vm

package
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 Go to latest Published: Jun 30, 2018 License: Apache-2.0 Imports: 29 Imported by: 0

Documentation

Overview

Package vm provides a compiler and virtual machine environment for executing mtail programs.

Package vm provides a compiler and virtual machine environment for executing mtail programs.

Index

Constants

View Source 
const EOF = 0

EOF is a marker for end of file.

Variables

View Source 
var (
	// LineCount counts the number of lines read by the program loader from the input channel.
	LineCount = expvar.NewInt("line_count")
	// ProgLoads counts the number of program load events.
	ProgLoads = expvar.NewMap("prog_loads_total")
	// ProgLoadErrors counts the number of program load errors.
	ProgLoadErrors = expvar.NewMap("prog_load_errors")
)
View Source 
var (
	Undef   = &TypeOperator{"Undef", []Type{}}
	Error   = &TypeOperator{"Error", []Type{}}
	None    = &TypeOperator{"None", []Type{}}
	Bool    = &TypeOperator{"Bool", []Type{}}
	Int     = &TypeOperator{"Int", []Type{}}
	Float   = &TypeOperator{"Float", []Type{}}
	String  = &TypeOperator{"String", []Type{}}
	Pattern = &TypeOperator{"Pattern", []Type{}}
)

Builtin types

View Source 
var Builtins = map[string]Type{
	"int":         Function(NewTypeVariable(), Int),
	"bool":        Function(NewTypeVariable(), Bool),
	"float":       Function(NewTypeVariable(), Float),
	"string":      Function(NewTypeVariable(), String),
	"timestamp":   Function(Int),
	"len":         Function(String, Int),
	"settime":     Function(Int, None),
	"strptime":    Function(String, String, None),
	"strtol":      Function(String, Int, Int),
	"tolower":     Function(String, String),
	"getfilename": Function(String),
}

Builtins is a mapping of the builtin language functions to their type definitions.

Functions

func Check 

func Check(node astNode) error

Check performs a semantic check of the astNode, and returns a list of errors found, or nil if the program is semantically valid. At the completion of Check, the symbol table and type annotation are also complete.

func CodeGen 

func CodeGen(name string, ast astNode) (*object, error)

CodeGen is the function that compiles the program to bytecode and data.

func CompileOnly 

func CompileOnly(l *MasterControl) error

CompileOnly sets the Loader to compile programs only, without executing them.

func DumpAst 

func DumpAst(l *MasterControl) error

DumpAst instructs the Loader to print the AST after program compilation.

func DumpAstTypes 

func DumpAstTypes(l *MasterControl) error

DumpAstTypes instructs the Loader to print the AST after type checking.

func DumpBytecode 

func DumpBytecode(l *MasterControl) error

DumpBytecode instructs the loader to print the compiled bytecode after code generation.

func Equals 

func Equals(t1, t2 Type) bool

Equals compares two types, testing for equality

func ErrorsAbort 

func ErrorsAbort(l *MasterControl) error

ErrorsAbort sets the Loader to abort the Loader on compile errors.

func IsComplete 

func IsComplete(t Type) bool

IsComplete returns true if the type and all its arguments have non-variable exemplars.

func IsDimension 

func IsDimension(t Type) bool

IsDimension returns true if the given type is a Dimension type.

func IsFunction 

func IsFunction(t Type) bool

IsFunction returns true if the given type is a Function type.

func MergePosition 

func MergePosition(a, b *position) *position

MergePosition returns the union of two positions such that the result contains both inputs.

func OmitMetricSource 

func OmitMetricSource(l *MasterControl) error

OmitMetricSource instructs the Loader to not annotate metrics with their program source when added to the metric store.

func OverrideLocation 

func OverrideLocation(loc *time.Location) func(*MasterControl) error

OverrideLocation sets the timezone location for the VM.

func Parse 

func Parse(name string, input io.Reader) (astNode, error)

Parse reads the program named name from the input, and if successful returns an astNode for the root of the AST, or parser errors.

func SyslogUseCurrentYear 

func SyslogUseCurrentYear(l *MasterControl) error

SyslogUseCurrentYear instructs the VM to annotate yearless timestamps with the current year.

func Unify 

func Unify(a, b Type) error

Unify performs type unification of both parameter Types. It returns the least upper bound of both types, the smallest type that is capable of representing both parameters. If either type is a type variable, then that variable is unified with the LUB. In reporting errors, it is assumed that a is the expected type and b is the type observed.

func Walk 

func Walk(v Visitor, node astNode)

Walk traverses (walks) an AST node with the provided Visitor v.

