Docker Support for Consul Health Checks

command/agent/agent.go

@@ -83,6 +83,9 @@ type Agent struct {
 	// checkTTLs maps the check ID to an associated check TTL
 	checkTTLs map[string]*CheckTTL
 
+	// checkDockers maps the check ID to an associated Docker Exec based check
+	checkDockers map[string]*CheckDocker
+
 	// checkLock protects updates to the check* maps
 	checkLock sync.Mutex
 
@@ -151,6 +154,7 @@ func Create(config *Config, logOutput io.Writer) (*Agent, error) {
 		checkTTLs:     make(map[string]*CheckTTL),
 		checkHTTPs:    make(map[string]*CheckHTTP),
 		checkTCPs:     make(map[string]*CheckTCP),
+		checkDockers:  make(map[string]*CheckDocker),
 		eventCh:       make(chan serf.UserEvent, 1024),
 		eventBuf:      make([]*UserEvent, 256),
 		shutdownCh:    make(chan struct{}),
@@ -905,7 +909,7 @@ func (a *Agent) AddCheck(check *structs.HealthCheck, chkType *CheckType, persist
 			tcp.Start()
 			a.checkTCPs[check.CheckID] = tcp
 
-		} else {
+		} else if chkType.IsMonitor() {
 			if existing, ok := a.checkMonitors[check.CheckID]; ok {
 				existing.Stop()
 			}
@@ -924,6 +928,27 @@ func (a *Agent) AddCheck(check *structs.HealthCheck, chkType *CheckType, persist
 			}
 			monitor.Start()
 			a.checkMonitors[check.CheckID] = monitor
+		} else if chkType.IsDocker() {
+			if existing, ok := a.checkDockers[check.CheckID]; ok {
+				existing.Stop()
+			}
+			if chkType.Interval < MinInterval {
+				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has interval below minimum of %v",
+					check.CheckID, MinInterval))
+				chkType.Interval = MinInterval
+			}
+
+			dockerCheck := &CheckDocker{
+				Notify:            &a.state,
+				CheckID:           check.CheckID,
+				DockerContainerId: chkType.DockerContainerId,
+				Shell:             chkType.Shell,
+				Script:            chkType.Script,
+				Interval:          chkType.Interval,
+				Logger:            a.logger,
+			}
+			dockerCheck.Start()
+			a.checkDockers[check.CheckID] = dockerCheck
 		}
 	}
 

command/agent/check.go

@@ -6,12 +6,14 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"os"
 	"os/exec"
 	"sync"
 	"syscall"
 	"time"
 
 	"github.com/armon/circbuf"
+	docker "github.com/fsouza/go-dockerclient"
 	"github.com/hashicorp/consul/consul/structs"
 	"github.com/hashicorp/go-cleanhttp"
 )
@@ -38,10 +40,12 @@ const (
 // Only one of the types needs to be provided
 //  TTL or Script/Interval or HTTP/Interval or TCP/Interval
 type CheckType struct {
-	Script   string
-	HTTP     string
-	TCP      string
-	Interval time.Duration
+	Script            string
+	HTTP              string
+	TCP               string
+	Interval          time.Duration
+	DockerContainerId string
+	Shell             string
 
 	Timeout time.Duration
 	TTL     time.Duration
@@ -54,7 +58,7 @@ type CheckTypes []*CheckType
 
 // Valid checks if the CheckType is valid
 func (c *CheckType) Valid() bool {
-	return c.IsTTL() || c.IsMonitor() || c.IsHTTP() || c.IsTCP()
+	return c.IsTTL() || c.IsMonitor() || c.IsHTTP() || c.IsTCP() || c.IsDocker()
 }
 
 // IsTTL checks if this is a TTL type
@@ -64,7 +68,7 @@ func (c *CheckType) IsTTL() bool {
 
 // IsMonitor checks if this is a Monitor type
 func (c *CheckType) IsMonitor() bool {
-	return c.Script != "" && c.Interval != 0
+	return c.Script != "" && c.DockerContainerId == "" && c.Interval != 0
 }
 
 // IsHTTP checks if this is a HTTP type
@@ -77,6 +81,10 @@ func (c *CheckType) IsTCP() bool {
 	return c.TCP != "" && c.Interval != 0
 }
 
