From 4467795c4a06380676ece748a62a2032007dd81c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jon=20B=C3=B6rjesson?= <jon@spuun.se>
Date: Fri, 7 Feb 2025 09:27:22 +0100
Subject: [PATCH 1/2] Make #resize able to increase size

---
 spec/mfile_spec.cr   | 22 ++++++++++++++++++++++
 src/lavinmq/mfile.cr | 14 +++++++++++---
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/spec/mfile_spec.cr b/spec/mfile_spec.cr
index 0fddbecd3b..0d3d5a6e70 100644
--- a/spec/mfile_spec.cr
+++ b/spec/mfile_spec.cr
@@ -29,4 +29,26 @@ describe MFile do
       file.delete
     end
   end
+
+  describe "#resize" do
+    it "can increase size" do
+      file = File.tempfile "mfile_spec"
+      file.print "hello world"
+      file.flush
+      data = "foo"
+      initial_size = file.size
+      MFile.open(file.path, initial_size) do |mfile|
+        mfile.capacity.should eq initial_size
+        expect_raises(IO::EOFError) { mfile.write data.to_slice }
+        mfile.resize(mfile.size + data.bytesize)
+        mfile.write data.to_slice
+        mfile.capacity.should eq(initial_size + data.bytesize)
+      end
+      file.size.should eq(initial_size + data.bytesize)
+      data = File.read(file.path)
+      data.should eq "hello worldfoo"
+    ensure
+      file.try &.delete
+    end
+  end
 end
diff --git a/src/lavinmq/mfile.cr b/src/lavinmq/mfile.cr
index 8101b7d5c3..17fcc7f344 100644
--- a/src/lavinmq/mfile.cr
+++ b/src/lavinmq/mfile.cr
@@ -271,9 +271,17 @@ class MFile < IO
   end
 
   def resize(new_size : Int) : Nil
-    raise ArgumentError.new("Can't expand file larger than capacity, use truncate") if new_size > @capacity
-    @size = new_size.to_i64
-    @pos = new_size.to_i64 if @pos > new_size
+    if new_size > @capacity
+      raise File::Error.new("Can't resize readonly file", file: @path) if @readonly
+      unsafe_unmap
+      @capacity = new_size.to_i64
+      code = LibC.ftruncate(@fd, @capacity)
+      raise File::Error.from_errno("Error truncating file", file: @path) if code < 0
+      @buffer = mmap
+    else
+      @size = new_size.to_i64
+      @pos = new_size.to_i64 if @pos > new_size
+    end
   end
 
   # Read from a specific position in the file

From 9ee24e6b2903cff3d3dca40ab26347f7247ea105 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jon=20B=C3=B6rjesson?= <jon@spuun.se>
Date: Fri, 7 Feb 2025 13:40:58 +0100
Subject: [PATCH 2/2] Use MFiles in follower

Close and unmap files that haven't been accessed for a moment
---
 src/lavinmq/clustering/client.cr | 65 +++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/src/lavinmq/clustering/client.cr b/src/lavinmq/clustering/client.cr
index 95b5e90b58..1a8727f79a 100644
--- a/src/lavinmq/clustering/client.cr
+++ b/src/lavinmq/clustering/client.cr
@@ -1,10 +1,62 @@
 require "../clustering"
 require "../clustering/proxy"
 require "../data_dir_lock"
+require "../mfile"
 require "lz4"
 
 module LavinMQ
   module Clustering
+    class ReplicatedFile
+      getter last_access = Time.monotonic
+      getter path : String
+
+      @file : MFile
+
+      def initialize(@path : String, @capacity : Int64)
+        # Ensure the file exists
+        @file = MFile.new(@path, @capacity)
+      end
+
+      def write(data : Bytes)
+        @last_access = Time.monotonic
+        resize_to_fit(data.size)
+        @file.write data
+      end
+
+      def resize_to_fit(bytes_to_fit)
+        new_capacity = size + bytes_to_fit
+        if new_capacity > @capacity
+          @file.resize new_capacity
+          @capacity = new_capacity
+        end
+      end
+
+      def size
+        @file.try &.size || File.size(@path)
+      end
+
+      def rename(new_filename)
+        @last_access = Time.monotonic
+        File.rename @path, new_filename
+        @path = new_filename
+      end
+
+      def delete
+        @last_access = Time.monotonic
+        File.delete @path
+      end
+
+      def close
+        @last_access = Time.monotonic
+        @file.close
+      end
+
+      private def with_file(&)
+        @last_access = Time.monotonic
+        yield (@file ||= MFile.new(@path, @capacity))
+      end
+    end
+
     class Client
       Log = LavinMQ::Log.for "clustering.client"
       @data_dir_lock : DataDirLock
@@ -19,10 +71,18 @@ module LavinMQ
       def initialize(@config : Config, @id : Int32, @password : String, proxy = true)
         System.maximize_fd_limit
         @data_dir = config.data_dir
-        @files = Hash(String, File).new do |h, k|
+        @files = Hash(String, ReplicatedFile).new do |h, k|
           path = File.join(@data_dir, k)
           Dir.mkdir_p File.dirname(path)
-          h[k] = File.open(path, "a").tap &.sync = true
+          h[k] = ReplicatedFile.new(path, Config.instance.segment_size)
+          h.reject! do |_, f|
+            if f.last_access < (Time.monotonic - 10.seconds)
+              f.close
+              true
+            end
+            false
+          end
+          h[k]
         end
         Dir.mkdir_p @data_dir
         @data_dir_lock = DataDirLock.new(@data_dir).tap &.acquire
@@ -213,6 +273,7 @@ module LavinMQ
           when .negative? # append bytes to file
             Log.debug { "Appending #{len.abs} bytes to #{filename}" }
             f = @files[filename]
+            f.resize_to_fit(len.abs)
             IO.copy(lz4, f, len.abs) == len.abs || raise IO::EOFError.new("Full append not received")
           when .zero? # file is deleted
             Log.debug { "Deleting #{filename}" }