Merge lp:~natefinch/juju-core/034-juju-mongo into lp:~go-bot/juju-core/trunk

[Nate Finch]

use juju-mongod if it exists

use juju-mongod if it exists

https://codereview.appspot.com/66230043/

[Nate Finch (natefinch)]

Reviewers: mp+207320_code.launchpad.net,

Message:
Please take a look.

Description:
use juju-mongod if it exists

https://code.launchpad.net/~natefinch/juju-core/034-juju-mongo/+merge/207320

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/66230043/

Affected files (+162, -26 lines):
   A [revision details]
   M provider/local/prereqs.go
   M provider/local/prereqs_test.go
   A upstart/export_test.go
   M upstart/service.go
   M upstart/upstart_test.go

[William Reade (fwereade)]

I think this looks good (modulo needing to actually install
juju-mongodb, bu I understand that's a distinct CL), but I'd like
another pair of eyes too please.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go
File provider/local/prereqs.go (left):

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go#oldcode90
provider/local/prereqs.go:90: // TODO(axw) verify version/SSL
capabilities
Remind me: what's the latest story on SSL support? did we finally get it
compiled into all the mongos we might use?

https://codereview.appspot.com/66230043/diff/1/upstart/service.go
File upstart/service.go (right):

https://codereview.appspot.com/66230043/diff/1/upstart/service.go#newcode31
upstart/service.go:31: return "mongod"
I has a nervous about changes. Does life get any better if we use the
result of `which mongod`?

https://codereview.appspot.com/66230043/diff/1/upstart/service.go#newcode32
upstart/service.go:32: }
Also, I remain twitchy about mixing the juju-specific bits into the
supposedly-generic upstart package. Is this a simple enough CL that we
could move them out?

https://codereview.appspot.com/66230043/

[Nate Finch (natefinch)]

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go
File provider/local/prereqs.go (left):

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go#oldcode90
provider/local/prereqs.go:90: // TODO(axw) verify version/SSL
capabilities
On 2014/02/20 10:03:15, fwereade wrote:
> Remind me: what's the latest story on SSL support? did we finally get
it
> compiled into all the mongos we might use?

Good question, I don't know.

https://codereview.appspot.com/66230043/diff/1/upstart/service.go
File upstart/service.go (right):

https://codereview.appspot.com/66230043/diff/1/upstart/service.go#newcode31
upstart/service.go:31: return "mongod"
On 2014/02/20 10:03:15, fwereade wrote:
> I has a nervous about changes. Does life get any better if we use the
result of
> `which mongod`?

That's what I wrote first, but the problem is, many tests overwrite
$PATH in order to isolate themselves, and then this code can't find
"which" to run it. I suppose I could hardcode the location of "which"
to /usr/bin/which ... but I figured the only diffference between running
the results of which mongod and just running "mongod" is that the former
just hardcodes whatever mongod existed at the time, and the latter uses
whatever is first in the path when upstart runs. I don't know which is
worse.

https://codereview.appspot.com/66230043/diff/1/upstart/service.go#newcode32
upstart/service.go:32: }
On 2014/02/20 10:03:15, fwereade wrote:
> Also, I remain twitchy about mixing the juju-specific bits into the
> supposedly-generic upstart package. Is this a simple enough CL that we
could
> move them out?

Absolutely. I actually put them here on purpose so someone would
complain and tell me where a better place would be. Keep in mind this
method is called both by upstart and the local provider.

https://codereview.appspot.com/66230043/

[Dimiter Naydenov (dimitern)]

LGTM with a few suggestions below.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go
File provider/local/prereqs.go (right):

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go#newcode94
provider/local/prereqs.go:94: " Juju requires version %v or greater.",
s/" Juju/"Juju/ - no need for the extra space in here where there's
another in the previous line.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go#newcode113
provider/local/prereqs.go:113: return version.Zero, errors.New("Couldn't
parse version")
s/Couldn't parse version/Could not parse mongod version/ - slightly
better and clearer I think.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs_test.go
File provider/local/prereqs_test.go (right):

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs_test.go#newcode129
provider/local/prereqs_test.go:129: c.Assert(err, gc.NotNil)
Check the actual error message?

https://codereview.appspot.com/66230043/diff/1/upstart/export_test.go
File upstart/export_test.go (right):

https://codereview.appspot.com/66230043/diff/1/upstart/export_test.go#newcode3
upstart/export_test.go:3: package upstart
Blank line before the package line. Also no need for 2013 in the
copyright.

