ArozOS Cluster – Implementation Tasks for Phases 3 to 9

This file is the work order for finishing the cluster. Phases 1 (membership, ACN transport) and 2 (identity) are done and verified. Everything below is written so that it can be implemented one task at a time, in order, without having to re-derive the design. Read README.md and CLAUDE.md first, then read this file top to bottom before starting any task. Do not skip the "Ground rules" section.

Status (2026-09-19): Phases 3 to 9 are implemented and verified. The cluster is feature complete; what follows is kept as the design record.

9.1: the scorer is its own package (scheduling/) rather than helpers inside jobs, because write placement and the replication planner needed the same ranking. jobs, storage and replication take a *scheduling.Manager and create their own when the host passes none.
9.2: the weights are one replicated metadata.KindSetting record (scheduling.weights), not a membership setting, so they follow the same log as the rest of the namespace state.
9.3: latency is the heartbeat round trip smoothed with an EWMA in membership (NodeView.LatencyMs), not a separate probe.
9.4: the disk-full guard sets Volume.ReadOnly and Volume.LowSpace at 5 % free and clears at 7 %, and fires OnDiskFull which the core publishes as a node.diskfull event.
9.3: site diversity is implemented, but the pairwise matrix is collected on demand rather than gossiped: latency vectors change constantly and would churn the membership records, so the planner pulls them from the members over the signed GET /cluster/acn/latency endpoint and caches the matrix for two minutes (membership.LatencyMatrix). Diversity is the distance to the nearest existing copy and only applies from three nodes up.
9.5: sched/explain takes a job id and is served by the core (clusterSchedExplain in src/cluster.jobs.go), because the scheduling package has no access to job records.
8.1: no separate MapReduceSpec; Spec gained Dataset and PartitionMax, and Kind: "mapreduce" marks the parent. Submitting with a dataset selects that kind automatically.
8.2: map outputs stay in the replicated record (capped at 8 MB of grouped values, which fails the job with a clear message) instead of being written to cluster:/.jobs/. Parents are guarded against re-entrant expansion, because submitting a child re-enters the scheduler.
8.2: locality scoring falls back to the metadata records when the host supplies no LocalityBytes, so the jobs package places map tasks correctly on its own.
7.1: spec and state live in ONE replicated record (jobs.Record, metadata.KindJob) instead of two parallel tables, so a merge can never leave them inconsistent. State.Blocked lists nodes that refused a job.
7.3: execution goes through agi.Gateway.ExecuteJobScript (new), which injects the _job_* functions and hands back a stopper for timeout and cancellation. The core adapter is src/cluster.jobs.go.
7.5: submit takes form fields (name, script, args, inputs, features, timeout, priority, cores); the script source is read from the submitter's file system. jobs/get replaces status?id= and output?id=.
6.1: node events are computed locally on every node (no fan-out needed); hooks read the event with postPara("event"); the web feed is served by the user router (any logged-in user); hooks listing at /system/cluster/events/hooks. 6.2: the provider interface is agi.ClusterProvider, wired after ClusterInit through AGIGateway.ClusterLibRegister() because AGI starts before the cluster. Deviations from the text below, kept deliberately small:
5.1/5.2: replication tasks are ephemeral (in memory on the leader, with a 50-entry history) instead of a repl_tasks table; the metadata records are the source of truth and a new leader re-plans within one interval. Empty files are replicated like any other. Over-replication drops require the remaining copies to be healthy, not strictly verified, because writers publish committed copies.
5.1: a stale copy on an online node is repaired in place (the planner prefers the volume that holds the stale copy as the target).
5.4: evacuation lives in storage (StartEvacuation, EvacuationStatus, FinishEvacuation, Volume.Evacuating) and the planner drives it; the leader retires the volume once nothing references it.
3.4: a follower whose applied counter is 0 (fresh node or new term) always takes a snapshot instead of paging the log, because the log may have been compacted below what it needs.
3.5: leaseTick also asks for a catch-up whenever a follower sees applied < lastSeq (learned from lease pushes), which keeps followers current between heartbeats.
4.5: Write publishes the record only after the bytes are in place (no intermediate writing location), matching the design's "only COMMITTED files become visible". LocWriting/LocPending remain for Phase 5.
4.5: Info lives in storage and clusterfs has its own Info; the core adapts between them (clusterBackend in src/cluster.go).
Membership timing constants became variables so tests can shorten them; storage and metadata tests set them in init().
4.6: the drive is mounted from cluster.go through membership.Manager.OnMembershipChange exactly as planned; listRoots reports it as Cluster=cluster:/.

Terminology: node = one ArozOS installation; member = node in the cluster; leader = the member currently holding the metadata lease; origin = the identity origin node (Phase 2); volume = a folder a node contributes to the cluster namespace; record = one entry in the metadata store.

0. Ground rules (apply to every task)

0.1 Repository conventions (enforced by hooks and CI)

Log only through logger.PrintAndLog("Cluster", message, err) from imuslab.com/arozos/mod/info/logger. Never import log.
Every new package under src/mod/ ships a *_test.go. Every new exported function is covered by a test. Style: t.TempDir(), t.Fatalf, table-driven where it fits.
No new dependencies unless MIT/BSD/Apache-2.0/MPL-2.0/ISC and truly needed. Everything below is designed to need no new module.
Authenticated HTTP endpoints for browsers go through prout.NewModuleRouter(...) (see src/cluster.go, the registerAdmin closure). Node-to-node endpoints go through acn.Server.HandleFunc (signed) and are mounted automatically under /cluster/acn/.
Stay portable: no hard-coded OS paths, no exec.Command in shared code, build tags for anything OS specific (see capability/diskusage_*.go).
No emoji anywhere (Go, HTML, JS, CSS). Use inline SVG or Semantic UI icons.

0.2 Things that bit us already (do not repeat)

Line endings. Several core files are checked out with CRLF. If an edit produces a whole-file diff in git diff --stat, run sed -i 's/\r$//' <file> on that file; the repository content is LF.
-race works since the switch to go.etcd.io/bbolt. The old github.com/boltdb/bolt panicked under checkptr; bbolt does not. The first -race run found a data race on the metadata.Manager.st swap in resetLocal (TestLeaveResetsStore), which still needs fixing.
Page scripts must not use var status: it shadows window.status and silently stringifies objects. Name page state clusterStatus etc.
go mod tidy pulls in modules imported by user files under src/files/. Do not run it blindly; if you must, revert unrelated additions in go.mod.
One millisecond is not unique. Every replicated record carries a version produced by nextVersion(prev) (membership/types.go), which is strictly greater than the previous value. Copy that helper into new packages (or export it) and never compare with >=.
Windows temp-dir cleanup fails for tests that keep a Bolt DB open; always Close() managers in t.Cleanup.
Do not run two ArozOS instances from src/ (Bolt lock on ao.db). See 0.5 for the two-node recipe.

