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We explain the purpose of this repository, the history behind it, where it's going & how can others help. We also captured all contributors to date. We also captured the Varnish + Fly.io config as it existed for: - Let's build a CDN - Part 1 - https://www.youtube.com/watch?v=8bDgWvyglno - Kaizen 15 - NOT a pipe dream - https://changelog.com/friends/50 There is a lot more context here: thechangelog/changelog.com#518 The most interesting part is the `run` script. To run it, you will need to: 1. Have a Fly.io account 2. Have a back-end app deployed 💡 https://fly.io/speedrun/ 3. Change the name of the backend app (i.e. `changelog-2024-01-12`) 4. Launch the app in this repository Signed-off-by: Gerhard Lazu <[email protected]>
thechangelog · Aug 16, 2024 · 0224c72 · 0224c72
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diff --git a/Dockerfile b/Dockerfile
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+# https://hub.docker.com/_/varnish
+FROM varnish:7.4.3
+ENV VARNISH_HTTP_PORT 9000
+COPY default.vcl /etc/varnish/default.vcl
diff --git a/LICENSE b/LICENSE
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+Content and Design Copyright (c) Changelog Media LLC. All rights reserved.
+
+Code Copyright (c) Changelog Media LLC and licensed under the following conditions:
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/README.md b/README.md
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+# The Pipe Dream™️
+
+A single-purpose, single-tenant CDN for [changelog.com](https://changelog.com).
+Runs [Varnish Cache](https://varnish-cache.org/releases/index.html) (open
+source) on [Fly.io](https://fly.io/changelog)
+
+This repository exists for a single reason: build the simplest CDN on Fly.io
+
+## How it started
+
+> I like the idea of having like this 20-line Varnish config that we deploy
+> around the world, and it’s like “Look at our CDN, guys.”
+>
+> It’s so simple, and it can do exactly what we want it to do, and nothing
+> more.
+>
+> But I understand that that’s a <strong>pipe dream</strong>, because that
+> Varnish config will be slightly longer than 20 lines, and we’d run into all
+> sorts of issues that we end up sinking all kinds of time into.
+>
+> Jerod Santo - March 29, 2024 - <a href="https://changelog.com/friends/38#transcript-208" target="_blank">Changelog & Friends #38</a>
+
+## How is it going
+
+- [x] Static backend, 1 day stale, stale on error, x-headers - `46` lines of VCL 
+- [ ] Dynamic backend, cache-status header - `55` lines of VCL
+
+## How can you help
+
+If you have any ideas on how to improve this, please open an issue or go
+straight for a pull request. We make this as easy as possible:
+- All commits emphasize [good commit messages](https://cbea.ms/git-commit/) (more text for humans than code for machines)
+- This repository is kept small & simple (the only purpose is to build the simplest CDN on Fly.io)
+- We are taking a slow & thoughtful approach - join our journey via [audio with transcripts](https://changelog.com/topic/kaizen) or [written](https://github.com/thechangelog/changelog.com/discussions/categories/kaizen)
+
+Hope to see you in our Slack: <https://changelog.slack.com> 👋
+
+## Contributors
+
+- [James A Rosen](https://www.jamesarosen.com/), Staff Engineer
+- [Matt Johnson](https://github.com/mttjohnson), Sr Site Reliability Engineer
diff --git a/default.vcl b/default.vcl
@@ -0,0 +1,117 @@
+# https://varnish-cache.org/docs/7.4/reference/vcl.html#versioning
+vcl 4.1;
+
+import std;
+
+# Thanks Matt Johnson! 👋
+# - https://github.com/magento/magento2/blob/03621bbcd75cbac4ffa8266a51aa2606980f4830/app/code/Magento/PageCache/etc/varnish6.vcl
+# - https://abhishekjakhotiya.medium.com/magento-internals-cache-purging-and-cache-tags-bf7772e60797
+
+backend default {
+  .host = "top1.nearest.of.changelog-2024-01-12.internal";
+  .host_header = "changelog-2024-01-12.fly.dev";
+  .port = "4000";
+  .first_byte_timeout = 5s;
+  .probe = {
+    .url = "/health";
+    .timeout = 2s;
+    .interval = 5s;
+    .window = 10;
+    .threshold = 5;
+  }
+}
+
+# https://varnish-cache.org/docs/7.4/users-guide/vcl-grace.html
+# https://docs.varnish-software.com/tutorials/object-lifetime/
+# https://www.varnish-software.com/developers/tutorials/http-caching-basics/
+# https://blog.markvincze.com/how-to-gracefully-fall-back-to-cache-on-5xx-responses-with-varnish/
+sub vcl_backend_response {
+  # Objects within ttl are considered fresh.
