Implements LRU cache for git repos on disk (#17)

The GitRepoLRUCache struct and associated methods is a Least Recently
Used cache whose main element is the GitRepoFilePath struct (which in
itself represents an on-disk git repository).

This also adds the git "providers" interface which wrap the methods for cloning
and loading up repos from the different implementers.

Signed-off-by: John McBride <[email protected]>

.env.example

@@ -1,11 +1,30 @@
 # This file is useful for doing local development
-# when needing to load the postgres database secrets.
+# when needing to load the postgres database secrets and start a locally running
+# pizza oven service
 
+# Database env vars
 DATABASE_PORT=9999
 DATABASE_HOST=localhost
 DATABASE_USER=opensauced-admin
 DATABASE_PASSWORD={YOUR-SECRET-PASSWORD-HERE}
 DATABASE_DBNAME=pizza
 
-# The port for the Pizza oven server
+# The port for the Pizza oven server to use
 SERVER_PORT=8080
+
+# The git provider to use for the pizza oven service.
+# Must be one of "cache" or "memory" to designate the git provider that will be
+# used to clone and access repos.
+# - The "cache" git provider uses a local cache on disk to clone git repos into.
+#   This uses much less memory than in-memory cloning.
+GIT_PROVIDER=cache
+
+# The settings for the cached git repos.
+# Must be set when "GIT_PROVIDER" is set to "cache"
+# 
+# The root directory where the git repo cache should be stored
+CACHE_DIR=/tmp
+# The minimum amount of free disk in Gb to keep. This ensures that the cache
+# does not completely fill the disk and allows for some buffer before items
+# are evicted from the cache.
+MIN_FREE_DISK_GB=25

README.md

@@ -66,6 +66,8 @@ This will start the go app, connect to your local postgres database
 using your `.env` file or existing environment variables,
 and start accepting requests.
 
+See the `.env.example` file to see what environment variables are expected.
+
 ### Local kubernetes setup
 
 To get a local environment setup with a postgres database without having to start and configure one yourself,

hack/setup.sh

@@ -79,7 +79,7 @@ metadata:
 spec:
   teamId: "opensauced"
   volume:
-    size: 2Gi
+    size: 25Gi
   numberOfInstances: 1
   users:
     # The database owner/admin for the pizza database
@@ -157,8 +157,20 @@ spec:
           value: "pizza"
         - name: SERVER_PORT
           value: "8080"
+        - name: GIT_PROVIDER
+          value: "cache"
+        - name: CACHE_DIR
+          value: "/data/cache"
+        - name: MIN_FREE_DISK_GB
+          value: "25"
         ports:
         - containerPort: 8080
+        volumeMounts:
+          - name: pizza-cache
+            mountPath: /data/cache
+      volumes:
+      - name: pizza-cache
+        emptyDir: {}
 EOF
 
     # The pod may take a second to be able to be waited on via kubectl
@@ -199,9 +211,10 @@ echo "Opening port to postgres operator to apply database migrations"
 echo
 forward_postgres_port &
 
-# Sleep for abit so the postgres database has time to initialize and
+# Wait for the postgres cluster to come and up and be ready to accept requests
 # be ready to accept requests and incoming queries
-sleep 10
+sleep 3
+kubectl wait --for=jsonpath='{.status.PostgresClusterStatus}'=Running postgresqls/opensauced-pizza-postgres-cluster
 
 # apply the migrations to the database
 echo

main.go

@@ -1,20 +1,46 @@
 package main
 
 import (
+	"flag"
 	"log"
 	"os"
+	"strconv"
 
 	"github.com/joho/godotenv"
+	"go.uber.org/zap"
 
 	"github.com/open-sauced/pizza/oven/pkg/database"
+	"github.com/open-sauced/pizza/oven/pkg/providers"
 	"github.com/open-sauced/pizza/oven/pkg/server"
 )
 
 func main() {
+	var logger *zap.Logger
+	var err error
+
+	// Initialize & parse flags
+	debugMode := flag.Bool("debug", false, "run in debug mode")
+	flag.Parse()
+
+	if *debugMode {
+		logger, err = zap.NewDevelopment()
+		if err != nil {
+			log.Fatalf("Could not initiate debug zap logger: %v", err)
+		}
+	} else {
+		logger, err = zap.NewProduction()
+		if err != nil {
+			log.Fatalf("Could not initiate production zap logger: %v", err)
+		}
+	}
+
+	sugarLogger := logger.Sugar()
+	sugarLogger.Infof("initiated zap logger with level: %d", sugarLogger.Level())
+
 	// Load the environment variables from the .env file
-	err := godotenv.Load()
+	err = godotenv.Load()
 	if err != nil {
-		log.Printf("Failed to load the dot env file. Continuing with existing environment: %v", err)
+		sugarLogger.Warnf("Failed to load the dot env file. Continuing with existing environment: %v", err)
 	}
 
 	// Envs for the pizza oven database handler
@@ -27,7 +53,41 @@ func main() {
 	// Env vars for the pizza oven server
 	serverPort := os.Getenv("SERVER_PORT")
 
