mctx: moved ctx code from m and kept fleshing it out, trying to figure out how to incorporate Logger

This commit is contained in:
Brian Picciano 2018-10-28 19:34:26 -04:00
parent 6c055d0255
commit e349d0fbd8
5 changed files with 235 additions and 142 deletions

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@ -1,73 +0,0 @@
package m
import (
"context"
"sync"
)
type ctxKey int
const (
ctxStateKey ctxKey = iota
)
type ctxState struct {
path []string
l sync.RWMutex
children map[string]context.Context
}
func newCtxState() *ctxState {
return &ctxState{
children: map[string]context.Context{},
}
}
// Ctx returns a new context which can be used as the root context for all
// purposes in this framework.
func Ctx() context.Context {
return context.WithValue(context.Background(), ctxStateKey, newCtxState())
}
func getCtxState(ctx context.Context) *ctxState {
s, _ := ctx.Value(ctxStateKey).(*ctxState)
if s == nil {
panic("non-conforming context used")
}
return s
}
// Path returns the sequence of names which were used to produce this context
// via the ChildOf function.
func Path(ctx context.Context) []string {
return getCtxState(ctx).path
}
// Children returns all children of this context which have been created by
// ChildOf, mapped by their name.
func Children(ctx context.Context) map[string]context.Context {
s := getCtxState(ctx)
out := map[string]context.Context{}
s.l.RLock()
defer s.l.RUnlock()
for name, childCtx := range s.children {
out[name] = childCtx
}
return out
}
// ChildOf creates a child of the given context with the given name and returns
// it. The Path of the returned context will be the path of the parent with its
// name appended to it. The Children function can be called on the parent to
// retrieve all children which have been made using this function.
func ChildOf(ctx context.Context, name string) context.Context {
s, childS := getCtxState(ctx), newCtxState()
s.l.Lock()
defer s.l.Unlock()
childS.path = make([]string, 0, len(s.path)+1)
childS.path = append(childS.path, s.path...)
childS.path = append(childS.path, name)
childCtx := context.WithValue(ctx, ctxStateKey, childS)
s.children[name] = childCtx
return childCtx
}

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@ -1,39 +0,0 @@
package m
import (
"context"
. "testing"
"github.com/mediocregopher/mediocre-go-lib/mtest/massert"
)
func TestContext(t *T) {
ctx := Ctx()
ctx1 := ChildOf(ctx, "1")
ctx1a := ChildOf(ctx1, "a")
ctx1b := ChildOf(ctx1, "b")
ctx2 := ChildOf(ctx, "2")
massert.Fatal(t, massert.All(
massert.Len(Path(ctx), 0),
massert.Equal(Path(ctx1), []string{"1"}),
massert.Equal(Path(ctx1a), []string{"1", "a"}),
massert.Equal(Path(ctx1b), []string{"1", "b"}),
massert.Equal(Path(ctx2), []string{"2"}),
))
massert.Fatal(t, massert.All(
massert.Equal(
map[string]context.Context{"1": ctx1, "2": ctx2},
Children(ctx),
),
massert.Equal(
map[string]context.Context{"a": ctx1a, "b": ctx1b},
Children(ctx1),
),
massert.Equal(
map[string]context.Context{},
Children(ctx2),
),
))
}

