Initial distributor implementation

appengine/cmd/dm/distributor/impl/jobsim/parser/grammar.peg

+// vim: syntax=go
+{
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package parser
+
+type retriesHolder uint64
+type identityHolder uint64
+
+var whitespaceRE = regexp.MustCompile("#[^\n]*\n|\\s+")
+
+// CleanPhrase removes all whitespace and comments from a phrase in preparation
+// for parsing it. The parsers defined in this package only operate on cleaned
+// phrases, and will fail to parse if you provide a phrase with whitespace.
+func CleanPhrase(p string) string {
+  return whitespaceRE.ReplaceAllLiteralString(p, "")
+}
+
+// ParsePhrase is a convenience function for the parser functions in this
+// package to return a typed Phrase object as the result of a string.
+func ParsePhrase(p string) (Phrase, error) {
+  ret, err := Parse("<string>", []byte(p))
+  if err != nil {
+    return nil, err
+  }
+  return ret.(Phrase), nil
+}
+}
+
+Overall = p:Phrase !. {
+  return p, nil
+} / p:Phrase ext:Extra {
+  return nil, fmt.Errorf("found extra: %q", ext.(string))
+} / !. {
+  return nil, fmt.Errorf("empty phrase")
+} / ext:Extra {
+  return nil, fmt.Errorf("expected phrase: %q", ext.(string))
+}
+
+Extra = .* {
+  return string(c.text), nil
+}
+
+Phrase = ret:ReturnStage {
+  return Phrase{ret.(Stage)}, nil
+} / first:Stage middleI:(',' Stage)* retI:(',' ReturnStage)? {
+  middle, _ := middleI.([]interface{})
+  retStage, _ := retI.([]interface{})
+
+  amt := 1
+  if middle != nil {
+    amt += len(middle)
+  }
+  if retStage != nil {
+    amt++
+  }
+
+  ret := make(Phrase, 0, amt)
+  ret = append(ret, first.(Stage))
+  for _, itm := range middle {
+    ret = append(ret, itm.([]interface{})[1].(Stage))
+  }
+  if retStage != nil {
+    ret = append(ret, retStage[1].(Stage))
+  }
+
+  return ret, nil
+} / ',' .* {
+  return nil, fmt.Errorf("expected stage in %q", string(c.text))
+}
+
+Stage = s:(FailureStage / StallStage / DepsStage) {
+  return s, nil
+}
+
+FailureStage = '%' num:Num {
+  return FailureStage(num.(uint64)), nil
+}
+
+StallStage = '@' amt:Duration {
+  return StallStage(amt.(time.Duration)), nil
+}
+
+ReturnStage = '=' val:Num exp:('<' Duration)? {
+  ret := &ReturnStage{Value: val.(uint64)}
+  if exp != nil {
+    ret.Expiration = exp.([]interface{})[1].(time.Duration)
+  }
+  return ret, nil
+}
+
+DepsStage = first:Dependency restI:('&' Dependency)* {
+  rest, _ := restI.([]interface{})
+
+  if rest == nil {
+    return DepsStage{first.(*Dependency)}, nil
+  }
+  ret := make(DepsStage, 0, 1+len(rest))
+  ret = append(ret, first.(*Dependency))
+  for _, itm := range rest{
+    ret = append(ret, itm.([]interface{})[1].(*Dependency))
+  }
+  return ret, nil
+} / '&' .* {
+  return nil, fmt.Errorf("expected dependency in %q", string(c.text))
+}
+
+Dependency = shards:Shards? attempts:Attempts? id:ID options:Option? subI:( '(' Phrase ')' )? {
+  ret := &Dependency{Name: id.(string)}
+
+  if shards != nil {
+    ret.ShardCount = shards.(uint64)
+  }
+
+  if attempts != nil {
+    ret.AttemptNums = attempts.(RangeSlice)
+  }
+
+  if options != nil {
+    switch x := options.(type) {
+    case retriesHolder:
+      if attempts != nil {
+        return nil, fmt.Errorf(
+          "in %q: retries are incompatible with specified Attempts",
+          string(c.text))
+      }
+      ret.Retries = uint64(x)
+
+    case identityHolder:
+      ret.Uniq = uint64(x)
+    }
+  }
+
+  sub, _ := subI.([]interface{})
+  if sub != nil {
+    ret.Substages = sub[1].(Phrase)
+  }
+
+  return ret, nil
+}
+
+Option = '+' num:Num  {
+  return retriesHolder(num.(uint64)), nil
+} / '^' num:Num  {
+  return identityHolder(num.(uint64)), nil
+}
+
+Shards = '{' num:Num '}' {
+  return num, nil
+}
+
+Attempts = '[' rs:RangeSlice ']' {
+  return rs, nil
+}
+
+RangeSlice = firstI:Range restI:(',' Range)* {
+  rest, _ := restI.([]interface{})
+
+  ret := make(RangeSlice, 0, 1+len(rest))
+  ret = append(ret, firstI.(Range))
+  for _, itm := range rest {
+    ret = append(ret, itm.([]interface{})[1].(Range))
+  }
+
+  return ret, nil
+}
+
+Range = loI:Num '-' hiI:Num {
+  lo := loI.(uint64)
+  hi := hiI.(uint64)
+
+  if lo >= hi {
+    return nil, fmt.Errorf("invalid range %q: lo >= hi", string(c.text))
+  }
+
+  return Range{lo, hi}, nil
+} / num:Num {
+  return Range{num.(uint64), 0}, nil
+}
+
+Duration = num:Num {
+  return time.Second * time.Duration(num.(uint64)), nil
+}
+
+Num = '0' {
+  return nil, fmt.Errorf("zero value not acceptable")
+} / [1-9][0-9]* {
+  return strconv.ParseUint(string(c.text), 10, 64)
+} / .* {
+  return nil, fmt.Errorf("expected number, got %q", string(c.text))
+}
+
+ID = [a-zA-Z'_]+ {
+  return string(c.text), nil
+}