Limit the number of concurrent git connections to 10, and make it configurable (#2044)

* (#2044) (#1957) Update git.rake - configurable max concurrent connections
Default git_max_concurrent_connections is set to 10 hosts per group.

Default git_wait_interval is set to 3 seconds.

This enables deployments for large number of servers with default Gitlab or similar git server configuration with default SSH settings (max 10 concurrent connections).

* ADD: rspec tests for default values

* UPDATE: docs/documentation/getting-started/configuration/index.markdown

docs/documentation/getting-started/configuration/index.markdown

@@ -150,6 +150,13 @@ The following variables are settable:
   * **default:** `current`
   * Name for `current` link pointing to the newest successful deployment's release folder.
 
+* `:git_max_concurrent_connections`
+  * **default:** `10`
+  * Number of concurrent connections to Git repository - useful when your Git server limits the number of simultaneous connections while using SSH (like Gitlab CE).
+
+* `:git_wait_interval`
+  * **default:** `3`
+  * Number of seconds to wait after you reach the limit of concurrent connections to Git repository server and disconnect afterwards to initialize new connections. This prevents from being cut out of SSH server when you use `fail2ban` or similar software for limiting connections to server.
 
 Capistrano plugins can provide their own configuration variables. Please refer
 to the plugin documentation for the specifics. Plugins are allowed to add or

lib/capistrano/scm/git.rb

@@ -18,6 +18,8 @@ class Capistrano::SCM::Git < Capistrano::SCM::Plugin
         git_ssh: fetch(:git_wrapper_path)
       }
     }
+    set_if_empty :git_max_concurrent_connections, 10
+    set_if_empty :git_wait_interval, 3
   end
 
   def register_hooks

lib/capistrano/scm/tasks/git.rake

@@ -4,7 +4,7 @@ git_plugin = self
 namespace :git do
   desc "Upload the git wrapper script, this script guarantees that we can script git without getting an interactive prompt"
   task :wrapper do
-    on release_roles :all do
+    on release_roles(:all), in: :groups, limit: fetch(:git_max_concurrent_connections), wait: fetch(:git_wait_interval) do
       execute :mkdir, "-p", File.dirname(fetch(:git_wrapper_path)).shellescape
       upload! StringIO.new("#!/bin/sh -e\nexec /usr/bin/ssh -o PasswordAuthentication=no -o StrictHostKeyChecking=no \"$@\"\n"), fetch(:git_wrapper_path)
       execute :chmod, "700", fetch(:git_wrapper_path).shellescape
@@ -14,7 +14,7 @@ namespace :git do
   desc "Check that the repository is reachable"
   task check: :'git:wrapper' do
     fetch(:branch)
-    on release_roles :all do
+    on release_roles(:all), in: :groups, limit: fetch(:git_max_concurrent_connections), wait: fetch(:git_wait_interval) do
       with fetch(:git_environmental_variables) do
         git_plugin.check_repo_is_reachable
       end
@@ -23,7 +23,7 @@ namespace :git do
 
   desc "Clone the repo to the cache"
   task clone: :'git:wrapper' do
-    on release_roles :all do
+    on release_roles(:all), in: :groups, limit: fetch(:git_max_concurrent_connections), wait: fetch(:git_wait_interval) do
       if git_plugin.repo_mirror_exists?
         info t(:mirror_exists, at: repo_path)
       else
@@ -38,7 +38,7 @@ namespace :git do
 
   desc "Update the repo mirror to reflect the origin state"
   task update: :'git:clone' do
-    on release_roles :all do
+    on release_roles(:all), in: :groups, limit: fetch(:git_max_concurrent_connections), wait: fetch(:git_wait_interval) do
       within repo_path do
         with fetch(:git_environmental_variables) do
           git_plugin.update_mirror
@@ -49,7 +49,7 @@ namespace :git do
 
   desc "Copy repo to releases"
   task create_release: :'git:update' do
-    on release_roles :all do
+    on release_roles(:all), in: :groups, limit: fetch(:git_max_concurrent_connections), wait: fetch(:git_wait_interval) do
       with fetch(:git_environmental_variables) do
         within repo_path do
           execute :mkdir, "-p", release_path
@@ -61,7 +61,7 @@ namespace :git do
 
   desc "Determine the revision that will be deployed"
   task :set_current_revision do
-    on release_roles :all do
+    on release_roles(:all), in: :groups, limit: fetch(:git_max_concurrent_connections), wait: fetch(:git_wait_interval) do
       within repo_path do
         with fetch(:git_environmental_variables) do
           set :current_revision, git_plugin.fetch_revision

spec/lib/capistrano/scm/git_spec.rb

@@ -36,6 +36,20 @@ module Capistrano
         subject.set_defaults
         expect(env.fetch(:git_wrapper_path)).to eq("/tmp/git-ssh-my_app-staging-(Git Web User) via ShipIt.sh")
       end
+
+      it "makes git_max_concurrent_connections" do
+        subject.set_defaults
+        expect(env.fetch(:git_max_concurrent_connections)).to eq(10)
+        env.set(:git_max_concurrent_connections, 7)
+        expect(env.fetch(:git_max_concurrent_connections)).to eq(7)
+      end
+
+      it "makes git_wait_interval" do
+        subject.set_defaults
+        expect(env.fetch(:git_wait_interval)).to eq(3)
+        env.set(:git_wait_interval, 5)
+        expect(env.fetch(:git_wait_interval)).to eq(5)
+      end
     end
 
     describe "#git" do