30
m/m.go
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@ -5,10 +5,7 @@
package m package m
import ( import (
"io"
"github.com/mediocregopher/mediocre-go-lib/mcfg" "github.com/mediocregopher/mediocre-go-lib/mcfg"
"github.com/mediocregopher/mediocre-go-lib/mlog"
) )
// CfgSource returns an mcfg.Source which takes in configuration info from the // CfgSource returns an mcfg.Source which takes in configuration info from the
@ -19,30 +16,3 @@ func CfgSource() mcfg.Source {
mcfg.SourceCLI{}, mcfg.SourceCLI{},
} }
} }
// TODO this isn't going to work. At some point there will be something like
// mhttp which will have some glue code for it in here, but then something
// within it which logs (like the http server), and then there'll be an import
// cycle.
//
// Ultimately it might be worthwhile to make Logger be a field on Cfg, that
// really seems like the only other place where code like this makes sense to
// go. But then that's greatly expanding the purview of Cfg, which is
// unfortunate....
// Log returns a Logger which will automatically include with the log extra
// contextual information based on the Cfg and the given KVs
//
// If the cfg is nil then mlog.DefaultLogger is returned.
func Log(cfg *mcfg.Cfg, kvs ...mlog.KVer) *mlog.Logger {
fn := cfg.FullName()
l := mlog.DefaultLogger.Clone()
l.SetWriteFn(func(w io.Writer, msg mlog.Message) error {
msg.Msg = "(" + fn + ") " + msg.Msg
return mlog.DefaultWriteFn(w, msg)
})
if len(kvs) > 0 {
l.AddKV(kvs...)
}
return l
}

177
mctx/ctx.go Normal file
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@ -0,0 +1,177 @@
// Package mctx provides a framework, based around the Context type, for
// managing configuration, initialization, runtime, and shutdown of a binary.
// The framework allows components to manage these aspects individually by means
// of a heirarchical system.
//
// Each node in the hierarchy is given a name and is aware of all of its
// ancestors, and can incorporate this information into its functionality.
package mctx
import (
"context"
"sync"
"time"
)
// Context is the same as the builtin type, but is used to indicate that the
// Context originally came from this package (aka New or ChildOf).
type Context context.Context
// CancelFunc is a direct alias of the type from the context package, see its
// docs.
type CancelFunc = context.CancelFunc
// WithValue mimics the function from the context package.
func WithValue(parent Context, key, val interface{}) Context {
return Context(context.WithValue(context.Context(parent), key, val))
}
// WithCancel mimics the function from the context package.
func WithCancel(parent Context) (Context, CancelFunc) {
ctx, fn := context.WithCancel(context.Context(parent))
return Context(ctx), fn
}
// WithDeadline mimics the function from the context package.
func WithDeadline(parent Context, t time.Time) (Context, CancelFunc) {
ctx, fn := context.WithDeadline(context.Context(parent), t)
return Context(ctx), fn
}
// WithTimeout mimics the function from the context package.
func WithTimeout(parent Context, d time.Duration) (Context, CancelFunc) {
ctx, fn := context.WithTimeout(context.Context(parent), d)
return Context(ctx), fn
}
////////////////////////////////////////////////////////////////////////////////
type ctxKey int
type ctxState struct {
path []string
l sync.RWMutex
parent Context
children map[string]Context
mutVals map[interface{}]interface{}
}
func getCtxState(ctx Context) *ctxState {
s, _ := ctx.Value(ctxKey(0)).(*ctxState)
if s == nil {
panic("non-conforming context used")
}
return s
}
func withCtxState(ctx Context, s *ctxState) Context {
return WithValue(ctx, ctxKey(0), s)
}
// New returns a new context which can be used as the root context for all
// purposes in this framework.
func New() Context {
return withCtxState(Context(context.Background()), &ctxState{
//logger: mlog.NewLogger(os.Stderr),
})
}
// Path returns the sequence of names which were used to produce this context
// via the ChildOf function.
func Path(ctx Context) []string {
return getCtxState(ctx).path
}
// Children returns all children of this context which have been created by
// ChildOf, mapped by their name.
func Children(ctx Context) map[string]Context {
s := getCtxState(ctx)
out := map[string]Context{}
s.l.RLock()
defer s.l.RUnlock()
for name, childCtx := range s.children {
out[name] = childCtx
}
return out
}
// Parent returns the parent Context of the given one, or nil if this is a root
// context (i.e. returned from New).
func Parent(ctx Context) Context {
return getCtxState(ctx).parent
}
// ChildOf creates a child of the given context with the given name and returns
// it. The Path of the returned context will be the path of the parent with its
// name appended to it. The Children function can be called on the parent to
// retrieve all children which have been made using this function.
func ChildOf(ctx Context, name string) Context {
s, childS := getCtxState(ctx), new(ctxState)
s.l.Lock()
defer s.l.Unlock()
// set child's path field
childS.path = make([]string, 0, len(s.path)+1)
childS.path = append(childS.path, s.path...)
childS.path = append(childS.path, name)
// set child's parent field
childS.parent = ctx
// set up child's logger
//pathStr := "/"
//if len(childS.path) > 0 {
// pathStr += path.Join(childS.path...)
//}
//childS.logger = s.logger.Clone()
//childS.logger.SetWriteFn(func(w io.Writer, msg mlog.Message) error {
// msg.Msg = "(" + pathStr + ") " + msg.Msg
// return mlog.DefaultWriteFn(w, msg)
//})
// copy mutable values
if len(s.mutVals) > 0 {
childS.mutVals = make(map[interface{}]interface{}, len(s.mutVals))
for key, val := range s.mutVals {
childS.mutVals[key] = val
}
}
// create child's ctx and store it in parent
childCtx := withCtxState(ctx, childS)
if s.children == nil {
s.children = map[string]Context{}
}
s.children[name] = childCtx
return childCtx
}
// TODO these might not be worth the effort, they're very subject to
// race-conditions
// SetMutableValue is like WithMutable, except rather than leaving the original
// ctx unaffected it modifies the value in that context. Children of this
// context will inherit an independent copy of its immutable values.
func SetMutableValue(ctx Context, key, value interface{}) {
s := getCtxState(ctx)
s.l.Lock()
defer s.l.Unlock()
if s.mutVals == nil {
s.mutVals = map[interface{}]interface{}{}
}
s.mutVals[key] = value
}
// MutableValue acts like the Value method, except that it only deals with
// keys/values set by SetMutableValue.
func MutableValue(ctx Context, key interface{}) interface{} {
s := getCtxState(ctx)
s.l.RLock()
defer s.l.RUnlock()
if s.mutVals == nil {
return nil
}
return s.mutVals[key]
}

