gps: fine grained source transitions #1250

jmank88 · 2017-10-09T12:14:37Z

What does this do / why do we need it?

This PR contains a set of changes primarily motivated by making sourceGateway state transitions more fine grained and special cases explicit, so that the persistent cache can be fully leveraged when integrated. From the changelog:

Reduce network access by trusting local source information and only pulling from upstream when necessary

What should your reviewer look out for in this PR?

~~Should a note be added to the CHANGELOG?~~ Did this.

Which issue(s) does this PR fix?

Toward #431

Fixes #415

jmank88 · 2017-10-09T12:27:12Z

internal/gps/source.go

+			return 0, err
+		}
+	}
+	//TODO(jmank88) broadcast sg.src.upstreamURL() changes here


Perhaps now is the time to address this, but I don't have a simple solution. Remapping the URLs would catch many cases, but it seems like there is always a worst case scenario where two of (or sets of) sources/gateways/caches have to be merged after both being in use. However, I may be considering a more general case than is necessary. This partially depends on the possible URLs available from maybeSources, and whether a source's upstreamURL is always from this set (meaning we could map the possibilities ahead of time).

i think our best solution is likely to be in changing the scopes of responsibility, here. something like the following: we create some new indirection layer that basically acts like a persistent sourceGateway factory: it takes a maybeSources and occupies all the corresponding URL slots in the sourceCoordinator's URL lookup map, and spits out a sourceGateway on request.

now, the sourceCoordinator is only responsible for mapping to families of related URLs, and the sourceGatewayFactory (or whatever) is doing the final layer of mapping work. it's likely that we'll need to rework some of sourceCoordinator.getSourceGatewayFor() to accommodate this, possibly including the way that sourceCoordinator.srcs and sourceCoordinator.nameToURL actually work.

that expands the scope of this PR significantly, though, and my gut currently says we'll be able to defer it until a later PR. for now, we'll probably be able to get away with just having a hard failure here where we might otherwise be able to recover by going back to other, possible upstream URLs.

for now, we'll probably be able to get away with just having a hard failure here where we might otherwise be able to recover by going back to other, possible upstream URLs.

FWIW I've been running with a panic on any url change and it hasn't happened yet (mostly ran tests and cockroachdb). A regular error is probably sufficient though.

it takes a maybeSources and occupies all the corresponding URL slots in the sourceCoordinator's URL lookup map, and spits out a sourceGateway on request.

Can we be certain about all of the possible URLs ahead of time? e.g. gopkgin code currently returns one url from maybeSource, but a different aliasURL from gopkginSource. That one would be trivial to change, and the others look pretty standard and static. For some reason I had it in my head that it would be possible to ping upstream and be forwarded to another remote or something. If that is not the case, then we may be able to get away with the existing data structures (with more mapping) and with some mechanism for merging additional maybeSources into a gateway.

FWIW I've been running with a panic on any url change and it hasn't happened yet (mostly ran tests and cockroachdb).

I take that back. Now I'm seeing test failures on CI like: upstream source url changed from "ssh://[email protected]/sdboyer/gpkt" to "https://github.com/sdboyer/gpkt" which seems like something we need to handle now.

This has been fixed.

jmank88 · 2017-10-09T12:28:43Z

internal/gps/source.go

+	existsCallsListVersions() bool
+	// listVersionsRequiresLocal returns true if calling listVersions first
+	// requires the source to exist locally.
+	listVersionsRequiresLocal() bool


These comments became out of sync. Any better name/doc suggestions before fixing?

these seem fine for now. there's a refactoring in store for these, anyway, i think.

jmank88 · 2017-10-10T22:28:57Z

@sdboyer This is green now. Let me know what you think of the gateway mapping change, and whether I should squash any or all of the commits.

jmank88 · 2017-10-11T13:43:47Z

Don't merge yet.

Tagging as WIP since I'm getting real-world failures, even though tests are passing.

jmank88 · 2017-10-12T16:47:43Z

After refactoring PackageTree caching, this is stable again and should be green soon.

jmank88 · 2017-10-15T20:41:59Z

Rebased.

sdboyer

holy crap, there's a lot in here 🎉

by and large, this looks like great progress. i've got a couple of more specific questions, but i'd ideally like to get this in ASAP so that it can percolate as long as possible before next release.

sdboyer · 2017-10-14T02:17:17Z

internal/gps/error.go

@@ -0,0 +1,34 @@
+// Copyright 2017 The Go Authors. All rights reserved.


i'm a little uneasy about giving this its own file. i appreciate that it doesn't really fit where it was, but...well, we already have a bunch of antipatterns with errors, and i think it's becoming increasingly harmful.

