├── Dockerfile ├── LICENSE ├── README.md ├── etc ├── litestream.primary.yml └── litestream.replica.yml ├── fly.toml ├── go.mod ├── go.sum ├── main.go └── run.sh /Dockerfile: -------------------------------------------------------------------------------- 1 | # Import Litestream docker image as a stage so we can pull the binary from it. 2 | FROM litestream/litestream:0.4.0-beta.2 AS litestream 3 | 4 | # Build our application in the second stage so we can pull the binary in the last stage. 5 | # Our Go build uses 'static' flags so that we can run in alpine. 6 | FROM golang:1.17 as builder 7 | COPY . /src/litestream-read-replica-example 8 | WORKDIR /src/litestream-read-replica-example 9 | RUN --mount=type=cache,target=/root/.cache/go-build \ 10 | --mount=type=cache,target=/go/pkg \ 11 | go build -ldflags '-s -w -extldflags "-static"' -tags osusergo,netgo,sqlite_omit_load_extension -o /usr/local/bin/litestream-read-replica-example . 12 | 13 | 14 | # This is where our final stage of the Docker build begins. 15 | # We are using alpine to make our image as small as possible. 16 | FROM alpine 17 | 18 | # Set environment variables. 19 | ENV DSN "/data/db" 20 | 21 | EXPOSE 8080 22 | 23 | # These lines copy the binaries from the previous builds. 24 | COPY --from=builder /usr/local/bin/litestream-read-replica-example /usr/local/bin/litestream-read-replica-example 25 | COPY --from=litestream /usr/local/bin/litestream /usr/local/bin/litestream 26 | 27 | # Copy both our primary configuration & replica configuration. 28 | # We will choose which one we use based at runtime. 29 | ADD etc/litestream.primary.yml /etc/litestream.primary.yml 30 | ADD etc/litestream.replica.yml /etc/litestream.replica.yml 31 | ADD run.sh /run.sh 32 | 33 | # We add sqlite so we can create an empty database for our replica to start with. 34 | # Add bash & cURL in case we want to ssh into our image. These are not necessary. 35 | RUN apk add sqlite bash ca-certificates curl 36 | 37 | # Set up directory to hold database. This may be mounted by the host. 38 | RUN mkdir -p /data 39 | 40 | # This script determines the replication mode, restores a back up if necessary, 41 | # and starts Litestream and the application. 42 | CMD /run.sh 43 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | Litestream Read Replica Example 2 | =============================== 3 | 4 | This repository is an example of how to setup and deploy a multi-node SQLite 5 | database using Litestream's live read replication feature. For more information, 6 | please see the [Read Replication Guide](https://litestream.io/guides/read-replica/) 7 | on the Litestream documentation site. 8 | 9 | This example provides a Dockerfile and deployment instructions for [fly.io](https://fly.io), 10 | however, any hosting provider can be used. 11 | 12 | ## Deployment 13 | 14 | ### Docker 15 | 16 | To build the Docker image, run: 17 | 18 | ```sh 19 | docker build -t litestream-read-replica-example . 20 | ``` 21 | 22 | ### Deploy to fly.io 23 | 24 | To deploy to [fly.io](https://fly.io), you'll need to create an application, 25 | volumes, and configure your primary region. 26 | 27 | ```sh 28 | # Application names are unique on fly.io so you'll need to pick one. 29 | export APPNAME=... 30 | 31 | # Create a new application but don't deploy yet. 32 | fly launch --name "$APPNAME" --region ord --no-deploy 33 | 34 | # Create a volume in our primary region first. 35 | fly volumes create --region ord --size 1 data 36 | ``` 37 | 38 | We'll also add `[env]` and `[mounts]` sections to the `fly.toml` file. This 39 | tells our application which region should be the primary and also attaches the 40 | persistent `data` volume to each instance. 