589a5f9aeb
The new version of the urfave/cli library is moving to generics, and it's completely unclear to me why this is an improvement. Their new API is very complicated to understand, which for me, defeats the purpose of golang. In parallel, I needed to do some upcoming cli API refactoring, so this was a good time to look into new libraries. After a review of the landscape, I found the alexflint/go-arg library which has a delightfully elegant API. It does have a few rough edges, but it's otherwise very usable, and I think it would be straightforward to add features and fix issues. Thanks Alex!
719 lines
22 KiB
Go
719 lines
22 KiB
Go
// Mgmt
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// Copyright (C) 2013-2024+ 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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// test with:
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// time ./mgmt run --hostname h1 --tmp-prefix --no-pgp lang examples/lang/schedule0.mcl
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// time ./mgmt run --hostname h2 --seeds=http://127.0.0.1:2379 --client-urls=http://127.0.0.1:2381 --server-urls=http://127.0.0.1:2382 --tmp-prefix --no-pgp lang examples/lang/schedule0.mcl
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// time ./mgmt run --hostname h3 --seeds=http://127.0.0.1:2379 --client-urls=http://127.0.0.1:2383 --server-urls=http://127.0.0.1:2384 --tmp-prefix --no-pgp lang examples/lang/schedule0.mcl
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// kill h2 (should see h1 and h3 pick [h1, h3] instead)
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// restart h2 (should see [h1, h3] as before)
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// kill h3 (should see h1 and h2 pick [h1, h2] instead)
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// restart h3 (should see [h1, h2] as before)
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// kill h3
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// kill h2
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// kill h1... all done!
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package coreworld
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import (
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"context"
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"fmt"
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"sort"
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"github.com/purpleidea/mgmt/etcd/scheduler" // TODO: is it okay to import this without abstraction?
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"github.com/purpleidea/mgmt/lang/funcs"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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"github.com/purpleidea/mgmt/util/errwrap"
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)
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const (
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// ScheduleFuncName is the name this function is registered as.
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ScheduleFuncName = "schedule"
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// DefaultStrategy is the strategy to use if none has been specified.
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DefaultStrategy = "rr"
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// StrictScheduleOpts specifies whether the opts passed into the
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// scheduler must be strictly what we're expecting, and nothing more.
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// If this was false, then we'd allow an opts struct that had a field
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// that wasn't used by the scheduler. This could be useful if we need to
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// migrate to a newer version of the function. It's probably best to
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// keep this strict.
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StrictScheduleOpts = true
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// arg names...
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scheduleArgNameNamespace = "namespace"
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scheduleArgNameOpts = "opts"
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)
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func init() {
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funcs.ModuleRegister(ModuleName, ScheduleFuncName, func() interfaces.Func { return &ScheduleFunc{} })
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}
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var _ interfaces.PolyFunc = &ScheduleFunc{} // ensure it meets this expectation
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// ScheduleFunc is special function which determines where code should run in
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// the cluster.
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type ScheduleFunc struct {
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Type *types.Type // this is the type of opts used if specified
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built bool // was this function built yet?
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init *interfaces.Init
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namespace string
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scheduler *scheduler.Result
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last types.Value
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result types.Value // last calculated output
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watchChan chan *schedulerResult
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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 *ScheduleFunc) String() string {
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return ScheduleFuncName
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}
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// validOpts returns the available mapping of valid opts fields to types.
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func (obj *ScheduleFunc) validOpts() map[string]*types.Type {
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return map[string]*types.Type{
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"strategy": types.TypeStr,
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"max": types.TypeInt,
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"reuse": types.TypeBool,
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"ttl": types.TypeInt,
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}
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}
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// ArgGen returns the Nth arg name for this function.
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func (obj *ScheduleFunc) ArgGen(index int) (string, error) {
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seq := []string{scheduleArgNameNamespace, scheduleArgNameOpts} // 2nd arg is optional
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if l := len(seq); index >= l {
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return "", fmt.Errorf("index %d exceeds arg length of %d", index, l)
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}
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return seq[index], nil
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}
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// Unify returns the list of invariants that this func produces.
