keepalive timer also closes a freshly dialed pooled connection during the HTTP/1.1 TLS upgrade

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#938 0 comentários 0 reações 0 responsáveis Ver no GitHub

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Avaliação

Dificuldade
4/5
Tempo estimado
3-5 dias
Facilidade para iniciantes
58/100
Tipo de issue
Bug
Clareza
Claramente especificada
Status de atividade
Ativa
Stack de tecnologia
erlang
Domínio
backend, networking

Direção de pesquisa

Start with the fresh-dial path in hackney_pool.erl:573-587 and 1005-1024, then trace connected and upgrade_to_ssl in hackney_conn.erl:845-869 and 996-1013. Compare the HTTP/1.1 and HTTP/2 upgrade branches, and run the pool-enabled HTTP/1 TLS-upgrade tests with a delayed handshake; done means a fresh connection is not closed by the keepalive timer during that handshake.

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Descrição

hackney 4.7.4 (also current master).

#934 disarms the keepalive timer in the is_ready probe, which covers a reused pooled connection. A fresh dial does not reach is_ready:

  • handle_call({checkout, ...}) takes the none -> start_connection branch (hackney_pool.erl:573-587).
  • The new conn arms idle_timeout = keepalive_timeout on entry to connected (hackney_conn.erl:845-869). keepalive_timeout is capped at 2000 ms by min/2 in hackney_pool.erl:476-482 (an infinity value also collapses to 2000 because of Erlang term order), and start_connection/6 does not take a per-checkout override (hackney_pool.erl:1005-1024).
  • The HTTP/1.1 branch of upgrade_to_ssl returns keep_state and leaves that state_timeout running (hackney_conn.erl:1012-1013). The HTTP/2 branch cancels it via init_h2_after_upgrade (:2995-3007).
  • ssl:connect/3 at :996 blocks the gen_statem. If the TLS handshake takes longer than the remaining timer, the timer fires (:915-917), the conn goes to closed, and the caller's {request, ...} hits the catch-all and gets {error, invalid_state} (:2005-2006 on 4.7.4; {error, closed} on master after #936). No byte of the request has been written at that point.

Reproduced with a TCP proxy in front of api.stripe.com that delays the ClientHello: a 1900 ms delay succeeds, a 2200 ms delay fails with invalid_state, with pool enabled and protocols: [http1]. With prewarm_count: 0 the fresh-dial path is the only path, so the failure rate is simply the fraction of handshakes slower than ~2 s.

Suggested fix: arm the idle timer in connected(enter) only when owner =:= pool_pid (prewarm conns set owner => PoolPid at hackney_pool.erl:1367; fresh-dial conns set owner => Requester at :1024), cancel it in set_owner when the new owner is not the pool, and add the HTTP/2 branch's CancelIdle action to the HTTP/1.1 branch of upgrade_to_ssl.

Related: #916 (stuck in upgrade_to_ssl), #922 (handshake bounded by connect_timeout), #934, #936.

Linguagem predominante
Erlang
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Forks
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Merge médio
11h 32min
PRs com merge (30d)
47

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