Updated documentation and defaults

README.md

@@ -77,7 +77,7 @@ To adjust timeouts, and connection pooling in the HTTP client use the following
 
 - `BUILDKITE_AGENT_METRICS_TIMEOUT` : Timeout, in seconds, TLS handshake and idle connections, for HTTP requests, to Buildkite API (default 15).
 - `BUILDKITE_AGENT_METRICS_MAX_IDLE_CONNS` : Maximum number of idle (keep-alive) HTTP connections 
-   for Buildkite Agent API. Zero means no limit, -1 disables pooling (default 0).
+   for Buildkite Agent API. Zero means no limit, -1 disables pooling (default 100).
 
 Additionally, one of the following groups of environment variables must be set
 in order to define how the Lambda function should obtain the required Buildkite
@@ -162,7 +162,7 @@ Usage of buildkite-agent-metrics:
   -interval duration
         Update metrics every interval, rather than once
   -max-idle-conns int
-        Maximum number of idle (keep-alive) HTTP connections for Buildkite Agent API. Zero means no limit, -1 disables pooling.
+        Maximum number of idle (keep-alive) HTTP connections for Buildkite Agent API. Zero means no limit, -1 disables connection reuse. (default 100)
   -newrelic-app-name string
         New Relic application name for metric events
   -newrelic-license-key string

lambda/main.go

@@ -100,7 +100,7 @@ func Handler(ctx context.Context, evt json.RawMessage) (string, error) {
 	}
 
 	if maxIdleConns == "" {
-		maxIdleConns = "0" // default to unlimited
+		maxIdleConns = "100" // Default to 100 in line with http.DefaultTransport
 	}
 
 	configuredTimeout, err := strconv.Atoi(timeout)

main.go

@@ -28,7 +28,7 @@ func main() {
 		dryRun       = flag.Bool("dry-run", false, "Whether to only print metrics")
 		endpoint     = flag.String("endpoint", "https://agent.buildkite.com/v3", "A custom Buildkite Agent API endpoint")
 		timeout      = flag.Int("timeout", 15, "Timeout, in seconds, TLS handshake and idle connections, for HTTP requests, to Buildkite API")
-		maxIdleConns = flag.Int("max-idle-conns", 0, "Maximum number of idle (keep-alive) HTTP connections for Buildkite Agent API. Zero means no limit, -1 disables pooling.")
+		maxIdleConns = flag.Int("max-idle-conns", 100, "Maximum number of idle (keep-alive) HTTP connections for Buildkite Agent API. Zero means no limit, -1 disables connection reuse.")
 
 		// backend config
 		backendOpt     = flag.String("backend", "cloudwatch", "Specify the backend to use: cloudwatch, newrelic, prometheus, stackdriver, statsd")