0.3 Building blocks that already exist (use these, do not reinvent)

Need	Use
Send a signed request to a member by ID	`clusterManager.Transport().DoJSON(ctx, nodeID, method, path, in, out)` or `.Do(...)` for raw bytes. Routing (direct / tunnel / relay) is automatic.
Add a signed node endpoint	`clusterManager.Server().HandleFunc(acn.BasePath+"/x", func(w, r, sender *acn.SignedIdentity, body []byte))`. Body is already read and verified.
Know who is in the cluster and their state	`clusterManager.NodeViews()` (`[]membership.NodeView`, has `State`, `Local`, `Capabilities`, `Health`, `AdvertiseURL`, `TunnelVia`).
Own node ID / cluster ID	`clusterManager.NodeID()`, `clusterManager.Cluster()` (nil when standalone), `clusterManager.InCluster()`.
Persist cluster-scoped state	`clusterManager.DB()` (`*database.Database`, file `system/cluster.db`). Register new table names with `membership.RegisterClusterTable(name)` (task 3.1 adds this) so they are wiped on leave.
React to cluster-wide setting changes	`clusterManager.OnClusterChange` (chain it: keep the previous callback, see `identity.New`).
Node capabilities and requirement matching	`capability.Manifest.Satisfies(capability.Requirements)`.
Disk free space of a path	`capability.DiskUsage(path)`.
Cross-node user identity	`clusterIdentity.Issue(username, ttl)` → token; `clusterIdentity.Attach(req, username)` sets `X-Aroz-User`; on the receiving side `clusterIdentity.FromRequest(r)` → `*identity.Assertion{User, Groups, Issuer}`.
Resolve a user on this node	`userHandler.GetUserInfoFromUsername(username)` → `*user.User` (has `CanRead/CanWrite(vpath)`, `GetAllFileSystemHandler()`).
Local file systems	`GetAllLoadedFsh()` in `src/storage.go`; each `*filesystem.FileSystemHandler` has `.UUID`, `.Path`, `.FileSystemAbstraction` (interface in `mod/filesystem/filesystem.go`), `.RequireBuffer`.
Run an AGI script as a user	`AGIGateway.ExecuteAGIScriptAsUser(fsh, scriptVpath, user, w, r)` and `AGIGateway.ExecuteAGIScript(content, fsh, scriptFile, scope, w, r, user)` (`mod/agi/agi.go`).
Register an AGI library	`g.RegisterLib("name", injectFunc)` in `mod/agi/moduleManager.go` `LoadAllFunctionalModules`; injection payload `static.AgiLibInjectionPayload{VM, User, ScriptFsh, ScriptPath, Writer, Request}`. Pattern: `mod/agi/agi.sysinfo.go`.
Periodic system tasks	`nightlyManager.RegisterNightlyTask(func())`, or your own `time.Ticker` goroutine stopped in `Close()`.
Settings page	Add a card to `src/web/SystemAO/cluster/cluster.html` (same CSS variables, `t(key, fallback)` for strings, `apiPost`/`$.getJSON` helpers) or a new page registered with `registerSetting(settingModule{Group: "Cluster", RequireAdmin: true, ...})` in `src/cluster.go`.

0.4 Testing pattern for multi-node logic

Copy the helper style from identity/identity_test.go: create N membership.NewManager instances with t.TempDir() databases, expose each with httptest.NewServer(m.ACNHandler()), set the URL through m.UpdateConfig, create a cluster on one, NewJoinToken + JoinCluster the others, and waitFor(...) conditions with a 5 s deadline. Build your new package's manager on top of each membership manager exactly like identity.New does. Never sleep fixed durations; poll with waitFor.

0.5 Live two-node verification

Build once (cd src && go build -o arozos.exe .), then make two isolated copies outside src/: copy src/system (delete logs, dev.uuid, cluster.db*, cluster/), create an empty files/, junction or copy src/web as web, copy the binary. Run each copy with .\arozos.exe -port 808X -allow_mdns=false -allow_ssdp=false -uuid node-x -hostname NodeX (use the explicit .\ or you may launch a stale binary from PATH). Set a known admin password only in the copies (write passhash/<user> in the copied ao.db with auth.Hash). Log in from a browser with fetch('/system/auth/login', {method:'POST', body:new URLSearchParams({username, password, rmbme:'false'})}) and open /SystemAO/cluster/cluster.html. Stop the processes when done; do not commit changes to .claude/launch.json or the system/ folders.

0.6 Definition of done for every task

cd src && go build ./... && go vet ./mod/cluster/... && gofmt -l <your files> clean.
go test ./mod/cluster/... green (no -race), repeated with -count=3.
sh scripts/check-conventions.sh <changed files> shows no ERROR lines attributable to your lines (pre-existing warnings in main.go, user.go, mod/auth/auth.go are known).
README.md roadmap row updated; any new endpoint listed in README.md.
If the change is visible in the UI, verified live per 0.5 with a screenshot.

Phase 3 – Metadata store (ACMS)

Goal. One replicated index of what files exist in the cluster namespace and where their copies are, plus a leader lease used to serialise decisions (placement, replication, scheduling). Files themselves never move through this layer. Consistency model (decided with the project owner): no Raft. Records are last-writer-wins by version; the log is only a replication vehicle; correctness can always be restored by rescanning real files.

Package: src/mod/cluster/metadata. Wire in src/cluster.go after the identity service as clusterMetadata *metadata.Manager.

Task 3.1 – Cluster-scoped tables registry (membership)

Files: membership/store.go, membership/store_test.go.

Add

var extraClusterTables = []string{}
var extraTablesMu sync.Mutex
// RegisterClusterTable declares a cluster.db table that belongs to cluster
// membership: it is created on open and dropped when the node leaves.
func RegisterClusterTable(name string)

newStore must create every registered table (call after db.NewTable(TableIdentity)), and wipeCluster must drop + recreate them. Because packages call RegisterClusterTable from their New(...), also create the table at registration time when a store is already open: give store a package-level pointer currentStore *store set in newStore and cleared in close(); RegisterClusterTable calls currentStore.db.NewTable(name) when non-nil.

Test: register a table, create a manager, write a key, LeaveCluster, assert the key is gone and the table still exists.

Task 3.2 – Prefix listing in the database package

Files: mod/database/database.go, database_core.go, database_openwrt.go, tests in both database_core_test.go/database_public_test.go.

