snapshot_worker_state.go RawHistoryFolder

1package daemon
2
3import (
4	"context"
5	"sync"
6)
7
8// snapshotWorker owns the state of the repository snapshot worker and of the
9// other durable writers joined with it (maintenance and restoration), so
10// WaitDurableWriters can read all three completion signals under one lock.
11//
12// Lock position: mu is a leaf with respect to Daemon.mu. No code path acquires
13// Daemon.mu, a session lock, or a pane lock while holding it, and capture,
14// queue, and worker code never takes Daemon.mu. noticeMu is likewise a leaf and
15// is never held together with mu.
16//
17// The zero value is usable for tests that build &Daemon{}: nil maps are
18// allocated lazily by the enqueue paths, and a nil jobs channel never becomes
19// ready in a select.
20type snapshotWorker struct {
21	// jobs is the bounded regular capture queue. It is never closed: producers
22	// can race shutdown without risking a send-on-closed panic.
23	jobs chan *snapshotCapture
24	// wake wakes the repository scheduler when a session becomes dirty
25	// or an attempt completes. It is never closed and producers only send
26	// non-blockingly.
27	wake chan struct{}
28
29	// mu guards every field below it.
30	mu sync.Mutex
31	// admitted contains every capture accepted by either worker queue,
32	// including captures buffered in jobs.
33	admitted  map[*snapshotCapture]struct{}
34	id        uint64
35	ctx       context.Context
36	cancel    context.CancelFunc
37	done      chan struct{}
38	flush     chan struct{}
39	finalWake chan struct{}
40	// finalJobs coalesces terminal captures by session when the bounded
41	// regular queue is full. It retains at most snapshotFinalQueueCapacity named
42	// sessions, each with only its newest terminal state while the worker blocks.
43	finalJobs  map[*session]*snapshotCapture
44	finalOrder []*session
45	closing    bool
46	inFlight   *snapshotCapture
47
48	// maintenanceWorkerCancel/Done and restoreWorkerDone are the other durable
49	// writers' ownership signals. They share mu with the snapshot worker and are
50	// joined together in WaitDurableWriters; never split them. Startup
51	// restoration reconciles durable checkpoints, so it is a durable writer.
52	maintenanceWorkerCancel context.CancelFunc
53	maintenanceWorkerDone   chan struct{}
54	restoreWorkerDone       chan struct{}
55
56	// noticeMu guards the active global persistence failure signature. It is
57	// separate from mu so notice routing cannot block a producer or a
58	// repository worker.
59	noticeMu               sync.Mutex
60	activeFailureSignature string
61}