lang: Initial implementation of the mgmt language
This is an initial implementation of the mgmt language. It is a declarative (immutable) functional, reactive, domain specific programming language. It is intended to be a language that is: * safe * powerful * easy to reason about With these properties, we hope this language, and the mgmt engine will allow you to model the real-time systems that you'd like to automate. This also includes a number of other associated changes. Sorry for the large size of this patch.
This commit is contained in:
James Shubin
271
lang/gapi.go
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271
lang/gapi.go
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// Mgmt
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// Copyright (C) 2013-2018+ 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 lang
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import (
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"fmt"
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"log"
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"strings"
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"sync"
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"github.com/purpleidea/mgmt/gapi"
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"github.com/purpleidea/mgmt/pgraph"
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"github.com/purpleidea/mgmt/recwatch"
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"github.com/purpleidea/mgmt/resources"
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multierr "github.com/hashicorp/go-multierror"
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errwrap "github.com/pkg/errors"
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"github.com/urfave/cli"
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)
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const (
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// Name is the name of this frontend.
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Name = "lang"
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// Start is the entry point filename that we use. It is arbitrary.
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Start = "/start." + FileNameExtension // FIXME: replace with a proper code entry point schema (directory schema)
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)
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func init() {
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gapi.Register(Name, func() gapi.GAPI { return &GAPI{} }) // register
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}
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// GAPI implements the main lang GAPI interface.
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type GAPI struct {
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InputURI string // input URI of code file system to run
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lang *Lang // lang struct
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data gapi.Data
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initialized bool
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closeChan chan struct{}
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wg *sync.WaitGroup // sync group for tunnel go routines
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configWatcher *recwatch.ConfigWatcher
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}
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// Cli takes a cli.Context, and returns our GAPI if activated. All arguments
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// should take the prefix of the registered name. On activation, if there are
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// any validation problems, you should return an error. If this was not
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// activated, then you should return a nil GAPI and a nil error.
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func (obj *GAPI) Cli(c *cli.Context, fs resources.Fs) (*gapi.Deploy, error) {
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if s := c.String(Name); c.IsSet(Name) {
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if s == "" {
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return nil, fmt.Errorf("input code is empty")
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}
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// read through this local path, and store it in our file system
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// since our deploy should work anywhere in the cluster, let the
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// engine ensure that this file system is replicated everywhere!
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// TODO: single file input for now
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if err := gapi.CopyFileToFs(fs, s, Start); err != nil {
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return nil, errwrap.Wrapf(err, "can't copy code from `%s` to `%s`", s, Start)
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}
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return &gapi.Deploy{
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Name: Name,
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Noop: c.GlobalBool("noop"),
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Sema: c.GlobalInt("sema"),
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GAPI: &GAPI{
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InputURI: fs.URI(),
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// TODO: add properties here...
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},
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}, nil
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}
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return nil, nil // we weren't activated!
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}
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// CliFlags returns a list of flags used by this deploy subcommand.
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func (obj *GAPI) CliFlags() []cli.Flag {
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return []cli.Flag{
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cli.StringFlag{
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Name: fmt.Sprintf("%s, %s", Name, Name[0:1]),
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Value: "",
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Usage: "language code path to deploy",
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},
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}
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}
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// Init initializes the lang GAPI struct.
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func (obj *GAPI) Init(data gapi.Data) error {
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if obj.initialized {
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return fmt.Errorf("already initialized")
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}
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if obj.InputURI == "" {
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return fmt.Errorf("the InputURI param must be specified")
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}
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obj.data = data // store for later
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obj.closeChan = make(chan struct{})
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obj.wg = &sync.WaitGroup{}
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obj.initialized = true
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obj.configWatcher = recwatch.NewConfigWatcher()
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return nil
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}
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// LangInit is a wrapper around the lang Init method.
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func (obj *GAPI) LangInit() error {
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if obj.lang != nil {
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return nil // already ran init, close first!
