The Last Piece of the Persistence Puzzle: Extending Instance Cleanup Retention in vast-manager

"Now extend the cleanup retention: [edit] /tmp/czk/cmd/vast-manager/main.go"

This deceptively short message, message 1398 in the opencode session, represents the final step in a critical data persistence overhaul for the vast-manager system. On its surface, it is a single edit command — a one-line change to a SQL query that extends the cleanup window for killed instances from 24 hours to 7 days. But to understand why this message exists, what motivated it, and what it accomplishes, we must trace the chain of reasoning that led here. This message is not an isolated edit; it is the capstone of a multi-step architectural intervention that transformed the vast-manager from a system that lost all historical data on instance death into one that preserves metadata, logs, and performance history for a full week after an instance is destroyed.

The Problem: Data Amnesia on Instance Death

The story begins with a user complaint at message 1377: "Logs and all instance metadata disappears when an instance is killed, should be kept around." This was a direct observation of a systemic weakness in the vast-manager's architecture. The vast-manager is a management service for GPU proving instances rented from Vast.ai — a marketplace for cloud GPU compute. When an instance is deployed, the manager tracks its lifecycle: registration, parameter download, benchmarking, and active proving. But when an instance is killed (either because the user terminated it, the benchmark failed, or the instance was destroyed on the Vast side), the manager had a critical blind spot.

The root cause, as the assistant diagnosed in message 1378, was straightforward: "killed instances have vast_id=0 because they're no longer in the vast cache (destroyed), so all the vast-sourced metadata (GPU, location, SSH, etc.) is lost." The vast-manager relied on the Vast.ai API cache to populate instance metadata — GPU name, location, SSH command, cost, and other details. When an instance was destroyed on the Vast side, it vanished from the cache, and the manager's dashboard would show a hollowed-out entry with none of the identifying information that made it useful for post-mortem analysis.

The Four-Step Plan

The assistant devised a comprehensive four-step plan to fix this, documented in message 1383:

  1. Add vast metadata columns to the instances table — new columns for vast_id, host_id, machine_id, gpu_name, num_gpus, dph_total, geolocation, cpu_name, cpu_ram_mb, gpu_ram_mb, ssh_cmd, public_ip, and status_msg.
  2. Persist vast metadata in the monitor cycle — when the monitor matches a DB instance to a Vast instance, write the metadata into the database.
  3. Use DB metadata as fallback in the dashboard handler — when the Vast cache no longer has an instance, fall back to the persisted database columns.
  4. Extend killed instance cleanup from 24 hours to 7 days — so that logs and metadata remain visible for a week after destruction. Messages 1385 through 1396 implemented steps 1 through 3. The assistant added a schema migration in NewServer using ALTER TABLE statements (since SQLite's CREATE TABLE IF NOT EXISTS would not modify an existing table), created a persistVastMeta method called from the monitor cycle, and updated the dashboard handler to read the new columns and use them as fallback when the Vast cache misses.

The Subject Message: Step 4

Message 1398 is the implementation of step 4. The assistant writes:

Now extend the cleanup retention: [edit] /tmp/czk/cmd/vast-manager/main.go Edit applied successfully.

>

LSP errors detected in this file, please fix: <diagnostics file="/tmp/czk/cmd/vast-manager/main.go"> ERROR [31:12] pattern ui.html: no matching files found </diagnostics>

The edit itself is not visible in the message text — the tool call output only shows "Edit applied successfully." But from the context of the todo list in message 1397 (which shows step 4 as the only remaining item), and from the assistant's earlier reasoning in message 1383 ("Keep killed instance cleanup at 7 days instead of 24 hours so logs and metadata remain visible"), we can infer the change: the cleanup query in the monitor cycle was modified from a 24-hour retention window to a 7-day window. This is almost certainly a change to the SQL query that deletes old killed instances, likely altering something like WHERE killed_at &lt; datetime(&#39;now&#39;, &#39;-1 day&#39;) to WHERE killed_at &lt; datetime(&#39;now&#39;, &#39;-7 days&#39;).

The LSP Error: A False Positive

The message also includes an LSP diagnostic: ERROR [31:12] pattern ui.html: no matching files found. This is a false positive from the Go language server. The vast-manager binary embeds the ui.html file using Go's //go:embed directive, and the LSP is checking whether the pattern ui.html matches any files at compile time. Since the edit was made to main.go and not to the UI file, this error is unrelated to the change. It's a pre-existing issue with the build environment — the LSP may be running from a directory where the pattern doesn't resolve, or the file reference is handled differently during the actual build. The assistant correctly ignores this diagnostic, as evidenced by the successful build and deployment in subsequent messages.

Assumptions and Reasoning

Several assumptions underpin this message. First, the assistant assumes that a 7-day retention window is sufficient for operational analysis without causing excessive database bloat. The instances table, even with the new metadata columns, is not expected to grow rapidly — the vast-manager manages a small number of GPU instances (tens, not thousands), so even a week's worth of killed instance records is manageable.

Second, the assistant assumes that the cleanup logic is the correct place to extend retention. The monitor cycle already has a step that deletes old killed instances, and modifying that query is the most straightforward approach. An alternative would have been to add a configurable retention period, but the assistant chose a simple constant change.

Third, the assistant assumes that extending retention is meaningful only after the metadata persistence changes (steps 1-3) are in place. Without persisted metadata, keeping killed instances around for 7 days would still show empty records. The order of implementation matters: metadata must be captured before an instance is killed, and then retention must be long enough for users to see it.

Input and Output Knowledge

To understand this message, one needs input knowledge of: the vast-manager's architecture (monitor cycle, dashboard handler, SQLite database), the Vast.ai API (instance lifecycle, cache behavior), SQLite schema migration limitations, and the Go embedding system. The output knowledge created by this message is a system that retains killed instance records for 7 days, preserving all the newly persisted metadata (GPU, location, cost, SSH command, etc.) and making it visible in the dashboard for post-mortem analysis.

The Broader Significance

This message, though brief, completes a transformation. Before this change, the vast-manager had a fundamental data integrity problem: the most interesting instances to study — those that failed or were killed — were precisely the ones whose data disappeared. After this change, every instance leaves a permanent record. The dashboard can show what GPU a killed instance had, where it was located, how much it cost, and what its benchmark results were. This turns the vast-manager from a purely operational tool into a historical analysis platform, enabling users to make informed decisions about which hosts to deploy on and which to avoid.

The edit itself may be a single line, but it represents the culmination of a careful diagnostic process: identify the data loss, trace it to the cache dependency, design a persistence layer, implement the schema and plumbing, and finally extend the retention window to make the data useful. Message 1398 is the last brick in that wall.