Add snapshot save command (local) by anisaoshafi · Pull Request #210 · localstack/lstk

anisaoshafi · 2026-04-28T11:23:04Z

Added a new snapshot subcommand with an initial save action that saves the current LocalStack state to a snapshot file.
Scope for this PR is saving a snapshot locally.
Saving remotely coming next.

carole-lavillonniere · 2026-04-29T13:42:45Z

+		_ = resp.Body.Close()
+		return nil, fmt.Errorf("LocalStack returned status %d", resp.StatusCode)
+	}
+	return resp.Body, nil


question: instead of returning io.ReadCloser can we instead pass the io.Writer destination as argument?
This way we're sure the caller won't forget to close the returned body.

@anisaoshafi were you able to explore this idea?

Sorry, I missed this. I gave it a try here 🤞🏼 2bf9e13

gtsiolis · 2026-04-29T14:55:34Z

I've posted a comment[1] in PRO-212 to discuss some potential changes, comments welcome!

Without this, a failed io.Copy left a corrupt/partial ZIP on disk. The user had no indication the file was incomplete. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Passing nil to runLstk inherited the developer's real $HOME, which could write to ~/.config/lstk/lstk.log and the file-keyring fallback. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Verify that ErrorEvent is routed to errOut and all other events go to out, and that nil writer arguments fall back safely without panicking. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

carole-lavillonniere · 2026-05-12T14:22:26Z

+		return nil, f.err
+	}
+	return io.NopCloser(bytes.NewReader(f.body)), nil
+}


nit: can we use gomock to generate this mock exporter?

Done here: b16938c

carole-lavillonniere · 2026-05-12T14:23:50Z

+// StateExporter retrieves state from the running LocalStack instance.
+type StateExporter interface {
+	ExportState(ctx context.Context, host string) (io.ReadCloser, error)
+}


nit: the go convention is rather to define an interface where it is used, that would be directly in save.go

TIL, done here: 8bdf86e

carole-lavillonniere · 2026-05-12T14:24:55Z

+		_ = resp.Body.Close()
+		return nil, fmt.Errorf("LocalStack returned status %d", resp.StatusCode)
+	}
+	return resp.Body, nil


@anisaoshafi were you able to explore this idea?

carole-lavillonniere · 2026-05-12T14:51:43Z

+	got, err := snapshot.ParseDestination("", now)
+	require.NoError(t, err)
+	assert.Equal(t, filepath.Join(wd, "snapshot-2026-05-11T21-04-32.zip"), got)
+}


nit: can't this test case go as a new row in TestParseDestination?

Good catch, addressed here: 832bbf8

carole-lavillonniere · 2026-05-12T14:52:19Z

+	_, err := snapshot.ParseDestination(dir, now)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "is a directory")
+}


question: isn't this test case already covered in TestParseDestination?

addressed here: 832bbf8

carole-lavillonniere · 2026-05-12T15:01:26Z

+
+Pass [destination] as an absolute or relative path for the exported file:
+
+  lstk snapshot save                    # saves to ./snapshot-<YYYY-MM-DDTHH-mm-ss>.zip


question: spec says:

Omitting REF generates snapshot-- and writes to CWD.

So it looks like we're missing a hash?
Not sure if it makes sense since it is unlikely to conflict with the timestamp being precise to the second.

@gtsiolis we agreed to remove the hash, but forgot to remove one reference in the spec. Is that correct?

Yes, I think we can safely skip it, the timestamp should be quite unique on every generation, right? Plus, system will place a second file next to each other in the rare case you try to generate one in the same second, correct?

snapshot-2026-05-12T20-07-31.zip
snapshot-2026-05-12T20-07-31 (1).zip

I see we don't handle the double saving on the same second and overwrite the existing one, but sounds like an edge case and ok to leave as is and skip the over-engineering. Could we continue skipping the hash and easily append the (1) on the filename?

Fix AWS-only guard to correctly reject non-AWS emulator configs, align container lookup with the for-loop pattern used in aws.go, route ErrorEvents to stderr via NewPlainSinkSplit, and minor code clarity improvements. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…implementation

anisaoshafi · 2026-05-12T17:06:48Z

@gtsiolis would really appreciate your UX input when you have time to test this 🙏🏼

gtsiolis · 2026-05-12T17:19:26Z

Looking at this now! 👀

gtsiolis

UX LGTM on first pass. 🏁

gtsiolis · 2026-05-12T17:17:51Z

+
+Pass [destination] as an absolute or relative path for the exported file:
+
+  lstk snapshot save                    # saves to ./snapshot-<YYYY-MM-DDTHH-mm-ss>.zip


I see we don't handle the double saving on the same second and overwrite the existing one, but sounds like an edge case and ok to leave as is and skip the over-engineering. Could we continue skipping the hash and easily append the (1) on the filename?

gtsiolis · 2026-05-12T17:22:50Z

+	defer func() {
+		sink.Emit(output.SpinnerStop())
+		if retErr == nil {
+			sink.Emit(output.MessageEvent{Severity: output.SeveritySuccess, Text: fmt.Sprintf("Snapshot saved to %s", dest)})


praise: Nice! 😋 Adding some screens for future reference.