+func (c *CheckType) IsDocker() bool {
+	return c.DockerContainerId != "" && c.Shell != "" && c.Interval != 0
+}
+
 // CheckNotifier interface is used by the CheckMonitor
 // to notify when a check has a status update. The update
 // should take care to be idempotent.
@@ -493,3 +501,134 @@ func (c *CheckTCP) check() {
 	c.Logger.Printf("[DEBUG] agent: check '%v' is passing", c.CheckID)
 	c.Notify.UpdateCheck(c.CheckID, structs.HealthPassing, fmt.Sprintf("TCP connect %s: Success", c.TCP))
 }
+
+// A custom interface since go-dockerclient doesn't have one
+// We will use this interface in our test to inject a fake client
+type DockerClient interface {
+	CreateExec(docker.CreateExecOptions) (*docker.Exec, error)
+	StartExec(string, docker.StartExecOptions) error
+	InspectExec(string) (*docker.ExecInspect, error)
+}
+
+// CheckDocker is used to periodically invoke a script to
+// determine the health of an application running inside a
+// Docker Container. We assume that the script is compatible
+// with nagios plugins and expects the output in the same format.
+type CheckDocker struct {
+	Notify            CheckNotifier
+	CheckID           string
+	Script            string
+	DockerContainerId string
+	Shell             string
+	Interval          time.Duration
+	Logger            *log.Logger
+
+	dockerClient DockerClient
+	cmd          []string
+	stop         bool
+	stopCh       chan struct{}
+	stopLock     sync.Mutex
+}
+
+// Start is used to start checks.
+// Docker Checks runs until stop is called
+func (c *CheckDocker) Start() {
+	c.stopLock.Lock()
+	defer c.stopLock.Unlock()
+
+	//create the docker client
+	if c.dockerClient == nil {
+		var err error
+		c.dockerClient, err = docker.NewClientFromEnv()
+		if err != nil {
+			c.Logger.Println("[DEBUG] Error creating the Docker Client : %s", err.Error())
+		}
+	}
+
+	//figure out the shell
+	if c.Shell == "" {
+		if otherShell := os.Getenv("SHELL"); otherShell != "" {
+			c.Shell = otherShell
+		} else {
+			c.Shell = "/bin/sh"
+		}
+	}
+
+	c.cmd = []string{c.Shell, "-c", c.Script}
+
+	c.stop = false
+	c.stopCh = make(chan struct{})
+	go c.run()
+}
+
+// Stop is used to stop a docker check.
+func (c *CheckDocker) Stop() {
+	c.stopLock.Lock()
+	defer c.stopLock.Unlock()
+	if !c.stop {
+		c.stop = true
+		close(c.stopCh)
+	}
+}
+
+// run is invoked by a goroutine to run until Stop() is called
+func (c *CheckDocker) run() {
+	// Get the randomized initial pause time
+	initialPauseTime := randomStagger(c.Interval)
+	c.Logger.Printf("[DEBUG] agent: pausing %v before first invocation of %s -c %s in container %s", initialPauseTime, c.Shell, c.Script, c.DockerContainerId)
+	next := time.After(initialPauseTime)
+	for {
+		select {
+		case <-next:
+			c.check()
+			next = time.After(c.Interval)
+		case <-c.stopCh:
+			return
+		}
+	}
+}
+
+func (c *CheckDocker) check() {
+	//Set up the Exec since
+	execOpts := docker.CreateExecOptions{
+		AttachStdin:  false,
+		AttachStdout: true,
+		AttachStderr: true,
+		Tty:          false,
+		Cmd:          c.cmd,
+		Container:    c.DockerContainerId,
+	}
+	var (
+		exec *docker.Exec
+		err  error
+	)
+	if exec, err = c.dockerClient.CreateExec(execOpts); err == nil {
+		exec = exec
+	} else {
+		c.Logger.Printf("[DEBUG] agent: Error while creating Exec: %s", err.Error())
+		c.Notify.UpdateCheck(c.CheckID, structs.HealthCritical, fmt.Sprintf("Unable to create Exec, error: %s", err.Error()))
+		return
+	}
+
+	err = c.dockerClient.StartExec(exec.ID, docker.StartExecOptions{Detach: false, Tty: false})
+	if err != nil {
+		c.Logger.Printf("[DEBUG] Error in executing health checks: %s", err.Error())
+		c.Notify.UpdateCheck(c.CheckID, structs.HealthCritical, fmt.Sprintf("Unable to start exec: %s", err.Error()))
+		return
+	}
+
+	execInfo, err := c.dockerClient.InspectExec(exec.ID)
+	if err != nil {
+		c.Logger.Printf("[DEBUG] Error in inspecting check result : %s", err.Error())
+		c.Notify.UpdateCheck(c.CheckID, structs.HealthCritical, fmt.Sprintf("Unable to inspect Exec: %s", err.Error()))
+		return
+	}
+
+	if execInfo.ExitCode == 0 {
+		c.Notify.UpdateCheck(c.CheckID, structs.HealthPassing, fmt.Sprintf("Script execution %s: Success", c.Script))
+	} else {
+		c.Logger.Printf("[DEBUG] Check failed with exit code: %d", execInfo.ExitCode)
+		c.Notify.UpdateCheck(c.CheckID, structs.HealthCritical, fmt.Sprintf("Script execution faied with exit code: %s", execInfo.ExitCode))
+	}
+
+}