Add fingerprint manager to manage fingerprinting node #3807

chelseakomlo · 2018-01-29T12:52:58Z

In the future, the fingerprint manager will later also be responsible for updating the node status of a healthy/unhealthy driver.

Considerations:

Should the fingerprint manager be responsible for updating the Node or should that stay in the client?

preetapan · 2018-02-05T14:33:50Z

client/fingerprint_manager.go

+
+// setupDrivers is used to fingerprint the node to see if these attributes are
+// supported
+func (fm *FingerprintManager) SetupFingerprints(fingerprints []string) error {


Better name suggestion - SetupFingerPrinters ?

Yep, although I think it should technically be SetupFingerprinters. Good idea.

preetapan · 2018-02-05T15:04:50Z

client/fingerprint_manager.go

+type FingerprintManager struct {
+	getConfig func() *config.Config
+	node      *structs.Node
+	client    *Client


Instead of giving this access to the whole client struct, consider using a func type to encapsulate what this does with the client. Something like

type FingerPrintResponseUpdater func(resp *structs.FingerPrintResponse) // in client.go when you initialize the FingerPrintManager.. responseUpdaterFunc := func() { c.updateNodeFromFingerprint(&response) } fingerprintManager := &FingerprintManager{ getConfig: func() *config.Config { c.configLock.Lock() defer c.configLock.Unlock() return c.config }, node: c.config.Node, responseUpdater: responseUpdaterFunc, shutDownCh:c.shutDownch, logger: c.logger, }

Doing it this way lets you tighten down exactly what FingerprintManager has access to - it shouldn't need to know about the client or need the whole client struct, instead, it calls a callback function that's passed into it when fingerprint responses are available.

Also see how AllocStateUpdater works for an example of this pattern.

Sure, this was something I was considering, but at the time it wasn't clear how much of the client the fingerprint manager needed access to. Adding the response updater and a shutdown channel seem still low overhead, so will change that. Thanks!

preetapan · 2018-02-05T15:06:10Z

client/fingerprint_manager.go

+				continue
+			}
+
+		case <-fm.client.shutdownCh:


ShutdownCh can be another member variable passed in the constructor.

preetapan · 2018-02-05T15:06:31Z

client/fingerprint_manager.go

+}
+
+// fingerprint does an initial fingerprint of the client. If the fingerprinter
+// is meant to be run continuously, a process is launched ro perform this


launched to

preetapan · 2018-02-05T15:07:40Z

client/fingerprint_manager.go

+	return response.Detected, nil
+}
+
+// setupDrivers is used to fingerprint the node to see if these attributes are


update this comment

preetapan · 2018-02-05T15:16:56Z

client/fingerprint_manager.go

+
+		d, err := driver.NewDriver(name, driverCtx)
+		if err != nil {
+			return err


Question about error handling during loop iteration - if some drivers worked and one returned an error in line 49, this returns immediatly. It could have already started periodic fingerprinting some drivers before it failed and returned. Is that desirable?

This should exit fast if there is an error during setting up the client. Otherwise, it should gracefully handle errors during periodic fingerprinting.

preetapan · 2018-02-05T15:23:44Z

client/fingerprint_manager.go

+		}
+	}
+
+	fm.logger.Printf("[DEBUG] fingerprint_manager: applied fingerprints %v", appliedFingerprints)


shouldn;t this be applied fingerprinters in the log message?

The type is called "fingerprints" - I'm ok with either in the log message, but I don't think we should do a full rename of the type.

I think the log message should be accurate - it was a source of confusion in a previous review too. Would be fine not renaming the type since that's not visible to users.

dadgar · 2018-02-05T21:54:32Z

CHANGELOG.md

@@ -11,6 +11,7 @@ IMPROVEMENTS:
 * cli: Use ISO_8601 time format for cli output
   [[GH-3814](https://github.com/hashicorp/nomad/pull/3814)]
 * client: Allow '.' in environment variable names [[GH-3760](https://github.com/hashicorp/nomad/issues/3760)]
+ * client: Add a fingerprint manager to abstract node fingerprinting [[GH-3807](https://github.com/hashicorp/nomad/pull/3807)]


Usually internal changes don't make it to the changelog

dadgar · 2018-02-05T21:55:25Z

client/client.go

@@ -230,13 +230,25 @@ func NewClient(cfg *config.Config, consulCatalog consul.CatalogAPI, consulServic
 		return nil, fmt.Errorf("node setup failed: %v", err)
 	}

