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EW-9327 Implement connection string override support #6742

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28 changes: 28 additions & 0 deletions src/workerd/api/http.c++
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include "worker-rpc.h"
#include "workerd/jsg/jsvalue.h"

#include <workerd/api/global-scope.h>
#include <workerd/io/features.h>
#include <workerd/io/io-context.h>
#include <workerd/jsg/ser.h>
Expand Down Expand Up @@ -2067,6 +2068,33 @@ jsg::Ref<Socket> Fetcher::connect(
return connectImpl(js, JSG_THIS, kj::mv(address), kj::mv(options));
}

void Fetcher::setPort(uint16_t p) {
KJ_ASSERT(port == kj::none);
port = p;
}

jsg::Optional<kj::StringPtr> Fetcher::getHost(jsg::Lock& js) {
if (port == kj::none) {
return kj::none;
}
if (!registeredConnectOverride) {
kj::FixedArray<kj::byte, 16> randomBytes;
workerd::getEntropy(randomBytes);
randomHost = kj::str(kj::encodeHex(randomBytes), ".hyperdrive.local");

// Returns the random hostname and ensures the connect override is registered on the
// ServiceWorkerGlobalScope for the Worker. This getter has a side effect: it registers (or
// re-registers) an entry in the ServiceWorkerGlobalScope's connectOverrides HashMap so that
// cloudflare:sockets's connect() will route connections to this magic hostname through the
// fetcher.
auto& globalScope = IoContext::current().getCurrentLock().getGlobalScope();
globalScope.setConnectOverride(kj::str(KJ_ASSERT_NONNULL(randomHost), ":", getPort()),
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[LOW] Consider using getPort() rather than accessing port field directly for consistency.

The Hyperdrive implementation calls getPort() for both the setConnectOverride key and the lambda body. Here you mix getPort() (line 2091) and direct self->port access (line 2092). Using self->getPort() in the lambda would also need unwrapping but would be more consistent.

Also: this line calls getPort() which returns jsg::Optional<uint16_t> — kj::str() with a Maybe will produce unexpected output here too. Should unwrap:

Suggested change
globalScope.setConnectOverride(kj::str(KJ_ASSERT_NONNULL(randomHost), ":", getPort()),
globalScope.setConnectOverride(kj::str(KJ_ASSERT_NONNULL(randomHost), ":", KJ_ASSERT_NONNULL(port)),

[self = JSG_THIS](jsg::Lock& js) mutable { return self->connect(js, kj::str(KJ_ASSERT_NONNULL(self->randomHost), ":", self->port), kj::none); });
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[HIGH] self->port is jsg::Optional<uint16_t> — stringifying a kj::Maybe instead of the unwrapped value.

self->port has type jsg::Optional<uint16_t> (which is kj::Maybe<uint16_t>). Passing it to kj::str() will not produce the numeric string you want — it will format the Maybe wrapper. Compare with the Hyperdrive implementation where getPort() returns a plain uint16_t.

Suggested change
[self = JSG_THIS](jsg::Lock& js) mutable { return self->connect(js, kj::str(KJ_ASSERT_NONNULL(self->randomHost), ":", self->port), kj::none); });
[self = JSG_THIS](jsg::Lock& js) mutable { return self->connect(js, kj::str(KJ_ASSERT_NONNULL(self->randomHost), ":", KJ_ASSERT_NONNULL(self->port)), kj::none); });

registeredConnectOverride = true;
}
return randomHost;
}

jsg::Promise<jsg::Ref<Response>> Fetcher::fetch(jsg::Lock& js,
kj::OneOf<jsg::Ref<Request>, kj::String> requestOrUrl,
jsg::Optional<kj::OneOf<RequestInitializerDict, jsg::Ref<Request>>> requestInit) {
Expand Down
23 changes: 21 additions & 2 deletions src/workerd/api/http.h
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Original file line number Diff line number Diff line change
Expand Up @@ -263,10 +263,14 @@ class Fetcher: public JsRpcClientProvider {
// URL that has no protocol or host.
//
// See pipeline.capnp or request-context.h for an explanation of `isInHouse`.
explicit Fetcher(uint channel, RequiresHostAndProtocol requiresHost, bool isInHouse = false)
explicit Fetcher(uint channel,
RequiresHostAndProtocol requiresHost,
bool isInHouse = false,
kj::Maybe<uint16_t> connectionStringOverridePort = kj::none)
: channelOrClientFactory(channel),
requiresHost(requiresHost),
isInHouse(isInHouse) {}
isInHouse(isInHouse),
port(connectionStringOverridePort) {}

// Create a Fetcher bound to an IoChannelFactory::SubrequestChannel object rather than a numeric
// channel. This Fetcher will inherently be bound to the current I/O context.
Expand Down Expand Up @@ -440,6 +444,12 @@ class Fetcher: public JsRpcClientProvider {
rpc::JsRpcTarget::Client getClientForOneCall(
jsg::Lock& js, kj::Vector<kj::StringPtr>& path) override;

void setPort(uint16_t port);
jsg::Optional<uint16_t> getPort() const {
return port;
}
jsg::Optional<kj::StringPtr> getHost(jsg::Lock& js);

JSG_RESOURCE_TYPE(Fetcher, CompatibilityFlags::Reader flags) {
// WARNING: New JSG_METHODs on Fetcher must be gated via compatibility flag to prevent
// conflicts with JS RPC methods (implemented via the wildcard property). Ideally, we do not
Expand All @@ -451,6 +461,9 @@ class Fetcher: public JsRpcClientProvider {
JSG_METHOD(fetch);
JSG_METHOD(connect);

JSG_LAZY_READONLY_INSTANCE_PROPERTY(host, getHost);
JSG_LAZY_READONLY_INSTANCE_PROPERTY(port, getPort);
Comment on lines +464 to +465
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[HIGH] Missing compat flag gate — shadows JS RPC wildcard property.

The comment right above (lines 453–459) warns:

WARNING: New JSG_METHODs on Fetcher must be gated via compatibility flag to prevent conflicts with JS RPC methods (implemented via the wildcard property).

This applies equally to properties. JSG_LAZY_READONLY_INSTANCE_PROPERTY registers concrete property names (host, port) that will shadow JSG_WILDCARD_PROPERTY(getRpcMethod). Since DurableObject extends Fetcher, a DO stub whose RPC target exposes a host or port property/method will silently get undefined (the Fetcher property with no port set) instead of making the RPC call.

These should be gated behind a compat flag, or alternatively moved to a subclass that only the connection-string-override Fetcher uses (not all Fetchers globally).


if (flags.getServiceBindingExtraHandlers()) {
JSG_METHOD(queue);
JSG_METHOD(scheduled);
Expand Down Expand Up @@ -527,6 +540,12 @@ class Fetcher: public JsRpcClientProvider {
channelOrClientFactory;
RequiresHostAndProtocol requiresHost;
bool isInHouse;

// used for optional connection string override. port being non-none indicates that an override
// has been requested.
bool registeredConnectOverride = false;
jsg::Optional<kj::String> randomHost;
jsg::Optional<uint16_t> port = kj::none;
};

// Type of the second parameter to Request's constructor. Also the type of the second parameter
Expand Down
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