Make golangci-lint pass. (#99)

This commit fixes various errors (mostly about ignoring returned
values) reported by golangci-lint.

Tested the changes with "go test ./..." and also:

    # Terminal A
    $ docker-compose up
    # Terminal B
    $ docker exec -it trcgfr_traceroute-caller_1 apt-get update
    $ tree local

connectionlistener/connectionlistener.go

@@ -44,7 +44,9 @@ func (cl *connectionListener) Close(ctx context.Context, timestamp time.Time, uu
 	cl.mutex.Unlock()
 
 	if ok {
-		go cl.cache.Trace(conn)
+		go func() {
+			_, _ = cl.cache.Trace(conn)
+		}()
 	}
 }
 

connectionlistener/connectionlistener_test.go

@@ -55,7 +55,9 @@ func TestListener(t *testing.T) {
 	rtx.Must(srv.Listen(), "Could not listen")
 	srvCtx, srvCancel := context.WithCancel(context.Background())
 	defer srvCancel()
-	go srv.Serve(srvCtx)
+	go func() {
+		_ = srv.Serve(srvCtx)
+	}()
 
 	// Create a new connectionlistener with a fake tracer.
 	ctx, cancel := context.WithCancel(context.Background())

connectionpoller/connectionpoller.go

@@ -144,7 +144,9 @@ func (c *connectionPoller) TraceClosedConnections() {
 	c.connectionPool = c.GetConnections()
 	for conn := range oldConn {
 		if _, hasConn := c.connectionPool[conn]; !hasConn {
-			go c.recentIPCache.Trace(conn)
+			go func() {
+				_, _ = c.recentIPCache.Trace(conn)
+			}()
 		}
 	}
 }

docker-compose.yaml

@@ -62,6 +62,5 @@ services:
       - -prometheusx.listen-address=:9992
       - -outputPath=/local/traceroute
       - -poll=false
-      - -ipservice.sock=/local/uuid-annotator.sock
       - -tcpinfo.eventsocket=/local/tcpevents.sock
       - -tracetool=scamper-daemon

ipcache/ipcache.go

@@ -71,7 +71,7 @@ func (rc *RecentIPCache) Trace(conn connection.Connection) (string, error) {
 	if cached {
 		<-c.dataReady
 		if c.err == nil {
-			t.TraceFromCachedTrace(conn, time.Now(), c.data)
+			_ = t.TraceFromCachedTrace(conn, time.Now(), c.data)
 			return c.data, nil
 		}
 		t.DontTrace(conn, c.err)

ipcache/ipcache_test.go

@@ -74,7 +74,7 @@ func TestTrace(t *testing.T) {
 	if tt.cctest != 0 {
 		t.Errorf("Should have had zero calls to CreateCachedTest, not %d", tt.cctest)
 	}
-	testCache.Trace(conn1) // This should be cached
+	_, _ = testCache.Trace(conn1) // This should be cached
 	if tt.cctest != 1 {
 		t.Errorf("Should have had one call to CreateCachedTest, not %d", tt.cctest)
 	}
@@ -117,7 +117,7 @@ func TestRecentIPCache(t *testing.T) {
 	defer cancel()
 	var tt testTracer
 	tmp := ipcache.New(ctx, &tt, 10*time.Millisecond, 1*time.Millisecond)
-	tmp.Trace(connection.Connection{
+	_, _ = tmp.Trace(connection.Connection{
 		RemoteIP:   "1.2.3.4",
 		RemotePort: 5,
 		LocalIP:    "6.7.8.9",

parser/json.go

@@ -1,4 +1,4 @@
-// parser package handles parsing of scamper JSONL.
+// Package parser handles parsing of scamper JSONL.
 // The format of JSON can be found at
 // https://www.caida.org/tools/measurement/scamper/.
 // NB: It is not clear where at that URL the format can be found.

tracer/paris_test.go

@@ -68,7 +68,7 @@ func TestParis(t *testing.T) {
 		Cookie:     "CDEF",
 	}
 	afterNow := time.Date(2003, 11, 9, 15, 58, 1, 0, time.UTC)
-	p.TraceFromCachedTrace(conn2, afterNow, out)
+	_ = p.TraceFromCachedTrace(conn2, afterNow, out)
 
 	contents, err = ioutil.ReadFile(dir + "/2003/11/09/20031109T15:58:01Z-UUID-" + prefix.UnsafeString() + "_000000000000CDEF.cached.paris")
 	rtx.Must(err, "Could not read file")
@@ -88,6 +88,6 @@ func TestParis(t *testing.T) {
 	if err == nil {
 		t.Error("You can't save data to /dev/null")
 	}
-	p.TraceFromCachedTrace(conn2, afterNow, out) // no crash == success
+	_ = p.TraceFromCachedTrace(conn2, afterNow, out) // no crash == success
 