https://codereview.appspot.com/66230043/diff/1/upstart/service.go
File upstart/service.go (right):

https://codereview.appspot.com/66230043/diff/1/upstart/service.go#newcode22
upstart/service.go:22: // MongoPath returns the executable path to be
used to run mongod on this machine.
// MongodPath ... (to match the func name). Also s/the executable//.
Actually, I'd prefer if you called this MongoDPath, so it matches the
SetMongoDPath from export_test.

https://codereview.appspot.com/66230043/diff/1/upstart/upstart_test.go
File upstart/upstart_test.go (right):

https://codereview.appspot.com/66230043/diff/1/upstart/upstart_test.go#newcode260
upstart/upstart_test.go:260: defer os.Remove(d)
os.RemoveAll(d) instead?

https://codereview.appspot.com/66230043/

[Nate Finch (natefinch)]

Please take a look.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go
File provider/local/prereqs.go (right):

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go#newcode94
provider/local/prereqs.go:94: " Juju requires version %v or greater.",
On 2014/02/20 16:41:56, dimitern wrote:
> s/" Juju/"Juju/ - no need for the extra space in here where there's
another in
> the previous line.

Done.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs.go#newcode113
provider/local/prereqs.go:113: return version.Zero, errors.New("Couldn't
parse version")
On 2014/02/20 16:41:56, dimitern wrote:
> s/Couldn't parse version/Could not parse mongod version/ - slightly
better and
> clearer I think.

Done.

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs_test.go
File provider/local/prereqs_test.go (right):

https://codereview.appspot.com/66230043/diff/1/provider/local/prereqs_test.go#newcode129
provider/local/prereqs_test.go:129: c.Assert(err, gc.NotNil)
On 2014/02/20 16:41:56, dimitern wrote:
> Check the actual error message?

Done.

https://codereview.appspot.com/66230043/diff/1/upstart/service.go
File upstart/service.go (right):

https://codereview.appspot.com/66230043/diff/1/upstart/service.go#newcode22
upstart/service.go:22: // MongoPath returns the executable path to be
used to run mongod on this machine.
On 2014/02/20 16:41:56, dimitern wrote:
> // MongodPath ... (to match the func name). Also s/the executable//.
> Actually, I'd prefer if you called this MongoDPath, so it matches the
> SetMongoDPath from export_test.

I removed the SetMongoDPath function since I needed to be able to set it
from outside the package too (for local provider tests)..... and I think
the capital d was a mistake anyway. The word should be all lowercase,
except for the first letter to make it public.

https://codereview.appspot.com/66230043/

[Go Bot (go-bot)]

The attempt to merge lp:~natefinch/juju-core/034-juju-mongo into lp:juju-core failed. Below is the output from the failed tests.

ok launchpad.net/juju-core 0.020s
ok launchpad.net/juju-core/agent 2.953s
ok launchpad.net/juju-core/agent/tools 0.446s
ok launchpad.net/juju-core/bzr 16.763s
ok launchpad.net/juju-core/cert 3.350s
ok launchpad.net/juju-core/charm 1.146s
? launchpad.net/juju-core/charm/hooks [no test files]
? launchpad.net/juju-core/charm/testing [no test files]
ok launchpad.net/juju-core/cloudinit 0.049s
ok launchpad.net/juju-core/cloudinit/sshinit 1.399s
ok launchpad.net/juju-core/cmd 0.280s
ok launchpad.net/juju-core/cmd/charm-admin 0.959s
? launchpad.net/juju-core/cmd/charmd [no test files]
? launchpad.net/juju-core/cmd/charmload [no test files]
ok launchpad.net/juju-core/cmd/juju 398.349s
[jujuc whatever]
[remote]
[/path/to/remote]
[remote --help]
[unknown]
[remote --error borken]
[remote --unknown]
[remote unwanted]

----------------------------------------------------------------------
FAIL: unit_test.go:240: UnitSuite.TestOpenStateFails