Add func (d *Database) ListTableWithPrefix(tableName string, prefix string) ([][][]byte, error) implemented with a Bolt cursor Seek([]byte(prefix)) looping while bytes.HasPrefix(k, prefix). Implement it in both core files (database_core.go and the mipsle/riscv64 database_openwrt.go) or the cross-compile breaks.
Test with keys a/1, a/2, b/1: prefix a/ returns exactly two.

Task 3.3 – Records and local store

File: metadata/types.go, metadata/store.go, metadata/store_test.go.

Copy nextVersion from membership (or export it as membership.NextVersion and use that). All Version fields use it.

// Volume is a folder one node contributes to the namespace.
type Volume struct {
ID        string `json:"id"`        // uuid
NodeID    string `json:"nodeId"`
Name      string `json:"name"`      // display
FshUUID   string `json:"fshUuid"`   // local file system handler the folder lives on
Subpath   string `json:"subpath"`   // path inside that fsh, always "/x/y" form
Capacity  int64  `json:"capacity"`  // bytes, refreshed by the owner node
Free      int64  `json:"free"`
ReadOnly  bool   `json:"readOnly"`
Removed   bool   `json:"removed"`
Version   int64  `json:"version"`
}

const (
LocPending   = "pending"   // placement decided, nothing written yet
LocWriting   = "writing"   // bytes are being written
LocCommitted = "committed" // fully written, checksum matched by the writer
LocVerified  = "verified"  // re-read and checksum matched after commit
LocStale     = "stale"     // node offline too long or checksum mismatch; do not read
LocFailed    = "failed"
)

type Location struct {
VolumeID string `json:"volumeId"`
NodeID   string `json:"nodeId"`
State    string `json:"state"`
Checksum string `json:"checksum"` // sha256 hex of the copy on that volume
Updated  int64  `json:"updated"`
}

type FileRecord struct {
ID        string     `json:"id"`       // uuid, stable across renames
Path      string     `json:"path"`     // logical path, "/photos/2026/a.jpg"; "/" for root; no trailing slash
IsDir     bool       `json:"isDir"`
Size      int64      `json:"size"`
ModTime   int64      `json:"modTime"`
Checksum  string     `json:"checksum"` // sha256 hex, "" for directories
Owner     string     `json:"owner"`    // username that created it
Primary   string     `json:"primary"`  // VolumeID of the preferred copy
Locations []Location `json:"locations"`
Replicas  int        `json:"replicas"` // desired copies, 0 = use folder policy
Removed   bool       `json:"removed"`  // tombstone
Version   int64      `json:"version"`
}

// Policy is the desired replica count for a top-level folder.
type Policy struct {
Folder   string `json:"folder"`   // "/photos"
Replicas int    `json:"replicas"` // >= 1
Version  int64  `json:"version"`
}

Tables (register all with membership.RegisterClusterTable): meta_files (ID → FileRecord), meta_paths (Path → ID), meta_volumes (ID → Volume), meta_policy (Folder → Policy), meta_log (zero-padded 20 digit Seq → Entry), meta_state (lease, applied, lastseq).

Store API (all methods take and return copies, guard with a sync.RWMutex, keep in-memory maps for files/paths/volumes/policies loaded at open): putFile(rec) (changed bool) – LWW on Version; when the path changed, delete the old meta_paths key and write the new one; tombstones keep their path entry so a re-create with a newer version wins. getFileByID, getFileByPath, listDir(path) []FileRecord – children are records whose Path has dir + "/" as prefix and no further / (skip tombstones); use ListTableWithPrefix on meta_paths for cold loads. putVolume, volumes(), putPolicy, policies(), policyFor(path) – walks up to the first path segment; default Policy{Replicas: 1}. appendLog(entry), logAfter(seq, max), compactLog(keepLast int), lastSeq(), applied()/setApplied(seq), lease()/setLease(). Tests: LWW (older version ignored), rename moves the path index, tombstone hides from listDir, prefix listing of nested dirs, policy lookup for /photos/2026/a.jpg returns the /photos policy.

Task 3.4 – Replicated log

File: metadata/log.go, metadata/log_test.go.

type Entry struct {
    Seq     uint64          `json:"seq"`  // assigned by the leader, 0 while pending
    Term    uint64          `json:"term"`
    Kind    string          `json:"kind"` // "file", "volume", "policy"
    Payload json.RawMessage `json:"payload"`
    Version int64           `json:"version"` // copied from the record
    Origin  string          `json:"origin"`  // node that produced the change
}

apply(entry) decodes by Kind and calls the matching put*. Applying is idempotent (LWW), so replays are harmless.

Flow:

Manager.Submit(kind, record) (public): stamp Version = nextVersion(old), apply locally immediately (the local view must reflect the change before returning), then if this node is leader → assign (Seq = lastSeq+1, Term = current) → appendLog → fan-out POST /cluster/acn/meta/append {Entries: [entry]} to every ONLINE peer (best effort, in goroutines). If not leader → push to pending queue (in memory + table meta_pending keyed by a uuid) and send POST /cluster/acn/meta/submit {Entry} to the leader; on success remove from pending. A background loop retries pending entries every 15 s.
Followers receiving append: apply each entry, setApplied(seq) if seq == applied+1, otherwise store and request catch-up.
Catch-up: GET /cluster/acn/meta/log?after=<applied> from the leader (max 500 entries per call, loop until caught up). If the leader answers 410 Gone (compacted), call GET /cluster/acn/meta/snapshot which returns every current record (files, volumes, policies) plus lastSeq; apply all, setApplied(lastSeq).
Leader compaction: keep the last 10 000 entries; run after every 1 000 appends.
On leadership change (new term), followers reset applied to 0 and do a full snapshot once (simple and safe).

Tests (3 managers over httptest): submit on leader replicates to both followers within 5 s; submit on a follower reaches everyone; a follower that was stopped (close its server, keep the manager) catches up by log when restarted within the log window and by snapshot after compactLog(0); an older version arriving later never overwrites a newer record.

Task 3.5 – Leader lease

File: metadata/lease.go, metadata/lease_test.go.

type Lease struct {
    Holder  string `json:"holder"`
    Term    uint64 `json:"term"`
    Expires int64  `json:"expires"` // unix seconds
}
const LeaseDuration = 30 * time.Second
const LeaseRenew    = 10 * time.Second

Algorithm (runs in a goroutine every 5 s on every member; deterministic, no quorum, works with 2 nodes):

candidate() = among NodeViews() with State ONLINE or DEGRADED (never MAINTENANCE/DRAINING/OFFLINE/UNKNOWN), the record with the smallest Joined, ties by smallest ID. The local node counts as ONLINE.
If the current lease is unexpired and its holder is still eligible → if holder is me, renew when Expires - now < LeaseRenew: bump Expires, push POST /cluster/acn/meta/lease {Lease} to all peers.
If the lease is expired or the holder is no longer eligible, and the candidate is me → claim: Term+1, Holder = me, push to peers.
Receiving lease: accept if in.Term > mine.Term, or same term and same holder (renewal). Reject otherwise (respond 409 with my lease so the sender learns the higher term and steps down).
IsLeader() = holder is me and not expired. Leader() returns holder or "". Callers that need the leader and get "" must retry later, never proceed locally except for Submit (which queues, see 3.4).
Log leadership changes once per change. Tests: with A (joined first) and B, A becomes leader within 15 s; stop A's server, B becomes leader after LeaseDuration; restart A, A sees B's higher term and stays follower until B's lease expires (A only claims when B is not eligible, i.e. offline). Split-brain healing: fake two leases with different terms, the higher term wins on both sides.

