@@ -18,6 +18,7 @@ import (
1818"cloud.google.com/go/compute/metadata"
1919"golang.org/x/xerrors"
2020"gopkg.in/natefinch/lumberjack.v2"
21+ "tailscale.com/util/clientmetric"
2122
2223"cdr.dev/slog"
2324"cdr.dev/slog/sloggers/sloghuman"
@@ -36,6 +37,7 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
3637noReap bool
3738sshMaxTimeout time.Duration
3839tailnetListenPort int64
40+ prometheusAddress string
3941)
4042cmd := & clibase.Cmd {
4143Use :"agent" ,
@@ -126,6 +128,13 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
126128agentPorts [port ]= "pprof"
127129}
128130
131+ prometheusSrvClose := ServeHandler (ctx ,logger ,prometheusMetricsHandler (),prometheusAddress ,"prometheus" )
132+ defer prometheusSrvClose ()
133+ // Do a best effort here. If this fails, it's not a big deal.
134+ if port ,err := urlPort (prometheusAddress );err == nil {
135+ agentPorts [port ]= "prometheus"
136+ }
137+
129138// exchangeToken returns a session token.
130139// This is abstracted to allow for the same looping condition
131140// regardless of instance identity auth type.
@@ -257,6 +266,13 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
257266Description :"Specify a static port for Tailscale to use for listening." ,
258267Value :clibase .Int64Of (& tailnetListenPort ),
259268},
269+ {
270+ Flag :"prometheus-address" ,
271+ Default :"127.0.0.1:2112" ,
272+ Env :"CODER_AGENT_PROMETHEUS_ADDRESS" ,
273+ Value :clibase .StringOf (& prometheusAddress ),
274+ Description :"The bind address to serve Prometheus metrics." ,
275+ },
260276}
261277
262278return cmd
@@ -343,3 +359,12 @@ func urlPort(u string) (int, error) {
343359}
344360return - 1 ,xerrors .Errorf ("invalid port: %s" ,u )
345361}
362+
363+ func prometheusMetricsHandler () http.Handler {
364+ // We don't have any other internal metrics so far, so it's safe to expose metrics this way.
365+ // Based on: https://github.com/tailscale/tailscale/blob/280255acae604796a1113861f5a84e6fa2dc6121/ipn/localapi/localapi.go#L489
366+ return http .HandlerFunc (func (w http.ResponseWriter ,r * http.Request ) {
367+ w .Header ().Set ("Content-Type" ,"text/plain" )
368+ clientmetric .WritePrometheusExpositionFormat (w )
369+ })
370+ }