+  set beresp.ttl = 60s;
+
+  # Objects within grace are considered stale.
+  # Serve stale content while refreshing in the background.
+  # 🤔 QUESTION: should we vary this based on backend health?
+  set beresp.grace = 24h;
+
+  if (beresp.status >= 500) {
+    # Don't cache a 5xx response
+    set beresp.uncacheable = true;
+
+    # If is_bgfetch is true, it means that we've found and returned the cached
+    # object to the client, and triggered an asynchoronus background update. In
+    # that case, since backend returned a 5xx, we have to abandon, otherwise
+    # the previously cached object would be erased from the cache (even if we
+    # set uncacheable to true).
+    if (bereq.is_bgfetch) {
+      return (abandon);
+    }
+  }
+
+  # 🤔 QUESTION: Should we configure beresp.keep?
+}
+
+# NOTE: vcl_recv is called at the beginning of a request, after the complete
+# request has been received and parsed. Its purpose is to decide whether or not
+# to serve the request, how to do it, and, if applicable, which backend to use.
+sub vcl_recv {
+  # https://varnish-cache.org/docs/7.4/users-guide/purging.html
+  if (req.method == "PURGE") {
+    return (purge);
+  }
+
+  # Implement a Varnish health-check
+  if (req.method == "GET" && req.url == "/varnish_status") {
+    return(synth(204));
+  }
+}
+
+# https://gist.github.com/leotsem/1246511/824cb9027a0a65d717c83e678850021dad84688d#file-default-vcl-pl
+# https://varnish-cache.org/docs/7.4/reference/vcl-var.html#obj
+sub vcl_deliver {
+  # What is the remaining TTL for this object?
+  set resp.http.x-ttl = obj.ttl;
+  # What is the max object staleness permitted?
+  set resp.http.x-grace = obj.grace;
+
+  # Did the response come from Varnish or from the backend?
+  if (obj.hits > 0) {
+    set resp.http.x-cache = "HIT";
+  } else {
+    set resp.http.x-cache = "MISS";
+  }
+
+  # Is this object stale?
+  if (obj.ttl < std.duration(integer=0)) {
+    set resp.http.x-cache = "STALE";
+  }
+
+  # How many times has this response been served from Varnish?
+  set resp.http.x-cache-hits = obj.hits;
+}
+
+# TODOS:
+# - ✅ Run in debug mode (locally)
+# - ✅ Connect directly to app - not Fly.io Proxy 🤦
+# - ✅ Serve stale content + background refresh
+#   - QUESTION: Should the app control this via Surrogate-Control? Should we remove this header?
+#   - EXPLORE: varnishstat
+#   - EXPLORE: varnishtop
+#   - EXPLORE: varnishncsa -c -F '%m %U %H %{x-cache}o %{x-cache-hits}o'
+# - ✅ Serve stale content on backend error
+#   - https://varnish-cache.org/docs/7.4/users-guide/vcl-grace.html#misbehaving-servers
+# - If the backend gets restarted (e.g. new deploy), backend remains sick in Varnish
+#   - https://info.varnish-software.com/blog/two-minute-tech-tuesdays-backend-health
+#   - EXPLORE: varnishlog -g raw -i backend_health
+# - Implement If-Modified-Since? keep
+# - Expose FLY_REGION=sjc env var as a custom header
+#   - https://varnish-cache.org/lists/pipermail/varnish-misc/2019-September/026656.html
+# - Add Feeds backend: /feed -> https://feeds.changelog.place/feed.xml
+# - Store cache on disk? A pre-requisite for static backend 
+#   - https://varnish-cache.org/docs/trunk/users-guide/storage-backends.html#file
+# - Add Static backend: cdn.changelog.com requests
+#
+# FOLLOW-UPs:
+# - Run varnishncsa as a separate process (will need a supervisor + log drain)
+#   - https://info.varnish-software.com/blog/varnish-and-json-logging
+# - How to cache purge across all varnish instances?