Task 3.6 – ACN and admin endpoints, wiring, UI

Files: metadata/handlers_acn.go, metadata/handlers_admin.go, src/cluster.go, cluster.html.

Signed: POST meta/append, POST meta/submit, GET meta/log?after=, GET meta/snapshot, POST meta/lease, GET meta/stat?path= (returns the record, used by Phase 4 for cache misses).
Admin (/system/cluster/meta/*): status → {leader, term, isLeader, leaseExpires, applied, lastSeq, files, dirs, volumes, pending}; ls?path=; stat?path=; policy/list, policy/set (folder, replicas).
UI: a "Metadata" card on cluster.html showing leader, term, counts, pending entries, and the policy table with an editable replica count per top-level folder.
Wiring: clusterMetadata, _ = metadata.New(metadata.Option{Membership: clusterManager}) after identity; Close() in ClusterShutdown before the membership manager.

Acceptance: two live nodes, status shows the same leader and term on both, setting a policy on one appears on the other within 15 s.

Phase 4 – Unified namespace (`cluster:/`)

Goal. A cluster:/ drive appears in File Manager (and every app, WebDAV, AGI filelib) on every member. Reads and writes go to whichever node holds the bytes; the user never sees nodes or paths. Files stay whole files on ordinary folders that admins picked (volumes). Transfers between nodes are 4 MiB chunks with per-chunk and whole-file SHA-256 because deployments sit behind Cloudflare (100 MB / 100 s limits).

Packages: src/mod/cluster/storage (volumes + chunk transfer, "ACS") and src/mod/filesystem/abstractions/clusterfs (the drive).

Task 4.1 – Volumes

Files: storage/volumes.go, storage/volumes_test.go, admin handlers, UI.

Admin picks a folder: POST /system/cluster/storage/volume/add with fsh=<uuid>&path=<subpath>&name=. Validate: fsh exists in GetAllLoadedFsh(), is local (Filesystem not a network type, !RequireBuffer), path exists or can be created, not already a volume, not the user root itself. Create Volume{ID: uuid, NodeID: self, ...}, compute Capacity/Free with capability.DiskUsage(realPath), and clusterMetadata.Submit("volume", v).
volume/remove sets Removed = true (data stays on disk; replication in Phase 5 re-creates copies elsewhere first when possible, see 5.4).
Every 60 s the owner refreshes Free for its volumes (Submit only when the value changed by more than 1 %).
realPath(vol, logical string) (string, error): join fsh.Path, vol.Subpath, logical; reject any result that escapes the volume root (filepath.Clean + prefix check). All local file access in this package goes through this helper and the local fsh's FileSystemAbstraction.
UI: "Storage" card listing this node's volumes (name, folder, free/total, file count) with add/remove, and a read-only list of other nodes' volumes. Default suggestion in the UI: user:/cluster (create it if missing).

Task 4.2 – Chunked transfer protocol (server side)

Files: storage/transfer_server.go, storage/transfer_test.go.

Constants: ChunkSize = 4 << 20, MaxChunkSize = 8 << 20, SessionTTL = 30 * time.Minute.

Endpoints (all signed, all operate on this node's volumes only; reject with 404 when VolumeID is not local): | Endpoint | Body / query | Reply | |---|---|---| | POST store/begin | {VolumeID, Path, Size, Checksum, FileID} | {SessionID, Have: []int} (chunk indexes already present when resuming an existing session for the same FileID+Checksum) | | POST store/chunk?session=&index= | raw bytes, header X-Aroz-Chunk-Sha256 | {Index, Received}; 409 on hash mismatch | | POST store/commit | {SessionID} | {Checksum, Size} after streaming SHA-256 of the assembled file equals Checksum; 409 otherwise (file deleted) | | POST store/abort | {SessionID} | ok | | GET store/read?volume=&path=&offset=&length= | length ≤ MaxChunkSize | raw bytes + X-Aroz-Chunk-Sha256 + X-Aroz-File-Size | | GET store/stat?volume=&path= | | {Exists, IsDir, Size, ModTime} | | POST store/mkdir, store/delete (file or empty dir; Recursive flag), store/rename (same volume) | {VolumeID, Path, NewPath, Recursive} | ok | | GET store/list?volume=&path= | | [{Name, IsDir, Size, ModTime}] (used by scan) | | POST store/checksum | {VolumeID, Path} | {Checksum} streamed SHA-256 |

Implementation notes:

Sessions live in a map guarded by a mutex; chunks are written with WriteAt into <realPath>.part-<SessionID>; on commit rename to the final path (os.Rename semantics through the local fsh: write .part, then Rename). Never leave partial files under the final name.
A sweeper goroutine removes sessions and .part files older than SessionTTL.
read must set Content-Length; compute the chunk hash while copying.
Bodies are already buffered by the ACN verifier (MaxSignedBody 64 MiB), so reading body []byte from the handler signature is fine. Tests: begin/chunk/commit round trip with a 10 MiB random file (3 chunks), resume after dropping one chunk (Have lists the others), corrupt chunk → 409, wrong final checksum → 409 and no file left, read with offsets reassembles the file bit-exactly, path escape (../) → 400.

Task 4.3 – Transfer client

File: storage/transfer_client.go, tests in transfer_test.go.

type Client struct{ Transport *acn.Transport }
func (c *Client) Upload(ctx, nodeID, volumeID, path string, fileID string, r io.Reader, size int64, checksum string, progress func(done int64)) error
func (c *Client) Download(ctx, nodeID, volumeID, path string, w io.Writer, expectChecksum string, progress func(done int64)) error
func (c *Client) Stat / Mkdir / Delete / Rename / List / Checksum (thin wrappers)

Upload: begin → for each chunk not in Have: read ChunkSize bytes, sha256, send with up to 3 retries (new nonce each time – the transport signs per request) → commit. Download: loop read with offset += length, verify each chunk hash, feed a running SHA-256, compare with expectChecksum at the end (return ErrChecksumMismatch). Both must abort on ctx.Done(). Use acn.Transport.Do for raw bodies (set Content-Type: application/octet-stream).

