add ability to configure timeout and other opts

Sequel supports various vendor-specific and connection-pool-specific
options that were not exposed to the plugin. This change introduces
a dedicated new configuration option to set a timeout and also a
catch-all configuration option for any other options that Sequel
supports upon opening a new database connection.

Fixes logstash-plugins#62.

lib/logstash/plugin_mixins/jdbc.rb

@@ -57,6 +57,37 @@ def setup_jdbc_config
     # Connection pool configuration.
     # How often to validate a connection (in seconds)
     config :jdbc_validation_timeout, :validate => :number, :default => 3600
+
+    # Connection pool configuration.
+    # The amount of seconds to wait to acquire a connection before raising a PoolTimeoutError (default 5)
+    config :jdbc_pool_timeout, :validate => :number, :default => 5
+
+    # General/Vendor-specific Sequel configuration options.
+    #
+    # An example of an optional connection pool configuration
+    #    max_connections - The maximum number of connections the connection pool
+    #
+    # examples of vendor-specific options can be found in this
+    # documentation page: https://github.com/jeremyevans/sequel/blob/master/doc/opening_databases.rdoc
+    config :sequel_opts, :validate => :hash, :default => {}
+  end
+
+  private
+  def jdbc_connect
+    opts = {
+      :user => @jdbc_user,
+      :password => @jdbc_password,
+      :pool_timeout => @jdbc_pool_timeout
+    }.merge(@sequel_opts)
+    begin
+      Sequel.connect(@jdbc_connection_string, opts=opts)
+    rescue Sequel::PoolTimeout => e
+      @logger.error("Failed to connect to database. #{@jdbc_pool_timeout} second timeout exceeded.")
+      raise e
+    rescue Sequel::Error => e
+      @logger.error("Unable to connect to database", :error_message => e.message)
+      raise e
+    end
   end
 
   public
@@ -76,7 +107,7 @@ def prepare_jdbc_connection
                 end
       raise LogStash::ConfigurationError, "#{e}. #{message}"
     end
-    @database = Sequel.connect(@jdbc_connection_string, :user=> @jdbc_user, :password=>  @jdbc_password.nil? ? nil : @jdbc_password.value)
+    @database = jdbc_connect()
     @database.extension(:pagination)
     if @jdbc_validate_connection
       @database.extension(:connection_validator)

spec/inputs/jdbc_spec.rb

@@ -310,4 +310,37 @@
       expect { plugin.register }.to raise_error(LogStash::ConfigurationError)
     end
   end
+
+  context "when timing out on connection" do
+    let(:settings) do
+      {
+        "statement" => "SELECT * FROM test_table",
+        "jdbc_pool_timeout" => 0,
+        "jdbc_connection_string" => 'mock://localhost:1527/db',
+        "sequel_opts" => {
+          "max_connections" => 1
+        }
+      }
+    end
+
+    it "should raise PoolTimeout error" do
+      plugin.register
+      db = plugin.instance_variable_get(:@database)
+      expect(db.pool.instance_variable_get(:@timeout)).to eq(0)
+      expect(db.pool.instance_variable_get(:@max_size)).to eq(1)
+
+      q, q1 = Queue.new, Queue.new
+      t = Thread.new{db.pool.hold{|c| q1.push nil; q.pop}}
+      q1.pop
+      expect{db.pool.hold {|c|}}.to raise_error(Sequel::PoolTimeout)
+      q.push nil
+      t.join
+    end
+
+    it "should log error message" do
+      allow(Sequel).to receive(:connect).and_raise(Sequel::PoolTimeout)
+      expect(plugin.logger).to receive(:error).with("Failed to connect to database. 0 second timeout exceeded.")
+      expect { plugin.register }.to raise_error(Sequel::PoolTimeout)
+    end
+  end
 end