[LOG] 52.64466 DEBUG juju.environs.configstore Making /tmp/gocheck-1598098976185383115/6/home/ubuntu/.juju/environments
[LOG] 52.75078 DEBUG juju.environs.tools reading v1.* tools
[LOG] 52.75083 INFO juju environs/testing: uploading FAKE tools 1.17.3-precise-amd64
[LOG] 52.75176 DEBUG juju.environs.tools no architecture specified when finding tools, looking for any
[LOG] 52.75177 DEBUG juju.environs.tools no series specified when finding tools, looking for any
[LOG] 52.75183 DEBUG juju.environs.simplestreams fetchData failed for "tools/streams/v1/index.sjson": file "tools/streams/v1/index.sjson" not found not found
[LOG] 52.75184 DEBUG juju.environs.simplestreams cannot load index "streams/v1/index.sjson": invalid URL "tools/streams/v1/index.sjson" not found
[LOG] 52.75188 DEBUG juju.environs.simplestreams fetchData failed for "tools/streams/v1/index.json": file "tools/streams/v1/index.json" not found not found
[LOG] 52.75189 DEBUG juju.environs.simplestreams cannot load index "streams/v1/index.json": invalid URL "tools/streams/v1/index.json" not found
[LOG] 52.75213 INFO juju.environs.tools Writing tools/streams/v1/index.json
[LOG] 52.75219 INFO juju.environs.tools Writing tools/streams/v1/com.ubuntu.juju:released:tools.json
[LOG] 52.75224 INFO juju.environs.bootstrap bootstrapping environment "dummyenv"
[LOG] 52.75227 DEBUG juju.environs.bootstrap looking for bootstrap tools: series="precise", arch=<nil>, version=1.17.3
[LOG] 52.75228 INFO juju.environs.tools reading tools with major.minor version 1.17
[LOG] 52.75229 INFO juju.environs.tools filtering tools by version: 1.17.3
[LOG] 52.75230 INFO juju.environs.tools filtering tools by series: precise
[LOG] 52.75232 DEBUG juju.environs.tools no architecture specified when finding tools, looking for any
[LOG] 52.75235 DEBUG juju.environs.simplestreams fetchData failed for "tools/streams/v1/index.sjson": file "tools/streams/v1/index.sjson" not found not found
[LOG] 52.75237 DEBUG juju.environs.simplestreams cannot load index "streams/v1/index.sjson": invalid URL "tools/streams/v1/index.sjson" not found
[LOG] ...

=== modified file 'environs/cloudinit/cloudinit_test.go'
--- environs/cloudinit/cloudinit_test.go	2014-02-20 15:03:08 +0000
+++ environs/cloudinit/cloudinit_test.go	2014-02-21 17:13:58 +0000
@@ -25,6 +25,7 @@
 	jc "launchpad.net/juju-core/testing/checkers"
 	"launchpad.net/juju-core/testing/testbase"
 	"launchpad.net/juju-core/tools"
+	"launchpad.net/juju-core/upstart"
 	"launchpad.net/juju-core/version"
 )
 
@@ -56,6 +57,9 @@
 	return cfg
 }
 
+// mongodPath is the path where we should expect mongod in the environment.
+var mongodPath = upstart.MongodPath()
+
 // Each test gives a cloudinit config - we check the
 // output to see if it looks correct.
 var cloudinitTests = []cloudinitTest{
@@ -132,7 +136,7 @@
 dd bs=1M count=1 if=/dev/zero of=/var/lib/juju/db/journal/prealloc\.1
 dd bs=1M count=1 if=/dev/zero of=/var/lib/juju/db/journal/prealloc\.2
 echo 'Starting MongoDB server \(juju-db\)'.*
-cat >> /etc/init/juju-db\.conf << 'EOF'\\ndescription "juju state database"\\nauthor "Juju Team <juju@lists\.ubuntu\.com>"\\nstart on runlevel \[2345\]\\nstop on runlevel \[!2345\]\\nrespawn\\nnormal exit 0\\n\\nlimit nofile 65000 65000\\nlimit nproc 20000 20000\\n\\nexec /usr/bin/mongod --auth --dbpath=/var/lib/juju/db --sslOnNormalPorts --sslPEMKeyFile '/var/lib/juju/server\.pem' --sslPEMKeyPassword ignored --bind_ip 0\.0\.0\.0 --port 37017 --noprealloc --syslog --smallfiles\\nEOF\\n
+cat >> /etc/init/juju-db\.conf << 'EOF'\\ndescription "juju state database"\\nauthor "Juju Team <juju@lists\.ubuntu\.com>"\\nstart on runlevel \[2345\]\\nstop on runlevel \[!2345\]\\nrespawn\\nnormal exit 0\\n\\nlimit nofile 65000 65000\\nlimit nproc 20000 20000\\n\\nexec ` + mongodPath + ` --auth --dbpath=/var/lib/juju/db --sslOnNormalPorts --sslPEMKeyFile '/var/lib/juju/server\.pem' --sslPEMKeyPassword ignored --bind_ip 0\.0\.0\.0 --port 37017 --noprealloc --syslog --smallfiles\\nEOF\\n
 start juju-db
 mkdir -p '/var/lib/juju/agents/bootstrap'
 install -m 644 /dev/null '/var/lib/juju/agents/bootstrap/format'

