docker-compose: map host.docker.internal to host-gateway - #10
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On a Linux docker engine the name only resolves inside containers when extra_hosts says so; docker desktop provides it implicitly. Without the mapping every container reference to a host process (the beacon's execution endpoint, the relay's blocksim) times out.
canercidam
approved these changes
Sep 9, 2026
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Summary
extra_hosts: ["host.docker.internal:host-gateway"]on each pod's network-owning (leader) container.host.docker.internaldoes not resolve inside containers unlessextra_hostssays so; Docker Desktop provides it implicitly. Without the mapping every container reference to a host process times out: the beacon node cannot reach a host-run EL's authrpc, the relay cannot reach a host-run blocksim, and the chain sits at block 0.network_mode: service:<leader>peer, and the peers share the leader's network namespace anyway, so the one entry covers the pod.host-gatewayis the engine's special value for the host's gateway address (Linux engine 20.10+, also honoured by Docker Desktop), so this is a no-op where the name already resolved.Test plan
deno lint,deno check renderers/docker-compose.tsreth-rbuilderand a bidding gateway as host processes and the beacon/relay in containers. Before: beacon → EL authrpc timeouts, chain stuck at block 0. After: chain advances and the flow runs end to end (used for the JIT route devnet in rbuilder-prismdecker/jit-router/).