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func (obj *ScheduleFunc) Unify(expr interfaces.Expr) ([]interfaces.Invariant, error) {
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var invariants []interfaces.Invariant
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var invar interfaces.Invariant
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// func(namespace str) []str
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// OR
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// func(namespace str, opts T1) []str
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namespaceName, err := obj.ArgGen(0)
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if err != nil {
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return nil, err
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}
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dummyNamespace := &interfaces.ExprAny{} // corresponds to the namespace type
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dummyOut := &interfaces.ExprAny{} // corresponds to the out string
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// namespace arg type of string
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invar = &interfaces.EqualsInvariant{
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Expr: dummyNamespace,
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Type: types.TypeStr,
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}
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invariants = append(invariants, invar)
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// return type of []string
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invar = &interfaces.EqualsInvariant{
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Expr: dummyOut,
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Type: types.NewType("[]str"),
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}
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invariants = append(invariants, invar)
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// generator function
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fn := func(fnInvariants []interfaces.Invariant, solved map[interfaces.Expr]*types.Type) ([]interfaces.Invariant, error) {
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for _, invariant := range fnInvariants {
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// search for this special type of invariant
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cfavInvar, ok := invariant.(*interfaces.CallFuncArgsValueInvariant)
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if !ok {
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continue
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}
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// did we find the mapping from us to ExprCall ?
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if cfavInvar.Func != expr {
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continue
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}
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// cfavInvar.Expr is the ExprCall! (the return pointer)
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// cfavInvar.Args are the args that ExprCall uses!
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if len(cfavInvar.Args) == 0 {
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return nil, fmt.Errorf("unable to build function with no args")
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}
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if l := len(cfavInvar.Args); l > 2 {
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return nil, fmt.Errorf("unable to build function with %d args", l)
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}
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// we can either have one arg or two
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var invariants []interfaces.Invariant
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var invar interfaces.Invariant
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// add the relationship to the returned value
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invar = &interfaces.EqualityInvariant{
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Expr1: cfavInvar.Expr,
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Expr2: dummyOut,
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}
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invariants = append(invariants, invar)
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// add the relationships to the called args
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invar = &interfaces.EqualityInvariant{
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Expr1: cfavInvar.Args[0],
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Expr2: dummyNamespace,
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}
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invariants = append(invariants, invar)
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// first arg must be a string
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invar = &interfaces.EqualsInvariant{
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Expr: cfavInvar.Args[0],
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Type: types.TypeStr,
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}
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invariants = append(invariants, invar)
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// full function
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mapped := make(map[string]interfaces.Expr)
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ordered := []string{namespaceName}
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mapped[namespaceName] = dummyNamespace
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if len(cfavInvar.Args) == 2 { // two args is more complex
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dummyOpts := &interfaces.ExprAny{}
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optsTypeKnown := false
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// speculate about the type?
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if typ, exists := solved[cfavInvar.Args[1]]; exists {
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optsTypeKnown = true
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if typ.Kind != types.KindStruct {
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return nil, fmt.Errorf("second arg must be of kind struct")
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}
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// XXX: the problem is that I can't
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// currently express the opts struct as
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// an invariant, without building a big
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// giant, unusable exclusive...
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validOpts := obj.validOpts()
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if StrictScheduleOpts {
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// strict opts field checking!
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for _, name := range typ.Ord {
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t := typ.Map[name]
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value, exists := validOpts[name]
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if !exists {
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return nil, fmt.Errorf("unexpected opts field: `%s`", name)
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}
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if err := t.Cmp(value); err != nil {
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return nil, errwrap.Wrapf(err, "expected different type for opts field: `%s`", name)
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}
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}
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} else {
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// permissive field checking...
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validOptsSorted := []string{}
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for name := range validOpts {
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validOptsSorted = append(validOptsSorted, name)
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}
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sort.Strings(validOptsSorted)
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for _, name := range validOptsSorted {
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value := validOpts[name] // type
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t, exists := typ.Map[name]
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if !exists {
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continue // ignore it
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}
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// if it exists, check the type
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if err := t.Cmp(value); err != nil {
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return nil, errwrap.Wrapf(err, "expected different type for opts field: `%s`", name)
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}
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}
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}
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invar := &interfaces.EqualsInvariant{
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Expr: dummyOpts,
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Type: typ,
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}
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invariants = append(invariants, invar)
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}
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// redundant?
