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fix(min): relay exec stdout to detect broken pipe and kill ssh - #1881
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norrietaylor merged 3 commits intoOct 5, 2026
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When `min session exec` runs a command whose local stdout closes early (e.g. `min session exec <s> -- sh -c 'yes' </dev/null | head -1`), the old exec path replaced this process with ssh, so nothing watched local stdout. When the reader closed, ssh's write failed with BrokenPipe but ssh didn't exit — it sent eow@openssh.com, which the daemon's russh-based SSH server doesn't handle, leaving the remote process running indefinitely. Fix: on the exec path, spawn ssh with stdout piped, relay stdout to this process, and on BrokenPipe kill the ssh child and exit 141 (128+SIGPIPE). Otherwise propagate ssh's exit code via exit_code_of. The interactive attach path (no wire) is unchanged. Routing-Key: inbox-route/I_kwDOSUhdos8AAAABUwHJ5A Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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📝 WalkthroughWalkthroughThe exec path now spawns SSH with piped stdout and relays its output locally. It waits for SSH on clean EOF, kills SSH and exits with status 141 on ChangesSSH Exec Output
Priority: ➖ Normal Estimated code review effort: 2 (Simple) | ~10 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant ExecPath
participant SSH
participant Relay as relay_exec_stdout
participant LocalStdout
ExecPath->>SSH: Spawn with piped stdout
SSH->>Relay: Provide stdout data
Relay->>LocalStdout: Copy and flush chunks
alt Clean EOF
Relay-->>ExecPath: Return success
ExecPath->>SSH: Wait for child status
SSH-->>ExecPath: Return exit status
else Local stdout is closed
Relay-->>ExecPath: Return BrokenPipe
ExecPath->>SSH: Kill child
ExecPath-->>ExecPath: Exit with status 141
end
Suggested reviewers: Merge Risk: 🔵 Low · up to The change fixes the common case where a closed pipe leaves 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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Inline comments:
Review comments at @crates/minimal/src/cmd/session.rs:
- Line 1496: Update relay_exec_stdout so it detects local stdout closure
independently while waiting for SSH output. When the reader closes, kill and
reap the child instead of hanging; preserve the existing SSH-output relay
behavior.
- Line 1507: In the SSH stdout relay error branch, kill and wait for the spawned
SSH child before returning any error other than BrokenPipe. Preserve the
existing relay error context and BrokenPipe handling.
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min is now ssh's parent on the exec path, so a SIGTERM, SIGHUP or SIGINT sent only to min's PID would orphan ssh with its stdout closed and the remote command running on. Catch those signals, kill ssh, and exit 128+signo. Log a failed kill instead of discarding it.
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CodeRabbit and minimal-review approved this head; 0 unresolved threads; all lanes green.
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…mon (3/7, spec 25) (#1995) * test: harden three flaky probes ahead of the telemetry series Three small test-only changes that the telemetry series relies on, kept separate so they can land on their own: - the walked-publication probe waits for the publication to settle - bep_stub tolerates EPIPE when the client hangs up first - the fresh-streak test waits for the streak counter to advance No product code changes. * feat(mlog): opt-in OpenTelemetry export, switches and a local spool The telemetry core for every minimal process (spec 25 TEL-001 to TEL-020, principles 1, 2, 7 and 8). Off unless MINIMAL_TELEMETRY=1; when off nothing starts: no thread, no exporter, no file. When on: - spans and logs leave over OTLP/HTTP (opentelemetry 0.33) to the endpoint the MINIMAL_OTEL_EXPORTER_OTLP_* variables name, base or per signal, and the plain OTEL_* ones only when no MINIMAL_ endpoint is set; per-signal endpoints and `*_EXPORTER=none` are honoured; - DO_NOT_TRACK (any non-empty value) and OTEL_SDK_DISABLED=true always win; - the exporter's own HTTP stack and the SDK never produce