The Diagnostic Pivot: When SSH Fails, the API Speaks

A Status Check That Reveals the Architecture of Distributed Proving Infrastructure

In the middle of a sprawling session to deploy and manage GPU instances for Filecoin proving on Vast.ai, a single assistant message at index 1191 performs what appears to be a trivial act: a status check. The assistant writes:

Belgium still not SSH-able. Let me check if it registered via the manager:

This is followed by a curl command to a local API endpoint on the controller host (10.1.2.104), querying the vast-manager dashboard, and the output reveals two active instances in different lifecycle states.

On its surface, this is a two-line diagnostic check. But beneath that simplicity lies a wealth of architectural reasoning, operational decision-making, and strategic context that makes this message a fascinating microcosm of the entire session's challenges. This article unpacks what this message reveals about the proving infrastructure, the assistant's troubleshooting methodology, and the assumptions that underpin the entire deployment.

The Context: A Session of Hard-Won Lessons

To understand message 1191, one must understand the cascade of failures that preceded it. The session had been grappling with a fundamental problem: GPU instances on Vast.ai were crashing, timing out, or underperforming in unpredictable ways. A Czechia instance with 2x RTX 3090 and 251GB RAM had suffered a gRPC "broken pipe" transport error during its first batch proof ([msg 1164]). A Belgium instance with 2x A40 and 2TB RAM had been killed by a 20-minute benchmark timeout ([msg 1170]). The assistant had responded with a series of tactical fixes: increasing the benchmark timeout to 45 minutes ([msg 1160]), adding a "post-restart warmup" proof to benchmark.sh to pre-warm GPU kernels before the timed batch ([msg 1177]), and refining partition worker logic for ~256GB machines ([msg 1177]).

By message 1191, two new instances had been deployed with the hardened Docker image: Belgium instance 32715193 (2x A40, 2TB RAM) and Czechia instance 32715618 (2x RTX 3090, 251GB RAM). The assistant had just verified that Czechia's direct SSH access worked ([msg 1187]) and confirmed the post-restart warmup fix was present in its benchmark script ([msg 1189]). But Belgium remained stubbornly inaccessible via SSH.

The Diagnostic Pivot: From Direct Access to Indirect Monitoring

The opening line — "Belgium still not SSH-able" — is a statement of failed expectation. The assistant had attempted direct SSH to Belgium's direct port 20381 at IP 154.42.3.18 ([msg 1186]) and received "Connection refused." It had also tried SSH through the Vast.ai proxy at ssh4.vast.ai:35192 ([msg 1183]) and received "Permission denied (publickey)." Both avenues were blocked.

This is where the assistant's reasoning becomes visible. Rather than continuing to hammer on a failed connection, the assistant pivots to an alternative monitoring channel: the vast-manager API. This is not an obvious move. It requires the assistant to know that:

  1. The vast-manager service is running on the controller host (10.1.2.104) and exposes a /api/dashboard endpoint.
  2. This endpoint returns the state of all registered instances, including those that are not directly accessible.
  3. The manager's state machine tracks instances through lifecycle stages like registered, params_done, benchmarking, and killed. The assistant's reasoning can be reconstructed as: "I cannot SSH into Belgium, but the manager is the central orchestrator. If Belgium has registered with the manager, the manager will know its state. Let me query the manager instead of the instance." This is a textbook example of layered monitoring — when direct observation fails, fall back to indirect observation through a management plane. The assistant is demonstrating operational maturity: don't trust a single channel; build redundancy into your observability.

What the API Response Reveals

The output of the curl command shows two instances that are not in the killed state:

State: registered, Label: C.32715618, GPUs: RTX 3090 x2, BenchRate: ?
State: params_done, Label: C.32715193, GPUs: A40 x2, BenchRate: ?

These two states tell a rich story. Czechia (32715618) is in registered state, meaning it has connected to the manager and identified itself, but has not yet completed its parameter download. This is consistent with the assistant's earlier observation that Czechia was still verifying parameters ([msg 1188]). Belgium (32715193), on the other hand, is in params_done state, meaning it has finished downloading the Filecoin proof parameters (the SRS files, ~134GB+) and is presumably about to start its benchmark.

The BenchRate: ? values indicate that neither instance has completed a benchmark yet — the benchmark rate is unknown because the benchmark hasn't run to completion. This is significant because the entire purpose of these instances is to measure their proving throughput (proofs per hour) and determine whether they meet the 50 proofs/hour minimum.

The Architecture Implicit in the Query

This single curl command reveals the architectural layers the assistant has built:

  1. The Instance Layer: GPU machines on Vast.ai, each running a Docker container with the cuzk proving engine, a daemon (cuzk-server), and a benchmark script.
  2. The Registration Layer: Each instance, upon boot, registers with the vast-manager service, providing its UUID, GPU count, RAM, and other metadata. This registration is the first sign of life after the container starts.
  3. The Management Layer: The vast-manager service running on the controller host (10.1.2.104) tracks all instances, their states, benchmark results, and lifecycle events. It exposes a dashboard API and handles instance destruction for underperformers.
  4. The SSH Layer: Direct SSH access to instances for debugging, which may or may not work depending on Vast.ai's network configuration and key setup. The assistant's pivot from SSH to API is a shift from layer 4 to layer 3 — from ad-hoc debugging to structured management. This is the right move when the debugging channel is unreliable.

