fix disk write scheduling to only run when needed

pkg/main/https_server_route.go

@@ -79,10 +79,21 @@ func (app *app) postKeyAndCert(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// schedule file update (which will cancel any other pending job, since it isn't needed when
-	// new payload is received from server via this handler) -- if files on disc don't actually
-	// need an update, logic will deal with it later in the job (and just not write files)
-	app.scheduleJobWriteCertsMemoryToDisk()
+	// run go routine to update files; first run update immediately to check for missing files
+	// which also returns if the disk needs an update. Then schedule job if the disk needs an
+	// update. If no disk update is needed, ensure cancel any old pending job.
+	go func() {
+		// write files to disk now if file(s) are missing
+		diskNeedsUpdate := app.updateCertFilesAndRestartContainers(true)
+
+		// schedule job if disk still needs an update
+		if diskNeedsUpdate {
+			app.scheduleJobWriteCertsMemoryToDisk()
+		} else if app.pendingJobCancel != nil {
+			// cancel any old pending job if no update needed and there is a job to cancel
+			app.pendingJobCancel()
+		}
+	}()
 
 	w.WriteHeader(http.StatusOK)
 }

pkg/main/update_schedule.go

@@ -85,11 +85,9 @@ func (app *app) nextFileUpdateWindowStart() time.Time {
 	return nextWindow.Add(time.Duration(addDays) * 24 * time.Hour)
 }
 
-// scheduleJobWriteCertsMemoryToDisk schedules a job to write the new cert files
-// using data already loaded into the client cert. This is used when the client
-// launched with valid key/cert files but newer ones were found on the lego
-// server. If the current time is within a permitted write time, the job runs
-// immediately
+// scheduleJobWriteCertsMemoryToDisk schedules a job to write the lego client's
+// key/cert pem from memory to disk (and generate any additional files on disk that
+// are configured)
 func (app *app) scheduleJobWriteCertsMemoryToDisk() {
 	go func() {
 		// cancel any old job
@@ -147,9 +145,10 @@ func (app *app) scheduleJobWriteCertsMemoryToDisk() {
 	}()
 }
 
-// scheduleJobFetchCertsAndWriteToDisk fetches the latest key/cert from LeGo
-// updates the client's key/cert. It repeats this task every 15 minutes until
-// it succeeds. Then it schedules a job to write the new files to disk.
+// scheduleJobFetchCertsAndWriteToDisk fetches the latest key/cert from LeGo server
+// and updates the client's key/cert. It repeats this task every 15 minutes until
+// it succeeds. Then it schedules a job to write lego client's key/cert pem from
+// memory to disk (along with any other files that are configured).
 func (app *app) scheduleJobFetchCertsAndWriteToDisk() {
 	go func() {
 		// cancel any old job