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RequestServer: Avoid multiple connections to incompatible servers

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This really only implements a heuristic, assuming that HTTP/1.0 servers
cannot handle having multiple active connections; this assumption has
lots of false positives, but ultimately HTTP/1.0 is an out-of-date HTTP
version and people using it should just switch to a newer standard
anyway.

Specifically, python's "SimpleHTTPRequestHandler" utilises a
single-threaded HTTP/1.0 server, which means no keepalive and more
importantly, hangs and races with more than a single connection present.
This commit makes it so we serialise all requests to servers that are
known to serve only a single request per connection (aka HTTP/1.0 with
our setup, as we unconditionally request keepalive)
This commit is contained in:
Ali Mohammad Pur 2024-01-06 09:24:26 +03:30 • committed by Andreas Kling
parent e770cf06b0
commit cd4ebc45a0
2 changed files with 23 additions and 2 deletions
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5
Userland/Services/RequestServer/ConnectionCache.cpp
View file

@ -13,6 +13,7 @@ namespace RequestServer::ConnectionCache {
HashMap<ConnectionKey, NonnullOwnPtr<Vector<NonnullOwnPtr<Connection<Core::TCPSocket, Core::Socket>>>>> g_tcp_connection_cache {};
HashMap<ConnectionKey, NonnullOwnPtr<Vector<NonnullOwnPtr<Connection<TLS::TLSv12>>>>> g_tls_connection_cache {};
HashMap<ByteString, InferredServerProperties> g_inferred_server_properties;
void request_did_finish(URL const& url, Core::Socket const* socket)
{
@ -37,6 +38,10 @@ void request_did_finish(URL const& url, Core::Socket const* socket)
}
auto& connection = *connection_it;
auto& properties = g_inferred_server_properties.ensure(partial_key.hostname);
if (!connection->socket->is_open())
properties.requests_served_per_connection = min(properties.requests_served_per_connection, connection->max_queue_length + 1);
if (connection->request_queue.is_empty()) {
// Immediately mark the connection as finished, as new jobs will never be run if they are queued
// before the deferred_invoke() below runs otherwise.

20
Userland/Services/RequestServer/ConnectionCache.h
View file

@ -98,6 +98,7 @@ struct Connection {
Core::ElapsedTimer timer {};
JobData job_data {};
Proxy proxy {};
size_t max_queue_length { 0 };
};
struct ConnectionKey {
@ -120,8 +121,13 @@ struct AK::Traits<RequestServer::ConnectionCache::ConnectionKey> : public AK::De
namespace RequestServer::ConnectionCache {
struct InferredServerProperties {
size_t requests_served_per_connection { NumericLimits<size_t>::max() };
};
extern HashMap<ConnectionKey, NonnullOwnPtr<Vector<NonnullOwnPtr<Connection<Core::TCPSocket, Core::Socket>>>>> g_tcp_connection_cache;
extern HashMap<ConnectionKey, NonnullOwnPtr<Vector<NonnullOwnPtr<Connection<TLS::TLSv12>>>>> g_tls_connection_cache;
extern HashMap<ByteString, InferredServerProperties> g_inferred_server_properties;
void request_did_finish(URL const&, Core::Socket const*);
void dump_jobs();
@ -173,12 +179,21 @@ ErrorOr<void> recreate_socket_if_needed(T& connection, URL const& url)
decltype(auto) get_or_create_connection(auto& cache, URL const& url, auto job, Core::ProxyData proxy_data = {})
{
using CacheEntryType = RemoveCVReference<decltype(*cache.begin()->value)>;
auto& sockets_for_url = *cache.ensure({ url.serialized_host().release_value_but_fixme_should_propagate_errors().to_byte_string(), url.port_or_default(), proxy_data }, [] { return make<CacheEntryType>(); });
auto hostname = url.serialized_host().release_value_but_fixme_should_propagate_errors().to_byte_string();
auto& properties = g_inferred_server_properties.ensure(hostname);
auto& sockets_for_url = *cache.ensure({ move(hostname), url.port_or_default(), proxy_data }, [] { return make<CacheEntryType>(); });
Proxy proxy { proxy_data };
using ReturnType = decltype(sockets_for_url[0].ptr());
auto it = sockets_for_url.find_if([](auto& connection) { return connection->request_queue.is_empty(); });
// Find the connection with an empty queue; if none exist, we'll find the least backed-up connection later.
// Note that servers that are known to serve a single request per connection (e.g. HTTP/1.0) usually have
// issues with concurrent connections, so we'll only allow one connection per URL in that case to avoid issues.
// This is a bit too aggressive, but there's no way to know if the server can handle concurrent connections
// without trying it out first, and that's not worth the effort as HTTP/1.0 is a legacy protocol anyway.
auto it = sockets_for_url.find_if([&](auto& connection) { return properties.requests_served_per_connection < 2 || connection->request_queue.is_empty(); });
auto did_add_new_connection = false;
auto failed_to_find_a_socket = it.is_end();
if (failed_to_find_a_socket && sockets_for_url.size() < ConnectionCache::MaxConcurrentConnectionsPerURL) {
@ -253,6 +268,7 @@ decltype(auto) get_or_create_connection(auto& cache, URL const& url, auto job, C
} else {
dbgln_if(REQUESTSERVER_DEBUG, "Enqueue request for URL {} in {} - {}", url, &connection, connection.socket);
connection.request_queue.append(decltype(connection.job_data)::create(job));
connection.max_queue_length = max(connection.max_queue_length, connection.request_queue.size());
}
return &connection;
}