Assumptions Embedded in the Message

Every diagnostic query carries assumptions, and this one is no exception. The assistant assumes that:

  1. The vast-manager is healthy and reachable: The controller host at 10.1.2.104 must be up, the vast-manager process must be running, and the API endpoint must be responsive. If the manager itself were down, this query would fail silently.
  2. The instance states are accurate: The manager's state machine assumes that instances transition through states in a predictable order (registered → params_done → benchmarking → done/killed). If an instance's state is stale or incorrect (e.g., the instance crashed but the manager hasn't detected it), the query would return misleading information.
  3. SSH inaccessibility does not imply instance death: The assistant implicitly assumes that "not SSH-able" is a network issue, not a fatal crash. This is a reasonable assumption given that Belgium had just been created and Vast.ai instances often have SSH configuration issues, but it's not guaranteed. The instance could have OOM-killed during parameter download.
  4. The API response is sufficient for diagnosis: The assistant is satisfied with the state information from the API and does not immediately attempt further debugging. This assumes that the state machine is a reliable proxy for actual instance health.

Mistakes and Incorrect Assumptions

While the message itself is correct and the query succeeds, there are potential pitfalls worth examining:

The "params_done" state may be misleading: Belgium is in params_done state, but this only means the parameter download script completed. It does not mean the daemon started successfully, or that the GPU is functional. The assistant later discovers that Belgium's benchmark eventually completes at only 35.9 proofs/hour ([chunk 8.1]), below the 50 proofs/hour minimum. The params_done state gave no indication of this impending failure.

SSH inaccessibility as a red herring: The assistant spends significant effort trying to SSH into Belgium, but the real problem turns out to be performance, not connectivity. The SSH issue was a distraction — the instance was running fine, it just wasn't reachable via SSH. This is a common operational trap: debugging a symptom (can't SSH) rather than the underlying concern (will this instance perform?).

The missing Belgium benchmark timeout: At this point, the assistant doesn't know that Belgium will fail its benchmark. The params_done state looks promising. But the assistant had increased the benchmark timeout to 45 minutes, and Belgium would need every minute of it — and still fall short.

Input Knowledge Required

To fully understand this message, a reader would need knowledge of:

  1. Vast.ai instance lifecycle: How instances are created, how SSH works (proxy vs direct), and the common failure modes (key configuration, port forwarding).
  2. The cuzk proving stack: The Filecoin proof-of-replication (PoRep) proving pipeline, the role of partition workers, the PCE (Pre-Compiled Constraint Evaluator) cache, and the parameter files (~134GB of SRS parameters).
  3. The vast-manager architecture: The custom management service built in Go, its state machine (registered → params_done → benchmarking → done/killed), its SQLite-backed database, and its REST API.
  4. The benchmark workflow: How entrypoint.sh orchestrates parameter download, daemon startup, warmup proof, daemon restart, and batch benchmark — and how each phase can fail.
  5. The hardware landscape: The difference between RTX 3090 (24GB VRAM, ~250GB system RAM) and A40 (48GB VRAM, ~2TB system RAM) GPUs, and how these specs affect proving throughput.

Output Knowledge Created

This message produces several pieces of actionable knowledge:

  1. Belgium is alive but not SSH-able: The instance is running and has completed parameter download. The SSH issue is a network/configuration problem, not a crash. This rules out the most catastrophic failure modes (OOM kill, daemon crash).
  2. Czechia is still downloading parameters: The instance is in registered state, which is earlier in the lifecycle than params_done. This confirms that Czechia is progressing normally but hasn't reached the benchmark phase yet.
  3. Both instances have unknown benchmark rates: Neither instance has produced a throughput measurement yet. The assistant must wait for the benchmarks to complete before making decisions about their viability.
  4. The management plane is functional: The vast-manager API is responding correctly, returning state information for both active instances. This validates the management infrastructure the assistant has built.

The Thinking Process: A Study in Operational Reasoning

The visible thinking in this message is compressed into a single sentence: "Belgium still not SSH-able. Let me check if it registered via the manager." But this sentence encodes a multi-step reasoning chain:

  1. Observation: Belgium is not SSH-able (multiple attempts failed).
  2. Hypothesis: The instance may still be alive but unreachable via SSH.
  3. Alternative channel: The vast-manager API can provide state information without SSH.
  4. Action: Query the manager API.
  5. Interpretation: The response shows both instances in expected states, confirming they are alive. This is a textbook application of the scientific method in an operational context: observe, hypothesize, test, interpret. The assistant resists the temptation to assume the worst (instance is dead) and instead seeks corroborating evidence from a different source.

Broader Significance: The Data-Driven Pivot

This message sits at a inflection point in the session. Immediately after this status check, the session undergoes a fundamental strategic shift. The persistent failures — Belgium achieving only 35.9 proofs/hour, Czechia crashing with bench_rate 0 — convince the assistant that hardcoded hardware thresholds are unreliable. The session pivots to building a data-driven experimental system with a host_perf database table, an offer search API with performance overlays, and a deploy endpoint ([chunk 8.1]).

Message 1191 is the calm before that storm. It's the last moment of "let's check if our tactical fixes worked" before the assistant concludes that tactical fixes are insufficient and a strategic overhaul is needed. The BenchRate: ? values in the API response are question marks in more than one sense — they represent not just unknown throughput, but the fundamental unpredictability of proving performance across heterogeneous hardware.

Conclusion

Message 1191 is a diagnostic pivot that reveals the layered architecture of a distributed proving infrastructure. When SSH fails, the assistant falls back to the management API, demonstrating operational maturity and a refusal to accept a single point of failure in observability. The message encodes assumptions about instance lifecycle, manager health, and the reliability of state machines. It produces actionable knowledge about two instances' status while leaving the critical question — will they perform? — unanswered.

In the broader arc of the session, this message represents a moment of waiting, of checking, of gathering data before a strategic pivot. The question marks in the API response are harbingers of the data-driven approach to come. Sometimes the most important thing a diagnostic message can do is tell you what you don't yet know.