Types

type ErrorList 

type ErrorList []*compileError

ErrorList contains a list of compile errors.

func (*ErrorList) Add 

func (p *ErrorList) Add(pos *position, msg string)

Add appends an error at a position to the list of errors.

func (*ErrorList) Append 

func (p *ErrorList) Append(l ErrorList)

Append puts an ErrorList on the end of this ErrorList.

func (ErrorList) Error 

func (p ErrorList) Error() string

ErrorList implements the error interface.

type MasterControl 

type MasterControl struct {
	VMsDone chan struct{} // Notify mtail when all running VMs are shutdown.
	// contains filtered or unexported fields
}

MasterControl handles the lifecycle of programs and virtual machines, by watching the configured program source directory, compiling changes to programs, and managing the running virtual machines that receive input from the lines channel.

func NewLoader 

func NewLoader(programPath string, store *metrics.Store, lines <-chan *tailer.LogLine, w watcher.Watcher, fs afero.Fs, options ...func(*MasterControl) error) (*MasterControl, error)

NewLoader creates a new program loader that reads programs from programPath.

func (*MasterControl) CompileAndRun 

func (l *MasterControl) CompileAndRun(name string, input io.Reader) error

CompileAndRun compiles a program read from the input, starting execution if it succeeds. If an existing virtual machine of the same name already exists, the previous virtual machine is terminated and the new loaded over it. If the new program fails to compile, any existing virtual machine with the same name remains running.

func (*MasterControl) LoadAllPrograms 

func (l *MasterControl) LoadAllPrograms() error

LoadAllPrograms loads all programs in a directory and starts watching the directory for filesystem changes. Any compile errors are stored for later retrieival. This function returns an error if an internal error occurs.

func (*MasterControl) LoadProgram 

func (l *MasterControl) LoadProgram(programPath string) error

LoadProgram loads or reloads a program from the path specified. The name of the program is the basename of the file.

func (*MasterControl) SetOption 

func (l *MasterControl) SetOption(options ...func(*MasterControl) error) error

SetOption takes one or more option functions and applies them in order to Loader.

func (*MasterControl) UnloadProgram 

func (l *MasterControl) UnloadProgram(pathname string)

UnloadProgram removes the named program from the watcher to prevent future updates, and terminates any currently running VM goroutine.

func (*MasterControl) WriteStatusHTML 

func (l *MasterControl) WriteStatusHTML(w io.Writer) error

WriteStatusHTML writes the current state of the loader as HTML to the given writer w.

type Scope 

type Scope struct {
	Parent  *Scope
	Symbols map[string]*Symbol
}

Scope maintains a record of the identifiers declared in the current program scope, and a link to the parent scope.

func NewScope 

func NewScope(parent *Scope) *Scope

NewScope creates a new scope within the parent scope

func (*Scope) CopyFrom 

func (s *Scope) CopyFrom(o *Scope)

CopyFrom copies all the symbols from another scope object into this one. It recurses up the input scope copying all visible symbols into one.

func (*Scope) Insert 

func (s *Scope) Insert(sym *Symbol) (alt *Symbol)

Insert attempts to insert a symbol into the scope. If the scope already contains an object alt with the same name, the scope is unchanged and the function returns alt. Otherwise the symbol is inserted, and returns nil.

func (*Scope) InsertAlias 

func (s *Scope) InsertAlias(sym *Symbol, alias string) (alt *Symbol)

InsertAlias attempts to insert a duplicate name for an existing symbol into the scope. If the scope already contains an object alt with the alias, the scope is unchanged and the function returns alt. Otherwise, the symbol is inserted and the function returns nil.

func (*Scope) Lookup 

func (s *Scope) Lookup(name string, kind SymbolKind) *Symbol

Lookup returns the symbol with the given name if it is found in this or any parent scope, otherwise nil.

func (*Scope) String 

func (s *Scope) String() string

String prints the current scope and all parents to a string, recursing up to the root scope. This method is only used for debugging.

type Sexp 

type Sexp struct {
	// contains filtered or unexported fields
}

Sexp is for converting program syntax trees into typed s-expression for printing

func (*Sexp) Dump 

func (s *Sexp) Dump(n astNode) string

Dump begins the dumping of the syntax tree, returning the s-expression as a single string

func (*Sexp) VisitAfter 

func (s *Sexp) VisitAfter(node astNode)

VisitAfter implements the astNode Visitor interface.

func (*Sexp) VisitBefore 

func (s *Sexp) VisitBefore(n astNode) Visitor

VisitBefore implements the astNode Visitor interface.

type Symbol 

type Symbol struct {
	Name    string      // identifier name
	Kind    SymbolKind  // kind of program object
	Type    Type        // object's type
	Pos     *position   // Source file position of definition
	Binding interface{} // binding to storage allocated in runtime
	Addr    int         // Address offset in another structure, object specific
	Used    bool        // Optional marker that this symbol is used after declaration.
}

Symbol describes a named program object.

func NewSymbol 

func NewSymbol(name string, kind SymbolKind, pos *position) (sym *Symbol)

NewSymbol creates a record of a given symbol kind, named name, found at loc

type SymbolKind 

type SymbolKind int

SymbolKind enumerates the kind of a Symbol. 

