Logging

DXOS logging (@dxos/log)

All application logging goes through @dxos/log (“dxlog”). Import: import { log, dbg } from '@dxos/log';

Message shape

• Static message first (lowercase phrase, no template literals in the message string).
• Structured context second (object). Do not stuff dynamic data only into the message; put it in context.

log('received queue batch', { count: items.length, spaceKey });
log.warn('plugin failed to activate', { pluginId, cause: err.message });

Levels

Use log('…', ctx) for DEBUG-level diagnostics. The callable log is log.debug (same level); prefer log(...) in new code and avoid writing log.debug so style stays consistent.

Rule of thumb: log.info and above are what operators and users normally see in the console; log(...) is for deep diagnosis and file buffers.

dbg

• dbg(value) (and related helpers from @dxos/log) are for local debugging only.
• Remove or replace before committing (or gate behind dev-only code paths).

Composer dev: app.log

With @dxos/vite-plugin-log enabled in Composer, browser @dxos/log output is serialized to NDJSON and appended to:

packages/apps/composer-app/app.log

(from the repo root; path is relative to process cwd when the dev server runs, usually repo root → that file).

Truncate/restart behavior is owned by the plugin (file cleared on dev server start).

Tests: LOG_FILTER (stdout)

In Node / vitest runs, @dxos/log reads process.env.LOG_FILTER when building the default config (packages/common/log/src/options.ts). Set it to control which levels and paths are printed to the test process stdout (same filter string shape as query-logs -q: level name, pathFragment:level, comma-separated list, etc.).

LOG_FILTER=debug moon run functions-runtime:test -- AgentService.test.ts

Use trace for maximum noise, info for quieter runs, or a path-scoped value (e.g. AgentService:debug, functions-runtime:debug) to narrow output. This does not write app.log; it only affects the console processor during that command.

Tests: NDJSON file sink (@dxos/vite-plugin-log/vitest)

Node Vitest projects wire @dxos/vite-plugin-log/vitest via vitest.base.config.ts (global-setup truncates once; per-worker setup installs a file processor). Logs flow: @dxos/log → serializeToJsonl → JsonlFileLogStore → <package>/test.log (NDJSON, compatible with scripts/query-logs.mjs).

LOG_FILTER=lifecycle:debug moon run functions-runtime:test -- AgentService.test.ts
node scripts/query-logs.mjs packages/core/compute/functions-runtime/test.log -q lifecycle:debug

Exported for reuse (e.g. edge Miniflare tail → JsonlFileLogStore.pushLines): JsonlFileLogStore, installNodeLogProcessor, resolveTestLogFilePath, truncateTestLogFile from @dxos/vite-plugin-log/vitest.

Querying logs: scripts/query-logs.mjs

From repo root:

node scripts/query-logs.mjs <file> [-q <filter>]... [-g <regexp>]...
pnpm query-logs -- <file> ...

• -q: comma-separated filters in LOG_FILTER style (see packages/common/log parseFilter + shouldLog).
  • Level only: debug, info, warn, error, trace, verbose.
  • Path substring + level: echo-db:debug — file path in the log line must contain echo-db, level must be ≥ debug.
  • Exclude: !substring — drop lines whose file path contains substring (after !). Use !rpc.ts to drop noisy RPC files. Bare !foo is treated as exclude at trace threshold internally.
  • Repeat -q: OR between groups; inside one -q, filters work like runtime shouldLog (includes + excludes).
• -g: RegExp (JavaScript) run on the raw JSON line. Repeat -g for AND.

Output columns: timestamp, level letter, file:line, scope (o), message (m), context (c), error (e).

Workflow

Run narrow queries and pipe to Unix tools:

# How many debug lines mention ProcessManager?
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q debug -g ProcessManager | wc -l

# Echo DB query pipeline only, exclude rpc.ts noise, first 20 lines
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q 'echo-db:debug,!rpc.ts' | head -20

# Automerge-related paths at debug
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q automerge:debug | less

# Invalid RPC response ids (example message grep)
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q debug -g 'invalid id' | head

# OR two path groups: client package OR space proxy, debug and above
node scripts/query-logs.mjs packages/apps/composer-app/app.log -q 'sdk/client/src:debug' -q 'space-proxy:debug' | wc -l

Requires @dxos/log built: moon run log:build (script imports packages/common/log/dist/...).

Path fragments to try (Composer f field)

These substrings match typical packages/... paths in NDJSON. Counts vary per session.

Add more fragments by copying a path prefix from an app.log line (f field) and using it in -q your-fragment:debug.

Related

• Log processors and filters: packages/common/log/src/context.ts, packages/common/log/src/options.ts (parseFilter).
• NDJSON capture shape: packages/common/log/src/log-buffer.ts.
• Composer wiring: tools/vite-plugin-log, packages/apps/composer-app/vite.config.ts (vitePluginLog in sharedPlugins).