Task 4.4 – The `clusterfs` abstraction

Files: mod/filesystem/abstractions/clusterfs/clusterfs.go, clusterfs_test.go.

Constructor:

type Backend interface {           // implemented by mod/cluster/storage.Service
    Stat(logical string) (*metadata.FileRecord, error)
    List(logical string) ([]metadata.FileRecord, error)
    Mkdir(logical string, owner string) error
    Remove(logical string, recursive bool) error
    Rename(old, new string) error
    OpenRead(logical string) (io.ReadCloser, error)
    Write(logical string, r io.Reader, size int64, owner string) error
    Ready() bool
}
func New(uuid string, backend Backend) *ClusterFileSystem

Mapping of FileSystemAbstraction methods (mirror webdavfs for the signature list):

Name() → "cluster"; hierarchy is always public; VirtualPathToRealPath strips cluster: and returns the logical path (/photos/a.jpg); RealPathToVirtualPath prefixes cluster:.
Stat → Backend.Stat → build an os.FileInfo (write a small fileInfo struct: Name = base, Size, Mode 0644 / 0755|ModeDir, ModTime).
ReadDir → Backend.List → []fs.DirEntry (write dirEntry wrapper).
ReadStream → Backend.OpenRead; WriteStream → Backend.Write (size unknown → pass -1; the service buffers to a local temp file first to compute size and checksum, see 4.5).
ReadFile/WriteFile via the stream methods. Mkdir/MkdirAll → Backend.Mkdir (MkdirAll creates parents from the top). Remove → non-recursive, RemoveAll → recursive. Rename → Backend.Rename.
Open, Create, OpenFile, Chmod, Chown, Chtimes → return errors.New("filesystem type not supported") (same as webdavfs; the core uses buffered streams when RequireBuffer is true).
FileExists/IsDir/GetFileSize/GetModTime from Stat.
Glob → emulate exactly like webdavfs.Glob (depth-limited ReadDir).
Walk → recursive List calling filepath.WalkFunc.
Heartbeat → nil when Backend.Ready(), else an error (the core reconnect loop in storage.go will otherwise try to rebuild the handler; make Ready() true whenever the node is in a cluster).
Close → nil. Tests use a fake Backend (map-based) and assert every method, including path normalisation (cluster:/a/../b → /b, Windows backslashes → /).

Task 4.5 – The storage service (placement, reads, writes)

File: storage/service.go, storage/service_test.go.

type Service struct {
    m       *membership.Manager
    meta    *metadata.Manager
    client  *Client
    tmpDir  string          // *tmp_directory from flags, use a "cluster" subfolder
    volumes func() []metadata.Volume // from metadata
}

Stat/List read the metadata store only (never the network).
Mkdir: create the FileRecord{IsDir:true} and its missing parents (Submit); no physical directory is made until a file is written under it.
Write (the important one):
1. Refuse when not in a cluster or when no volume exists (error text: "no cluster volume available; add one in System Settings > Cluster").
2. Spool the reader to tmpDir/<uuid>.spool while hashing (SHA-256) and counting bytes → size, checksum.
3. Placement pickVolume(size): candidates = volumes not Removed, not ReadOnly, owner node ONLINE/DEGRADED, Free > size*1.1 + 64 MiB. Prefer (a) a local volume, (b) the volume whose node currently holds the record's Primary (overwrite case), (c) the volume with most free space. If the leader is reachable ask it (POST meta/place {Size, Path}, the leader runs the same function over its view) so two nodes writing at once do not both pick the same nearly-full volume; if the leader is unreachable, decide locally.
4. Create/refresh the record: Locations=[{VolumeID, NodeID, State: writing}], Primary = VolumeID, Size, Checksum, ModTime = now, Owner; Submit. Parents that do not exist get directory records.
5. Copy bytes: local volume → stream the spool to realPath via a .part rename; remote → client.Upload(...). On failure set the location failed, delete the spool, return the error (the record stays with a failed location; a retry overwrites).
6. Set the location committed (Checksum) and Submit; delete the spool; events.Publish("file.created"|"file.updated") (Phase 6; leave a hook OnFileWritten func(rec) for now).
OpenRead: pick a location in order: local volume with State committed/verified → open the real file; else remote locations sorted by node state ONLINE first, then lowest measured latency (Phase 9; use the order of NodeViews() for now) → io.Pipe fed by client.Download in a goroutine, verifying the checksum from the record. If every location fails return ErrNoHealthyCopy.
Remove: mark the record (and children when recursive) as tombstones via Submit, then delete the physical copies on every location (local directly, remote via client.Delete); failures are logged and the location marked stale so the reconcile job (4.7) cleans up later.
Rename: metadata first (path index moves, ID unchanged), then physical renames on each location's volume; on physical failure mark that location stale and let replication (Phase 5) restore a copy under the new name. Renaming a directory renames every record beneath it (batch Submit). Tests with the fake transport from identity_test.go style plus real managers: write on A lands on A's volume; write on B when only A has a volume uploads to A and is readable from B; rename keeps the ID; remove leaves a tombstone and deletes the physical file; read of a record whose only location is on an OFFLINE node returns ErrNoHealthyCopy.

Task 4.6 – Mount the drive

Files: src/cluster.go, src/storage.go, mod/filesystem/arozfs/arozfs.go, mod/filesystem/config.go.

Add "cluster" to arozfs.GetSupportedFileSystemTypes() and to IsNetworkDrive; add "cluster" to the reserved UUID list in filesystem.ValidateOption.
In cluster.go, function clusterMountDrive(): when clusterManager.InCluster() and no handler with UUID cluster is in baseStoragePool, build &fs.FileSystemHandler{Name: "Cluster", UUID: "cluster", Path: "cluster:/", Hierarchy: "public", RequireBuffer: true, Filesystem: "cluster", FileSystemAbstraction: clusterfs.New("cluster", clusterStorage), InitiationTime: now, RuntimePersistenceConfig: {LocalBufferPath: *tmp_directory}} and baseStoragePool.AttachFsHandler. clusterUnmountDrive() detaches it. Call mount at boot (after StorageInit and ClusterInit) and from OnClusterChange/after join; call unmount from leave/evict (add a membership.Manager.OnMembershipChange func(inCluster bool) callback fired by CreateCluster, JoinCluster, LeaveCluster, wipeLocalState).
Users see it immediately because User.HomeDirectories points at the same pool object. Check system_fs_listDrives output in the File Manager.
Uploads through the web UI go via RequireBuffer paths in file_system.go (buffer to local temp, then WriteStream); nothing to change there, but test a 20 MB upload and a download from the other node. Acceptance (live): upload a photo on node A into cluster:/photos, open Photo on node B and view it; delete it on B, gone on A.

