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Add sync mechanism to prevent background crashes and fix ndb reopen order

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This adds a sync mechanism in Ndb.swift to coordinate certain usage of
nostrdb.c calls and the need to close nostrdb due to app lifecycle
requirements. Furthermore, it fixes the order of operations when
re-opening NostrDB, to avoid race conditions where a query uses an older
Ndb generation.

This sync mechanism allows multiple queries to happen simultaneously
(from the Swift-side), while preventing ndb from simultaneously closing
during such usages. It also does that while keeping the Ndb interface
sync and nonisolated, which keeps the API easy to use from
Swift/SwiftUI and allows for parallel operations to occur.

If Swift Actors were to be used (e.g. creating an NdbActor), the Ndb.swift
interface would change in such a way that it would propagate the need for
several changes throughout the codebase, including loading logic in
some ViewModels. Furthermore, it would likely decrease performance by
forcing Ndb.swift operations to run sequentially when they could run in
parallel.

Changelog-Fixed: Fixed crashes that happened when the app went into background mode
Closes: https://github.com/damus-io/damus/issues/3245
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
This commit is contained in:
Daniel D’Aquino
2025-11-12 16:04:47 -08:00
parent 6d9107f662
commit 20dc672dbf
59 changed files with 790 additions and 416 deletions
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11
nostrdb/Test/NdbTests.swift
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@@ -63,15 +63,14 @@ final class NdbTests: XCTestCase {
do {
let ndb = Ndb(path: db_dir)!
let id = NoteId(hex: "d12c17bde3094ad32f4ab862a6cc6f5c289cfe7d5802270bdf34904df585f349")!
guard let txn = NdbTxn(ndb: ndb) else { return XCTAssert(false) }
let note = ndb.lookup_note_and_copy(id)
let note = try? ndb.lookup_note_and_copy(id)
XCTAssertNotNil(note)
guard let note else { return }
let pk = Pubkey(hex: "32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245")!
XCTAssertEqual(note.pubkey, pk)
let profile = ndb.lookup_profile_and_copy(pk)
let lnurl = ndb.lookup_profile_lnurl(pk)
let profile = try? ndb.lookup_profile_and_copy(pk)
let lnurl = try? ndb.lookup_profile_lnurl(pk)
XCTAssertNotNil(profile)
guard let profile else { return }
@@ -91,14 +90,14 @@ final class NdbTests: XCTestCase {
do {
let ndb = Ndb(path: db_dir)!
let note_ids = ndb.text_search(query: "barked")
let note_ids = (try? ndb.text_search(query: "barked")) ?? []
XCTAssertEqual(note_ids.count, 1)
let expected_note_id = NoteId(hex: "b17a540710fe8495b16bfbaf31c6962c4ba8387f3284a7973ad523988095417e")!
guard note_ids.count > 0 else {
XCTFail("Expected at least one note to be found")
return
}
let note_id = ndb.lookup_note_by_key(note_ids[0], borrow: { maybeUnownedNote -> NoteId? in
let note_id = try? ndb.lookup_note_by_key(note_ids[0], borrow: { maybeUnownedNote -> NoteId? in
switch maybeUnownedNote {
case .none: return nil
case .some(let unownedNote): return unownedNote.id