telemetry, errors never reach a console, and the exit flush is bounded (200 ms in the CLI); - every finished span and log record is appended synchronously to an OTLP/JSON spool under <state>/telemetry/spool (0700/0600, 4 MiB segments, pruned to 50 MiB / 7 days, torn lines contained), so a crash or SIGKILL keeps what was already written; - the endpoint and the switches have one recognizer each (url::Url, a byte-exact flag grammar), ambient OTEL_EXPORTER_OTLP_HEADERS are refused when the endpoint came from a MINIMAL_ variable, and secrets never appear in the init summary or the logs. The switch decision and the spool prune plan are pure functions with Kani harnesses beside their unit tests. * feat(min, minimald): one trace per request across the CLI and the daemon Wire mlog's telemetry into the CLI and the daemon (spec 25 TEL-021 to TEL-029). - The CLI mints or adopts a TRACEPARENT, exports its `cmd` span, and ends and flushes it before any hand-off; the daemon adopts the context from the channel environment and records `rpc` and `exec` spans under it. - `min session exec` / `run` relays ssh rather than exec()ing it (#1881), so every way out of a command is an exit or signal hand-off and the `cmd` span covers the command; `run` finishes the hand-off once the span has ended and been flushed. - Work the daemon does for a request stays in that request's trace: actor mailboxes carry the sender's span, the blocking pool, spawned tasks (`traced::spawn`, with a guard test against bare spawns), package fetches, orchestrator and check tasks, checkouts (remotes scrubbed), git upload and receive, and the periodic cache clean in its own root. - Boxes receive only the exec span's TRACEPARENT (never headers, baggage or OTEL_* variables), and only when that span is recorded; a nested `min` inside a box, a task run and the in-box helper socket forward it, so daemon-side work for them joins the outer trace. - `min net forward` carries the context on the direct-tcpip open; attach adopts it; SIGHUP and exit paths flush within the shutdown bound.
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Oct 14, 2026
…nto the guest (4/7, spec 25) (#1996) * test: harden three flaky probes ahead of the telemetry series Three small test-only changes that the telemetry series relies on, kept separate so they can land on their own: - the walked-publication probe waits for the publication to settle - bep_stub tolerates EPIPE when the client hangs up first - the fresh-streak test waits for the streak counter to advance No product code changes. * feat(mlog): opt-in OpenTelemetry export, switches and a local spool The telemetry core for every minimal process (spec 25 TEL-001 to TEL-020, principles 1, 2, 7 and 8). Off unless MINIMAL_TELEMETRY=1; when off nothing starts: no thread, no exporter, no file. When on: - spans and logs leave over OTLP/HTTP (opentelemetry 0.33) to the endpoint the MINIMAL_OTEL_EXPORTER_OTLP_* variables name, base or per signal, and the plain OTEL_* ones only when no MINIMAL_ endpoint is set; per-signal endpoints and `*_EXPORTER=none` are honoured; - DO_NOT_TRACK (any non-empty value) and OTEL_SDK_DISABLED=true always win; - the exporter's own HTTP stack and the SDK never produce telemetry, errors never reach a console, and the exit flush is bounded (200 ms in the CLI); - every finished span and log record is appended synchronously to an OTLP/JSON spool under <state>/telemetry/spool (0700/0600, 4 MiB segments, pruned to 50 MiB / 7 days, torn lines contained), so a crash or SIGKILL keeps what was already written; - the endpoint and the switches have one recognizer each (url::Url, a byte-exact flag grammar), ambient OTEL_EXPORTER_OTLP_HEADERS are refused when the endpoint came from a MINIMAL_ variable, and secrets never appear in the init summary or the logs. The switch decision and the spool prune plan are pure functions with Kani harnesses beside their unit tests. * feat(min, minimald): one trace per request across the CLI and the daemon Wire mlog's telemetry into the CLI and the daemon (spec 25 TEL-021 to TEL-029). - The CLI mints or adopts a TRACEPARENT, exports its `cmd` span, and ends and flushes it before any hand-off; the daemon adopts the context from