Saving Snapshot Saved Snapshot

gtsiolis · 2026-05-12T17:27:15Z

+	defer func() {
+		sink.Emit(output.SpinnerStop())
+		if retErr == nil {
+			sink.Emit(output.MessageEvent{Severity: output.SeveritySuccess, Text: fmt.Sprintf("Snapshot saved to %s", dest)})


question: There's some hard text wrapping on long file path. Any quick wins to make this render better on small width terminals? Like ...

If it's under CWD → ./snapshot-….zip

If it's under $HOME → ~/snapshot-….zip

Otherwise leave the absolute path

Text wrapping for saved snapshot on a small terminal width

gtsiolis

Missed one important question before.

gtsiolis · 2026-05-12T17:29:52Z

+// ParseDestination resolves the user-supplied path to an absolute local path.
+// When dest is empty, a default name based on now (UTC) is used, e.g.
+// "snapshot-2026-05-11T21-04-32.zip", saved in the current working directory.
+// The returned path always has a .zip extension.


question: Can we drop the .zip filename later, following the relevant discussion?

anisaoshafi added the semver: minor label Apr 28, 2026

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch 4 times, most recently from f6bbfbf to 6a24cdf Compare April 28, 2026 13:42

anisaoshafi requested review from carole-lavillonniere and gtsiolis April 28, 2026 16:36

carole-lavillonniere reviewed Apr 29, 2026

View reviewed changes

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch from 19cab09 to cc8b494 Compare April 29, 2026 16:45

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch 5 times, most recently from e2a83f0 to b09a963 Compare May 11, 2026 17:02

anisaoshafi marked this pull request as ready for review May 11, 2026 17:27

anisaoshafi requested a review from silv-io as a code owner May 11, 2026 17:27

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch from 36170a5 to 7e45925 Compare May 11, 2026 17:47

anisaoshafi requested a review from carole-lavillonniere May 11, 2026 17:51

anisaoshafi changed the title ~~Add snapshot save command~~ Add snapshot save command (local) May 11, 2026

anisaoshafi added 10 commits May 12, 2026 15:29

Add snapshot save command

f044e16

Absolute path and different error

c90f989

snapshot only works for aws

291014d

OS-agnostic destination check

5edfb43

Drop needless interface

7d8f77e

Handle conflicts

a3a0bdb

Drop 'snapshot' subcommand in favor of simplicity

73aba82

Restore 'snapshot' command in favor of clarity

75bfe81

Fix linting & paralellize tests

d236187

Improvements

6e8a827

anisaoshafi and others added 7 commits May 12, 2026 15:29

Move ExportState into aws.Client

3672660

change default snapshot name

7707408

local snapshot save always has .zip extension

1050ac5

Remove partial snapshot file when write fails mid-stream

dd5671a

Without this, a failed io.Copy left a corrupt/partial ZIP on disk. The user had no indication the file was incomplete. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Use isolated HOME in TestSnapshotSaveLocalStackNotRunning

b5bf3e0

Passing nil to runLstk inherited the developer's real $HOME, which could write to ~/.config/lstk/lstk.log and the file-keyring fallback. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Test NewPlainSinkSplit event routing behavior

1f61ef1

Verify that ErrorEvent is routed to errOut and all other events go to out, and that nil writer arguments fall back safely without panicking. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Nits

f705762

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch from 7e45925 to cc13c98 Compare May 12, 2026 13:30

Improve parsing logic

c680041

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch from cc13c98 to c680041 Compare May 12, 2026 13:48

carole-lavillonniere reviewed May 12, 2026

View reviewed changes

anisaoshafi force-pushed the drg-764-migrate-state-commands-from-cli-v1-export branch from 570047a to e5dfa92 Compare May 12, 2026 16:07

anisaoshafi added 4 commits May 12, 2026 18:13

Use gomock instead

b16938c

Move StateExporter interface where it's used

8bdf86e

Remove redundant tests; handle as test cases

832bbf8

Change ExportState so HTTP response body is always closed inside the …

2bf9e13

…implementation

gtsiolis approved these changes May 12, 2026

View reviewed changes

gtsiolis reviewed May 12, 2026

View reviewed changes


		Pass [destination] as an absolute or relative path for the exported file:

		lstk snapshot save # saves to ./snapshot-<YYYY-MM-DDTHH-mm-ss>.zip

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anisaoshafi commented Apr 28, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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gtsiolis commented Apr 29, 2026

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anisaoshafi commented May 12, 2026

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gtsiolis May 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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anisaoshafi commented Apr 28, 2026 •

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