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Full-DB memory block: explain why node count does not help

Motivation

A user with a 10-node cluster hit the full-database (non-sharded) memory block on core_nt and read it as a contradiction: the message said the cluster node (Standard_E16s_v5) "provides only 126 GB usable" while they had ten such nodes active. The block itself is correct — a full-database BLAST loads the entire database into each node, so node count gives query parallelism, not memory relief, and ElasticBLAST's own submit pre-flight rejects the same run — but the wording never said so, making a correct safety gate look like a bug.

User-facing change

The full-DB memory block message (shown in the "Required before submitting" checklist and the submit summary rail) now states that a full-database BLAST loads the whole database into a single node, that adding more nodes does not help, and that the Sharded throughput profile spreads the database across the available nodes. No logic changed — the same runs are blocked/allowed as before.

Before:

'core_nt' needs 249.7 GB for a full-database BLAST but the cluster node (Standard_E16s_v5) provides only 126 GB usable (128 GB RAM minus 2 GB system reserve). Switch to the Sharded throughput execution profile, or use a cluster with a larger machine type.

After:

'core_nt' needs 249.7 GB for a full-database BLAST, which loads the entire database into a single node — adding more nodes does not help. The cluster node (Standard_E16s_v5) provides only 126 GB usable (128 GB RAM minus 2 GB system reserve). Switch to the Sharded throughput execution profile to spread the database across your nodes, or use a cluster with a larger machine type.

API / IaC diff summary

  • web/src/pages/blastSubmit/memoryFit.ts — deriveFullDbMemoryFit blocked-reason wording (frontend client mirror of the gate).
  • api/services/blast/submit_gates.py — _gate_node_memory_fit blocking message kept in lockstep with the frontend. The action / action_type fields and all gate verdicts are unchanged.

Validation evidence

  • uv run ruff check api/services/blast/submit_gates.py — clean.
  • uv run pytest -q api/tests/test_blast_submit_gates.py — 35 passed (asserts on error_code, action_type, and the preserved "system reserve" substring).
  • npx vitest run src/pages/blastSubmit/memoryFit.test.ts src/pages/blastSubmit/submitValidation.test.ts — 17 passed.
  • npm run build — succeeds.