Task 4.7 – Scan and reconcile

File: storage/reconcile.go, tests. Runs on each node for its own volumes every 30 min and on demand (POST /system/cluster/storage/rescan):

Walk the volume folder (skip .part-*). For each file: find the record by logical path (vol root = /); if none → create a record with a single committed location on this volume (this is how pre-existing files in a contributed folder join the namespace, and how a rebuilt metadata store recovers). If the record exists but has no location on this volume → add one as committed after checksumming. If the size differs from the record → checksum; if it differs from the record's checksum, mark this location stale (the newer mtime wins only if the record's own location list has no verified copy; otherwise the stale copy is repaired by Phase 5).
For each record location on this volume whose file is missing → mark stale.
Delete orphaned .part-* older than SessionTTL. Never delete real files during reconcile.

Phase 5 – Replication

Goal. Every file has the number of verified copies its folder policy asks for, on different nodes; copies are checksum verified; a dead node's files are still readable; an admin can move a volume's content elsewhere.

Package: src/mod/cluster/replication. Runs only on the leader (clusterMetadata.IsLeader()); every node executes the transfer work it is told to do.

Task 5.1 – Planner

replication/planner.go + tests. Every 60 s on the leader:

For each non-tombstone file record (skip dirs, skip Size == 0): want = rec.Replicas || policyFor(rec.Path).Replicas; have = count(locations with State in {committed, verified} on nodes that are ONLINE/DEGRADED and volumes not Removed).
If have < want: choose a target volume: not on a node that already has a copy, owner ONLINE, Free > size*1.1, most free space; skip if none. Create Task{ID, FileID, Path, SourceNode, SourceVolume, TargetNode, TargetVolume, Checksum, State: queued, Attempts, LeaseExpires} in table repl_tasks (registered cluster table) and send POST /cluster/acn/repl/pull {Task} to the target node.
If have > want (policy lowered) and every extra copy is verified: delete the copy on the volume with the least free space (client.Delete
- remove the location). Never go below 1 verified copy.
Limit: at most 4 tasks in flight per target node, 16 in total. Unit test the planner with an in-memory metadata store: under-replicated file gets exactly one task; over-replicated file loses the right copy; no task when no eligible volume.

Task 5.2 – Worker

replication/worker.go + tests. On the target node, pull:

Set a location {TargetVolume, State: writing} on the record (Submit).
client.Download from SourceNode/SourceVolume into realPath + .part, verifying the checksum; rename into place.
Set the location verified with the checksum; Submit; answer the leader with POST /cluster/acn/repl/done {TaskID, OK, Error}.
Renew the task lease every 10 s (POST repl/lease); the leader re-queues tasks whose lease expired (Attempts++, give up after 5 and log). Test with 3 real managers: policy 2 on /docs, write a file on A, within 10 s (use short intervals in tests via Option.PlanInterval) it has a verified copy on B or C; stop B's server, wait, the file stays readable from C; corrupt B's copy on disk and force a verify (5.3) → location stale → a new copy is made.

Task 5.3 – Verification and failover

replication/verify.go. Nightly (nightlyManager.RegisterNightlyTask) each node re-checksums up to 1 GB of its own copies (oldest verified first) and downgrades mismatches to stale; the planner then repairs them. The leader marks every location on a node that has been OFFLINE for more than 10 min as stale (it does not delete); when the node is back and reconcile (4.7) confirms the files, the locations return to committed → verify → verified. Reads (4.5) already skip stale.

Task 5.4 – Migration / evacuation

Admin action POST /system/cluster/storage/volume/evacuate?id= on the owner node: sets Volume.ReadOnly = true, then for every record with a location on that volume with fewer verified copies elsewhere than want, creates a replication task to another node with Priority high; when every file has another verified copy, deletes local copies and marks the volume Removed. Progress endpoint volume/evacuate/status?id=. UI: "Evacuate" button with a progress bar; "Remove" is only allowed when the volume holds no sole copies (otherwise the UI offers Evacuate).

Task 5.5 – UI

Cluster page "Replication" card: policies (from 3.6) with replica counts, counters (under-replicated, in flight, stale), a "Repair now" button (runs the planner once), and a per-file inspector stat?path= showing locations with state badges (reuse cl-badge classes: verified=ONLINE, writing= DEGRADED, stale=OFFLINE).

Phase 6 – AGI `cluster` library and the event bus (AEB)

Task 6.1 – Event bus

Package src/mod/cluster/events.

type Event struct {
    ID     string          `json:"id"`     // uuid, used for de-duplication
    Type   string          `json:"type"`   // "file.created" "file.updated" "file.removed" "file.renamed"
                                          // "node.online" "node.offline" "node.joined" "node.left"
                                          // "replica.verified" "replica.stale" "job.completed" "job.failed"
    Node   string          `json:"node"`   // origin node
    Path   string          `json:"path,omitempty"`
    FileID string          `json:"fileId,omitempty"`
    User   string          `json:"user,omitempty"`
    Time   int64           `json:"time"`
    Data   json.RawMessage `json:"data,omitempty"`
}
type Bus struct{ ... }
func (b *Bus) Publish(e Event)                       // local subscribers + fan-out to peers
func (b *Bus) Subscribe(types []string, fn func(Event)) (unsubscribe func())

Fan-out: POST /cluster/acn/events/publish {Events: [...]} to every ONLINE peer, batched every 200 ms, fire-and-forget, retried once. Receivers drop IDs seen in the last 10 min (ring buffer + map).
Node events come from membership: add membership.Manager.OnNodeState func(nodeID string, old, new NodeState) fired from a 5 s ticker that compares computed states with the previous tick.
File events come from storage.Service (OnFileWritten, removed, renamed hooks) and replication (replica.*).
Web clients: GET /system/cluster/events/ws (admin router with AdminOnly: false, module "System Setting") upgrades to a WebSocket and streams JSON events; optional ?types=file.created,file.removed. Use gorilla/websocket like src/cast.go; ping every 30 s.
AGI script hooks: table event_hooks (registered cluster table) keyed by uuid → {Owner, Types, ScriptVpath, FshUUID}. On each event, for each matching hook run the script with AGIGateway.ExecuteAGIScriptAsUser after setting a global EVENT (JSON string) – add an injectEventGlobal helper in mod/agi that the runner calls before execution (do this by writing the event to the request context: create a fake *http.Request with a body containing the event and have the script read it with the existing POST helpers; simplest: pass the event as POST field event). Run at most 4 hooks concurrently; log failures. Tests: local publish/subscribe with type filter, de-dup of the same ID, fan-out between two managers reaches the other side's subscriber.

