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fix(envd): bind HTTP listener before sync init chain to eliminate startup race #3611

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fix(envd): bind HTTP listener before sync init chain to eliminate startup race #3611

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22 changes: 20 additions & 2 deletions packages/envd/main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import (
"fmt"
"io"
"log"
"net"
"net/http"
"os"
"path/filepath"
Expand Down Expand Up @@ -182,6 +183,20 @@ func run(stop <-chan struct{}) error {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()

// Bind the listener before any blocking initializer so the TCP port is
// reachable from process start. Incoming connections are queued in the
// kernel's accept backlog; nothing is dispatched until s.Serve(ln) below.
// Without this, a slow or hanging initializer (e.g. writeCgroupProp under
// memory pressure) produces a window where the process is alive but the port
// returns ECONNREFUSED — indistinguishable from a crashed envd to any
// TCP-based health check or orchestrator readiness probe.
ln, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", port))
if err != nil {
return fmt.Errorf("bind envd listener: %w", err)
}
defer ln.Close()
fmt.Fprintf(os.Stderr, "envd: HTTP listener bound on :%d\n", port)

if err := os.MkdirAll(host.E2BRunDir, 0o755); err != nil {
fmt.Fprintf(os.Stderr, "error creating E2B run directory: %v\n", err)
}
Expand Down Expand Up @@ -217,7 +232,9 @@ func run(stop <-chan struct{}) error {
fsLogger := l.With().Str("logger", "filesystem").Logger()
filesystemService := filesystemRpc.Handle(m, &fsLogger, defaults)

fmt.Fprintf(os.Stderr, "envd startup: creating cgroup manager\n")
cgroupManager := createCgroupManager()
fmt.Fprintf(os.Stderr, "envd startup: cgroup manager ready\n")
defer func() {
err := cgroupManager.Close()
if err != nil {
Expand Down Expand Up @@ -476,7 +493,7 @@ func run(stop <-chan struct{}) error {
}
})

// A stop request closes the listener, which makes ListenAndServe return.
// A stop request closes the listener, which makes Serve return.
stopped := make(chan struct{})
defer close(stopped)
go func() {
Expand All @@ -487,7 +504,8 @@ func run(stop <-chan struct{}) error {
}
}()

err := s.ListenAndServe()
// err is already declared by net.Listen at the top of run().
err = s.Serve(ln)
if errors.Is(err, http.ErrServerClosed) {
select {
case <-stop:
Expand Down