From 2dd42f3a3085d9c346668b956cd6c2c3e7f00874 Mon Sep 17 00:00:00 2001
From: Luka Vandervelden <lukc@upyum.com>
Date: Mon, 20 Jul 2020 14:23:10 +0200
Subject: [PATCH] Some tests and extra code for parallelization of DODB.

---
 spec/test.cr | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/dodb.cr  | 26 ++++++++++++++++-----
 2 files changed, 84 insertions(+), 6 deletions(-)

diff --git a/spec/test.cr b/spec/test.cr
index 43863d1..31c5778 100644
--- a/spec/test.cr
+++ b/spec/test.cr
@@ -482,5 +482,69 @@ describe "DODB::DataBase" do
 			end
 		end
 	end
+
+	describe "parallel support" do
+		# Not sure how many forks would be safe in a test like that.
+		fork_count = 25
+		entries_per_fork = 100
+
+		it "works for pushing values" do
+			db = DODB::SpecDataBase.new
+
+			processes = [] of Process
+
+			fork_count.times do |fork_id|
+				processes << Process.fork do
+					entries_per_fork.times do |entry_id|
+						db << Ship.new("entry-#{fork_id}-#{entry_id}", "???")
+					end
+				end
+			end
+
+			processes.each &.wait
+
+			dump = db.to_a
+
+			dump.size.should eq fork_count * entries_per_fork
+		end
+
+		it "works for updating values" do
+			db = DODB::SpecDataBase.new
+			db_entries_by_name = db.new_index "name", &.name
+
+			# First pass, creating data.
+			processes = [] of Process
+			fork_count.times do |fork_id|
+				processes << Process.fork do
+					entries_per_fork.times do |entry_id|
+						db << Ship.new("entry-#{fork_id}-#{entry_id}", "???")
+					end
+				end
+			end
+			processes.each &.wait
+
+			# Second pass, updating data.
+			processes = [] of Process
+			fork_count.times do |fork_id|
+				processes << Process.fork do
+					entries_per_fork.times do |entry_id|
+						db_entries_by_name.update Ship.new("entry-#{fork_id}-#{entry_id}", "???", tags: ["updated"])
+					end
+				end
+			end
+			processes.each &.wait
+
+			# Third pass, testing database content.
+			dump = db.to_a
+
+			fork_count.times do |fork_id|
+				entries_per_fork.times do |entry_id|
+					entry = db_entries_by_name.get "entry-#{fork_id}-#{entry_id}"
+
+					entry.tags.should eq ["updated"]
+				end
+			end
+		end
+	end
 end
 
diff --git a/src/dodb.cr b/src/dodb.cr
index 72dabe4..e5f1411 100644
--- a/src/dodb.cr
+++ b/src/dodb.cr
@@ -44,9 +44,9 @@ class DODB::DataBase(V)
 		end
 	end
 
-	def request_lock(name)
+	def request_lock(name, subname = nil)
 		r = -1
-		file_path = get_lock_file_path name
+		file_path = get_lock_file_path name, subname
 		file_perms = 0o644
 
 		flags = LibC::O_EXCL | LibC::O_CREAT
@@ -56,8 +56,8 @@ class DODB::DataBase(V)
 
 		LibC.close r
 	end
-	def release_lock(name)
-		File.delete get_lock_file_path name
+	def release_lock(name, subname = nil)
+		File.delete get_lock_file_path name, subname
 	end
 
 	##
@@ -107,11 +107,17 @@ class DODB::DataBase(V)
 	end
 
 	def <<(item : V)
+		request_lock "index"
+
 		index = last_index + 1
 
 		self[index] = item
 
 		self.last_index = index
+
+		release_lock "index"
+
+		index # FIXME: Should we really return the internal key?
 	end
 
 	def []?(key : Int32) : V?
@@ -160,6 +166,8 @@ class DODB::DataBase(V)
 	end
 
 	def pop
+		request_lock "index"
+
 		index = last_index
 
 		# Some entries may have been removed. We’ll skip over those.
@@ -178,6 +186,8 @@ class DODB::DataBase(V)
 
 		last_index = index - 1
 
+		release_lock "index"
+
 		poped
 	end
 
@@ -306,8 +316,12 @@ class DODB::DataBase(V)
 		"#{@directory_name}/locks"
 	end
 
-	private def get_lock_file_path(name : String)
-		"#{locks_directory}/#{name}.lock"
+	private def get_lock_file_path(name : String, subname : String? = nil)
+		if subname
+			"#{locks_directory}/#{name}-#{subname}.lock" # FIXME: Separator that causes less collisions?
+		else
+			"#{locks_directory}/#{name}.lock"
+		end
 	end
 
 	private def read(file_path : String)