Repro Slow Import Jsonschema
`mcp.types` pulls in fastmcp, uvicorn, watchfiles, jsonschema, etc. during the module import. 6 +- On a machine capped at 0.5 vCPU the first import takes 8–12 s, blocking our server startup.
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Slow Import Reproduction
This folder contains a minimal Docker Compose project that reproduces the slow
first-import behaviour we observe for mcp.types and the jsonschema
package. Both services share the same Dockerfile and pin the versions that
are problematic in our production image.
Prerequisites
- Docker 24+
- Docker Compose V2
Usage
# Build the shared base image
docker compose build
# Reproduce the jsonschema import delay (default command)
docker compose run --rm jsonschema
# Reproduce the mcp.types import delay
docker compose run --rm mcp
The compose services enforce a low CPU quota (0.5 cores) and a tight memory
limit (1g) to match the constrained hosts where the slowdown is most visible.
Inspecting detailed import timings
Enable CPython's import profiler to gather the per-module breakdown:
PYTHONPROFILEIMPORTTIME=1 docker compose run --rm jsonschema
PYTHONPROFILEIMPORTTIME=1 docker compose run --rm mcp
The scripts print the wall-clock duration of the target import, while the profiler dumps the per-module timings to stdout for inclusion in upstream issues.