Task 6.2 – AGI library `cluster`

File mod/agi/agi.cluster.go (+ agi.cluster_test.go for pure helpers), registered in LoadAllFunctionalModules only when g.Option.ClusterProvider != nil (add that field to AgiSysInfo; the core passes an adapter struct built in src/agi.go).

Functions (all return plain JSON-able values; errors become JS exceptions via vm.MakeCustomError):

requirelib("cluster");
cluster.inCluster()               -> bool
cluster.self()                    -> {id, name, state, capabilities}
cluster.nodes()                   -> [ {id, name, state, os, arch, cores, ram, features:[...], local:true} ]
cluster.status()                  -> {cluster:{id,name}, leader, identityOrigin, volumes:[...]}
cluster.stat("cluster:/photos/a.jpg")     -> {path, isDir, size, modTime, checksum, replicas, locations:[{node, volume, state}]}
cluster.list("cluster:/photos")           -> [stat-like objects]
cluster.setReplicas("cluster:/photos/a.jpg", 2)   // admin only, per file
cluster.policy("/photos", 2)                       // admin only, per folder
cluster.on("file.created", "cluster:/apps/indexer/hook.agi")   -> hookId   (owner = current user)
cluster.off(hookId)
cluster.hooks()                   -> [ {id, types, script} ]
cluster.emit("app.custom", {any json})          // Type is prefixed "app." if missing

Permission: stat/list check u.CanRead(vpath); setReplicas/policy require u.IsAdmin(). Path arguments accept cluster:/... or /.... Reuse static.RelativeVpathRewrite like agi.file.go. Document every function in mod/agi/README.md and add the section to src/web/Terminal/docs/api.json (see the README maintainer note).

Ordinary file access does not need this library: filelib already works on cluster:/ paths through the mounted drive.

Phase 7 – Job runtime (AJR) and scheduler (AJS)

Goal. agi.Compute.Run(job) from the design: an application submits a job; the cluster picks a node that satisfies the job's requirements and holds the input data; the node runs the job as the submitting user; results are readable from anywhere. Jobs are AGI scripts (JavaScript), the only portable payload across heterogeneous nodes.

Package src/mod/cluster/jobs. Tables (registered): jobs_spec, jobs_state. Leader-only scheduling loop; execution anywhere.

Task 7.1 – Job model

type Spec struct {
    ID           string                  `json:"id"`
    Name         string                  `json:"name"`
    Owner        string                  `json:"owner"`        // username; the job runs with this user's permissions on the executing node
    Script       string                  `json:"script"`       // full JS source captured at submit time (nodes may not share the source path)
    ScriptName   string                  `json:"scriptName"`   // for logs, e.g. "transcode.agi"
    Args         json.RawMessage         `json:"args"`
    Inputs       []string                `json:"inputs"`       // cluster:/ paths used for locality scoring
    Requirements capability.Requirements `json:"requirements"`
    Priority     int                     `json:"priority"`     // higher first, default 0
    TimeoutSec   int                     `json:"timeoutSec"`   // default 3600
    MaxAttempts  int                     `json:"maxAttempts"`  // default 3
    Kind         string                  `json:"kind"`         // "run" | "map" | "reduce" (Phase 8)
    ParentID     string                  `json:"parentId,omitempty"`
    Created      int64                   `json:"created"`
    Version      int64                   `json:"version"`
}
type State struct {
    ID           string `json:"id"`
    Status       string `json:"status"` // queued scheduled running succeeded failed cancelled
    Node         string `json:"node"`
    Attempts     int    `json:"attempts"`
    LeaseExpires int64  `json:"leaseExpires"`
    Progress     float64 `json:"progress"` // 0..1
    Output       json.RawMessage `json:"output,omitempty"`  // whatever the script returned via job.output()
    Log          []string `json:"log"`     // last 200 lines from job.log()
    Error        string `json:"error,omitempty"`
    Started, Finished int64
    Version      int64
}

Both are replicated through the metadata log (Kind: "jobspec", "jobstate"), so every node can answer status queries locally.

Task 7.2 – Script contract (what job authors write)

A job script defines one of:

// single-node job
function run(job) {           // job = {id, name, args, inputs, node}
    job.log("starting");      // appended to State.Log
    job.progress(0.5);        // 0..1
    var f = requirelib("filelib");  // normal AGI libraries work; paths like cluster:/... work
    return {ok: true, frames: 120}; // becomes State.Output (JSON)
}

The runtime executes the script source with the standard user scope, then evaluates run(JOB) where JOB is the injected object. job.log, job.progress, job.output, job.abortIfCancelled() are Go functions injected as _job_log etc. and wrapped in a JS prelude the runtime prepends:

var JOB = JSON.parse(_job_spec()); JOB.log=function(m){_job_log(String(m))}; JOB.progress=function(p){_job_progress(p)}; JOB.abortIfCancelled=function(){if(_job_cancelled()){throw new Error("cancelled")}};

and appends _job_output(JSON.stringify(run(JOB))). Missing run → failed with a clear error. A script may also define setup(ctx) (called once with {node, capabilities} before run); optional.

Task 7.3 – Execution on a node

jobs/runner.go. Endpoint POST /cluster/acn/jobs/run {SpecID} (leader → node). The node:

Loads the spec from its replicated table (or asks the leader GET jobs/spec?id= if not yet replicated).
Resolves the owner with userHandler.GetUserInfoFromUsername; if the user does not exist on this node → answer 409 user-not-available (the scheduler picks another node; Phase 2 replication makes this rare).
Runs in a goroutine: build the source = prelude + spec.Script + epilogue; call AGIGateway.ExecuteAGIScript(source, nil /*fsh*/, spec.ScriptName, "", recorder, nil, user) with a httptest.ResponseRecorder-like writer to capture sendResp output; apply TimeoutSec with vm.Interrupt (the AGI runtime already supports timeouts through the VM registry; add an option to ExecuteAGIScript if needed).
Sends POST jobs/lease {ID} to the leader every 10 s while running; POST jobs/done {ID, OK, Output, Error, Log} at the end.
At most runtime.NumCPU() jobs run concurrently per node; more are queued locally (report Status: scheduled until started).

Task 7.4 – Scheduler (leader)

jobs/scheduler.go. Every 3 s on the leader:

Candidates = NodeViews() with State ONLINE or DEGRADED (not MAINTENANCE/DRAINING), Capabilities.Satisfies(spec.Requirements).
Score each candidate (Phase 9 refines): locality = bytes of spec.Inputs that have a verified location on that node ÷ total input bytes (0 when no inputs); load = 1 − CPUUsage/100; mem = free RAM fraction; running = jobs currently assigned there. score = 0.6*locality + 0.25*load + 0.15*mem − 0.1*running; DEGRADED nodes ×0.5.
Assign the best node: state scheduled, Node, LeaseExpires = now+30s, Attempts++; Submit; send jobs/run. On send failure → back to queued immediately.
Jobs whose lease expired while running/scheduled → queued again (Attempts kept); if Attempts >= MaxAttempts → failed with "node lost". Emit job.completed / job.failed events.
Cancel: POST /system/cluster/jobs/cancel?id= marks the state cancelled; the running node polls _job_cancelled() from the state table and interrupts the VM.