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if typ, err := cfavInvar.Args[1].Type(); err == nil {
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invar := &interfaces.EqualsInvariant{
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Expr: cfavInvar.Args[1],
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Type: typ,
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}
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invariants = append(invariants, invar)
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}
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// If we're strict, require it, otherwise let
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// in whatever, and let Build() deal with it.
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if StrictScheduleOpts && !optsTypeKnown {
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return nil, fmt.Errorf("the type of the opts struct is not known")
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}
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// expression must match type of the input arg
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invar := &interfaces.EqualityInvariant{
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Expr1: dummyOpts,
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Expr2: cfavInvar.Args[1],
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}
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invariants = append(invariants, invar)
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mapped[scheduleArgNameOpts] = dummyOpts
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ordered = append(ordered, scheduleArgNameOpts)
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}
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invar = &interfaces.EqualityWrapFuncInvariant{
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Expr1: expr, // maps directly to us!
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Expr2Map: mapped,
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Expr2Ord: ordered,
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Expr2Out: dummyOut,
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}
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invariants = append(invariants, invar)
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// TODO: do we return this relationship with ExprCall?
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invar = &interfaces.EqualityWrapCallInvariant{
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// TODO: should Expr1 and Expr2 be reversed???
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Expr1: cfavInvar.Expr,
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//Expr2Func: cfavInvar.Func, // same as below
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Expr2Func: expr,
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}
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invariants = append(invariants, invar)
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// TODO: are there any other invariants we should build?
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return invariants, nil // generator return
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}
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// We couldn't tell the solver anything it didn't already know!
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return nil, fmt.Errorf("couldn't generate new invariants")
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}
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invar = &interfaces.GeneratorInvariant{
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Func: fn,
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}
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invariants = append(invariants, invar)
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return invariants, nil
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}
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// Polymorphisms returns the list of possible function signatures available for
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// this static polymorphic function. It relies on type and value hints to limit
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// the number of returned possibilities.
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func (obj *ScheduleFunc) Polymorphisms(partialType *types.Type, partialValues []types.Value) ([]*types.Type, error) {
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// TODO: technically, we could generate all permutations of the struct!
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//variant := []*types.Type{}
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//t0 := types.NewType("func(namespace str) []str")
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//variant = append(variant, t0)
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//validOpts := obj.validOpts()
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//for ? := ? range { // generate all permutations of the struct...
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// t := types.NewType(fmt.Sprintf("func(namespace str, opts %s) []str", ?))
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// variant = append(variant, t)
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//}
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//if partialType == nil {
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// return variant, nil
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//}
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if partialType == nil {
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return nil, fmt.Errorf("zero type information given")
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}
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var typ *types.Type
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if tOut := partialType.Out; tOut != nil {
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if err := tOut.Cmp(types.NewType("[]str")); err != nil {
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return nil, errwrap.Wrapf(err, "return type must be a list of strings")
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}
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}
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ord := partialType.Ord
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if partialType.Map != nil {
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if len(ord) == 0 {
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return nil, fmt.Errorf("must have at least one arg in schedule func")
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}
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if tNamespace, exists := partialType.Map[ord[0]]; exists && tNamespace != nil {
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if err := tNamespace.Cmp(types.TypeStr); err != nil {
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return nil, errwrap.Wrapf(err, "first arg must be an str")
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}
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}
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if len(ord) == 1 {
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return []*types.Type{types.NewType("func(namespace str) []str")}, nil // done!
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}
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if len(ord) != 2 {
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return nil, fmt.Errorf("must have either one or two args in schedule func")
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}
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if tOpts, exists := partialType.Map[ord[1]]; exists {
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if tOpts == nil { // usually a `struct{}`
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typFunc := types.NewType("func(namespace str, opts variant) []str")
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return []*types.Type{typFunc}, nil // solved!