 }

tracer/scamper.go

@@ -160,7 +160,9 @@ func (d *ScamperDaemon) MustStart(ctx context.Context) {
 	// if the user started those processes. This is also why we don't use
 	// CommandContext in the exec package - if the process isn't successfully
 	// killed by SIGKILL, then the code in that package doesn't work correctly.
-	command.Process.Signal(syscall.SIGKILL)
+	if err := command.Process.Signal(syscall.SIGKILL); err != nil {
+		log.Printf("failed to send SIGKILL to scamper daemon, error: %v\n", err)
+	}
 }
 
 // Trace starts a sc_attach connecting to the scamper process for each
@@ -186,7 +188,9 @@ func (d *ScamperDaemon) Trace(conn connection.Connection, t time.Time) (out stri
 func (d *ScamperDaemon) TraceAll(connections []connection.Connection) {
 	for _, c := range connections {
 		log.Printf("PT start: %s %d", c.RemoteIP, c.RemotePort)
-		go d.Trace(c, time.Now())
+		go func(c connection.Connection) {
+			_, _ = d.Trace(c, time.Now())
+		}(c)
 	}
 }
 

tracer/scamper_test.go

@@ -15,7 +15,6 @@ import (
 	"github.com/m-lab/go/prometheusx"
 	"github.com/m-lab/go/rtx"
 	"github.com/m-lab/traceroute-caller/connection"
-	"github.com/m-lab/traceroute-caller/ipcache"
 	"github.com/m-lab/uuid/prefix"
 )
 
@@ -281,13 +280,13 @@ func TestCreateCacheTest(t *testing.T) {
 	{"type":"tracelb", "version":"0.1", "userid":0, "method":"icmp-echo", "src":"::ffff:180.87.97.101", "dst":"::ffff:1.47.236.62", "start":{"sec":1566691298, "usec":476221, "ftime":"2019-08-25 00:01:38"}, "probe_size":60, "firsthop":1, "attempts":3, "confidence":95, "tos":0, "gaplimit":3, "wait_timeout":5, "wait_probe":250, "probec":0, "probec_max":3000, "nodec":0, "linkc":0}
 	{"type":"cycle-stop", "list_name":"/tmp/scamperctrl:51811", "id":1, "hostname":"ndt-plh7v", "stop_time":1566691298}`
 
-	d.TraceFromCachedTrace(c, faketime, "Broken cached test")
+	_ = d.TraceFromCachedTrace(c, faketime, "Broken cached test")
 	_, errInvalidTest := ioutil.ReadFile(tempdir + "/2019/04/01/20190401T034551Z_" + prefix.UnsafeString() + "_0000000000000001.jsonl")
 	if errInvalidTest == nil {
 		t.Error("should fail to generate cached test")
 	}
 
-	d.TraceFromCachedTrace(c, faketime, cachedTest)
+	_ = d.TraceFromCachedTrace(c, faketime, cachedTest)
 
 	// Unmarshal the first line of the output file.
 	b, err := ioutil.ReadFile(tempdir + "/2019/04/01/20190401T034551Z_" + prefix.UnsafeString() + "_0000000000000001.jsonl")
@@ -351,7 +350,7 @@ func TestRecovery(t *testing.T) {
 
 	// Run both trace methods.
 	d.TraceAll([]connection.Connection{c})
-	d.Trace(c, time.Now())
+	_, _ = d.Trace(c, time.Now())
 	// If this doesn't crash, then the recovery process works!
 }
 
@@ -381,9 +380,3 @@ func TestGetMetaline(t *testing.T) {
 		t.Error("Fail to generate meta ", meta)
 	}
 }
-
-//lint:ignore U1000 This performs a compile time check.
-// If this successfully compiles, then ScamperDaemon implements the Tracer interface.
-func assertScamperDaemonIsTracer(d *ScamperDaemon) {
-	func(t ipcache.Tracer) {}(d)
-}