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}
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fs, err := obj.data.World.Fs(obj.InputURI) // open the remote file system
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if err != nil {
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return errwrap.Wrapf(err, "can't load code from file system `%s`", obj.InputURI)
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}
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b, err := fs.ReadFile(Start) // read the single file out of it
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if err != nil {
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return errwrap.Wrapf(err, "can't read code from file `%s`", Start)
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}
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code := strings.NewReader(string(b))
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obj.lang = &Lang{
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Input: code, // string as an interface that satisfies io.Reader
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Hostname: obj.data.Hostname,
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World: obj.data.World,
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Debug: obj.data.Debug,
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}
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if err := obj.lang.Init(); err != nil {
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return errwrap.Wrapf(err, "can't init the lang")
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}
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return nil
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}
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// LangClose is a wrapper around the lang Close method.
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func (obj *GAPI) LangClose() error {
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if obj.lang != nil {
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err := obj.lang.Close()
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obj.lang = nil // clear it to avoid double closing
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return errwrap.Wrapf(err, "can't close the lang") // nil passthrough
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}
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return nil
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}
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// Graph returns a current Graph.
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func (obj *GAPI) Graph() (*pgraph.Graph, error) {
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if !obj.initialized {
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return nil, fmt.Errorf("%s: GAPI is not initialized", Name)
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}
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g, err := obj.lang.Interpret()
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if err != nil {
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return nil, errwrap.Wrapf(err, "%s: interpret error", Name)
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}
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return g, nil
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}
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// Next returns nil errors every time there could be a new graph.
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func (obj *GAPI) Next() chan gapi.Next {
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ch := make(chan gapi.Next)
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obj.wg.Add(1)
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go func() {
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defer obj.wg.Done()
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defer close(ch) // this will run before the obj.wg.Done()
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if !obj.initialized {
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next := gapi.Next{
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Err: fmt.Errorf("%s: GAPI is not initialized", Name),
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Exit: true, // exit, b/c programming error?
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}
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ch <- next
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return
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}
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startChan := make(chan struct{}) // start signal
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close(startChan) // kick it off!
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streamChan := make(chan error)
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//defer obj.LangClose() // close any old lang
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var ok bool
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for {
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var err error
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var langSwap bool // do we need to swap the lang object?
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select {
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// TODO: this should happen in ConfigWatch instead :)
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case <-startChan: // kick the loop once at start
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startChan = nil // disable
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err = nil // set nil as the message to send
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langSwap = true
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case err, ok = <-streamChan: // a variable changed
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if !ok { // the channel closed!
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return
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}
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case <-obj.closeChan:
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return
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}
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log.Printf("%s: Generating new graph...", Name)
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// skip this to pass through the err if present
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if langSwap && err == nil {
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log.Printf("%s: Swap!", Name)
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// run up to these three but fail on err
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if e := obj.LangClose(); e != nil { // close any old lang
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err = e // pass through the err
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} else if e := obj.LangInit(); e != nil { // init the new one!
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err = e // pass through the err
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// Always run LangClose after LangInit
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// when done. This is currently needed
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// because we should tell the lang obj
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// to shut down all the running facts.
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if e := obj.LangClose(); e != nil {
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err = multierr.Append(err, e) // list of errors
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}
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} else {
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if obj.data.NoStreamWatch { // TODO: do we want to allow this for the lang?
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streamChan = nil
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} else {
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// stream for lang events
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streamChan = obj.lang.Stream() // update stream
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}
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continue // wait for stream to trigger
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}
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}
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next := gapi.Next{
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Exit: err != nil, // TODO: do we want to shutdown?
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Err: err,
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}
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select {
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case ch <- next: // trigger a run (send a msg)
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if err != nil {
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return
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}
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// unblock if we exit while waiting to send!
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case <-obj.closeChan:
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return
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}
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}
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}()
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return ch
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}
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// Close shuts down the lang GAPI.
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func (obj *GAPI) Close() error {
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if !obj.initialized {
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return fmt.Errorf("%s: GAPI is not initialized", Name)
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}
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obj.configWatcher.Close()
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obj.LangClose() // close lang, esp. if blocked in Stream() wait
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close(obj.closeChan)
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obj.wg.Wait()
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obj.initialized = false // closed = true
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return nil
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}
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