Proxy: Use connection pools for images (#4326)

Theoretically this should improve memory usage and performance by quite a bit
as we aren't creating a new HTTP::Client and in a turn a new connection for
every image we request from YouTube.

Closes issue 4009

3 files changed, 62 insertions, 95 deletions

diff --git a/src/invidious.cr b/src/invidious.cr
index ccb70ba5..56aca802 100644
--- a/src/invidious.cr
+++ b/src/invidious.cr
@@ -93,6 +93,10 @@ SOFTWARE = {
 
 YT_POOL = YoutubeConnectionPool.new(YT_URL, capacity: CONFIG.pool_size)
 
+# Image request pool
+
+GGPHT_POOL = YoutubeConnectionPool.new(URI.parse("https://yt3.ggpht.com"), capacity: CONFIG.pool_size)
+
 # CLI
 Kemal.config.extra_options do |parser|
   parser.banner = "Usage: invidious [arguments]"
diff --git a/src/invidious/routes/images.cr b/src/invidious/routes/images.cr
index b6a2e110..639697db 100644
--- a/src/invidious/routes/images.cr
+++ b/src/invidious/routes/images.cr
@@ -11,29 +11,9 @@ module Invidious::Routes::Images
       end
     end
 
-    # We're encapsulating this into a proc in order to easily reuse this
-    # portion of the code for each request block below.
-    request_proc = ->(response : HTTP::Client::Response) {
-      env.response.status_code = response.status_code
-      response.headers.each do |key, value|
-        if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase)
-          env.response.headers[key] = value
-        end
-      end
-
-      env.response.headers["Access-Control-Allow-Origin"] = "*"
-
-      if response.status_code >= 300
-        env.response.headers.delete("Transfer-Encoding")
-        return
-      end
-
-      proxy_file(response, env)
-    }
-
     begin
-      HTTP::Client.get("https://yt3.ggpht.com#{url}") do |resp|
-        return request_proc.call(resp)
+      GGPHT_POOL.client &.get(url, headers) do |resp|
+        return self.proxy_image(env, resp)
       end
     rescue ex
     end
@@ -61,27 +41,10 @@ module Invidious::Routes::Images
       end
     end
 
-    request_proc = ->(response : HTTP::Client::Response) {
-      env.response.status_code = response.status_code
-      response.headers.each do |key, value|
-        if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase)
-          env.response.headers[key] = value
-        end
-      end
-
-      env.response.headers["Connection"] = "close"
-      env.response.headers["Access-Control-Allow-Origin"] = "*"
-
-      if response.status_code >= 300
-        return env.response.headers.delete("Transfer-Encoding")
-      end
-
-      proxy_file(response, env)
-    }
-
     begin
-      HTTP::Client.get("https://#{authority}.ytimg.com#{url}") do |resp|
-        return request_proc.call(resp)
+      get_ytimg_pool(authority).client &.get(url, headers) do |resp|
+        env.response.headers["Connection"] = "close"
+        return self.proxy_image(env, resp)
       end
     rescue ex
     end
@@ -101,26 +64,9 @@ module Invidious::Routes::Images
       end
     end
 
-    request_proc = ->(response : HTTP::Client::Response) {
-      env.response.status_code = response.status_code
-      response.headers.each do |key, value|
-        if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase)
-          env.response.headers[key] = value
-        end
-      end
-
-      env.response.headers["Access-Control-Allow-Origin"] = "*"
-
-      if response.status_code >= 300 && response.status_code != 404
-        return env.response.headers.delete("Transfer-Encoding")
-      end
-
-      proxy_file(response, env)
-    }
-
     begin
-      HTTP::Client.get("https://i9.ytimg.com#{url}") do |resp|
-        return request_proc.call(resp)
+      get_ytimg_pool("i9").client &.get(url, headers) do |resp|
+        return self.proxy_image(env, resp)
       end
     rescue ex
     end
@@ -165,8 +111,7 @@ module Invidious::Routes::Images
     if name == "maxres.jpg"
       build_thumbnails(id).each do |thumb|
         thumbnail_resource_path = "/vi/#{id}/#{thumb[:url]}.jpg"
-        # This can likely be optimized into a (small) pool sometime in the future.
-        if HTTP::Client.head("https://i.ytimg.com#{thumbnail_resource_path}").status_code == 200
+        if get_ytimg_pool("i9").client &.head(thumbnail_resource_path, headers).status_code == 200
           name = thumb[:url] + ".jpg"
           break
         end
@@ -181,29 +126,28 @@ module Invidious::Routes::Images
       end
     end
 