no change to make here, just making a note of it.

sdboyer · 2017-10-25T02:24:28Z

internal/gps/manager_test.go

@@ -432,8 +476,20 @@ func TestSourceCreationCounts(t *testing.T) {
 				ProjectIdentifier{ProjectRoot: ProjectRoot("github.com/sdboyer/gpkt"), Source: "https://github.com/sdboyeR/gpkt"},
 				mkPI("github.com/sdboyeR/gpkt"),
 			},
-			namecount: 6,
-			srccount:  1,
+			names: []string{


sometimes i feel like you just follow my code around, tidying up icky tests ❤️

Heh, well this one had to change. Actually the name should probably be changed.

sdboyer · 2017-10-25T02:26:11Z

internal/gps/manager_test.go

-				} else if srcg == srcg4 {
-					t.Error("explicit http source should create a new src")
+				} else if srcg != srcg4 {
+					t.Error("explicit http source should reuse autodetected https source")


hang on, this feels like a significant departure from existing logic. is this suggesting that http should fold in with https?

what about doing this is worth breaking the simpler rules of the existing model?

What exactly are those rules? Since the map was keyed on both name and url, I thought it was in line with existing behavior to fold them all together. Was sharing a map only valid since the url was static?

so the "rule" here - no, not expressed anywhere, because i have, as we know, not been great at articulating these really low-level invariants anywhere, 💯 my fault - is that if an explicit request is made for e.g. an http protocol access pattern for a URL, then we have to respect it, and that's how we access. it's only in the default inference case, where no protocol is provided (a bare import path) where we can "pick" from the various possibilities, and where the specific one used may vary from one run to the next (but, once selected, is fixed within the duration of any given SourceMgr's lifetime).

this might seem to push us in a direction that i was considering (and i think we discussed somehwere?), where the sourceGateway effectively becomes more of a factory/intermediate layer that hangs on to the entire maybeSources set and multiplexes to children that are responsible for each individual URL, depending on which particular input pattern comes in.

(if we're thinking about that, one crucial reminder about the maybeSources model is that e.g. bitbucket abstracts maybeSources to allow for a project to be either git or hg - so we're encompassing in there the idea that ).

sdboyer · 2017-10-25T02:52:56Z

internal/gps/source.go

@@ -268,43 +258,38 @@ func newSourceGateway(maybe maybeSource, superv *supervisor, cachedir string) *s
 	return sg
 }

+func (sg *sourceGateway) addMaybeSources(mb maybeSources) {
+	sg.maybeMu.Lock()
+	sg.maybe = append(sg.maybe, mb...)


so we're conjoining gateways and caches for multiple maybeSources, then - only one ever active per SourceMgr? interesting. seems like that can work.

the big question i have (without having checked for myself) - is there a scenario where the user can get stuck if a repo exists on local disk for one scheme, but the credentials they'd previously configured to access that scheme no longer work/are missing? in such a case, we should ideally continue moving through the maybeSource options - is that where this PR moves us?

They should not get stuck. In that case, whenever sourceExistsUpstream is required and fails, another source would be chosen.

sdboyer · 2017-10-25T02:56:39Z

internal/gps/source.go

 }

-func (sg *sourceGateway) existsUpstream(ctx context.Context) bool {
+func (sg *sourceGateway) existsUpstream(ctx context.Context) error {


hmm...i think i may want us to more broadly refactor these. i think (not quite sure yet) that this PR is taking us into territory where local can diverge from upstream. hand-in-hand with that is being a lot more careful about being able to inquire about current state without having the SourceMgr change it.

Well we have to allow divergence from upstream at some level to benefit from caching, but I hope I haven't done that unintentionally. Much of the language unfortunately becomes fuzzy. For example, when does 'exists' mean now and when does it mean within the cache window? I tried to be careful about these, and to document the sourceStates in a helpful way.

cool, that sounds reasonable for now, at least. but we're going to need to articulate this very, very clearly (i think i need to sketch a fuller FSM) if we have any hope of keeping track of this in a clear, understandable way.

sdboyer · 2017-10-25T03:03:29Z

internal/gps/source.go

+// otherwise it returns a slice of all errors. If force is true, then each
+// maybeSource may make a second attempt after removing the cache directory. testFn
+// is an optional check which may access src and return additional sourceState.
+func (sg *sourceGateway) setUpSource(ctx context.Context, force bool, testFn func(context.Context) (sourceState, error)) (sourceState, errorSlice) {


if we're going to re-expose these methods, we need to be diligent about not calling them from the outside. there was a rather huge mess back before i refactored to use the FSM, and much of it arose from mixing locks with intra-source object calls.

