Add sql connection pool

src/api/lib.zig

@@ -94,15 +94,15 @@ pub fn setupAdmin(db: sql.Db, origin: []const u8, username: []const u8, password
 }
 
 pub const ApiSource = struct {
-    db_conn: *sql.Conn,
+    db_conn_pool: *sql.ConnPool,
 
     pub const Conn = ApiConn(sql.Db);
 
     const root_username = "root";
 
-    pub fn init(db_conn: *sql.Conn) !ApiSource {
+    pub fn init(pool: *sql.ConnPool) !ApiSource {
         return ApiSource{
-            .db_conn = db_conn,
+            .db_conn_pool = pool,
         };
     }
 
@@ -110,7 +110,7 @@ pub const ApiSource = struct {
         var arena = std.heap.ArenaAllocator.init(alloc);
         errdefer arena.deinit();
 
-        const db = try self.db_conn.acquire();
+        const db = try self.db_conn_pool.acquire();
         const community = try services.communities.getByHost(db, host, arena.allocator());
 
         return Conn{
@@ -125,7 +125,7 @@ pub const ApiSource = struct {
         var arena = std.heap.ArenaAllocator.init(alloc);
         errdefer arena.deinit();
 
-        const db = try self.db_conn.acquire();
+        const db = try self.db_conn_pool.acquire();
         const community = try services.communities.getByHost(db, host, arena.allocator());
 
         const token_info = try services.auth.verifyToken(
@@ -157,6 +157,7 @@ fn ApiConn(comptime DbConn: type) type {
 
         pub fn close(self: *Self) void {
             self.arena.deinit();
+            self.db.releaseConnection();
         }
 
         fn isAdmin(self: *Self) bool {

src/main/main.zig

@@ -64,7 +64,10 @@ fn runAdminSetup(db: sql.Db, alloc: std.mem.Allocator) !void {
     try api.setupAdmin(db, origin, username, password, alloc);
 }
 
-fn prepareDb(db: sql.Db, alloc: std.mem.Allocator) !void {
+fn prepareDb(pool: *sql.ConnPool, alloc: std.mem.Allocator) !void {
+    const db = try pool.acquire();
+    defer db.releaseConnection();
+
     try migrations.up(db);
 
     if (!try api.isAdminSetup(db)) {
@@ -93,10 +96,10 @@ pub fn main() !void {
 
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     var cfg = try loadConfig(gpa.allocator());
-    var db_conn = try sql.Conn.open(cfg.db);
+    var pool = try sql.ConnPool.init(cfg.db);
-    try prepareDb(try db_conn.acquire(), gpa.allocator());
+    try prepareDb(&pool, gpa.allocator());
 
-    var api_src = try api.ApiSource.init(&db_conn);
+    var api_src = try api.ApiSource.init(&pool);
     var srv = try RequestServer.init(gpa.allocator(), &api_src, cfg);
     return srv.listenAndRun(std.net.Address.parseIp("0.0.0.0", 8080) catch unreachable);
 }

src/main/migrations.zig

@@ -16,10 +16,15 @@ fn execStmt(tx: anytype, stmt: []const u8, alloc: std.mem.Allocator) !void {
 }
 
 fn execScript(db: anytype, script: []const u8, alloc: std.mem.Allocator) !void {
+    const tx = try db.beginOrSavepoint();
+    errdefer tx.rollback();
+
     var iter = util.SqlStmtIter.from(script);
     while (iter.next()) |stmt| {
-        try execStmt(db, stmt, alloc);
+        try execStmt(tx, stmt, alloc);
     }
+
+    try tx.commitOrRelease();
 }
 
 fn wasMigrationRan(db: anytype, name: []const u8, alloc: std.mem.Allocator) !bool {

src/sql/engines/null.zig

@@ -28,6 +28,10 @@ pub const Db = struct {
         unreachable;
     }
 
+    pub fn openUri(_: anytype) common.OpenError!Db {
+        unreachable;
+    }
+
     pub fn close(_: Db) void {
         unreachable;
     }

src/sql/engines/sqlite.zig

@@ -49,7 +49,15 @@ pub const Db = struct {
     db: *c.sqlite3,
 
     pub fn open(path: [:0]const u8) common.OpenError!Db {
-        const flags = c.SQLITE_OPEN_READWRITE | c.SQLITE_OPEN_CREATE | c.SQLITE_OPEN_EXRESCODE;
+        return openInternal(path, false);
+    }
+
+    pub fn openUri(path: [:0]const u8) common.OpenError!Db {
+        return openInternal(path, true);
+    }
+
+    fn openInternal(path: [:0]const u8, is_uri: bool) common.OpenError!Db {
+        const flags = c.SQLITE_OPEN_READWRITE | c.SQLITE_OPEN_CREATE | c.SQLITE_OPEN_EXRESCODE | if (is_uri) c.SQLITE_OPEN_URI else 0;
 