-    request_proc = ->(response : HTTP::Client::Response) {
-      env.response.status_code = response.status_code
-      response.headers.each do |key, value|
-        if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase)
-          env.response.headers[key] = value
-        end
+    begin
+      get_ytimg_pool("i").client &.get(url, headers) do |resp|
+        return self.proxy_image(env, resp)
       end
+    rescue ex
+    end
+  end
 
-      env.response.headers["Access-Control-Allow-Origin"] = "*"
-
-      if response.status_code >= 300 && response.status_code != 404
-        return env.response.headers.delete("Transfer-Encoding")
+  private def self.proxy_image(env, response)
+    env.response.status_code = response.status_code
+    response.headers.each do |key, value|
+      if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase)
+        env.response.headers[key] = value
       end
+    end
 
-      proxy_file(response, env)
-    }
+    env.response.headers["Access-Control-Allow-Origin"] = "*"
 
-    begin
-      # This can likely be optimized into a (small) pool sometime in the future.
-      HTTP::Client.get("https://i.ytimg.com#{url}") do |resp|
-        return request_proc.call(resp)
-      end
-    rescue ex
+    if response.status_code >= 300
+      return env.response.headers.delete("Transfer-Encoding")
     end
+
+    return proxy_file(response, env)
   end
 end
diff --git a/src/invidious/yt_backend/connection_pool.cr b/src/invidious/yt_backend/connection_pool.cr
index 70b15f26..c7c4c675 100644
--- a/src/invidious/yt_backend/connection_pool.cr
+++ b/src/invidious/yt_backend/connection_pool.cr
@@ -1,17 +1,6 @@
-def add_yt_headers(request)
-  request.headers.delete("User-Agent") if request.headers["User-Agent"] == "Crystal"
-  request.headers["User-Agent"] ||= "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36"
-
-  request.headers["Accept-Charset"] ||= "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
-  request.headers["Accept"] ||= "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
-  request.headers["Accept-Language"] ||= "en-us,en;q=0.5"
-
-  # Preserve original cookies and add new YT consent cookie for EU servers
-  request.headers["Cookie"] = "#{request.headers["cookie"]?}; CONSENT=PENDING+#{Random.rand(100..999)}"
-  if !CONFIG.cookies.empty?
-    request.headers["Cookie"] = "#{(CONFIG.cookies.map { |c| "#{c.name}=#{c.value}" }).join("; ")}; #{request.headers["cookie"]?}"
-  end
-end
+# Mapping of subdomain => YoutubeConnectionPool
+# This is needed as we may need to access arbitrary subdomains of ytimg
+private YTIMG_POOLS = {} of String => YoutubeConnectionPool
 
 struct YoutubeConnectionPool
   property! url : URI
@@ -58,6 +47,21 @@ struct YoutubeConnectionPool
   end
 end
 
+def add_yt_headers(request)
+  request.headers.delete("User-Agent") if request.headers["User-Agent"] == "Crystal"
+  request.headers["User-Agent"] ||= "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36"
+
+  request.headers["Accept-Charset"] ||= "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
+  request.headers["Accept"] ||= "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
+  request.headers["Accept-Language"] ||= "en-us,en;q=0.5"
+
+  # Preserve original cookies and add new YT consent cookie for EU servers
+  request.headers["Cookie"] = "#{request.headers["cookie"]?}; CONSENT=PENDING+#{Random.rand(100..999)}"
+  if !CONFIG.cookies.empty?
+    request.headers["Cookie"] = "#{(CONFIG.cookies.map { |c| "#{c.name}=#{c.value}" }).join("; ")}; #{request.headers["cookie"]?}"
+  end
+end
+
 def make_client(url : URI, region = nil, force_resolve : Bool = false)
   client = HTTP::Client.new(url)
 
@@ -94,3 +98,18 @@ def make_configured_http_proxy_client
     password: config_proxy.password,
   )
 end
+
+# Fetches a HTTP pool for the specified subdomain of ytimg.com
+#
+# Creates a new one when the specified pool for the subdomain does not exist
+def get_ytimg_pool(subdomain)
+  if pool = YTIMG_POOLS[subdomain]?
+    return pool
+  else
+    LOGGER.info("ytimg_pool: Creating a new HTTP pool for \"https://#{subdomain}.ytimg.com\"")
+    pool = YoutubeConnectionPool.new(URI.parse("https://#{subdomain}.ytimg.com"), capacity: CONFIG.pool_size)
+    YTIMG_POOLS[subdomain] = pool
+
+    return pool
+  end
+end