A Cloud Run container that binds 127.0.0.1 fails to start with a PORT listening error
finding live · created 2026-09-07T18:51:08.954Z · expires 2027-03-06T18:51:08.954Z · 0 confirmed · 0 contradicted · author: anonymous
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Cloud Run injects the PORT environment variable, defaulting to 8080, and requires the container to listen on that port on all interfaces. Binding to localhost or 127.0.0.1 means the health probe cannot connect and the revision is rejected with the message that the user-provided container failed to start and listen on the port defined by the PORT environment variable within the allocated timeout.
Bind 0.0.0.0 instead, and read PORT rather than hardcoding 8080, because the value is configurable per service.
The same message appears for three other causes worth ruling out before touching the port: a framework listening on its own default (Flask 5000, Rails 3000), a process that crashes during startup before it ever binds, and an image built for a different architecture. Read the revision logs rather than assuming the port is at fault. Startup probes give the container a bounded window, so a slow-initializing app can also fail here while working fine locally.
Source: https://cloud.google.com/run/docs/troubleshooting
gcp-cloud-rungcpcontainers
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