Support streaming bodies when using Rack::Events#2375
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When `Rack::Events` is used, it would use `EventedBodyProxy` to wrap the body. Unlike `BodyProxy`, `EventedBodyProxy` always implements `#each`. As per the spec, streaming bodies must both implement `#call` and not implement `#each`, and if both are present, the server must call `#each`, not `#call`. When a streaming body was wrapped by an `EventedBodyProxy`, the proxy will nonetheless `.respond_to?(:each)`. This would cause the server to call `#each` on the proxy. The proxy would then forward the call to `#each` to the body that it proxies, which does not implement `#each`, raising a `NoMethodError`. To fix this, `EventedBodyProxy` will only `.respond_to?(:each)` if the body it proxies responds to `#each`. Note that, while this fixes the `NoMethodError`, this means that the `on_send` handler will never be invoked for streaming bodies.
When using the `Rack::Events` middleware, call `on_send` on the middleware's handlers when `#call` is invoked, in the same way it is done when `#each` is invoked.
unflxw
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Rack::Events
jeremyevans
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Sep 1, 2025
ioquatix
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Sep 1, 2025
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Thanks for your contribution. As this is a bug fix, we could consider backporting. WDYT @jeremyevans? |
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No objections to backporting this fix to 3.2. |
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A fix for the issue where `::Rack::Events` breaks streaming bodies was introduced in version 3.2.1. Define `Appsignal::Rack::Events`, our patched implementation, only when the Rack version present is below 3.2.1. Otherwise, alias it to `::Rack::Events`. Modify how the deprecation warning is silenced, doing so through `Appsignal::Rack::EventMiddleware`, not `Appsignal::Rack::Events`. Test the deprecation warning's behaviour more precisely by testing the behaviour of `Appsignal::Rack::EventHandler` via the middleware that it is initialised, rather than in isolation. See #1445, rack/rack#2373, rack/rack#2375 for context.
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A fix for the issue where `::Rack::Events` breaks streaming bodies was introduced in version 3.2.1. Define `Appsignal::Rack::Events`, our patched implementation, only when the Rack version present is below 3.2.1. Otherwise, alias it to `::Rack::Events`. Modify how the deprecation warning is silenced, doing so through `Appsignal::Rack::EventMiddleware`, not `Appsignal::Rack::Events`. Test the deprecation warning's behaviour more precisely by testing the behaviour of `Appsignal::Rack::EventHandler` via the middleware that it is initialised, rather than in isolation. See #1445, rack/rack#2373, rack/rack#2375 for context.
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Fixes #2373.
Fix streaming bodies when using
Rack::EventsWhen
Rack::Eventsis used, it would useEventedBodyProxyto wrapthe body. Unlike
BodyProxy,EventedBodyProxyalways implements#each.As per the spec, streaming bodies must both implement
#calland notimplement
#each, and if both are present, the server must call#each, not#call.When a streaming body was wrapped by an
EventedBodyProxy, the proxywill nonetheless
.respond_to?(:each). This would cause the server tocall
#eachon the proxy. The proxy would then forward the call to#eachto the body that it proxies, which does not implement#each,raising a
NoMethodError.To fix this,
EventedBodyProxywill only.respond_to?(:each)ifthe body it proxies responds to
#each.Note that, while this fixes the
NoMethodError, this means that theon_sendhandler will never be invoked for streaming bodies.Call
on_sendhandler for streaming bodiesWhen using the
Rack::Eventsmiddleware, callon_sendon themiddleware's handlers when
#callis invoked, in the same way itis done when
#eachis invoked.