a1a23b66c8
These changes are needed for the lambdas implementation. Co-authored-by: Samuel Gélineau <gelisam@gmail.com>
130 lines
3.6 KiB
Go
130 lines
3.6 KiB
Go
// Mgmt
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// Copyright (C) 2013-2023+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package structs
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import (
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"context"
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"fmt"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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)
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const (
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// ChannelBasedSinkFuncArgName is the name for the edge which connects
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// the input value to ChannelBasedSinkFunc.
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ChannelBasedSinkFuncArgName = "channelBasedSinkFuncArg"
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)
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// ChannelBasedSinkFunc is a Func which receives values from upstream nodes and
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// emits them to a golang channel.
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type ChannelBasedSinkFunc struct {
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Name string
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EdgeName string
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Target interfaces.Func // for drawing dashed edges in the Graphviz visualization
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Chan chan types.Value
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Type *types.Type
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init *interfaces.Init
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last types.Value // last value received to use for diff
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}
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// String returns a simple name for this function. This is needed so this struct
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// can satisfy the pgraph.Vertex interface.
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func (obj *ChannelBasedSinkFunc) String() string {
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return obj.Name
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}
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// ArgGen returns the Nth arg name for this function.
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func (obj *ChannelBasedSinkFunc) ArgGen(index int) (string, error) {
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if index != 0 {
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return "", fmt.Errorf("the ChannelBasedSinkFunc only has one argument")
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}
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return obj.EdgeName, nil
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}
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// Validate makes sure we've built our struct properly. It is usually unused for
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// normal functions that users can use directly.
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func (obj *ChannelBasedSinkFunc) Validate() error {
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if obj.Chan == nil {
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return fmt.Errorf("the Chan was not set")
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}
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return nil
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}
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// Info returns some static info about itself.
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func (obj *ChannelBasedSinkFunc) Info() *interfaces.Info {
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return &interfaces.Info{
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Pure: false,
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Memo: false,
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Sig: types.NewType(fmt.Sprintf("func(%s %s) %s", obj.EdgeName, obj.Type, obj.Type)),
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Err: obj.Validate(),
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}
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}
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// Init runs some startup code for this function.
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func (obj *ChannelBasedSinkFunc) Init(init *interfaces.Init) error {
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obj.init = init
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return nil
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}
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// Stream returns the changing values that this func has over time.
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func (obj *ChannelBasedSinkFunc) Stream(ctx context.Context) error {
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defer close(obj.init.Output) // the sender closes
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defer close(obj.Chan) // the sender closes
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for {
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select {
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case input, ok := <-obj.init.Input:
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if !ok {
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return nil // can't output any more
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}
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value, exists := input.Struct()[obj.EdgeName]
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if !exists {
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return fmt.Errorf("programming error, can't find edge")
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}
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if obj.last != nil && value.Cmp(obj.last) == nil {
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continue // value didn't change, skip it
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}
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obj.last = value // store so we can send after this select
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case <-ctx.Done():
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return nil
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}
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select {
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case obj.Chan <- obj.last: // send
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case <-ctx.Done():
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return nil
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}
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// Also send the value downstream. If we don't, then when we
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// close the Output channel, the function engine is going to
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// complain that we closed that channel without sending it any
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// value.
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select {
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case obj.init.Output <- obj.last: // send
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case <-ctx.Done():
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return nil
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}
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}
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}
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