Remove block profile rate config (#818)

Tiny clean-up, as we rarely use Datadog profiling (and I've never heard of us setting this env var).

cmd/zoekt-sourcegraph-indexserver/main.go

@@ -1235,7 +1235,6 @@ type rootConfig struct {
 	listen           string
 	hostname         string
 	cpuFraction      float64
-	blockProfileRate int
 
 	// config values related to shard merging
 	disableShardMerging bool
@@ -1258,7 +1257,6 @@ func (rc *rootConfig) registerRootFlags(fs *flag.FlagSet) {
 	fs.StringVar(&rc.listen, "listen", ":6072", "listen on this address.")
 	fs.StringVar(&rc.hostname, "hostname", zoekt.HostnameBestEffort(), "the name we advertise to Sourcegraph when asking for the list of repositories to index. Can also be set via the NODE_NAME environment variable.")
 	fs.Float64Var(&rc.cpuFraction, "cpu_fraction", 1.0, "use this fraction of the cores for indexing.")
-	fs.IntVar(&rc.blockProfileRate, "block_profile_rate", getEnvWithDefaultInt("BLOCK_PROFILE_RATE", -1), "Sampling rate of Go's block profiler in nanoseconds. Values <=0 disable the blocking profiler Var(default). A value of 1 includes every blocking event. See https://pkg.go.dev/runtime#SetBlockProfileRate")
 	fs.DurationVar(&rc.backoffDuration, "backoff_duration", getEnvWithDefaultDuration("BACKOFF_DURATION", 10*time.Minute), "for the given duration we backoff from enqueue operations for a repository that's failed its previous indexing attempt. Consecutive failures increase the duration of the delay linearly up to the maxBackoffDuration. A negative value disables indexing backoff.")
 	fs.DurationVar(&rc.maxBackoffDuration, "max_backoff_duration", getEnvWithDefaultDuration("MAX_BACKOFF_DURATION", 120*time.Minute), "the maximum duration to backoff from enqueueing a repo for indexing.  A negative value disables indexing backoff.")
 
@@ -1369,10 +1367,6 @@ func newServer(conf rootConfig) (*Server, error) {
 	// Tune GOMAXPROCS to match Linux container CPU quota.
 	_, _ = maxprocs.Set()
 
-	// Set the sampling rate of Go's block profiler: https://github.com/DataDog/go-profiler-notes/blob/main/guide/README.md#block-profiler.
-	// The block profiler is disabled by default and should be enabled with care in production
-	runtime.SetBlockProfileRate(conf.blockProfileRate)
-
 	// Automatically prepend our own path at the front, to minimize
 	// required configuration.
 	if l, err := os.Readlink("/proc/self/exe"); err == nil {