+	fingerprintManager := &FingerprintManager{
+		getConfig: func() *config.Config {


getConfig: c.GetConfig() and just add locking there?

dadgar · 2018-02-05T22:08:06Z

client/fingerprint_manager.go

+
+	// updateNode is a callback to the client to update the state of its
+	// associated node
+	updateNode func(*cstructs.FingerprintResponse)


Should this maybe return the updated node back? All the fingerprinters will be operating on stale nodes right now

Hm, I was under the impression that the fingerprint manager just holds a pointer to the original node, which is only updated (not replaced). If this isn't true (or not the pattern that we want) then it can re-assign the node based on what this function returns.

dadgar · 2018-02-05T22:08:25Z

client/fingerprint_manager.go

+
+		detected, err := fm.fingerprint(name, d)
+		if err != nil {
+			fm.logger.Printf("[DEBUG] fingerprint_manager: fingerprinting for %v failed: %+v", name, err)


client.fingerprint_manager

dadgar · 2018-02-05T22:09:55Z

client/client.go

 	// Fingerprint the node
-	if err := c.fingerprint(); err != nil {
+	if err := c.fingerprint(fingerprintManager); err != nil {


I would move both of these into the fingerprint manager. Create a Run() error method that does the initial setup and then calls run.

dadgar · 2018-02-05T22:10:04Z

client/client.go

@@ -230,13 +230,25 @@ func NewClient(cfg *config.Config, consulCatalog consul.CatalogAPI, consulServic
 		return nil, fmt.Errorf("node setup failed: %v", err)
 	}

+	fingerprintManager := &FingerprintManager{


Can we use a constructor

dadgar · 2018-02-12T21:37:17Z

client/client_test.go

@@ -208,17 +209,19 @@ func TestClient_RPC_Passthrough(t *testing.T) {

 func TestClient_Fingerprint(t *testing.T) {
 	t.Parallel()
+	require := require.New(t)
+	if _, ok := driver.BuiltinDrivers["mock_driver"]; !ok {
+		t.Skip(`test requires mock_driver; run with "-tags nomad_test"`)


Can you add this to a driver/testing.go helper and replace existing uses of this with the shared helper.

dadgar · 2018-02-12T21:38:32Z

client/fingerprint_manager.go

+	}
+
+	if node := fm.updateNode(&response); node != nil {
+		fm.node = node


This should be locked. There are concurrent writers and accessors

dadgar · 2018-02-12T21:39:43Z

client/fingerprint_manager.go

+	return nil
+}
+
+func (fp *FingerprintManager) Run() error {


Comment on the method

lock concurrent accesses to node comment exported method

github-actions · 2023-03-12T02:18:06Z

I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.

chelseakomlo force-pushed the f-client-add-fingerprint-manager branch 3 times, most recently from 02df0f1 to 9cf572a Compare February 2, 2018 17:28

preetapan suggested changes Feb 5, 2018

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dadgar requested changes Feb 5, 2018

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chelseakomlo force-pushed the f-client-add-fingerprint-manager branch from e0c5e0a to bc8150a Compare February 7, 2018 22:39

chelseakomlo added 3 commits February 7, 2018 18:10

add fingerprint manager

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remove dependency on client for fingerprint manager

ca3b28c

code review feedback

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chelseakomlo force-pushed the f-client-add-fingerprint-manager branch from bc8150a to 1a26950 Compare February 7, 2018 23:11

chelseakomlo mentioned this pull request Feb 8, 2018

Client driver health checks for Docker #3856

Merged

preetapan approved these changes Feb 12, 2018

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dadgar approved these changes Feb 12, 2018

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extract test helper

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lock concurrent accesses to node comment exported method

chelseakomlo merged commit 6820c96 into master Feb 13, 2018

chelseakomlo deleted the f-client-add-fingerprint-manager branch February 13, 2018 16:22

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Add fingerprint manager to manage fingerprinting node #3807

Add fingerprint manager to manage fingerprinting node #3807

chelseakomlo commented Jan 29, 2018 •

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Add fingerprint manager to manage fingerprinting node #3807

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chelseakomlo commented Jan 29, 2018 • edited Loading

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chelseakomlo commented Jan 29, 2018 •

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