vm

package
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 Go to latest Published: Apr 25, 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

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 Equals 

func Equals(t1, t2 Type) bool

Equals compares two types, testing for equality

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

func Parse 

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

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)

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)

func (ErrorList) Error 

func (p ErrorList) Error() string

ErrorList implements the error interface.

type Loader 

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

Loader 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(o LoaderOptions) (*Loader, error)

NewLoader creates a new program loader. It takes a filesystem watcher and a filesystem interface as arguments. If fs is nil, it will use the default filesystem interface.

func (*Loader) CompileAndRun 

func (l *Loader) 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 (*Loader) LoadAllPrograms 

func (l *Loader) 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 (*Loader) LoadProgram 

func (l *Loader) 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 (*Loader) UnloadProgram 

func (l *Loader) UnloadProgram(pathname string)

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

func (*Loader) WriteStatusHTML 

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

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

type LoaderOptions 

type LoaderOptions struct {
	Store *metrics.Store
	Lines <-chan *tailer.LogLine

	ProgramPath string // Path containing mtail programs

	W  watcher.Watcher // Not required, will use watcher.LogWatcher if zero.
	FS afero.Fs        // Not required, will use afero.OsFs if zero.

	OverrideLocation     *time.Location // if not nil, overrides the timezone in strptime().
	CompileOnly          bool           // Compile, don't start execution.
	ErrorsAbort          bool           // Compiler errors abort the loader.
	DumpAst              bool           // print the AST after type check
	DumpAstTypes         bool           // Instructs the loader to dump to stdout the compiled program after compilation.
	DumpBytecode         bool           // Instructs the loader to dump the program bytecode after compilation.
	SyslogUseCurrentYear bool           // If true, override empty year with the current in strptime().
	OmitMetricSource     bool           // Don't put the source in the metric when added to the Store.
}

LoaderOptions contains the required and optional parameters for creating a new Loader.

type Options 

type Options struct {
	CompileOnly          bool           // Do not start the program after compilation.
	SyslogUseCurrentYear bool           // Use the current year if no year is present in the log file timestamp.
	EmitAst              bool           // Print the AST after parse
	EmitAstTypes         bool           // Print the AST with types after typechecking
	OverrideLocation     *time.Location //
}

Options contains all the parameters that affect the behaviour of the compiler.

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) 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)

func (*Sexp) VisitBefore 

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

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
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

type TypeError 

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

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

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

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)

func (*Unparser) VisitBefore 

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

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, o *Options) (*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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