Explicit shard selection; Rails tests (#24)

* Explicit shard selection; Rails tests

* try running ruby tests

* try without lockfile

* aha

* ok

.circleci/config.yml

@@ -25,7 +25,7 @@ jobs:
           key: cargo-lock-2-{{ checksum "Cargo.lock" }}
       - run:
           name: "Install dependencies"
-          command: "sudo apt-get update && sudo apt-get install -y psmisc postgresql-contrib-12 postgresql-client-12"
+          command: "sudo apt-get update && sudo apt-get install -y psmisc postgresql-contrib-12 postgresql-client-12 ruby ruby-dev libpq-dev"
       - run:
           name: "Build" 
           command: "cargo build"

.circleci/run_tests.sh

@@ -34,6 +34,14 @@ psql -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_test_select.sql > /
 # Replica/primary selection & more sharding tests
 psql -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_test_primary_replica.sql > /dev/null
 
+#
+# ActiveRecord tests!
+#
+cd tests/ruby
+sudo gem install bundler
+bundle install
+ruby tests.rb
+
 # Attempt clean shut down
 killall pgcat -s SIGINT
 

src/query_router.rs

@@ -10,11 +10,13 @@ use sqlparser::parser::Parser;
 use crate::config::Role;
 use crate::sharding::Sharder;
 
-const SHARDING_REGEX: &str = r"SET SHARDING KEY TO '[0-9]+';";
+const SHARDING_REGEX: &str = r"SET SHARDING KEY TO '[0-9]+'";
-const ROLE_REGEX: &str = r"SET SERVER ROLE TO '(PRIMARY|REPLICA)';";
+const SET_SHARD_REGEX: &str = r"SET SHARD TO '[0-9]+'";
+const ROLE_REGEX: &str = r"SET SERVER ROLE TO '(PRIMARY|REPLICA)'";
 
 static SHARDING_REGEX_RE: OnceCell<Regex> = OnceCell::new();
 static ROLE_REGEX_RE: OnceCell<Regex> = OnceCell::new();
+static SET_SHARD_REGEX_RE: OnceCell<Regex> = OnceCell::new();
 
 pub struct QueryRouter {
     // By default, queries go here, unless we have better information
@@ -60,7 +62,17 @@ impl QueryRouter {
             Err(_) => false,
         };
 
-        a && b
+        let c = match SET_SHARD_REGEX_RE.set(
+            RegexBuilder::new(SET_SHARD_REGEX)
+                .case_insensitive(true)
+                .build()
+                .unwrap(),
+        ) {
+            Ok(_) => true,
+            Err(_) => false,
+        };
+
+        a && b && c
     }
 
     pub fn new(
@@ -99,12 +111,17 @@ impl QueryRouter {
         let len = buf.get_i32();
         let query = String::from_utf8_lossy(&buf[..len as usize - 4 - 1]); // Don't read the ternminating null
 
-        let rgx = match SHARDING_REGEX_RE.get() {
+        let sharding_key_rgx = match SHARDING_REGEX_RE.get() {
             Some(r) => r,
             None => return false,
         };
 
-        if rgx.is_match(&query) {
+        let set_shard_rgx = match SET_SHARD_REGEX_RE.get() {
+            Some(r) => r,
+            None => return false,
+        };
+
+        if sharding_key_rgx.is_match(&query) {
             let shard = query.split("'").collect::<Vec<&str>>()[1];
 
             match shard.parse::<i64>() {
@@ -120,6 +137,15 @@ impl QueryRouter {
                 // case anyway.
                 Err(_) => false,
             }
+        } else if set_shard_rgx.is_match(&query) {
+            let shard = query.split("'").collect::<Vec<&str>>()[1];
+            match shard.parse::<usize>() {
+                Ok(shard) => {
+                    self.active_shard = Some(shard);
+                    true
+                }
+                Err(_) => false,
+            }
         } else {
             false
         }
@@ -439,4 +465,28 @@ mod test {
         assert!(query_router.infer_role(res));
         assert_eq!(query_router.role(), Some(Role::Replica));
     }
+
+    #[test]
+    fn test_set_shard_explicitely() {
+        QueryRouter::setup();
+
+        let default_server_role: Option<Role> = None;
+        let shards = 5;
+
+        let mut query_router = QueryRouter::new(default_server_role, shards, false, false);
+
+        // Build the special syntax query.
+        let mut message = BytesMut::new();
+        let query = BytesMut::from(&b"SET SHARD TO '1'\0"[..]);
+
+        message.put_u8(b'Q'); // Query
+        message.put_i32(query.len() as i32 + 4);
+        message.put_slice(&query[..]);
+
+        assert!(query_router.select_shard(message));
+        assert_eq!(query_router.shard(), 1); // See sharding.rs (we are using 5 shards on purpose in this test)
+
+        query_router.reset();
+        assert_eq!(query_router.shard(), 0);
+    }
 }

