chore: update readme, update default CLI arg values

Signed-off-by: arkbriar <[email protected]>

Author: arkbriar

README.md

@@ -1,5 +1,31 @@
 # PROMPROXY
 
 Prometheus Proxy is a simple proxy server that can be used to simulate namespaced Prometheus
-instances. Full Prometheus v1 API is supported and will be exposed under `/{namespace}/api/v1/`
-path. Grafana datasource configuration is also supported.
+instances. A selected set of Prometheus v1 API will be exposed under `/{key1}/{key2}/api/v1/`
+path to be a data source of general purpose Prometheus client, such as Grafana.
+
+## HTTP API Endpoints
+
+The following Prometheus v1 API endpoints are supported:
+
+- `/api/v1/query`: Query Prometheus for metrics.
+- `/api/v1/query_range`: Query Prometheus for metrics over a range of time.
+- `/api/v1/query_exemplars`: Query Prometheus for exemplars.
+- `/api/v1/series`: Get a list of series by label selectors.
+- `/api/v1/labels`: Get a list of label names.
+- `/api/v1/label/{name}/values`: Get a list of label values.
+- `/api/v1/rules`: Get a list of alerting and recording rules.
+
+## Configuration
+
+The proxy server can be configured using the following CLI flags:
+
+- `-listen-addr`: The address to listen on for incoming HTTP requests. (default ":8080")
+- `-upstream-endpoint`: The address of the upstream Prometheus server. (
+  default "http://localhost:9090")
+- `-upstream-tls`: Enable TLS for the upstream Prometheus server. (default false)
+- `-upstream-tls-cert-dir`: The directory containing the TLS certificate and key for the upstream
+  Prometheus server. (default "")
+- `-label-matchers`: The label matchers to be used for the proxy server. (default "")
+- `-isolation-keys`: The isolation keys to be used for the proxy server. (default "")
+- `-print-access-log`: Print access log. (default false)

main.go

@@ -29,12 +29,12 @@ var (
 
 func init() {
 	flag.StringVar(&listenAddr, "listen-addr", ":8080", "address to listen on")
-	flag.StringVar(&upstreamEndpoint, "upstream-endpoint", "", "upstream Prometheus endpoint")
+	flag.StringVar(&upstreamEndpoint, "upstream-endpoint", "http://localhost:9090", "upstream Prometheus endpoint")
 	flag.BoolVar(&upstreamTLS, "upstream-tls", false, "use TLS for upstream connection")
 	flag.StringVar(&upstreamTLSCertDir, "upstream-tls-cert-dir", "", "directory to load certificates from")
 	flag.StringVar(&labelMatchers, "label-matchers", "", "label matchers to apply to all queries")
 	flag.BoolVar(&printAccessLog, "print-access-log", false, "print access log")
-	flag.StringVar(&isolationKeys, "isolation-keys", "", "keys to isolate on, separated by commas")
+	flag.StringVar(&isolationKeys, "isolation-keys", "namespace", "keys to isolate on, separated by commas")
 }
 
 func newProxy() (*proxy.Proxy, error) {