Return a 502 when container is down

If the app container is down or not responding then traefik will return a 404 response code. This is not ideal as it suggests a client rather than a server problem. To fix this, we'll define a catch all route that always returns a 502. This is not ideal as this route would take priority over a shorter route with priorty 1. TODO: up the priority of the app route.
basecamp · Nov 3, 2023 · 24a2f51 · 24a2f51
1 parent 8f53104
commit 24a2f51
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Showing 5 changed files with 29 additions and 29 deletions.
diff --git a/lib/kamal/commands/traefik.rb b/lib/kamal/commands/traefik.rb
@@ -6,6 +6,14 @@ class Kamal::Commands::Traefik < Kamal::Commands::Base
   DEFAULT_ARGS = {
     'log.level' => 'DEBUG'
   }
+  DEFAULT_LABELS = {
+    # These ensure we serve a 502 rather than a 404 if no containers are available
+    "traefik.http.routers.catchall.entryPoints" => "http",
+    "traefik.http.routers.catchall.rule" => "PathPrefix(`/`)",
+    "traefik.http.routers.catchall.service" => "unavailable",
+    "traefik.http.routers.catchall.priority" => 1,
+    "traefik.http.services.unavailable.loadbalancer.server.port" => "0"
+  }
 
   def run
     docker :run, "--name traefik",
@@ -97,7 +105,7 @@ def host_env_directory
     end
 
     def labels
-      config.traefik["labels"] || []
+      DEFAULT_LABELS.merge(config.traefik["labels"] || {})
     end
 
     def image

diff --git a/test/cli/traefik_test.rb b/test/cli/traefik_test.rb
@@ -4,7 +4,7 @@ class CliTraefikTest < CliTestCase
   test "boot" do
     run_command("boot").tap do |output|
       assert_match "docker login", output
-      assert_match "docker run --name traefik --detach --restart unless-stopped --publish 80:80 --volume /var/run/docker.sock:/var/run/docker.sock --env-file .kamal/env/traefik/traefik.env --log-opt max-size=\"10m\" #{Kamal::Commands::Traefik::DEFAULT_IMAGE} --providers.docker --log.level=\"DEBUG\"", output
+      assert_match "docker run --name traefik --detach --restart unless-stopped --publish 80:80 --volume /var/run/docker.sock:/var/run/docker.sock --env-file .kamal/env/traefik/traefik.env --log-opt max-size=\"10m\" --label traefik.http.routers.catchall.entryPoints=\"http\" --label traefik.http.routers.catchall.rule=\"PathPrefix(\\`/\\`)\" --label traefik.http.routers.catchall.service=\"unavailable\" --label traefik.http.routers.catchall.priority=\"1\" --label traefik.http.services.unavailable.loadbalancer.server.port=\"0\" #{Kamal::Commands::Traefik::DEFAULT_IMAGE} --providers.docker --log.level=\"DEBUG\"", output
     end
   end
 
@@ -14,7 +14,7 @@ class CliTraefikTest < CliTestCase
     run_command("reboot").tap do |output|
       assert_match "docker container stop traefik", output
       assert_match "docker container prune --force --filter label=org.opencontainers.image.title=Traefik", output
-      assert_match "docker run --name traefik --detach --restart unless-stopped --publish 80:80 --volume /var/run/docker.sock:/var/run/docker.sock --env-file .kamal/env/traefik/traefik.env --log-opt max-size=\"10m\" #{Kamal::Commands::Traefik::DEFAULT_IMAGE} --providers.docker --log.level=\"DEBUG\"", output
+      assert_match "docker run --name traefik --detach --restart unless-stopped --publish 80:80 --volume /var/run/docker.sock:/var/run/docker.sock --env-file .kamal/env/traefik/traefik.env --log-opt max-size=\"10m\" --label traefik.http.routers.catchall.entryPoints=\"http\" --label traefik.http.routers.catchall.rule=\"PathPrefix(\\`/\\`)\" --label traefik.http.routers.catchall.service=\"unavailable\" --label traefik.http.routers.catchall.priority=\"1\" --label traefik.http.services.unavailable.loadbalancer.server.port=\"0\" #{Kamal::Commands::Traefik::DEFAULT_IMAGE} --providers.docker --log.level=\"DEBUG\"", output
     end
   end