=== modified file 'provider/local/prereqs.go'
--- provider/local/prereqs.go	2013-12-02 21:39:03 +0000
+++ provider/local/prereqs.go	2014-02-21 17:13:58 +0000
@@ -6,12 +6,13 @@
 import (
 	"errors"
 	"fmt"
-	"os"
 	"os/exec"
+	"regexp"
 	"runtime"
 
 	"launchpad.net/juju-core/container/kvm"
 	"launchpad.net/juju-core/instance"
+	"launchpad.net/juju-core/upstart"
 	"launchpad.net/juju-core/utils"
 	"launchpad.net/juju-core/version"
 )
@@ -46,9 +47,8 @@
 const errUnsupportedOS = `Unsupported operating system: %s
 The local provider is currently only available for Linux`
 
-// mongodPath is the path to "mongod", the MongoDB server.
-// This is a variable only to support unit testing.
-var mongodPath = "/usr/bin/mongod"
+// lowestMongoVersion is the lowest version of mongo that juju supports.
+var lowestMongoVersion = version.Number{Major: 2, Minor: 2, Patch: 4}
 
 // lxclsPath is the path to "lxc-ls", an LXC userspace tool
 // we check the presence of to determine whether the
@@ -60,6 +60,9 @@
 // This is a variable only to support unit testing.
 var goos = runtime.GOOS
 
+// This is the regex for processing the results of mongod --verison
+var mongoVerRegex = regexp.MustCompile(`db version v(\d+\.\d+\.\d+)`)
+
 // VerifyPrerequisites verifies the prerequisites of
 // the local machine (machine 0) for running the local
 // provider.
@@ -80,17 +83,38 @@
 }
 
 func verifyMongod() error {
-	if _, err := os.Stat(mongodPath); err != nil {
-		if os.IsNotExist(err) {
-			return wrapMongodNotExist(err)
-		} else {
-			return err
-		}
-	}
-	// TODO(axw) verify version/SSL capabilities
+	path := upstart.MongodPath()
+
+	ver, err := mongodVersion(path)
+	if err != nil {
+		return err
+	}
+	if ver.Compare(lowestMongoVersion) < 0 {
+		return fmt.Errorf("installed version of mongod (%v) is not supported by Juju. "+
+			"Juju requires version %v or greater.",
+			ver,
+			lowestMongoVersion)
+	}
 	return nil
 }
 
+func mongodVersion(path string) (version.Number, error) {
+	data, err := utils.RunCommand(path, "--version")
+	if err != nil {
+		return version.Zero, wrapMongodNotExist(err)
+	}
+
+	return parseVersion(data)
+}
+
+func parseVersion(data string) (version.Number, error) {
+	matches := mongoVerRegex.FindStringSubmatch(data)
+	if len(matches) < 2 {
+		return version.Zero, errors.New("could not parse mongod version")
+	}
+	return version.Parse(matches[1])
+}
+
 func verifyLxc() error {
 	_, err := exec.LookPath(lxclsPath)
 	if err != nil {

=== modified file 'provider/local/prereqs_test.go'
--- provider/local/prereqs_test.go	2013-11-22 01:21:57 +0000
+++ provider/local/prereqs_test.go	2014-02-21 17:13:58 +0000
@@ -4,6 +4,7 @@
 package local
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -12,12 +13,14 @@
 