+	// User specify which git provider to use
+	gitProvider := os.Getenv("GIT_PROVIDER")
+
+	// Initialize the database handler
 	pizzaOven := database.NewPizzaOvenDbHandler(databaseHost, databasePort, databaseUser, databasePwd, databaseDbName)
-	pizzaOvenServer := server.NewPizzaOvenServer(pizzaOven)
+
+	var pizzaGitProvider providers.GitRepoProvider
+	switch gitProvider {
+	case "cache":
+		sugarLogger.Infof("Initiating cache git provider")
+
+		// Env vars for the git provider
+		cacheDir := os.Getenv("CACHE_DIR")
+		minFreeDisk := os.Getenv("MIN_FREE_DISK_GB")
+
+		// Validates the provided minimum free disk int is parsable as a uint64
+		//
+		// TODO - should dynamically check file system bit size after compilation.
+		// 64 bit wide words should be fine for almost all use cases for now.
+		minFreeDiskUint64, err := strconv.ParseUint(minFreeDisk, 10, 64)
+		if err != nil {
+			sugarLogger.Fatalf(": %s", err.Error())
+		}
+
+		pizzaGitProvider, err = providers.NewLRUCacheGitRepoProvider(cacheDir, minFreeDiskUint64, sugarLogger)
+		if err != nil {
+			sugarLogger.Fatalf("Could not create a cache git provider: %s", err.Error())
+		}
+	case "memory":
+		sugarLogger.Infof("Initiating in-memory git provider")
+		pizzaGitProvider = providers.NewInMemoryGitRepoProvider(sugarLogger)
+	default:
+		sugarLogger.Fatal("must specify the GIT_PROVIDER env variable (i.e. cache, memory)")
+	}
+
+	pizzaOvenServer := server.NewPizzaOvenServer(pizzaOven, pizzaGitProvider, sugarLogger)
 	pizzaOvenServer.Run(serverPort)
 }

pkg/cache/gitrepofilepath.go

@@ -0,0 +1,63 @@
+package cache
+
+import (
+	"sync"
+
+	"github.com/go-git/go-git/v5"
+)
+
+// GitRepoFilePath is a key / value pair with a locking mutex which represents
+// the key to a git repository (typically the remote URL) and its file path on disk.
+// This is used as the primary element in GitRepoLRUCache.
+//
+// When processing and operations are completed for an individual GitRepoFilePath,
+// always call "Done" to ensure no deadlocks occur on individual elements within
+// a given GItRepoLRUCache.
+// Example: "repo.Done()"
+type GitRepoFilePath struct {
+	// A locking mutex is used to ensure that on-disk git repos are not
+	// modified during processing.
+	// Locking is done manually via "element.lock.Lock()" within the cache package.
+	// Once operations are completed, in order to free up the resource, the "Done()"
+	// method should be called.
+	lock sync.Mutex
+
+	// The key for the GitRepoFilePath key/value pair, generally, is the
+	// remote URL for the git repository
+	key string
+
+	// path is the value in the GitRepoFilePath key/value and denotes the
+	// filepath on-disk to the cloned git repository
+	path string
+}
+
+// OpenAndFetch opens a git repository on-disk and fetches the latest changes.
+// If the git.NoErrAlreadyUpToDate error is produced, this function does not
+// return an error but, instead, continues and returns the repo.
+func (g *GitRepoFilePath) OpenAndFetch() (*git.Repository, error) {
+	repo, err := git.PlainOpen(g.path)
+	if err != nil {
+		return nil, err
+	}
+
+	// Get the worktree for the repository
+	w, err := repo.Worktree()
+	if err != nil {
+		return nil, err
+	}
+
+	// Pull the latest changes from the origin remote and merge into the current branch
+	err = w.Pull(&git.PullOptions{})
+	if err != nil && err != git.NoErrAlreadyUpToDate {
+		return nil, err
+	}
+
+	return repo, nil
+}
+
+// Done is a thin wrapper for unlocking the GitRepoFilePath's mutex.
+// This should ALWAYS be called when operations and processing for this
+// individual on-disk repo are completed in order to prevent a deadlock.
+func (g *GitRepoFilePath) Done() {
+	g.lock.Unlock()
+}

pkg/cache/gitrepofilepath_test.go

@@ -0,0 +1,49 @@
+package cache
+
+import "testing"
+
+func TestOpenAndFetch(t *testing.T) {
+	tests := []struct {
+		name     string
+		cacheDir string
+		repos    []string
+	}{
+		{
+			name:     "Puts repos into cache in sequential order",
+			cacheDir: t.TempDir(),
+			repos: []string{
+				"https://github.com/open-sauced/pizza",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create a new LRU cache
+			c, err := NewGitRepoLRUCache(tt.cacheDir, 100)
+			if err != nil {
+				t.Fatalf("unexpected err: %s", err.Error())
+			}
+
+			// Populate the cache with the repos
+			for _, repo := range tt.repos {
+				repoFp, err := c.Put(repo)
+				if err != nil {
+					t.Fatalf("unexpected err putting to cache: %s", err.Error())
+				}
+				repoFp.Done()
+			}
+
+			// Get the first element in the cache
+			repoFp := c.dll.Front().Value.(*GitRepoFilePath)
+			repoFp.lock.Lock()
+			defer repoFp.Done()
+
+			// Open and fetch the repo ensuring a non-nil git repo is returned
+			openedRepo, err := repoFp.OpenAndFetch()
+			if openedRepo == nil || err != nil {
+				t.Fatalf("Opened repo unexpectedly failed to open and/or fetch: %s", err.Error())
+			}
+		})
+	}
+}