the channel environment and records `rpc` and `exec` spans under it. - `min session exec` / `run` relays ssh rather than exec()ing it (#1881), so every way out of a command is an exit or signal hand-off and the `cmd` span covers the command; `run` finishes the hand-off once the span has ended and been flushed. - Work the daemon does for a request stays in that request's trace: actor mailboxes carry the sender's span, the blocking pool, spawned tasks (`traced::spawn`, with a guard test against bare spawns), package fetches, orchestrator and check tasks, checkouts (remotes scrubbed), git upload and receive, and the periodic cache clean in its own root. - Boxes receive only the exec span's TRACEPARENT (never headers, baggage or OTEL_* variables), and only when that span is recorded; a nested `min` inside a box, a task run and the in-box helper socket forward it, so daemon-side work for them joins the outer trace. - `min net forward` carries the context on the direct-tcpip open; attach adopts it; SIGHUP and exit paths flush within the shutdown bound. * feat(minvmd): export the VM host daemon's spans and carry telemetry into the guest minvmd exports a bounded root per command with `net.switch.start`, `vm.boot`, `vm.stop` and `guest.shutdown` as children, in the CLI's trace (spec 25 TEL-032 to TEL-036). The host decides the telemetry switches and writes them onto the guest's boot line with one byte-exact writer under a fixed budget: the opt-in, the spool and filter settings, the exporter switches and TRACEPARENT, never an endpoint, headers, resource attributes or baggage (TEL-033), because everything in the guest can read the boot line as /proc/cmdline. With no endpoint the guest exports nothing here: both signals are `none` and its records stay in its own spool until the VM channel carries them to the host. The whole set is forwarded or dropped, so a guest never boots with a partial configuration, and the logged boot line names the telemetry tokens by key only. The guest daemon builds its OTLP client without platform CA roots (an http:// collector needs none) and flushes before it powers off. RUST_LOG filters the console per layer, so it never gates export. A failed `minvmd boot` marks `vm.boot` with an error status, as `run` does. The boot line's alphabet, budget and all-or-none rules are proven with Kani.
bryan-minimal
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Oct 14, 2026
…ry settings (5/7, spec 25) (#1997) * test: harden three flaky probes ahead of the telemetry series Three small test-only changes that the telemetry series relies on, kept separate so they can land on their own: - the walked-publication probe waits for the publication to settle - bep_stub tolerates EPIPE when the client hangs up first - the fresh-streak test waits for the streak counter to advance No product code changes. * feat(mlog): opt-in OpenTelemetry export, switches and a local spool The telemetry core for every minimal process (spec 25 TEL-001 to TEL-020, principles 1, 2, 7 and 8). Off unless MINIMAL_TELEMETRY=1; when off nothing starts: no thread, no exporter, no file. When on: - spans and logs leave over OTLP/HTTP (opentelemetry 0.33) to the endpoint the MINIMAL_OTEL_EXPORTER_OTLP_* variables name, base or per signal, and the plain OTEL_* ones only when no MINIMAL_ endpoint is set; per-signal endpoints and `*_EXPORTER=none` are honoured; - DO_NOT_TRACK (any non-empty value) and OTEL_SDK_DISABLED=true always win; - the exporter's own HTTP stack and the SDK never produce telemetry, errors never reach a console, and the exit flush is bounded (200 ms in the CLI); - every finished span and log record is appended synchronously to an OTLP/JSON spool under <state>/telemetry/spool (0700/0600, 4 MiB segments, pruned to 50 MiB / 7 days, torn lines contained), so a crash or SIGKILL keeps what was already written; - the endpoint and the switches have one recognizer each (url::Url, a byte-exact flag grammar), ambient OTEL_EXPORTER_OTLP_HEADERS are refused when the endpoint came from a MINIMAL_ variable, and secrets never appear in the init summary or the logs. The switch decision and the spool prune plan are pure functions with Kani harnesses beside their unit tests. * feat(min, minimald): one