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}
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if tOpts.Kind != types.KindStruct {
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return nil, fmt.Errorf("second arg must be of kind struct")
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}
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validOpts := obj.validOpts()
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for _, name := range tOpts.Ord {
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t := tOpts.Map[name]
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value, exists := validOpts[name]
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if !exists {
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return nil, fmt.Errorf("unexpected opts field: `%s`", name)
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}
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if err := t.Cmp(value); err != nil {
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return nil, errwrap.Wrapf(err, "expected different type for opts field: `%s`", name)
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}
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}
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typ = tOpts // solved
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}
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}
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if typ == nil {
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return nil, fmt.Errorf("not enough type information")
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}
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typFunc := types.NewType(fmt.Sprintf("func(namespace str, opts %s) []str", typ.String()))
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// TODO: type check that the partialValues are compatible
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return []*types.Type{typFunc}, nil // solved!
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}
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// Build is run to turn the polymorphic, undetermined function, into the
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// specific statically typed version. It is usually run after Unify completes,
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// and must be run before Info() and any of the other Func interface methods are
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// used. This function is idempotent, as long as the arg isn't changed between
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// runs.
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func (obj *ScheduleFunc) Build(typ *types.Type) (*types.Type, error) {
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// typ is the KindFunc signature we're trying to build...
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if typ.Kind != types.KindFunc {
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return nil, fmt.Errorf("input type must be of kind func")
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}
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if len(typ.Ord) != 1 && len(typ.Ord) != 2 {
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return nil, fmt.Errorf("the schedule function needs either one or two args")
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}
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if typ.Out == nil {
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return nil, fmt.Errorf("return type of function must be specified")
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}
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if typ.Map == nil {
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return nil, fmt.Errorf("invalid input type")
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}
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if err := typ.Out.Cmp(types.NewType("[]str")); err != nil {
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return nil, errwrap.Wrapf(err, "return type must be a list of strings")
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}
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tNamespace, exists := typ.Map[typ.Ord[0]]
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if !exists || tNamespace == nil {
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return nil, fmt.Errorf("first arg must be specified")
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}
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if len(typ.Ord) == 1 {
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obj.Type = nil
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obj.built = true
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return obj.sig(), nil // done early, 2nd arg is absent!
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}
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tOpts, exists := typ.Map[typ.Ord[1]]
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if !exists || tOpts == nil {
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return nil, fmt.Errorf("second argument was missing")
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}
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if tOpts.Kind != types.KindStruct {
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return nil, fmt.Errorf("second argument must be of kind struct")
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}
|
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|
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validOpts := obj.validOpts()
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|
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if StrictScheduleOpts {
|
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// strict opts field checking!
|
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for _, name := range tOpts.Ord {
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t := tOpts.Map[name]
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value, exists := validOpts[name]
|
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if !exists {
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return nil, fmt.Errorf("unexpected opts field: `%s`", name)
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}
|
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|
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if err := t.Cmp(value); err != nil {
|
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return nil, errwrap.Wrapf(err, "expected different type for opts field: `%s`", name)
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}
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}
|
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} else {
|
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// permissive field checking...
|
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validOptsSorted := []string{}
|
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for name := range validOpts {
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validOptsSorted = append(validOptsSorted, name)
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}
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sort.Strings(validOptsSorted)
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for _, name := range validOptsSorted {
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value := validOpts[name] // type
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t, exists := tOpts.Map[name]
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if !exists {
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continue // ignore it
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}
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|
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// if it exists, check the type
|
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if err := t.Cmp(value); err != nil {
|
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return nil, errwrap.Wrapf(err, "expected different type for opts field: `%s`", name)
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}
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}
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}
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obj.Type = tOpts // type of opts struct, even an empty: `struct{}`
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obj.built = true
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return obj.sig(), nil
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}
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|
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// Validate tells us if the input struct takes a valid form.
|
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func (obj *ScheduleFunc) Validate() error {
|
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if !obj.built {
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return fmt.Errorf("function wasn't built yet")
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}
|
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// obj.Type can be nil if no 2nd arg is given, or a struct (even empty!)
