cdc: add CDCPartitioner

This is a special partitioner that will be used by
CDC Log. It works only with partition key that is blob
composed of two ints. The first int is a token this
partitioner will map the key to. The second int is there
to make it possible to create multiple keys that are different
from each other but map to the same token.

Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>

cdc/cdc_partitioner.cc

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2020 ScyllaDB
+ */
+
+/*
+ * This file is part of Scylla.
+ *
+ * Scylla is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Scylla is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "cdc_partitioner.hh"
+#include "dht/token.hh"
+#include "schema.hh"
+#include "sstables/key.hh"
+#include "utils/class_registrator.hh"
+#include "cdc/generation.hh"
+#include "keys.hh"
+
+static const sstring cdc_partitioner_name = "com.scylladb.dht.CDCPartitioner";
+
+namespace cdc {
+
+const sstring cdc_partitioner::name() const {
+    return cdc_partitioner_name;
+}
+
+static dht::token to_token(int64_t value) {
+    return dht::token(dht::token::kind::key, value);
+}
+
+static dht::token to_token(bytes_view key) {
+    if (key.empty()) {
+        return dht::minimum_token();
+    }
+    return to_token(stream_id::token_from_bytes(key));
+}
+
+dht::token
+cdc_partitioner::get_token(const sstables::key_view& key) const {
+    return to_token(bytes_view(key));
+}
+
+dht::token
+cdc_partitioner::get_token(const schema& s, partition_key_view key) const {
+    auto exploded_key = key.explode(s);
+    return to_token(exploded_key[0]);
+}
+
+using registry = class_registrator<dht::i_partitioner, cdc_partitioner>;
+static registry registrator(cdc_partitioner_name);
+static registry registrator_short_name("CDCPartitioner");
+
+}

cdc/cdc_partitioner.hh

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2020 ScyllaDB
+ */
+
+/*
+ * This file is part of Scylla.
+ *
+ * Scylla is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Scylla is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <seastar/core/sstring.hh>
+
+#include "bytes.hh"
+#include "dht/i_partitioner.hh"
+
+class schema;
+class partition_key_view;
+
+namespace sstables {
+
+class key_view;
+
+}
+
+namespace cdc {
+
+struct cdc_partitioner final : public dht::i_partitioner {
+    cdc_partitioner() = default;
+    virtual const sstring name() const override;
+    virtual dht::token get_token(const schema& s, partition_key_view key) const override;
+    virtual dht::token get_token(const sstables::key_view& key) const override;
+};
+
+
+}

configure.py

@@ -546,6 +546,7 @@ scylla_core = (['database.cc',
                 'transport/event_notifier.cc',
                 'transport/server.cc',
                 'transport/messages/result_message.cc',
+                'cdc/cdc_partitioner.cc',
                 'cdc/log.cc',
                 'cdc/split.cc',
                 'cdc/generation.cc',