trace per request across the CLI and the daemon Wire mlog's telemetry into the CLI and the daemon (spec 25 TEL-021 to TEL-029). - The CLI mints or adopts a TRACEPARENT, exports its `cmd` span, and ends and flushes it before any hand-off; the daemon adopts the context from the channel environment and records `rpc` and `exec` spans under it. - `min session exec` / `run` relays ssh rather than exec()ing it (#1881), so every way out of a command is an exit or signal hand-off and the `cmd` span covers the command; `run` finishes the hand-off once the span has ended and been flushed. - Work the daemon does for a request stays in that request's trace: actor mailboxes carry the sender's span, the blocking pool, spawned tasks (`traced::spawn`, with a guard test against bare spawns), package fetches, orchestrator and check tasks, checkouts (remotes scrubbed), git upload and receive, and the periodic cache clean in its own root. - Boxes receive only the exec span's TRACEPARENT (never headers, baggage or OTEL_* variables), and only when that span is recorded; a nested `min` inside a box, a task run and the in-box helper socket forward it, so daemon-side work for them joins the outer trace. - `min net forward` carries the context on the direct-tcpip open; attach adopts it; SIGHUP and exit paths flush within the shutdown bound. * feat(minvmd): export the VM host daemon's spans and carry telemetry into the guest minvmd exports a bounded root per command with `net.switch.start`, `vm.boot`, `vm.stop` and `guest.shutdown` as children, in the CLI's trace (spec 25 TEL-032 to TEL-036). The host decides the telemetry switches and writes them onto the guest's boot line with one byte-exact writer under a fixed budget: the opt-in, the spool and filter settings, the exporter switches and TRACEPARENT, never an endpoint, headers, resource attributes or baggage (TEL-033), because everything in the guest can read the boot line as /proc/cmdline. With no endpoint the guest exports nothing here: both signals are `none` and its records stay in its own spool until the VM channel carries them to the host. The whole set is forwarded or dropped, so a guest never boots with a partial configuration, and the logged boot line names the telemetry tokens by key only. The guest daemon builds its OTLP client without platform CA roots (an http:// collector needs none) and flushes before it powers off. RUST_LOG filters the console per layer, so it never gates export. A failed `minvmd boot` marks `vm.boot` with an error status, as `run` does. The boot line's alphabet, budget and all-or-none rules are proven with Kani. * feat(diag): `min bug` carries the telemetry spool and redacts telemetry settings Spec 25 TEL-044: the daemon's bundle carries the newest spool files under telemetry/spool/, tail-capped and line-scrubbed like a log; the host bundle does the same for the CLI's and minvmd's spool, which on a VM host exists nowhere else. MINIMAL_OTEL_* endpoint and header values are reported by name only, in both bundles.
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Summary
Fixes
min session exechanging when its local stdout closes early (e.g.min session exec <s> -- sh -c 'yes' </dev/null | head -1).Root cause
The exec path (
wireisSome) calledssh.exec(), replacing this process with ssh. Nothing watched local stdout, so when the reader closed, ssh's write failed withBrokenPipe. ssh doesn't exit on that — it sendseow@openssh.com, which the daemon's russh-based SSH server doesn't handle — so the remote process kept running and the channel never closed.Fix
On the exec path, spawn ssh with stdout piped, relay stdout to this process, and on
BrokenPipekill the ssh child and exit 141 (128+SIGPIPE). Otherwise propagate ssh's exit code viaexit_code_of. The interactive attach path (nowire) is unchanged.Testing
cargo fmt --all --check— cleancargo clippy --workspace --locked— clean (only pre-existingminimaldwarnings)cargo build --workspace --locked— cleancargo test -p minimal --lib— new testexec_stdout_relay_copies_and_detects_broken_pipepasses; one pre-existing unrelated failure (legacy_network_spellings_parse_with_hint)Routing-Key: inbox-route/I_kwDOSUhdos8AAAABUwHJ5A
Summary by CodeRabbit