libcurl Multi Proxy Transfers: Connection Limits and Queues
CONNECT is supported; an occupied host or total connection allowance can leave a transfer waiting before it attempts a socket.
A report that multi proxy transfers block needs its libcurl release and TLS backend. It does not establish that every CONNECT transfer needs an OS thread.
| Wait | What to inspect |
|---|---|
| Allowance for one endpoint | CURLMOPT_MAX_HOST_CONNECTIONS counts the proxy as host, even across destination websites |
| Allowance across the multi handle | Total connection limit can create another queue |
| After a connection attempt | Actual proxy response or release-specific blocking behavior |
Compare event-loop integration, limits and timeout budgets with the installed release's interface. Raising concurrency can move the queue into the proxy without fixing its cause.
Identify client queue, slow response or implementation-specific blocking before changing the application's concurrency architecture.