 	"launchpad.net/juju-core/instance"
 	"launchpad.net/juju-core/testing/testbase"
+	"launchpad.net/juju-core/upstart"
+	"launchpad.net/juju-core/version"
 )
 
 type prereqsSuite struct {
 	testbase.LoggingSuite
-	tmpdir  string
-	oldpath string
+	tmpdir         string
+	testMongodPath string
 }
 
 var _ = gc.Suite(&prereqsSuite{})
@@ -32,25 +35,25 @@
 	// all of the non-prereqs tests to pass
 	// even when mongodb and lxc-ls can't be
 	// found.
-	mongodPath = "/bin/true"
 	lxclsPath = "/bin/true"
 }
 
 func (s *prereqsSuite) SetUpTest(c *gc.C) {
 	s.LoggingSuite.SetUpTest(c)
 	s.tmpdir = c.MkDir()
-	s.oldpath = os.Getenv("PATH")
-	mongodPath = filepath.Join(s.tmpdir, "mongod")
+	s.testMongodPath = filepath.Join(s.tmpdir, "mongod")
 	lxclsPath = filepath.Join(s.tmpdir, "lxc-ls")
-	os.Setenv("PATH", s.tmpdir)
+	s.PatchEnvironment("PATH", s.tmpdir)
+
+	upstart.JujuMongodPath = "/somewhere/that/doesnt/exist"
+
 	os.Setenv("JUJUTEST_LSB_RELEASE_ID", "Ubuntu")
 	err := ioutil.WriteFile(filepath.Join(s.tmpdir, "lsb_release"), []byte(lsbrelease), 0777)
 	c.Assert(err, gc.IsNil)
 }
 
 func (s *prereqsSuite) TearDownTest(c *gc.C) {
-	os.Setenv("PATH", s.oldpath)
-	mongodPath = "/bin/true"
+	s.testMongodPath = ""
 	lxclsPath = "/bin/true"
 	s.LoggingSuite.TearDownTest(c)
 }
@@ -64,6 +67,72 @@
 	c.Assert(err, gc.ErrorMatches, "Unsupported operating system: windows(.|\n)*")
 }
 
+const fakeMongoFmt = `#!/bin/sh
+echo db version v%d.%d.%d
+echo Thu Feb 13 15:53:58.210 git version: b9925db5eac369d77a3a5f5d98a145eaaacd9673
+`
+
+func (s *prereqsSuite) setMongoVersion(major, minor, patch int) {
+	script := fmt.Sprintf(fakeMongoFmt, major, minor, patch)
+	err := ioutil.WriteFile(s.testMongodPath, []byte(script), 0777)
+
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (s *prereqsSuite) TestParseMongoVersion(c *gc.C) {
+	s.setMongoVersion(2, 2, 2)
+
+	ver, err := mongodVersion(s.testMongodPath)
+	c.Assert(err, gc.IsNil)
+	c.Assert(ver, gc.Equals, version.Number{2, 2, 2, 0})
+}
+
+func (s *prereqsSuite) TestVerifyMongod(c *gc.C) {
+	lowver := version.Number{2, 2, 2, 0}
+	s.PatchValue(&lowestMongoVersion, lowver)
+
+	s.setMongoVersion(3, 0, 0)
+	c.Assert(verifyMongod(), gc.IsNil)
+
+	s.setMongoVersion(2, 3, 0)
+	c.Assert(verifyMongod(), gc.IsNil)
+
+	s.setMongoVersion(2, 2, 3)
+	c.Assert(verifyMongod(), gc.IsNil)
+
+	s.setMongoVersion(2, 2, 2)
+	c.Assert(verifyMongod(), gc.IsNil)
+
+	expected := fmt.Sprintf("installed version of mongod .* is not supported by Juju. "+
+		"Juju requires version %v or greater.", lowver)
+
+	s.setMongoVersion(2, 2, 1)
+	c.Assert(verifyMongod(), gc.ErrorMatches, expected)
+
+	s.setMongoVersion(2, 1, 3)
+	c.Assert(verifyMongod(), gc.ErrorMatches, expected)
+
+	s.setMongoVersion(1, 3, 3)
+	c.Assert(verifyMongod(), gc.ErrorMatches, expected)
+}
+
+func (s *prereqsSuite) TestParseVersion(c *gc.C) {
+	data := `
+db version v3.2.1
+Thu Feb 13 15:53:58.210 git version: b9925db5eac369d77a3a5f5d98a145eaaacd9673
+`[1:]
+	v, err := parseVersion(data)
+	c.Assert(err, gc.IsNil)
+	c.Assert(v, gc.Equals, version.Number{3, 2, 1, 0})
+
+	data = "this is total garbage"
+	v, err = parseVersion(data)
+	c.Assert(err, gc.ErrorMatches, "could not parse mongod version")
+	c.Assert(v, gc.Equals, version.Zero)
+}
+
 func (s *prereqsSuite) TestMongoPrereq(c *gc.C) {
 	err := VerifyPrerequisites(instance.LXC)
 	c.Assert(err, gc.ErrorMatches, "(.|\n)*MongoDB server must be installed(.|\n)*")
@@ -74,8 +143,8 @@
 	c.Assert(err, gc.ErrorMatches, "(.|\n)*MongoDB server must be installed(.|\n)*")
 	c.Assert(err, gc.Not(gc.ErrorMatches), "(.|\n)*apt-get install(.|\n)*")
 
