Wipe configchecksums also on assignment changes (#353)

If an assignemnt is changed to switch a backend from
one configuration to another, we would still send configuration requests
using the old checksum.
The server will respond with `NotModified` and we don't try to restart
the backend.

Instead of also resetting the checksum when we update the assignment
store, simply wipe the entire checksum map if either the assignment
or the backends have changed.

Fixes #352

assignments/assignment.go

@@ -17,6 +17,7 @@ package assignments
 
 import (
 	"github.com/Graylog2/collector-sidecar/common"
+	"reflect"
 )
 
 var (
@@ -59,7 +60,11 @@ func (as *assignmentStore) AssignedBackendIds() []string {
 	return result
 }
 
-func (as *assignmentStore) Update(assignments []ConfigurationAssignment) {
+func (as *assignmentStore) Update(assignments []ConfigurationAssignment) bool {
+	beforeUpdate := make(map[string]string)
+	for k, v := range as.assignments {
+		beforeUpdate[k] = v
+	}
 	if len(assignments) != 0 {
 		var activeIds []string
 		for _, assignment := range assignments {
@@ -70,6 +75,7 @@ func (as *assignmentStore) Update(assignments []ConfigurationAssignment) {
 	} else {
 		Store.cleanup([]string{})
 	}
+	return !reflect.DeepEqual(beforeUpdate, as.assignments)
 }
 
 func (as *assignmentStore) cleanup(validBackendIds []string) {

daemon/daemon.go

@@ -111,7 +111,7 @@ func (dc *DaemonConfig) GetRunnerByBackendId(id string) Runner {
 	return nil
 }
 
-func (dc *DaemonConfig) SyncWithAssignments(configChecksums map[string]string, context *context.Ctx) {
+func (dc *DaemonConfig) SyncWithAssignments(context *context.Ctx) {
 	if dc.Runner == nil {
 		return
 	}
@@ -125,7 +125,6 @@ func (dc *DaemonConfig) SyncWithAssignments(configChecksums map[string]string, c
 			log.Infof("[%s] Updating process configuration", runner.Name())
 			runnerServiceType := runnerBackend.ServiceType
 			runner.SetBackend(*backend)
-			configChecksums[backend.Id] = ""
 			if backend.ServiceType != runnerServiceType {
 				log.Infof("Changing process runner (%s -> %s) for: %s",
 					runnerServiceType, backend.ServiceType, backend.Name)
@@ -146,7 +145,6 @@ func (dc *DaemonConfig) SyncWithAssignments(configChecksums map[string]string, c
 		if backend == nil || assignments.Store.GetAll()[backend.Id] == "" {
 			log.Info("Removing process runner: " + backend.Name)
 			dc.DeleteRunner(id)
-			configChecksums[backend.Id] = ""
 		}
 	}
 	assignedBackends := []*backends.Backend{}

services/periodicals.go

@@ -45,23 +45,28 @@ func StartPeriodicals(context *context.Ctx) {
 		for {
 			time.Sleep(time.Duration(context.UserConfig.UpdateInterval) * time.Second)
 
-			// registration response contains configuration assignments
-			response, err := updateCollectorRegistration(httpClient, assignmentChecksum, context)
+			// registration regResponse contains configuration assignments
+			regResponse, err := updateCollectorRegistration(httpClient, assignmentChecksum, context)
 			if err != nil {
 				continue
 			}
-			assignmentChecksum = response.Checksum
+			assignmentChecksum = regResponse.Checksum
 			// backend list is needed before configuration assignments are updated
 			backendResponse, err := fetchBackendList(httpClient, backendChecksum, context)
 			if err != nil {
 				continue
 			}
 			backendChecksum = backendResponse.Checksum
 
-			if !response.NotModified || !backendResponse.NotModified {
-				assignments.Store.Update(response.Assignments)
+			if !regResponse.NotModified || !backendResponse.NotModified {
+				modified := assignments.Store.Update(regResponse.Assignments)
+				// regResponse.NotModified is always false, because graylog does not implement caching yet.
+				// Thus we need to double check.
+				if modified || !backendResponse.NotModified {
+					configChecksums = make(map[string]string)
+				}
 				// create process instances
-				daemon.Daemon.SyncWithAssignments(configChecksums, context)
+				daemon.Daemon.SyncWithAssignments(context)
 				// test for new or updated configurations and start the corresponding collector
 				if assignments.Store.Len() == 0 {
 					if logOnce {