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context.go
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context.go
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// Copyright 2022 geebytes
// Licensed under the Apache License, Version 2.0 (the 'License');
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an 'AS IS' BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tegenaria
import (
"context"
"time"
)
// Context spider crawl request schedule unit
// it is used on all data flow
type Context struct {
// Request
Request *Request
// DownloadResult downloader handler result
DownloadResult *RequestResult
//parent parent context
parent context.Context
// CtxId
CtxId string
// Error
Error error
//
Cancel context.CancelFunc
}
type ContextOption func(c *Context)
func NewContext(request *Request, opts ...ContextOption) *Context {
parent, cancel := context.WithCancel(context.TODO())
ctx := &Context{
Request: request,
parent: parent,
CtxId: GetUUID(),
DownloadResult: NewDownloadResult(),
Cancel: cancel,
}
for _, o := range opts {
o(ctx)
}
return ctx
}
func WithContext(ctx context.Context) ContextOption {
return func(c *Context) {
parent, cancel := context.WithCancel(ctx)
c.parent = parent
c.Cancel = cancel
}
}
// Deadline returns that there is no deadline (ok==false) when c has no Context.
func (c *Context) Deadline() (deadline time.Time, ok bool) {
if c.Request == nil || c.parent == nil {
return time.Time{}, false
}
return c.parent.Deadline()
}
// Done returns nil (chan which will wait forever) when c.Request has no Context.
func (c *Context) Done() <-chan struct{} {
if c.Request == nil || c.parent == nil {
return nil
}
return c.parent.Done()
}
// Err returns nil when ct has no Context.
func (c *Context) Err() error {
if c.Request == nil || c.parent == nil {
return nil
}
return c.parent.Err()
}
// Value returns the value associated with this context for key, or nil
// if no value is associated with key. Successive calls to Value with
// the same key returns the same result.
func (c *Context) Value(key interface{}) interface{} {
if key == 0 {
return c.Request
}
if c.Request == nil || c.parent == nil {
return nil
}
return c.parent.Value(key)
}
func (c Context) GetCtxId() string {
return c.CtxId
}