in fact, i'd probably be more comfortable if we separated these out by hiding the ones we expect SourceMgr itself to call (which should be mutex-protected) directly into an interface, and leaving the remainder unexposed.

sdboyer · 2017-10-25T03:07:01Z

internal/gps/source.go

+	existsCallsListVersions() bool
+	// listVersionsRequiresLocal returns true if calling listVersions first
+	// requires the source to exist locally.
+	listVersionsRequiresLocal() bool


these seem fine for now. there's a refactoring in store for these, anyway, i think.

sdboyer · 2017-10-25T03:08:39Z

internal/gps/source_cache.go

+		ImportRoot: string(pr),
+		Packages:   make(map[string]pkgtree.PackageOrErr),
+	}
+	// Return a copy, with full import paths.


Use PackageTree.Copy() here instead of re-rolling what's already there - even if it means another iteration pass over the packages.

Or, implement a new CopyWithRoot() func that does the same as here, then reimplement Copy() in terms of that.

sdboyer · 2017-10-25T03:13:21Z

internal/gps/source_test.go


-	// Run test twice so that we cover both the existing and non-existing case;
-	// only difference in results is the initial setup state.
-	t.Run("empty", do(sourceIsSetUp|sourceExistsUpstream|sourceHasLatestVersionList))


haven't fully grokked changes to tests here yet, but i do look at the loss of these and worry that we're losing some of the meager set of state-changing cases that we do manage to cover now. no?

Looking back at this, it is still valuable to cover existing and non-existing cases (though the states will be the same). I'll restore that. Is there something else that is lost?

i don't think so, that's all that i was introducing with the second pass.

jmank88 · 2017-12-31T23:22:49Z

Rebased and ready for review again.

jmank88 · 2018-01-24T16:21:14Z

Rebased and infinitely queued on OSX build.

gps: source coord: set-up sources before returning gateways gps: source cache: improve PackageTree ProjectRoot handling

jmank88 · 2018-01-31T21:11:22Z

Green again.

sdboyer · 2018-02-21T14:41:20Z

gps/pkgtree/pkgtree.go

 		strcount = strcount + len(poe.P.Imports) + len(poe.P.TestImports)
 	}
 	pool := make([]string, strcount)

-	for path, poe := range t.Packages {
+	for path, poe := range p {
 		var poe2 PackageOrErr

 		if poe.Err != nil {


Why are drop all this? It's necessary to safely copy the various possible Err types.

It was broken. The new TestPackageTreeCopy fails with the old logic - a build.NoGoError's Dir field is not copied.

Why do we need to copy them? Wouldn't it be a mistake to mutate an error anyways?

Alternatively, we could call .Error() and make a new error from the string. This is how the cache persists them.

jmank88 · 2018-02-21T16:54:31Z

gps/source.go

-		url = toFold(url)
+		src, st, err := m.try(ctx, sc.cachedir, sc.supervisor)
+		if err == nil {
+			srcGate = newSourceGateway(st, src, sc.supervisor, sc.cachedir)


We no longer defer trying the source. Instead we try up front, and the gateway gets a single fixed source.

There is more work while holding sc.srcmut, but I haven't noticed a slowdown.

jmank88 · 2018-02-21T16:56:02Z

gps/deduce.go

@@ -104,7 +104,7 @@ type pathDeducer interface {
 	// So the return of the above string would be
 	// "github.com/some-user/some-package"
 	deduceRoot(string) (string, error)
-	deduceSource(string, *url.URL) (maybeSource, error)
+	deduceSource(string, *url.URL) (maybeSources, error)


Using concrete maybeSources everywhere was more significant in a previous iteration, but is still an overall simplifying change - barring some test boilerplate.

jmank88 · 2018-02-21T16:59:48Z

gps/source.go

@@ -21,34 +22,50 @@ import (
 type sourceState int32

 const (
-	sourceIsSetUp sourceState = 1 << iota
-	sourceExistsUpstream
+	// sourceExistsUpstream means the chosen source was verified upstream, during this execution.


sourceIsSetUp goes away, since it's implied by the existence of the gateway.

jmank88 · 2018-02-21T17:10:29Z

gps/vcs_repo.go

-		// treat it as a new not-yet-cloned repo.
-
-		// TODO(marwan-at-work): warn/give progress of the above comment.
-		os.RemoveAll(path)


This was essentially inlined into each maybeSource, which allows them to directly create their respective vcs.Repos, rather than switching on the type, at the cost of bit of duplication. IMHO it is clearer, especially when trying to unravel the chain of similarly named types we create.