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if obj.Type != nil && obj.Type.Kind != types.KindStruct { // build must be run first
|
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return fmt.Errorf("type must be nil or a struct")
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}
|
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return nil
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}
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|
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// Info returns some static info about itself. Build must be called before this
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// will return correct data.
|
|
func (obj *ScheduleFunc) Info() *interfaces.Info {
|
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// It's important that you don't return a non-nil sig if this is called
|
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// before you're built. Type unification may call it opportunistically.
|
|
var sig *types.Type
|
|
if obj.built {
|
|
sig = obj.sig() // helper
|
|
}
|
|
return &interfaces.Info{
|
|
Pure: false, // definitely false
|
|
Memo: false,
|
|
// output is list of hostnames chosen
|
|
Sig: sig, // func kind
|
|
Err: obj.Validate(),
|
|
}
|
|
}
|
|
|
|
// helper
|
|
func (obj *ScheduleFunc) sig() *types.Type {
|
|
sig := types.NewType(fmt.Sprintf("func(%s str) []str", scheduleArgNameNamespace)) // simplest form
|
|
if obj.Type != nil {
|
|
sig = types.NewType(fmt.Sprintf("func(%s str, %s %s) []str", scheduleArgNameNamespace, scheduleArgNameOpts, obj.Type.String()))
|
|
}
|
|
return sig
|
|
}
|
|
|
|
// Init runs some startup code for this function.
|
|
func (obj *ScheduleFunc) Init(init *interfaces.Init) error {
|
|
obj.init = init
|
|
obj.watchChan = make(chan *schedulerResult)
|
|
//obj.init.Debug = true // use this for local debugging
|
|
return nil
|
|
}
|
|
|
|
// Stream returns the changing values that this func has over time.
|
|
func (obj *ScheduleFunc) Stream(ctx context.Context) error {
|
|
defer close(obj.init.Output) // the sender closes
|
|
for {
|
|
select {
|
|
// TODO: should this first chan be run as a priority channel to
|
|
// avoid some sort of glitch? is that even possible? can our
|
|
// hostname check with reality (below) fix that?
|
|
case input, ok := <-obj.init.Input:
|
|
if !ok {
|
|
obj.init.Input = nil // don't infinite loop back
|
|
continue // no more inputs, but don't return!
|
|
}
|
|
//if err := input.Type().Cmp(obj.Info().Sig.Input); err != nil {
|
|
// return errwrap.Wrapf(err, "wrong function input")
|
|
//}
|
|
|
|
if obj.last != nil && input.Cmp(obj.last) == nil {
|
|
continue // value didn't change, skip it
|
|
}
|
|
obj.last = input // store for next
|
|
|
|
namespace := input.Struct()[scheduleArgNameNamespace].Str()
|
|
if namespace == "" {
|
|
return fmt.Errorf("can't use an empty namespace")
|
|
}
|
|
|
|
opts := make(map[string]types.Value) // empty "struct"
|
|
if val, exists := input.Struct()[scheduleArgNameOpts]; exists {
|
|
opts = val.Struct()
|
|
}
|
|
|
|
if obj.init.Debug {
|
|
obj.init.Logf("namespace: %s", namespace)
|
|
}
|
|
|
|
schedulerOpts := []scheduler.Option{}
|
|
// don't add bad or zero-value options
|
|
|
|
defaultStrategy := true
|
|
if val, exists := opts["strategy"]; exists {
|
|
if strategy := val.Str(); strategy != "" {
|
|
if obj.init.Debug {
|
|
obj.init.Logf("opts: strategy: %s", strategy)
|
|
}
|
|
defaultStrategy = false
|
|
schedulerOpts = append(schedulerOpts, scheduler.StrategyKind(strategy))
|
|
}
|
|
}
|
|
if defaultStrategy { // we always need to add one!
|
|
schedulerOpts = append(schedulerOpts, scheduler.StrategyKind(DefaultStrategy))
|
|
}
|
|
if val, exists := opts["max"]; exists {
|
|
// TODO: check for overflow
|
|
if max := int(val.Int()); max > 0 {
|
|
if obj.init.Debug {
|
|
obj.init.Logf("opts: max: %d", max)
|
|
}
|
|
schedulerOpts = append(schedulerOpts, scheduler.MaxCount(max))
|
|
}
|
|
}
|
|
if val, exists := opts["reuse"]; exists {
|
|
reuse := val.Bool()
|
|
if obj.init.Debug {
|
|
obj.init.Logf("opts: reuse: %t", reuse)
|
|
}
|
|
schedulerOpts = append(schedulerOpts, scheduler.ReuseLease(reuse))
|
|
}
|
|
if val, exists := opts["ttl"]; exists {
|
|
// TODO: check for overflow
|
|
if ttl := int(val.Int()); ttl > 0 {
|
|
if obj.init.Debug {
|
|
obj.init.Logf("opts: ttl: %d", ttl)
|
|
}
|
|
schedulerOpts = append(schedulerOpts, scheduler.SessionTTL(ttl))
|
|
}
|
|
}
|
|
|
|
// TODO: support changing the namespace over time...
