Merge pull request #209 from guilhem/watchdog

daemon: add watchdog checker

Author: lucab

daemon/watchdog.go

@@ -0,0 +1,58 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package daemon
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+)
+
+// SdWatchdogEnabled return watchdog information for a service.
+// Process should send daemon.SdNotify("WATCHDOG=1") every time / 2.
+//
+// It returns one of the following:
+// (0, nil) - watchdog isn't enabled or we aren't the watched PID.
+// (0, err) - an error happened (e.g. error converting time).
+// (time, nil) - watchdog is enabled and we can send ping.
+//   time is delay before inactive service will be killed.
+func SdWatchdogEnabled() (time.Duration, error) {
+	wusec := os.Getenv("WATCHDOG_USEC")
+	if wusec == "" {
+		return 0, nil
+	}
+	s, err := strconv.Atoi(wusec)
+	if err != nil {
+		return 0, fmt.Errorf("error converting WATCHDOG_USEC: %s", err)
+	}
+	if s <= 0 {
+		return 0, fmt.Errorf("error WATCHDOG_USEC must a positive number")
+	}
+
+	wpid := os.Getenv("WATCHDOG_PID")
+	if wpid == "" {
+		return 0, nil
+	}
+	p, err := strconv.Atoi(wpid)
+	if err != nil {
+		return 0, fmt.Errorf("error converting WATCHDOG_PID: %s", err)
+	}
+	if os.Getpid() != p {
+		return 0, nil
+	}
+
+	return time.Duration(s) * time.Microsecond, nil
+}

daemon/watchdog_test.go

@@ -0,0 +1,81 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package daemon
+
+import (
+	"os"
+	"strconv"
+	"testing"
+	"time"
+)
+
+func must(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func TestSdWatchdogEnabled(t *testing.T) {
+	mypid := strconv.Itoa(os.Getpid())
+	tests := []struct {
+		usec string // empty => unset
+		pid  string // empty => unset
+
+		werr   bool
+		wdelay time.Duration
+	}{
+		// Success cases
+		{"100", mypid, false, 100 * time.Microsecond},
+		{"50", mypid, false, 50 * time.Microsecond},
+		{"1", mypid, false, 1 * time.Microsecond},
+
+		// No-op cases
+		{"", mypid, false, 0}, // WATCHDOG_USEC not set
+		{"1", "", false, 0},   // WATCHDOG_PID not set
+		{"1", "0", false, 0},  // WATCHDOG_PID doesn't match
+		{"", "", false, 0},    // Both not set
+
+		// Failure cases
+		{"-1", mypid, true, 0},                // Negative USEC
+		{"string", "1", true, 0},              // Non-integer USEC value
+		{"1", "string", true, 0},              // Non-integer PID value
+		{"stringa", "stringb", true, 0},       // E v e r y t h i n g
+		{"-10239", "-eleventythree", true, 0}, // i s   w r o n g
+	}
+
+	for i, tt := range tests {
+		if tt.usec != "" {
+			must(os.Setenv("WATCHDOG_USEC", tt.usec))
+		} else {
+			must(os.Unsetenv("WATCHDOG_USEC"))
+		}
+		if tt.pid != "" {
+			must(os.Setenv("WATCHDOG_PID", tt.pid))
+		} else {
+			must(os.Unsetenv("WATCHDOG_PID"))
+		}
+
+		delay, err := SdWatchdogEnabled()
+
+		if tt.werr && err == nil {
+			t.Errorf("#%d: want non-nil err, got nil", i)
+		} else if !tt.werr && err != nil {
+			t.Errorf("#%d: want nil err, got %v", i, err)
+		}
+		if tt.wdelay != delay {
+			t.Errorf("#%d: want delay=%d, got %d", i, tt.wdelay, delay)
+		}
+	}
+}