articles/fly-io-postgres-read-replica: rewrite to be single file

Remove Gemfile, Gemfile.lock, and .solargraph.yml.

articles/fly-io-postgres-read-replica-multi-region-ruby.md

@@ -1,51 +1,31 @@
 # Fly.io Multi-Region Ruby with Postgres Read Replicas
 
-For latency (or, less relevant to this article, data residency) reasons,
+For latency reasons,
 you might want to deploy your app to a specific region.
 [Fly.io has 20+ regions](https://fly.io/docs/reference/regions/)
-on their own Points of Presence
-(not on public clouds like AWS).
+on their own Points of Presence (not on public clouds like AWS).
 
 If you have a read-heavy application, look at Fly's
 [multi-region Postgres read replicas](https://fly.io/docs/getting-started/multi-region-databases/).
-The big caveat is
-[Fly, unlike Heroku, is not managed Postgres](https://fly.io/docs/rails/getting-started/migrate-from-heroku/#databases).
+The caveat is
+[Fly Postgres is not managed](https://fly.io/docs/rails/getting-started/migrate-from-heroku/#databases).
 
 ## Ruby app
 
-In this example, we'll write and deploy a Ruby app to Fly.io using popular gems:
-
-* [Connection Pool](https://rubygems.org/gems/connection_pool)
-* [PG](https://rubygems.org/gems/pg)
-* [Puma](https://rubygems.org/gems/puma)
-* [Sinatra](https://rubygems.org/gems/sinatra)
-
-The `Gemfile` looks like this:
-
-```embed
-code/fly-ruby-read-replica/Gemfile all
-```
-
-Install the gems:
-
-```bash
-bundle
-```
-
-The `api.rb` looks like this:
+In this example, we'll write and deploy a Ruby app to Fly.io:
 
 ```embed
-code/fly-ruby-read-replica/api.rb all
+code/fly-read-replica/main.rb
 ```
 
 ## Develop
 
-Develop locally:
+Run locally:
 
 ```bash
-bundle
-createdb example_dev
-DATABASE_URL="postgres:///example_dev" bundle exec ruby api.rb
+createdb db
+chmod +x main.rb
+DATABASE_URL=postgres:///db ./main.rb
 ```
 
 ## Fly
@@ -62,42 +42,48 @@ Connect to your account:
 fly auth login
 ```
 
-Deploy using Fly's `--remote-only` option,
-which will use a remote Docker builder Fly sets up in your account.
-If you previously had a Docker installation, avoid
-[a gotcha](https://community.fly.io/t/failed-to-fetch-builder-image-when-deploying-ruby-example/3726/7),
-by deleting `~/.docker` before you deploy:
+If you don't have Docker installed,
+use Fly's `--remote-only` option,
+which will use a remote Docker builder in your Fly account:
 
 ```bash
-rm -rf ~/.docker
 fly launch --remote-only
 ```
 
-Configure region where the primary database is:
+If you have Docker installed,
+deploy with Fly's `--nixpacks` option,
+which will use [nixpacks](https://github.com/railwayapp/nixpacks) as the builder.
+It deploys faster:
+
+```bash
+fly launch --nixpacks
+```
+
+Configure region the primary database location,
+such as Sunnyvale, California:
 
 ```bash
 fly secrets set PRIMARY_REGION=sjc
 ```
 
-Create the regions where the read replicas will go:
+Add the regions where the read replicas will go,
+such as Frankfurt, Germany and Sydney, Australia:
 
 ```bash
-fly regions add ams lhr syd yul
+fly regions add fra syd
 ```
 
 Create read replicas in those regions:
 
 ```bash
-fly volumes create pg_data -a example-read-replicas-db --size 1 --region ams
-fly volumes create pg_data -a example-read-replicas-db --size 1 --region lhr
+fly volumes create pg_data -a example-read-replicas-db --size 1 --region fra
 fly volumes create pg_data -a example-read-replicas-db --size 1 --region syd
-fly volumes create pg_data -a example-read-replicas-db --size 1 --region yul
 ```
 
 Scale 1 instance per region:
 