|
|
// TODO: possibly removing our stored value there first!
|
|
if obj.namespace == "" {
|
|
obj.namespace = namespace // store it
|
|
|
|
if obj.init.Debug {
|
|
obj.init.Logf("starting scheduler...")
|
|
}
|
|
var err error
|
|
obj.scheduler, err = obj.init.World.Scheduler(obj.namespace, schedulerOpts...)
|
|
if err != nil {
|
|
return errwrap.Wrapf(err, "can't create scheduler")
|
|
}
|
|
|
|
// process the stream of scheduling output...
|
|
go func() {
|
|
defer close(obj.watchChan)
|
|
// XXX: maybe we could share the parent
|
|
// ctx, but I have to work out the
|
|
// ordering logic first. For now this is
|
|
// just a port of what it was before.
|
|
newCtx, cancel := context.WithCancel(context.Background())
|
|
go func() {
|
|
defer cancel() // unblock Next()
|
|
defer obj.scheduler.Shutdown()
|
|
select {
|
|
case <-ctx.Done():
|
|
return
|
|
}
|
|
}()
|
|
for {
|
|
hosts, err := obj.scheduler.Next(newCtx)
|
|
select {
|
|
case obj.watchChan <- &schedulerResult{
|
|
hosts: hosts,
|
|
err: err,
|
|
}:
|
|
|
|
case <-ctx.Done():
|
|
return
|
|
}
|
|
}
|
|
}()
|
|
|
|
} else if obj.namespace != namespace {
|
|
return fmt.Errorf("can't change namespace, previously: `%s`", obj.namespace)
|
|
}
|
|
|
|
continue // we send values on the watch chan, not here!
|
|
|
|
case schedulerResult, ok := <-obj.watchChan:
|
|
if !ok { // closed
|
|
// XXX: maybe etcd reconnected? (fix etcd implementation)
|
|
|
|
// XXX: if we close, perhaps the engine is
|
|
// switching etcd hosts and we should retry?
|
|
// maybe instead we should get an "etcd
|
|
// reconnect" signal, and the lang will restart?
|
|
return nil
|
|
}
|
|
if err := schedulerResult.err; err != nil {
|
|
if err == scheduler.ErrEndOfResults {
|
|
//return nil // TODO: we should probably fix the reconnect issue and use this here
|
|
return fmt.Errorf("scheduler shutdown, reconnect bug?") // XXX: fix etcd reconnects
|
|
}
|
|
return errwrap.Wrapf(err, "channel watch failed on `%s`", obj.namespace)
|
|
}
|
|
|
|
if obj.init.Debug {
|
|
obj.init.Logf("got hosts: %+v", schedulerResult.hosts)
|
|
}
|
|
|
|
var result types.Value
|
|
l := types.NewList(obj.Info().Sig.Out)
|
|
for _, val := range schedulerResult.hosts {
|
|
if err := l.Add(&types.StrValue{V: val}); err != nil {
|
|
return errwrap.Wrapf(err, "list could not add val: `%s`", val)
|
|
}
|
|
}
|
|
result = l // set list as result
|
|
|
|
if obj.init.Debug {
|
|
obj.init.Logf("result: %+v", result)
|
|
}
|
|
|
|
// if the result is still the same, skip sending an update...
|
|
if obj.result != nil && result.Cmp(obj.result) == nil {
|
|
continue // result didn't change
|
|
}
|
|
obj.result = result // store new result
|
|
|
|
case <-ctx.Done():
|
|
return nil
|
|
}
|
|
|
|
select {
|
|
case obj.init.Output <- obj.result: // send
|
|
// pass
|
|
case <-ctx.Done():
|
|
return nil
|
|
}
|
|
}
|
|
}
|
|
|
|
// schedulerResult combines our internal events into a single message packet.
|
|
type schedulerResult struct {
|
|
hosts []string
|
|
err error
|
|
}
|