tests/ruby/.ruby-version

@@ -0,0 +1 @@
+2.7.1

tests/ruby/Gemfile

@@ -0,0 +1,4 @@
+source "https://rubygems.org"
+
+gem "pg"
+gem "activerecord"

tests/ruby/Gemfile.lock

@@ -0,0 +1,30 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    activemodel (7.0.2.2)
+      activesupport (= 7.0.2.2)
+    activerecord (7.0.2.2)
+      activemodel (= 7.0.2.2)
+      activesupport (= 7.0.2.2)
+    activesupport (7.0.2.2)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
+    concurrent-ruby (1.1.9)
+    i18n (1.10.0)
+      concurrent-ruby (~> 1.0)
+    minitest (5.15.0)
+    pg (1.3.2)
+    tzinfo (2.0.4)
+      concurrent-ruby (~> 1.0)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  activerecord
+  pg
+
+BUNDLED WITH
+   2.3.7

tests/ruby/tests.rb

@@ -1,11 +1,74 @@
-require 'pg'
+require "active_record"
 
-conn = PG.connect(host: '127.0.0.1', port: 5433, dbname: 'test')
+ActiveRecord.verbose_query_logs = true
+ActiveRecord::Base.logger = Logger.new(STDOUT)
 
-conn.exec( "SELECT * FROM pg_stat_activity" ) do |result|
+ActiveRecord::Base.establish_connection(
-  puts "     PID | User             | Query"
+  adapter: "postgresql",
-  result.each do |row|
+  host: "127.0.0.1",
-    puts " %7d | %-16s | %s " %
+  port: 6432,
-      row.values_at('pid', 'usename', 'query')
+  username: "sharding_user",
+  password: "sharding_user",
+  database: "rails_dev",
+  prepared_statements: false, # Transaction mode
+  advisory_locks: false, # Same
+)
+
+class TestTable < ActiveRecord::Base
+  self.table_name = "test_table"
+end
+
+# # Create the table.
+class CreateTestTable < ActiveRecord::Migration[7.0]
+  # Disable transasctions or things will fly out of order!
+  disable_ddl_transaction!
+
+  SHARDS = 3
+
+  def change
+    SHARDS.times do |x|
+      # This will make this migration reversible!
+      reversible do
+        connection.execute "SET SHARD TO '#{x.to_i}'"
+      end
+
+      # Always wrap the entire migration inside a transaction. If that's not possible,
+      # execute a `SET SHARD` command before every statement and make sure AR doesn't need
+      # to load database information beforehand (i.e. it's not the first query in the migration).
+      connection.transaction do
+        create_table :test_table, if_not_exists: true do |t|
+          t.string :name
+          t.string :description
+
+          t.timestamps
+        end
+      end
+    end
   end
 end
+
+begin
+  CreateTestTable.migrate(:down)
+rescue Exception
+  puts "Tables don't exist yet"
+end
+
+CreateTestTable.migrate(:up)
+
+10.times do |x|
+  x += 1 # Postgres ids start at 1
+  r = TestTable.connection.execute "SET SHARDING KEY TO '#{x.to_i}'"
+
+  # Always wrap writes inside explicit transactions like these because ActiveRecord may fetch table info
+  # before actually issuing the `INSERT` statement. This ensures that that happens inside a transaction
+  # and the write goes to the correct shard.
+  TestTable.connection.transaction do
+    TestTable.create(id: x, name: "something_special_#{x.to_i}", description: "It's a surprise!")
+  end
+end
+
+10.times do |x|
+  x += 1 # 0 confuses our sharding function
+  TestTable.connection.execute "SET SHARDING KEY TO '#{x.to_i}'"
+  puts TestTable.find_by_id(x).id
+end