mongo stuff to agent/mongod, add EnsureMongoServer

agent/mongo/mongo.go

+package mongo
+
+import (
+        "fmt"
+        "os"
+        "os/exec"
+        "path"
+        "path/filepath"
+        "strings"
+
+        "launchpad.net/loggo"
+
+        "launchpad.net/juju-core/upstart"
+        "launchpad.net/juju-core/utils"
+)
+
+const (
+        maxFiles              = 65000
+        maxProcs              = 20000
+        JujuMongodPathDefault = "/usr/lib/juju/bin/mongod"
+)
+
+var (
+        logger = loggo.GetLogger("juju.agent.mongo")
+
+        oldMongoServiceName = "juju-db"
+
+        // JujuMongodPath is the path to the juju-specific mongod instance.
+        JujuMongodPath = JujuMongodPathDefault

[rog, 2014/03/04 16:24:46]

or just:
JujuMongodPath = "/usr/lib/juju/bin/mongod"

[natefinch, 2014/03/04 17:01:05]

Done.

+)
+
+// MongoPath returns the executable path to be used to run mongod on this
+// machine. If the juju-bundled version of mongo exists, it will return that
+// path, otherwise it will return the command to run mongod from the path.
+func MongodPath() (string, error) {
+        if _, err := os.Stat(JujuMongodPath); err == nil {
+                return JujuMongodPath, nil
+        }
+
+        s, err := exec.Command("/usr/bin/which", "mongod").Output()

[rog, 2014/03/04 16:24:46]

path, err := exec.LookPath("mongod")
if err != nil {
    return err
}
return path, nil

[natefinch, 2014/03/04 17:01:05]

I always forget about LookPath.  Done.

+        if err != nil {
+                // this should never happen, unless which doesn't exist
+                return "", fmt.Errorf("cannot determine mongod path: %v", err)
+        }
+        path := strings.TrimSpace(string(s))
+        if path == "" {
+                return path, fmt.Errorf("cannot find mongod in $PATH")
+        }
+        return path, nil
+}
+
+// EnsureMongoServer ensures that the correct mongo upstart script is installed
+// and running.
+//
+// This method will remove old versions of the mongo upstart script as necessary
+// before installing the new version.
+func EnsureMongoServer(dir string, port int) error {
+        name := makeServiceName(mongoScriptVersion)
+        service, err := MongoUpstartService(name, dir, port)
+        if err != nil {
+                return err
+        }
+        if service.Installed() {
+                return nil
+        }
+
+        if err := removeOldMongoServices(mongoScriptVersion); err != nil {
+                return err
+        }
+
+        if err := makeJournalDirs(dir); err != nil {
+                return err
+        }
+
+        if err := service.Install(); err != nil {
+                return fmt.Errorf("failed to install mongo service %q: %v", service.Name, err)
+        }
+        return service.Start()
+}
+
+func makeJournalDirs(dir string) error {
+        journalDir := path.Join(dir, "journal")
+
+        if err := os.MkdirAll(journalDir, 0700); err != nil {
+                logger.Errorf("failed to make mongo journal dir %s: %v", journalDir, err)
+                return err
+        }
+
+        // manually create the prealloc files, since otherwise they get created as 100M files.
+        zeroes := make([]byte, 64*1024) // should be enough for anyone
+        for x := 0; x < 3; x++ {
+                name := fmt.Sprintf("prealloc.%d", x)
+                filename := filepath.Join(journalDir, name)
+                f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0700)
+                if err != nil {
+                        return fmt.Errorf("failed to open mongo prealloc file %q: %v", filename, err)
+                }
+                defer f.Close()
+                // write 64kb 16x = 1mb
+                for y := 0; y < 16; y++ {

[rog, 2014/03/04 16:24:46]

or a little more directly.

for total := 0; total < 1024 * 1024; {
     n, err := f.Write(zeroes)
     if err != nil {
        ...
     }
     total += n
}

[natefinch, 2014/03/04 17:01:05]

Done.

+                        if _, err := f.Write(zeroes); err != nil {
+                                return fmt.Errorf("failed to write to mongo prealloc file %q: %v", filename, err)
+                        }
+                }
+        }
+        return nil
+}
+
+// removeOldMongoServices looks for any old juju mongo upstart scripts and
+// removes them.
+func removeOldMongoServices(curVersion int) error {
+        old := upstart.NewService(oldMongoServiceName)
+        if err := old.StopAndRemove(); err != nil {
+                logger.Errorf("Failed to remove old mongo upstart service %q: %v", old.Name, err)
+                return err
+        }
+
+        // the new formatting for the script name started at version 2
+        for x := 2; x < curVersion; x++ {
+                old := upstart.NewService(makeServiceName(x))
+                if err := old.StopAndRemove(); err != nil {
+                        logger.Errorf("Failed to remove old mongo upstart service %q: %v", old.Name, err)
+                        return err
+                }
+        }
+        return nil
+}
+
+func makeServiceName(version int) string {
+        return fmt.Sprintf("juju-db-v%d", version)
+}
+
+// mongoScriptVersion keeps track of changes to the mongo upstart script.
+// Update this version when you update the script that gets installed from
+// MongoUpstartService.
+const mongoScriptVersion = 2
+
+// MongoUpstartService returns the upstart config for the mongo state service.
+//
+// This method assumes there is a server.pem keyfile in dataDir.
+func MongoUpstartService(name, dataDir string, port int) (*upstart.Conf, error) {
+
+        keyFile := path.Join(dataDir, "server.pem")
+        svc := upstart.NewService(name)
+
+        dbDir := path.Join(dataDir, "db")
+
+        mongodpath, err := MongodPath()
+        if err != nil {
+                return nil, err
+        }
+
+        conf := &upstart.Conf{
+                Service: *svc,
+                Desc:    "juju state database",
+                Limit: map[string]string{
+                        "nofile": fmt.Sprintf("%d %d", maxFiles, maxFiles),
+                        "nproc":  fmt.Sprintf("%d %d", maxProcs, maxProcs),
+                },
+                Cmd: mongodpath +
+                        " --auth" +
+                        " --dbpath=" + dbDir +
+                        " --sslOnNormalPorts" +
+                        " --sslPEMKeyFile " + utils.ShQuote(keyFile) +
+                        " --sslPEMKeyPassword ignored" +
+                        " --bind_ip 0.0.0.0" +
+                        " --port " + fmt.Sprint(port) +
+                        " --noprealloc" +
+                        " --syslog" +
+                        " --smallfiles",
+                // TODO(Nate): uncomment when we commit HA stuff
+                // +
+                //      " --replSet juju",
+        }
+        return conf, nil
+}