 ```bash
-fly autoscale standard min=5 max=5
+fly autoscale standard min=3 max=3
 ```
 
 Done!

code/fly-ruby-read-replica/api.rb → code/fly-read-replica/main.rb

@@ -1,7 +1,23 @@
-# begindoc: all
-require "connection_pool"
-require "pg"
-require "sinatra"
+#!/usr/bin/env ruby
+
+# createdb db
+# chmod +x main.rb
+# DATABASE_URL=postgres:///db ./main.rb
+
+require "bundler/inline"
+
+gemfile do
+  source "https://rubygems.org"
+
+  gem "connection_pool"
+  gem "pg"
+  gem "puma"
+  gem "sinatra"
+
+  group :development do
+    gem "standard"
+  end
+end
 
 class DB
   def initialize
@@ -51,4 +67,5 @@ def do_exec(sql)
   content_type :json
   {status: "ok"}.to_json
 end
-# enddoc: all
+
+Sinatra::Application.run!

config.json

@@ -1,4 +1,9 @@
 [
+  {
+    "description": "Serve a web app from multiple Fly.io regions and route read requests to Postgres read replicas when possible",
+    "id": "fly-io-postgres-read-replica-multi-region-ruby",
+    "updated": "2022-12-05"
+  },
   {
     "description": "Pair programmed with OpenAI's ChatGPT",
     "id": "heroku-dataclips-clone-in-sinatra",
@@ -9,11 +14,6 @@
     "id": "schedule-deno-builds-with-github-actions",
     "updated": "2022-11-23"
   },
-  {
-    "description": "Serve a web app from multiple Fly.io regions and route read requests to Postgres read replicas when possible",
-    "id": "fly-io-postgres-read-replica-multi-region-ruby",
-    "updated": "2022-09-21"
-  },
   {
     "description": "Restore a production database into staging and development environments",
     "id": "heroku-postgres-restore-staging-development",

main.go

@@ -243,6 +243,12 @@ puts "here"
 The lines between magic comments
 are embedded back in the original code fence.
 
+To embed the entire file, don't include an ID or magic comments...
+
+```embed
+code/example.rb
+```
+
 Bad input in the Markdown document or source code file
 will stop the program with a non-zero exit code and error text.
 */
@@ -277,35 +283,42 @@ func preProcess(filepath string) (title, body string) {
 
 		if isEmbed {
 			parts := strings.Split(line, " ")
-			if len(parts) != 2 {
-				exitWith("error: embed line must be filepath id like: code/test.rb id")
+			if len(parts) != 1 && len(parts) != 2 {
+				exitWith("error: embed line must be filepath id (code/test.rb id) or filepath (code/test.rb)")
 			}
-			filename := parts[0]
-			id := parts[1]
 
+			filename := parts[0]
 			srcCode, err := ioutil.ReadFile(wd + "/" + filename)
 			check(err)
 
-			sep := "begindoc: " + id + "\n"
-			begindoc := strings.Index(string(srcCode), sep)
-			if begindoc == -1 {
-				exitWith("error: embed separator not found " + sep + " in " + filename)
-			}
-			// end of comment line
-			begindoc += len(sep)
+			begindoc := 0
+			enddoc := len(srcCode) - 1
+
+			if len(parts) == 2 {
+				id := parts[1]
+				sep := "begindoc: " + id + "\n"
+				begindoc := strings.Index(string(srcCode), sep)
+				if begindoc == -1 {
+					exitWith("error: embed separator not found " + sep + " in " + filename)
+				}
+				// end of comment line
+				begindoc += len(sep)
 
-			sep = "enddoc: " + id
-			enddoc := strings.Index(string(srcCode), sep)
-			if enddoc == -1 {
-				exitWith("error: embed separator not found " + sep + " in " + filename)
+				sep = "enddoc: " + id
+				enddoc := strings.Index(string(srcCode), sep)
+				if enddoc == -1 {
+					exitWith("error: embed separator not found " + sep + " in " + filename)
+				}
+				// backtrack to last newline to cut out comment character(s)
+				enddoc = strings.LastIndex(string(srcCode[0:enddoc]), "\n")
 			}
-			// backtrack to last newline to cut out comment character(s)
-			enddoc = strings.LastIndex(string(srcCode[0:enddoc]), "\n")
 
 			rawLines := strings.Split(string(srcCode[begindoc:enddoc]), "\n")
+
 			leadingWhitespace := regexp.MustCompile("(?m)(^[ \t]*)(?:[^ \t])")
 			var margin string
 			var lines []string
+
 			for i, l := range rawLines {
 				if i == 0 {
 					margin = leadingWhitespace.FindAllStringSubmatch(l, -1)[0][1]