-	err = ioutil.WriteFile(mongodPath, nil, 0777)
-	c.Assert(err, gc.IsNil)
+	s.PatchValue(&lowestMongoVersion, version.Number{2, 2, 2, 0})
+	s.setMongoVersion(3, 0, 0)
 	err = ioutil.WriteFile(filepath.Join(s.tmpdir, "lxc-ls"), nil, 0777)
 	c.Assert(err, gc.IsNil)
 	err = VerifyPrerequisites(instance.LXC)
@@ -83,10 +152,10 @@
 }
 
 func (s *prereqsSuite) TestLxcPrereq(c *gc.C) {
-	err := ioutil.WriteFile(mongodPath, nil, 0777)
-	c.Assert(err, gc.IsNil)
+	s.PatchValue(&lowestMongoVersion, version.Number{2, 2, 2, 0})
+	s.setMongoVersion(3, 0, 0)
 
-	err = VerifyPrerequisites(instance.LXC)
+	err := VerifyPrerequisites(instance.LXC)
 	c.Assert(err, gc.ErrorMatches, "(.|\n)*Linux Containers \\(LXC\\) userspace tools must be\ninstalled(.|\n)*")
 	c.Assert(err, gc.ErrorMatches, "(.|\n)*apt-get install lxc(.|\n)*")
 

=== modified file 'upstart/service.go'
--- upstart/service.go	2013-11-19 08:53:40 +0000
+++ upstart/service.go	2014-02-21 17:13:58 +0000
@@ -5,6 +5,7 @@
 
 import (
 	"fmt"
+	"os"
 	"path"
 
 	"launchpad.net/juju-core/utils"
@@ -15,6 +16,22 @@
 	maxAgentFiles = 20000
 )
 
+// JujuMongodPath is the path of the mongod that is bundled specifically for juju.
+// This value is public only for testing purposes, please do not change.
+var JujuMongodPath = "/usr/lib/juju/bin/mongod"
+
+// 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 {
+	if _, err := os.Stat(JujuMongodPath); err == nil {
+		return JujuMongodPath
+	}
+
+	// just use whatever is in the path
+	return "mongod"
+}
+
 // MongoUpstartService returns the upstart config for the mongo state service.
 func MongoUpstartService(name, dataDir, dbDir string, port int) *Conf {
 	keyFile := path.Join(dataDir, "server.pem")
@@ -26,7 +43,7 @@
 			"nofile": fmt.Sprintf("%d %d", maxMongoFiles, maxMongoFiles),
 			"nproc":  fmt.Sprintf("%d %d", maxAgentFiles, maxAgentFiles),
 		},
-		Cmd: "/usr/bin/mongod" +
+		Cmd: MongodPath() +
 			" --auth" +
 			" --dbpath=" + dbDir +
 			" --sslOnNormalPorts" +

=== modified file 'upstart/upstart_test.go'
--- upstart/upstart_test.go	2014-02-18 17:08:55 +0000
+++ upstart/upstart_test.go	2014-02-21 17:13:58 +0000
@@ -254,3 +254,23 @@
 	c.Assert(err, gc.IsNil)
 	c.Assert(&conf.Service, jc.Satisfies, (*upstart.Service).Running)
 }
+
+func (s *UpstartSuite) TestJujuMongodPath(c *gc.C) {
+	d := c.MkDir()
+	defer os.RemoveAll(d)
+	mongoPath := filepath.Join(d, "mongod")
+	upstart.JujuMongodPath = mongoPath
+
+	err := ioutil.WriteFile(mongoPath, []byte{}, 0777)
+	c.Assert(err, gc.IsNil)
+
+	obtained := upstart.MongodPath()
+	c.Assert(obtained, gc.Equals, mongoPath)
+}
+
+func (s *UpstartSuite) TestDefaultMongodPath(c *gc.C) {
+	upstart.JujuMongodPath = "/not/going/to/exist/mongod"
+
+	obtained := upstart.MongodPath()
+	c.Assert(obtained, gc.Equals, "mongod")
+}