41 | 42 | ```toml 43 | [env] 44 | FLY_PRIMARY_REGION = "ord" 45 | 46 | [mounts] 47 | source="data" 48 | destination="/data" 49 | ``` 50 | 51 | Finally, we'll deploy our application: 52 | 53 | ```sh 54 | fly deploy 55 | ``` 56 | 57 | Once we confirm that our primary is successfully running, we'll deploy our 58 | replicas: 59 | 60 | ```sh 61 | # Create volumes for each replica. 62 | fly volumes create --region lhr --size 1 data 63 | fly volumes create --region syd --size 1 data 64 | 65 | # Scale the app so we have one instance for each volume. 66 | fly scale count 3 67 | ``` 68 | 69 | Once you are done with your application, you can tear it down with the following: 70 | 71 | ```sh 72 | fly apps destroy "$APPNAME" 73 | ``` 74 | 75 | ## Usage 76 | 77 | The included application only has two endpoints: 78 | 79 | 1. `POST /` - creates a new record 80 | 2. `GET /` - returns a list of all records 81 | 82 | First, we'll add some records: 83 | 84 | ```sh 85 | curl -X POST https://${APPNAME}.fly.dev/ -d 'foo' 86 | curl -X POST https://${APPNAME}.fly.dev/ -d 'bar' 87 | curl -X POST https://${APPNAME}.fly.dev/ -d 'baz' 88 | ``` 89 | 90 | Then we can retrieve a list of those records: 91 | 92 | ```sh 93 | curl https://${APPNAME}.fly.dev/ 94 | ``` 95 | 96 | This should return the following: 97 | 98 | ``` 99 | Record #1: "foo" 100 | Record #2: "bar" 101 | Record #3: "baz" 102 | ``` 103 | 104 | ### Viewing replica data 105 | 106 | Fly.io automatically routes requests to the nearest instance so we'll need to 107 | log into our instances if we want to verify the replicated data. First, you'll 108 | need to set up access to your private network over Wireguard: 109 | 110 | https://fly.io/docs/reference/private-networking/#private-network-vpn 111 | 112 | Once set up, we can cURL against a specific region's server: 113 | 114 | ```sh 115 | curl lhr.${APPNAME}.internal:8080 116 | ``` 117 | 118 | You can also SSH into the node and verify with the SQLite CLI. Be sure to use 119 | the `-readonly` flag to ensure you do not accidentally alter the database on 120 | the replica. 121 | 122 | ```sh 123 | fly ssh console lhr.${APPNAME}.internal 124 | 125 | sqlite3 -readonly /data/db 126 | 127 | sqlite> SELECT * FROM records; 128 | 1|foo 129 | 2|bar 130 | 3|baz 131 | ``` 132 | 133 | -------------------------------------------------------------------------------- /etc/litestream.primary.yml: -------------------------------------------------------------------------------- 1 | addr: ":9090" 2 | 3 | dbs: 4 | - path: "$DSN" 5 | -------------------------------------------------------------------------------- /etc/litestream.replica.yml: -------------------------------------------------------------------------------- 1 | addr: ":9090" 2 | 3 | dbs: 4 | - path: "$DSN" 5 | upstream: 6 | url: http://${FLY_PRIMARY_REGION}.${FLY_APP_NAME}.internal:9090 7 | -------------------------------------------------------------------------------- /fly.toml: -------------------------------------------------------------------------------- 1 | app = "lrre2" 2 | 3 | kill_signal = "SIGINT" 4 | kill_timeout = 5 5 | processes = [] 6 | 7 | [env] 8 | FLY_PRIMARY_REGION = "ord" 9 | 10 | [mounts] 11 | destination = "/data" 12 | source = "data" 13 | 14 | [[services]] 15 | http_checks = [] 16 | internal_port = 8080 17 | processes = ["app"] 18 | protocol = "tcp" 19 | script_checks = [] 20 | 21 | [services.concurrency] 22 | hard_limit = 25 23 | soft_limit = 20 24 | type = "connections" 25 | 26 | [[services.ports]] 27 | force_https = true 28 | handlers = ["http"] 29 | port = 80 30 | 31 | [[services.ports]] 32 | handlers = ["tls", "http"] 33 | port = 443 34 | 35 | [[services.tcp_checks]] 36 | grace_period = "1s" 37 | interval = "15s" 38 | restart_limit = 0 39 | timeout = "2s" 40 | -------------------------------------------------------------------------------- /go.mod: -------------------------------------------------------------------------------- 1 | module github.com/benbjohnson/litestream-read-replica-example 2 | 3 | go 1.18 4 | 5 | require ( 6 | github.com/fsnotify/fsnotify v1.5.1 7 | github.com/mattn/go-sqlite3 v1.14.12 8 | ) 9 | 10 | require golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c // indirect 11 | -------------------------------------------------------------------------------- /go.sum: -------------------------------------------------------------------------------- 1 | github.com/fsnotify/fsnotify v1.5.1 h1:mZcQUHVQUQWoPXXtuf9yuEXKudkV2sx1E06UadKWpgI= 2 | github.com/fsnotify/fsnotify v1.5.1/go.mod h1:T3375wBYaZdLLcVNkcVbzGHY7f1l/uK5T5Ai1i3InKU= 3 | github.com/mattn/go-sqlite3 v1.14.12 h1:TJ1bhYJPV44phC+IMu1u2K/i5RriLTPe+yc68XDJ1Z0= 4 | github.com/mattn/go-sqlite3 v1.14.12/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A/KQRfk6bU= 5 | golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c h1:F1jZWGFhYfh0Ci55sIpILtKKK8p3i2/krTr0H1rg74I= 6 | golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg= 7 | -------------------------------------------------------------------------------- /main.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "context" 5 | "database/sql" 6 | "flag" 7 | "fmt" 8 | "io" 9 | "log" 10 | "net/http" 11 | "os" 12 | 13 | _ "github.com/mattn/go-sqlite3" 14 | ) 15 | 16 | func main() { 17 | if err := run(context.Background()); err != nil { 18 | fmt.Println(err) 19 | os.Exit(1) 20 | } 21 | } 22 | 23 | func run(ctx context.Context) error { 24 | // Parse command line flags. 25 | dsn := flag.String("dsn", "", "datasource name") 26 | addr := flag.String("addr", ":8080", "bind address") 27 | flag.Parse() 28 | if *dsn == "" { 29 | return fmt.Errorf("flag required: -dsn DSN") 30 | } 31 | 32 | // Ensure app name, primary region & current region are both set via env vars. 33 | if os.Getenv("FLY_APP_NAME") == "" { 34 | return fmt.Errorf("FLY_APP_NAME must be set") 35 | } else if os.Getenv("FLY_REGION") == "" { 36 | return fmt.Errorf("FLY_REGION must be set") 37 | } else if os.Getenv("FLY_PRIMARY_REGION") == "" { 38 | return fmt.Errorf("FLY_PRIMARY_REGION must be set") 39 | } 40 | 41 | // Set "readonly" mode if this is a replica. 42 | if !isPrimary() { 43 | *dsn += "?mode=ro" 44 | } 45 | 46 | // Open local SQLite database connection. 47 | db, err := sql.Open("sqlite3", *dsn) 48 | if err != nil { 49 | return fmt.Errorf("open database: %w", err) 50 | } 51 | defer db.Close() 52 | 53 | // Build schema if this is the primary node. 54 | if isPrimary() { 55 | if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS records (id INTEGER PRIMARY KEY, value TEXT NOT NULL)`); err != nil { 56 | return fmt.Errorf("create table: %w", err) 57 | } 58 | } 59 | 60 | // Start HTP server. 61 | log.Printf("listening on %s", *addr) 62 | 63 | return http.ListenAndServe(*addr, &Handler{db: db}) 64 | } 65 | 66 | // Handler represents an HTTP handler. 67 | type Handler struct { 68 | db *sql.DB 69 | } 70 | 71 | func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) { 72 | // We only support the root path. 73 | if r.URL.Path != "/" { 74 | http.Error(w, "Not found", http.StatusNotFound) 75 | return 76 | } 77 | 78 | // Our endpoint only supports a GET to read data and POST to write data. 79 | switch r.Method { 80 | case "GET": 81 | h.serveGet(w, r) 82 | case "POST": 83 | h.servePost(w, r) 84 | default: 85 | http.Error(w, "Method not allowed", http.StatusMethodNotAllowed) 86 | } 87 | } 88 | 89 | // serveGet returns a list of all records that have been created. 