diff --git a/fly.toml b/fly.toml
@@ -0,0 +1,43 @@
+# Full app config reference: https://fly.io/docs/reference/configuration/
+app = "cdn-2024-01-26"
+# Closest to James
+primary_region = "sjc"
+# Secondary region will be "lhr", closest to Gerhard
+
+kill_signal = "SIGTERM"
+kill_timeout = 30
+
+[env]
+VARNISH_SIZE="500M"
+
+[[vm]]
+size = "shared-cpu-1x"
+memory = "256MB"
+
+[deploy]
+strategy = "bluegreen"
+
+[[services]]
+internal_port = 9000
+protocol = "tcp"
+
+[[services.http_checks]]
+grace_period = "5s"
+interval = "5s"
+method = "get"
+path = "/varnish_status"
+protocol = "http"
+timeout = "4s"
+
+[[services.ports]]
+handlers = ["tls", "http"]
+port = 443
+
+[[services.ports]]
+handlers = ["http"]
+port = "80"
+
+[services.concurrency]
+hard_limit = 2500
+soft_limit = 2000
+type = "connections"
diff --git a/regions.txt b/regions.txt
@@ -0,0 +1,36 @@
+NAME                        	CODE	GATEWAY	LAUNCH PLAN + ONLY	GPUS 
+Amsterdam, Netherlands      	ams 	✓      	                  	✓   	
+Ashburn, Virginia (US)      	iad 	✓      	                  	✓   	
+Atlanta, Georgia (US)       	atl 	       	                  	    	
+Bogotá, Colombia            	bog 	       	                  	    	
+Boston, Massachusetts (US)  	bos 	       	                  	    	
+Bucharest, Romania          	otp 	       	                  	    	
+Chicago, Illinois (US)      	ord 	✓      	                  	    	
+Dallas, Texas (US)          	dfw 	✓      	                  	    	
+Denver, Colorado (US)       	den 	       	                  	    	
+Ezeiza, Argentina           	eze 	       	                  	    	
+Frankfurt, Germany          	fra 	✓      	✓                 	    	
+Guadalajara, Mexico         	gdl 	       	                  	    	
+Hong Kong, Hong Kong        	hkg 	✓      	                  	    	
+Johannesburg, South Africa  	jnb 	       	                  	    	
+London, United Kingdom      	lhr 	✓      	                  	    	
+Los Angeles, California (US)	lax 	✓      	                  	    	
+Madrid, Spain               	mad 	       	                  	    	
+Miami, Florida (US)         	mia 	       	                  	    	
+Montreal, Canada            	yul 	       	                  	    	
+Mumbai, India               	bom 	       	✓                 	    	
+Paris, France               	cdg 	✓      	                  	    	
+Phoenix, Arizona (US)       	phx 	       	                  	    	
+Querétaro, Mexico           	qro 	✓      	                  	    	
+Rio de Janeiro, Brazil      	gig 	       	                  	    	
+San Jose, California (US)   	sjc 	✓      	                  	✓   	
+Santiago, Chile             	scl 	✓      	                  	    	
+Sao Paulo, Brazil           	gru 	       	                  	    	
+Seattle, Washington (US)    	sea 	✓      	                  	    	
+Secaucus, NJ (US)           	ewr 	✓      	                  	    	
+Singapore, Singapore        	sin 	✓      	                  	    	
+Stockholm, Sweden           	arn 	       	                  	    	
+Sydney, Australia           	syd 	✓      	                  	✓   	
+Tokyo, Japan                	nrt 	✓      	                  	    	
+Toronto, Canada             	yyz 	✓      	                  	    	
+Warsaw, Poland              	waw