         var db: ?*c.sqlite3 = null;
         switch (c.sqlite3_open_v2(@ptrCast([*c]const u8, path), &db, flags, null)) {
@@ -121,7 +129,6 @@ pub const Db = struct {
                 // of 0, and we must not bind the argument.
                 const name = std.fmt.comptimePrint("${}", .{i + 1});
                 const db_idx = c.sqlite3_bind_parameter_index(stmt.?, name);
-                std.log.debug("param {s} got index {}", .{ name, db_idx });
                 if (db_idx != 0)
                     try self.bindArgument(stmt.?, @intCast(u15, db_idx), arg)
                 else if (!opts.ignore_unused_arguments)
@@ -167,7 +174,6 @@ pub const Db = struct {
                 else
                     @compileError("SQLite: Could not serialize " ++ @typeName(T) ++ " into staticly sized string");
 
-                std.log.debug("binding type {any}: {s}", .{ T, arr });
                 const len = std.mem.len(&arr);
                 return self.bindString(stmt, idx, arr[0..len]);
             },
@@ -194,8 +200,6 @@ pub const Db = struct {
             return error.BindException;
         };
 
-        std.log.debug("binding string {s} to idx {}", .{ str, idx });
-
         switch (c.sqlite3_bind_text(stmt, idx, str.ptr, len, c.SQLITE_TRANSIENT)) {
             c.SQLITE_OK => {},
             else => |result| {

src/sql/lib.zig

@@ -10,6 +10,7 @@ const Allocator = std.mem.Allocator;
 
 const errors = @import("./errors.zig").library_errors;
 
+pub const AcquireError = OpenError || error{NoConnectionsLeft};
 pub const OpenError = errors.OpenError;
 pub const QueryError = errors.QueryError;
 pub const RowError = errors.RowError;
@@ -24,12 +25,14 @@ pub const Engine = enum {
     sqlite,
 };
 
+// TODO: make this suck less
 pub const Config = union(Engine) {
     postgres: struct {
         pg_conn_str: [:0]const u8,
     },
     sqlite: struct {
         sqlite_file_path: [:0]const u8,
+        sqlite_is_uri: bool = false,
     },
 };
 
@@ -160,16 +163,58 @@ pub const ConstraintMode = enum {
     immediate,
 };
 
-pub const Conn = struct {
+pub const ConnPool = struct {
-    engine: union(Engine) {
+    const max_conns = 4;
-        postgres: postgres.Db,
+    const Conn = struct {
-        sqlite: sqlite.Db,
+        engine: union(Engine) {
-    },
+            postgres: postgres.Db,
-    current_tx_level: u8 = 0,
+            sqlite: sqlite.Db,
-    is_tx_failed: bool = false,
+        },
+        in_use: std.atomic.Atomic(bool) = std.atomic.Atomic(bool).init(false),
+        current_tx_level: u8 = 0,
+    };
 
-    pub fn open(cfg: Config) OpenError!Conn {
+    config: Config,
-        return switch (cfg) {
+    connections: [max_conns]Conn,
+
+    pub fn init(cfg: Config) OpenError!ConnPool {
+        var self = ConnPool{
+            .config = cfg,
+            .connections = undefined,
+        };
+        var count: usize = 0;
+        errdefer for (self.connections[0..count]) |*c| closeConn(c);
+        for (self.connections) |*c| {
+            c.* = try self.createConn();
+            count += 1;
+        }
+
+        return self;
+    }
+
+    pub fn deinit(self: *ConnPool) void {
+        for (self.connections) |*c| closeConn(c);
+    }
+
+    pub fn acquire(self: *ConnPool) AcquireError!Db {
+        for (self.connections) |*c| {
+            if (tryAcquire(c)) return Db{ .conn = c };
+        }
+        return error.NoConnectionsLeft;
+    }
+
+    fn tryAcquire(conn: *Conn) bool {
+        const acquired = !conn.in_use.swap(true, .AcqRel);
+        if (acquired) {
+            if (conn.current_tx_level != 0) @panic("Transaction still open on unused db connection");
+            return true;
+        }
+
+        return false;
+    }
+
+    fn createConn(self: *ConnPool) OpenError!Conn {
+        return switch (self.config) {
             .postgres => |postgres_cfg| Conn{
                 .engine = .{
                     .postgres = try postgres.Db.open(postgres_cfg.pg_conn_str),
@@ -177,27 +222,22 @@ pub const Conn = struct {
             },
             .sqlite => |lite_cfg| Conn{
                 .engine = .{
-                    .sqlite = try sqlite.Db.open(lite_cfg.sqlite_file_path),
+                    .sqlite = if (lite_cfg.sqlite_is_uri)
+                        try sqlite.Db.openUri(lite_cfg.sqlite_file_path)
+                    else
+                        try sqlite.Db.open(lite_cfg.sqlite_file_path),
                 },
             },
         };
     }
 
