Enable GIT_TRACE/GIT_TRACE_PACKET/GIT_TRACE_PERFORMANCE by providing the git_trace_log_file config key59-git-tracing

The value of the variable if present must be a writable absolute path. If it’s
not the case we log a proper message and not enable tracing to not throw output to the users.

5 files changed, 107 insertions, 1 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 57b074a..54ccc82 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,6 @@
+v3.6.2
+  - Enable GIT_TRACE/GIT_TRACE_PACKET/GIT_TRACE_PERFORMANCE by providing the git_trace_log_file config key
+
 v3.6.1
   - Set a low IO priority for storage moves to lower performance impact
 
diff --git a/config.yml.example b/config.yml.example
index cd66022..0164830 100644
--- a/config.yml.example
+++ b/config.yml.example
@@ -68,3 +68,10 @@ audit_usernames: false
 # For Debian and Ubuntu systems this can be done with: sudo apt-get install git-annex
 # For CentOS: sudo yum install epel-release && sudo yum install git-annex
 git_annex_enabled: false
+
+# Git trace log file.
+# If set, git commands receive GIT_TRACE* environment variables
+# See https://git-scm.com/book/es/v2/Git-Internals-Environment-Variables#Debugging for documentation
+# An absolute path starting with / – the trace output will be appended to that file.
+# It needs to exist so we can check permissions and avoid to throwing warnings to the users.
+git_trace_log_file:
diff --git a/lib/gitlab_config.rb b/lib/gitlab_config.rb
index beaf173..781c706 100644
--- a/lib/gitlab_config.rb
+++ b/lib/gitlab_config.rb
@@ -50,4 +50,8 @@ class GitlabConfig
   def git_annex_enabled?
     @config['git_annex_enabled'] ||= false
   end
+
+  def git_trace_log_file
+    @config['git_trace_log_file']
+  end
 end
diff --git a/lib/gitlab_shell.rb b/lib/gitlab_shell.rb
index 971b22f..f72ce74 100644
--- a/lib/gitlab_shell.rb
+++ b/lib/gitlab_shell.rb
@@ -1,4 +1,5 @@
 require 'shellwords'
+require 'pathname'
 
 require_relative 'gitlab_net'
 
@@ -150,6 +151,14 @@ class GitlabShell
       env.merge!({ 'GIT_ANNEX_SHELL_LIMITED' => '1' })
     end
 
+    if git_trace_available?
+      env.merge!({
+        'GIT_TRACE' => @config.git_trace_log_file,
+        'GIT_TRACE_PACKET' => @config.git_trace_log_file,
+        'GIT_TRACE_PERFORMANCE' => @config.git_trace_log_file,
+      })
+    end
+
     Kernel::exec(env, *args, unsetenv_others: true)
   end
 
@@ -232,6 +241,23 @@ class GitlabShell
     end
   end
 
+  def git_trace_available?
+    return false unless @config.git_trace_log_file
+
+    if Pathname(@config.git_trace_log_file).relative?
+      $logger.warn "gitlab-shell: is configured to trace git commands with #{@config.git_trace_log_file.inspect} but an absolute path needs to be provided"
+      return false
+    end
+
+    begin
+      File.open(@config.git_trace_log_file, 'a') { nil }
+      return true
+    rescue => ex
+      $logger.warn "gitlab-shell: is configured to trace git commands with #{@config.git_trace_log_file.inspect} but it's not possible to write in that path #{ex.message}"
+      return false
+    end
+  end
+
   def repo_path=(repo_path)
     raise ArgumentError, "Repository path not provided. Please make sure you're using GitLab v8.10 or later." unless repo_path
     raise InvalidRepositoryPathError if File.absolute_path(repo_path) != repo_path
diff --git a/spec/gitlab_shell_spec.rb b/spec/gitlab_shell_spec.rb
index 96cae40..b9b8659 100644
--- a/spec/gitlab_shell_spec.rb
+++ b/spec/gitlab_shell_spec.rb
@@ -361,7 +361,7 @@ describe GitlabShell do
 
   describe :exec_cmd do
     let(:shell) { GitlabShell.new(key_id) }
-    before { Kernel.stub!(:exec) }
+    before { Kernel.stub(:exec) }
 
     it "uses Kernel::exec method" do
       Kernel.should_receive(:exec).with(kind_of(Hash), 1, 2, unsetenv_others: true).once
@@ -376,6 +376,72 @@ describe GitlabShell do
       Kernel.should_receive(:exec).with(kind_of(Hash), [1, 2], unsetenv_others: true).once
       shell.send :exec_cmd, [1, 2]
     end
+
+    context "when specifying a git_tracing log file" do
+      let(:git_trace_log_file) { '/tmp/git_trace_performance.log' }
+
+      before do
+        GitlabConfig.any_instance.stub(git_trace_log_file: git_trace_log_file)
+        shell
+      end
+
+      it "uses GIT_TRACE_PERFORMANCE" do
+        expected_hash = hash_including(
+          'GIT_TRACE' => git_trace_log_file,
+          'GIT_TRACE_PACKET' => git_trace_log_file,
+          'GIT_TRACE_PERFORMANCE' => git_trace_log_file
+        )
+        Kernel.should_receive(:exec).with(expected_hash, [1, 2], unsetenv_others: true).once
+
+        shell.send :exec_cmd, [1, 2]
+      end
+
+      context "when provides a relative path" do
+        let(:git_trace_log_file) { 'git_trace_performance.log' }
+
+        it "does not uses GIT_TRACE*" do
+          # If we try to use it we'll show a warning to the users
+          expected_hash = hash_excluding(
+            'GIT_TRACE', 'GIT_TRACE_PACKET', 'GIT_TRACE_PERFORMANCE'
+          )
+          Kernel.should_receive(:exec).with(expected_hash, [1, 2], unsetenv_others: true).once
+
+          shell.send :exec_cmd, [1, 2]
+        end
+
+        it "writes an entry on the log" do
+          expect($logger).to receive(:warn).
+            with("gitlab-shell: is configured to trace git commands with #{git_trace_log_file.inspect} but an absolute path needs to be provided")
+
+          Kernel.should_receive(:exec).with(kind_of(Hash), [1, 2], unsetenv_others: true).once
+          shell.send :exec_cmd, [1, 2]
+        end
+      end
+
+      context "when provides a file not writable" do
+        before do
+          expect(File).to receive(:open).with(git_trace_log_file, 'a').and_raise(Errno::EACCES)
+        end
+
+        it "does not uses GIT_TRACE*" do
+          # If we try to use it we'll show a warning to the users
+          expected_hash = hash_excluding(
+            'GIT_TRACE', 'GIT_TRACE_PACKET', 'GIT_TRACE_PERFORMANCE'
+          )
+          Kernel.should_receive(:exec).with(expected_hash, [1, 2], unsetenv_others: true).once
+
+          shell.send :exec_cmd, [1, 2]
+        end
+
+        it "writes an entry on the log" do
+          expect($logger).to receive(:warn).
+            with("gitlab-shell: is configured to trace git commands with #{git_trace_log_file.inspect} but it's not possible to write in that path Permission denied")
+
+          Kernel.should_receive(:exec).with(kind_of(Hash), [1, 2], unsetenv_others: true).once
+          shell.send :exec_cmd, [1, 2]
+        end
+      end
+    end
   end
 
   describe :api do