Task 7.5 – APIs and UI

Admin/user router (AdminOnly: false, module "Tasks Scheduler"): /system/cluster/jobs/submit (POST JSON spec; Owner forced to the session user; Script read from scriptVpath on the submitting node), list (own jobs; admins see all), status?id=, cancel?id=, output?id=.
AGI (cluster lib): cluster.jobs.submit({name, script:"cluster:/x.agi", args, inputs, requirements}) -> id, cluster.jobs.status(id), cluster.jobs.cancel(id), cluster.jobs.wait(id, timeoutSec) (polls every second inside Go, not JS).
UI: src/web/SystemAO/cluster/jobs.html (register as setting "Cluster Jobs", group "Cluster", RequireAdmin false): table of jobs with status badge, node, progress bar, duration; a detail panel with log and output; submit form (script path picker, args JSON, requirements checkboxes built from the union of node features). Tests: 2 managers, submit a job whose script returns {sum: args.a+args.b} → succeeded with that output; requirement features:["nonexistent"] → stays queued and the status explains "no eligible node"; kill the executing node's server mid-job (script sleeps via _job_sleep(ms) helper you add for tests) → rescheduled on the other node.

Phase 8 – Map/Reduce

Build on Phase 7. Package jobs/mapreduce.go.

Task 8.1 – Model

type MapReduceSpec struct {
    Spec                  // Kind: "mapreduce"; Script holds BOTH mapper and reducer functions
    Dataset      string   `json:"dataset"`      // glob on cluster:/ e.g. "cluster:/photos/**/*.jpg"
    PartitionMax int      `json:"partitionMax"` // files per map task, default 50
    ReduceOn     string   `json:"reduceOn"`     // "" = leader picks
}

Script contract:

function mapper(files, emit) {            // files = ["cluster:/photos/a.jpg", ...] all on THIS node when possible
    files.forEach(function(f){ emit(keyFor(f), 1); });
}
function reducer(key, values) { return values.length; }   // called once per key with all values

Task 8.2 – Expansion and partitioning (leader)

Expand Dataset with a glob over metadata paths (support *, **, ?; implement metadata.Glob(pattern) []FileRecord, tests included).
Group files by the node holding a verified copy (first choice: the node that holds most of the file's bytes; files with no online copy → fail the job with the list). Split each group into partitions of PartitionMax.
Create one child Spec{Kind:"map", ParentID, Inputs: partition, Script: parent script, Requirements: parent requirements} per partition; the scheduler's locality scoring then places them on the data.
Map prelude/epilogue: var EMITTED=[]; function emit(k,v){EMITTED.push([k,v])} … mapper(JOB.inputs, emit); _job_output(JSON.stringify(EMITTED)).
When all map children succeeded: gather outputs (they are in the replicated state table; cap each at 8 MiB, else write to cluster:/.jobs/<id>/part-N.json and pass paths), group by key, create one reduce child whose Args = {groups: {key: [values]}} (or the part paths), epilogue evaluates reducer per key and outputs {key: result}.
Parent Output = reducer output; parent Progress = done children ÷ total. Any child failing after retries fails the parent with the child's error. Tests: 3 nodes, 9 files spread over two nodes, mapper emits (extension, 1), reducer sums → parent output {"jpg": 6, "png": 3}; assert every map job ran on a node holding its inputs (inspect State.Node vs locations).

Phase 9 – Intelligent scheduling and placement

Task 9.1 – Network cost matrix

membership: extend ProbeNode results into a rolling average per peer (latency map[string]float64, EWMA α=0.3) refreshed by the heartbeat loop (measure heartbeat round trips; no extra traffic). Expose Manager.Latency(nodeID) (ms float64, known bool). Gossip is unnecessary: each node only needs its own view.

Task 9.2 – Scoring v2

Replace the Phase 7 formula with a pluggable Scorer interface and the default:

score = w_loc*locality + w_cpu*(1-cpu) + w_mem*memFree + w_disk*diskFree
      - w_q*queueDepth - w_lat*(latencyToInputsMs/1000) - w_deg*(degraded?1:0)

Weights default {0.45, 0.2, 0.1, 0.05, 0.1, 0.05, 0.05} and are editable in System Settings (table sched_weights, replicated as a metadata entry Kind: "schedweights"). Add capability preference: a job may list Preferred []string features (e.g. cuda) that add +0.1 when present without being required.

Task 9.3 – Placement v2 for writes and replicas

Use the same scorer for pickVolume (Phase 4.5) and the replication planner (5.1): prefer the writer's node, then nodes with low latency to the writer, then free space; keep at least Free > size*1.1 + 64 MiB. Spread replicas across nodes with the largest pairwise latency (site diversity) when three or more nodes exist.

Task 9.4 – Health-aware behaviour

DEGRADED nodes receive no new jobs or replicas unless no other node qualifies.
Nodes in MAINTENANCE/DRAINING never receive work; DRAINING nodes have their running jobs finished and their replicas re-created elsewhere (reuse 5.4 evacuation logic for all their volumes), then the admin can safely turn the node off.
A node whose disk free falls under 5 % is treated as ReadOnly for placement and an event node.diskfull is emitted.

Task 9.5 – Observability

Cluster page "Scheduling" card: weights editor, per-node score preview for a sample requirement, current queue depths, latency matrix. Expose /system/cluster/sched/explain?job=<id> returning the scored candidate list so users can see why a node was chosen.

Order of work and estimates

Step	Tasks	Notes
1	3.1, 3.2, 3.3	pure storage code, fully unit-testable
2	3.4, 3.5, 3.6	first multi-node behaviour; verify live
3	4.1, 4.2, 4.3	transfer protocol; test with 10 MiB+ files
4	4.4, 4.5, 4.6	the drive appears; biggest user-visible milestone
5	4.7, 5.1, 5.2, 5.3	durability
6	5.4, 5.5, 6.1, 6.2	admin comfort + developer API
7	7.1–7.5	compute
8	8.1, 8.2	map/reduce
9	9.1–9.5	tuning

Each numbered task is one pull request sized unit. Finish a task completely (code, tests, README row, UI when applicable, live check) before starting the next. When something in this file turns out to be impossible as written, change the smallest thing necessary, document the deviation at the top of the relevant section in this file, and keep going.

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