90 | func (h *Handler) serveGet(w http.ResponseWriter, r *http.Request) { 91 | // Fetch all records from the database. 92 | rows, err := h.db.QueryContext(r.Context(), `SELECT id, value FROM records ORDER BY id`) 93 | if err != nil { 94 | http.Error(w, err.Error(), http.StatusInternalServerError) 95 | return 96 | } 97 | defer rows.Close() 98 | 99 | // Read each row and print it to the response body. 100 | var n int 101 | for ; rows.Next(); n++ { 102 | var id int 103 | var value string 104 | if err := rows.Scan(&id, &value); err != nil { 105 | http.Error(w, err.Error(), http.StatusInternalServerError) 106 | return 107 | } 108 | 109 | fmt.Fprintf(w, "Record #%d: %q\n", id, value) 110 | } 111 | if err := rows.Close(); err != nil { 112 | http.Error(w, err.Error(), http.StatusInternalServerError) 113 | return 114 | } 115 | 116 | // Return a message if no records are found. 117 | if n == 0 { 118 | fmt.Fprintf(w, "No records found. Please POST to add one.\n") 119 | return 120 | } 121 | } 122 | 123 | // servePost creates a new record using the contents of the request body. 124 | func (h *Handler) servePost(w http.ResponseWriter, r *http.Request) { 125 | // If this is not the primary, redirect to the primary. 126 | if !isPrimary() { 127 | log.Printf("redirecting to primary") 128 | w.Header().Set("fly-replay", "region="+os.Getenv("FLY_PRIMARY_REGION")) 129 | return 130 | } 131 | 132 | // Read body from HTTP request. 133 | body, err := io.ReadAll(r.Body) 134 | if err != nil { 135 | http.Error(w, err.Error(), http.StatusInternalServerError) 136 | return 137 | } else if len(body) == 0 { 138 | http.Error(w, "request body required", http.StatusBadRequest) 139 | return 140 | } 141 | 142 | // Insert record into the database. 143 | result, err := h.db.ExecContext(r.Context(), `INSERT INTO records (value) VALUES (?)`, string(body)) 144 | if err != nil { 145 | http.Error(w, err.Error(), http.StatusInternalServerError) 146 | return 147 | } 148 | 149 | // Report the record ID back to the user. 150 | id, err := result.LastInsertId() 151 | if err != nil { 152 | http.Error(w, err.Error(), http.StatusInternalServerError) 153 | return 154 | } 155 | fmt.Fprintf(w, "Record #%d successfully inserted.\n", id) 156 | } 157 | 158 | // isPrimary returns true if the current region is the primary region. 159 | func isPrimary() bool { 160 | return os.Getenv("FLY_PRIMARY_REGION") == os.Getenv("FLY_REGION") 161 | } 162 | -------------------------------------------------------------------------------- /run.sh: -------------------------------------------------------------------------------- 1 | #!/bin/bash 2 | 3 | # Determine which configuration file to use based on region. 4 | if [ "$FLY_REGION" == "$FLY_PRIMARY_REGION" ] 5 | then 6 | REPLICATION_MODE="primary" 7 | else 8 | REPLICATION_MODE="replica" 9 | fi 10 | 11 | echo "Starting instance as ${REPLICATION_MODE}" 12 | 13 | # Use correct configuration file based on replication mode. 14 | mv /etc/litestream.${REPLICATION_MODE}.yml /etc/litestream.yml 15 | 16 | # Create an empty database if we are a replica since our application will open as read-only. 17 | if [ "$REPLICATION_MODE" == "replica" ] && [ ! -f "$DSN" ] 18 | then 19 | echo "Initializing empty replica database" 20 | sqlite3 "$DSN" "PRAGMA journal_mode = wal" 21 | fi 22 | 23 | echo "Starting Litestream & application" 24 | 25 | # Start litestream and the main application 26 | litestream replicate -exec "/usr/local/bin/litestream-read-replica-example -dsn "$DSN" -addr :8080" 27 | --------------------------------------------------------------------------------