-    pub fn close(self: *Conn) void {
+    fn closeConn(conn: *Conn) void {
-        switch (self.engine) {
+        if (conn.in_use.loadUnchecked()) @panic("DB Conn still open");
+        switch (conn.engine) {
             .postgres => |pg| pg.close(),
             .sqlite => |lite| lite.close(),
         }
     }
-
-    pub fn acquire(self: *Conn) !Db {
-        if (self.current_tx_level != 0) return error.BadTransactionState;
-        return Db{ .conn = self };
-    }
-
-    pub fn sqlEngine(self: *Conn) Engine {
-        return self.engine;
-    }
 };
 
 pub const Db = Tx(0);
@@ -216,11 +256,22 @@ fn Tx(comptime tx_level: u8) type {
             std.fmt.comptimePrint("save_{}", .{tx_level});
         const next_savepoint_name = Tx(tx_level + 1).savepoint_name;
 
-        conn: *Conn,
+        conn: *ConnPool.Conn,
 
         /// The type of SQL engine being used. Use of this function should be discouraged
         pub fn sqlEngine(self: Self) Engine {
-            return self.conn.sqlEngine();
+            return self.conn.engine;
+        }
+
+        /// Return the connection to the pool
+        pub fn releaseConnection(self: Self) void {
+            if (tx_level != 0) @compileError("close must be called on root db");
+            if (self.conn.current_tx_level != 0) {
+                std.log.warn("Database released while transaction in progress!", .{});
+                self.rollbackUnchecked() catch {};
+            }
+
+            if (!self.conn.in_use.swap(false, .AcqRel)) @panic("Double close on db conection");
         }
 
         // ********* Transaction management functions **********
@@ -277,7 +328,7 @@ fn Tx(comptime tx_level: u8) type {
             if (tx_level >= 2) @compileError("Cannot rollback a transaction using a savepoint");
             if (self.conn.current_tx_level == 0) return error.BadTransactionState;
 
-            try self.exec("ROLLBACK", {}, null);
+            try self.rollbackUnchecked();
 
             self.conn.current_tx_level = 0;
         }
@@ -453,5 +504,9 @@ fn Tx(comptime tx_level: u8) type {
 
             while (try results.row()) |_| {}
         }
+
+        fn rollbackUnchecked(self: Self) !void {
+            try self.exec("ROLLBACK", {}, null);
+        }
     };
 }

tests/api_integration/lib.zig

@@ -5,11 +5,10 @@ const sql = @import("sql");
 const util = @import("util");
 
 const test_config = .{
-    .db = .{
+    .db = .{ .sqlite = .{
-        .sqlite = .{
+        .sqlite_file_path = "file::memory:?cache=shared",
-            .sqlite_file_path = ":memory:",
+        .sqlite_is_uri = true,
-        },
+    } },
-    },
 };
 
 const ApiSource = api.ApiSource;
@@ -18,12 +17,16 @@ const root_password = "password1234";
 const admin_host = "example.com";
 const admin_origin = "https://" ++ admin_host;
 
-fn makeDb(alloc: std.mem.Allocator) !sql.Conn {
+fn makeDb(alloc: std.mem.Allocator) !sql.ConnPool {
     try util.seedThreadPrng();
-    var db = try sql.Conn.open(test_config.db);
+    var pool = try sql.ConnPool.init(test_config.db);
-    try migrations.up(try db.acquire());
+    {
-    try api.setupAdmin(try db.acquire(), admin_origin, root_user, root_password, alloc);
+        var db = try pool.acquire();
-    return db;
+        defer db.releaseConnection();
+        try migrations.up(db);
+        try api.setupAdmin(db, admin_origin, root_user, root_password, alloc);
+    }
+    return pool;
 }
 
 fn connectAndLogin(
@@ -42,6 +45,7 @@ fn connectAndLogin(
 test "login as root" {
     const alloc = std.testing.allocator;
     var db = try makeDb(alloc);
+    defer db.deinit();
     var src = try ApiSource.init(&db);
 
     const login = try connectAndLogin(&src, admin_host, root_user, root_password, alloc);
@@ -59,6 +63,7 @@ test "login as root" {
 test "create community" {
     const alloc = std.testing.allocator;
     var db = try makeDb(alloc);
+    defer db.deinit();
     var src = try ApiSource.init(&db);
 
     const login = try connectAndLogin(&src, admin_host, root_user, root_password, alloc);
@@ -80,6 +85,7 @@ test "create community" {
 test "create community and transfer to new owner" {
     const alloc = std.testing.allocator;
     var db = try makeDb(alloc);
+    defer db.deinit();
     var src = try ApiSource.init(&db);
 
     const root_login = try connectAndLogin(&src, admin_host, root_user, root_password, alloc);