jmank88 · 2018-02-21T17:14:03Z

gps/vcs_repo.go

-		panic(fmt.Sprintf("Unrecognized format: %v", s))
-	}
+// ensureCleaner is an optional extension of ctxRepo.
+type ensureCleaner interface {


Generalized from git specific, and used in baseVCSSource.updateLocal()

jmank88 · 2018-02-21T17:16:18Z

gps/vcs_repo_test.go

@@ -52,73 +48,6 @@ func TestErrs(t *testing.T) {
 	}
 }

-func TestNewCtxRepoHappyPath(t *testing.T) {


Perhaps these tests should be revived and adapted to the maybeSources.

jmank88 · 2018-02-21T17:32:59Z

primarily motivated by making sourceGateway state transitions more fine grained and special cases explicit, so that the persistent cache can be fully leveraged when integrated.

I wasn't very clear in the initial post, but I said it better in the changelog:

Reduce network access by trusting local source information and only pulling from upstream when necessary

Basically, by adding the persistent cache, what was previously an optimization by going to the network sooner might undermine the cache entirely in situations where it's no longer necessary to eventually go to the network.

jmank88 · 2018-02-22T14:59:48Z

@sdboyer Updated with a version of the changes discussed last night. Restoring those ctxRepo tests adapted for a maybeSource was going to be messy with the extra work that the try() methods were doing, so rather than adding the pings to each try, I generalized and moved the repeated checkLocal/ping logic into newSourceGateway. This separates some responsibilities more (try doesn't need a supervisor and becomes simpler; sourceGateway handles its own sourceState), and it allows us to leverage the proper sourceGateway.sourceExistsUpstream() method which handles the 'ls-remote instead of ping' style optimizations.

jmank88 · 2018-02-22T16:24:01Z

Here is a clean preview of the next step: https://github.com/jmank88/dep/compare/source_opt...jmank88:opt_cache

sdboyer

This looks good. Onward and upward!

jmank88 requested a review from sdboyer as a code owner October 9, 2017 12:14

googlebot added the cla: yes label Oct 9, 2017

jmank88 commented Oct 9, 2017

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jmank88 changed the title ~~gps: fine grained source transitions~~ [WIP] gps: fine grained source transitions Oct 11, 2017

ibrasho added the area: gps label Oct 13, 2017

jmank88 closed this Oct 15, 2017

jmank88 reopened this Oct 15, 2017

jmank88 changed the title ~~[WIP] gps: fine grained source transitions~~ gps: fine grained source transitions Oct 17, 2017

sdboyer suggested changes Oct 25, 2017

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sdboyer assigned jmank88 Oct 26, 2017

sdboyer mentioned this pull request Oct 26, 2017

gps: Adaptively clean dirty git repos #1279

Merged

jmank88 mentioned this pull request Nov 8, 2017

gps: vcs: suppress git password prompts #1357

Merged

jmank88 changed the title ~~gps: fine grained source transitions~~ WIP: gps: fine grained source transitions Nov 8, 2017

jmank88 mentioned this pull request Dec 12, 2017

gps: remove unused gopkgin code #1447

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jmank88 changed the title ~~WIP: gps: fine grained source transitions~~ gps: fine grained source transitions Dec 31, 2017

jmank88 mentioned this pull request Jan 18, 2018

Feature Request: Don't fetch source updates if needed revision is found locally #1546

Closed

sdboyer mentioned this pull request Jan 27, 2018

Command line args, --no-recurse, --shallow #1589

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gps: vcs: fine grained source transitions

b9a79ad

gps: source coord: set-up sources before returning gateways gps: source cache: improve PackageTree ProjectRoot handling

jmank88 closed this Jan 31, 2018

jmank88 reopened this Jan 31, 2018

jmank88 mentioned this pull request Feb 4, 2018

dep status runs significantly slower in a docker container on a mac #1624

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sdboyer reviewed Feb 21, 2018

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jmank88 commented Feb 21, 2018

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gps: source: ping upstream when no local state exists

98031fc

sdboyer approved these changes Feb 24, 2018

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sdboyer merged commit 338675d into golang:master Feb 24, 2018

		@@ -0,0 +1,34 @@
		// Copyright 2017 The Go Authors. All rights reserved.

gps: fine grained source transitions #1250

gps: fine grained source transitions #1250

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jmank88 commented Oct 9, 2017 • edited Loading

What does this do / why do we need it?

What should your reviewer look out for in this PR?

Which issue(s) does this PR fix?

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jmank88 commented Dec 31, 2017

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