != nil {
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panic(err)
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}
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s.Consume(token.RPAREN)
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default:
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panic(errors.Errorf("errorfs: unexpected token %s; expected RPAREN | FLOAT", tok.String()))
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}
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return Randomly(p, seed)
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}
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