58
mctx/ctx_test.go Normal file
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@ -0,0 +1,58 @@
package mctx
import (
. "testing"
"github.com/mediocregopher/mediocre-go-lib/mtest/massert"
)
func TestContext(t *T) {
ctx := New()
SetMutableValue(ctx, "one", 1)
ctx1 := ChildOf(ctx, "1")
ctx1a := ChildOf(ctx1, "a")
SetMutableValue(ctx1, "one", 2)
ctx1b := ChildOf(ctx1, "b")
SetMutableValue(ctx1b, "one", 3)
ctx2 := ChildOf(ctx, "2")
massert.Fatal(t, massert.All(
massert.Len(Path(ctx), 0),
massert.Equal(Path(ctx1), []string{"1"}),
massert.Equal(Path(ctx1a), []string{"1", "a"}),
massert.Equal(Path(ctx1b), []string{"1", "b"}),
massert.Equal(Path(ctx2), []string{"2"}),
))
massert.Fatal(t, massert.All(
massert.Equal(
map[string]Context{"1": ctx1, "2": ctx2},
Children(ctx),
),
massert.Equal(
map[string]Context{"a": ctx1a, "b": ctx1b},
Children(ctx1),
),
massert.Equal(
map[string]Context{},
Children(ctx2),
),
))
massert.Fatal(t, massert.All(
massert.Nil(Parent(ctx)),
massert.Equal(Parent(ctx1), ctx),
massert.Equal(Parent(ctx1a), ctx1),
massert.Equal(Parent(ctx1b), ctx1),
massert.Equal(Parent(ctx2), ctx),
))
massert.Fatal(t, massert.All(
massert.Equal(MutableValue(ctx, "one"), 1),
massert.Equal(MutableValue(ctx1, "one"), 2),
massert.Equal(MutableValue(ctx1a, "one"), 1),
massert.Equal(MutableValue(ctx1b, "one"), 3),
massert.Equal(MutableValue(ctx2, "one"), 1),
))
}