const (
	VarSymbol     SymbolKind = iota // Variables
	CaprefSymbol                    // Capture group references
	DecoSymbol                      // Decorators
	PatternSymbol                   // Named pattern constants
)

SymbolKind enumerates the kinds of symbols found in the program text.

func (SymbolKind) String 

func (k SymbolKind) String() string

type Type 

type Type interface {
	// Root returns an exemplar Type after unification occurs.  If the type
	// system is complete after unification, Root will be a TypeOperator.
	Root() Type

	// String returns a string representation of a Type.
	String() string
}

Type represents a type in the mtail program.

func FreshType 

func FreshType(t Type) Type

FreshType returns a new type from the provided type scheme, replacing any unbound type variables with new type variables.

func LeastUpperBound 

func LeastUpperBound(a, b Type) Type

LeastUpperBound returns the smallest type that may contain both parameter types.

type TypeError 

type TypeError struct {
	// contains filtered or unexported fields
}

TypeError describes an error in which a type was expected, but another was encountered.

func (*TypeError) Error 

func (e *TypeError) Error() string

type TypeOperator 

type TypeOperator struct {
	// Name is a common name for this operator
	Name string
	// Args is the sequence of types that are parameters to this type.  They
	// may be fully bound type operators, or partially defined (i.e. contain
	// TypeVariables) in which case they represent polymorphism in the operator
	// they are argyments to.
	Args []Type
}

TypeOperator represents a type scheme in the type system.

func Dimension 

func Dimension(args ...Type) *TypeOperator

Dimension is a convenience method which instantiates a new Dimension type scheme, with the given args as the dimensions of the type.

func Function 

func Function(args ...Type) *TypeOperator

Function is a convenience method, which instantiates a new Function type scheme, with the given args as parameters.

func (*TypeOperator) Root 

func (t *TypeOperator) Root() Type

Root returns an exemplar of a TypeOperator, i.e. itself.

func (*TypeOperator) String 

func (t *TypeOperator) String() (s string)

type TypeVariable 

type TypeVariable struct {
	ID int

	Instance *Type
	// contains filtered or unexported fields
}

TypeVariable represents an unbound type variable in the type system.

func NewTypeVariable 

func NewTypeVariable() *TypeVariable

NewTypeVariable constructs a new unique TypeVariable.

func (*TypeVariable) Root 

func (t *TypeVariable) Root() Type

Root returns an exemplar of this TypeVariable, in this case the root of the unification tree.

func (*TypeVariable) SetInstance 

func (t *TypeVariable) SetInstance(t1 *Type)

SetInstance sets the exemplar instance of this TypeVariable, during unification.

func (*TypeVariable) String 

func (t *TypeVariable) String() string

type Unparser 

type Unparser struct {
	// contains filtered or unexported fields
}

Unparser is for converting program syntax trees back to program text.

func (*Unparser) Unparse 

func (u *Unparser) Unparse(n astNode) string

Unparse begins the unparsing of the syntax tree, returning the program text as a single string.

func (*Unparser) VisitAfter 

func (u *Unparser) VisitAfter(n astNode)

VisitAfter implements the astNode Visitor interface.

func (*Unparser) VisitBefore 

func (u *Unparser) VisitBefore(n astNode) Visitor

VisitBefore implements the astNode Visitor interface.

type VM 

type VM struct {
	// contains filtered or unexported fields
}

VM describes the virtual machine for each program. It contains virtual segments of the executable bytecode, constant data (string and regular expressions), mutable state (metrics), and a stack for the current thread of execution.

func Compile 

func Compile(name string, input io.Reader, emitAst bool, emitAstTypes bool, syslogUseCurrentYear bool, loc *time.Location) (*VM, error)

Compile compiles a program from the input into a virtual machine or a list of compile errors. It takes the program's name and the metric store as additional arguments to build the virtual machine.

func New 

func New(name string, obj *object, syslogUseCurrentYear bool, loc *time.Location) *VM

New creates a new virtual machine with the given name, and compiler artifacts for executable and data segments.

func (*VM) DumpByteCode 

func (v *VM) DumpByteCode(name string) string

DumpByteCode emits the program disassembly and program objects to a string.

func (*VM) ParseTime 

func (v *VM) ParseTime(layout, value string) (tm time.Time)

ParseTime performs location and syslog-year aware timestamp parsing.

func (*VM) Run 

func (v *VM) Run(_ uint32, lines <-chan *tailer.LogLine, shutdown chan<- struct{}, started chan<- struct{})

Run executes the virtual machine on each line of input received. When the input closes, it signals to the loader that it has terminated by closing the shutdown channel.

type Visitor 

type Visitor interface {
	VisitBefore(n astNode) (v Visitor)
	VisitAfter(n astNode)
}

Visitor VisitBefore method is invoked for each node encountered by Walk. If the result Visitor v is not nil, Walk visits each of the children of that node with v. VisitAfter is called on n at the end.

Source Files

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