Deploying MariaDB for High Availability on Google Cloud Platform
Google Cloud Platform (GCP) is a rising star in the world of cloud infrastructure. Of course there is Google CloudSQL, but sometimes you need more control over your databases.
Pythian Group Inc., 2017 Matthias Crauwels • Living in Ghent, Belgium • Bachelor Computer Science • ~20 years Linux user / admin • ~10 years PHP developer • ~8 years MySQL DBA • 3rd year at Pythian • Currently Lead Database Consultant • GCP Certified Professional Architect • AWS Solutions Architect Associate • Father of Leander
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Group Inc., 2019 9 • Public cloud by Google • Started as "AppEngine" (GA since Nov 2011) • New services grew quickly, Compute Engine, CloudSQL, ... Google Cloud Platform
Group Inc., 2019 10 Service comparison to AWS Google Cloud Platform (GCP) Amazon Web Services (AWS) Google Compute Engine (GCE) Elastic Compute Cloud (EC2) Google Cloud Storage (GCS) Simple Storage Service (S3) Google Kubernetes Engine (GKE) Elastic Container Service for Kubernetes Google CloudSQL Relational Database Service (RDS) Google BigQuery Redshift ... ...
Pythian Group Inc., 2019 Google CloudSQL Google Spanner • Managed service for MySQL and PostgreSQL • Scales up to 10 TB storage • Regional availability • Fully managed service • Read replicas in multiple zones • Relational database store • Horizontally scalable • Heavily sharded • Global availability • Highly Available • Fully managed service
Group Inc., 2019 14 • Stability CloudSQL is still a pretty young product, it's not really mature (yet). • Flexibility There are still limits to the SQL you can run, not a simple lift-and-shift • Cost Spanner is more expensive than Compute Engine Why do something else?
Group Inc., 2019 16 • MariaDB + Galera cluster • Minimum 3 nodes (always odd number of nodes) • Preferably within the same region (latency) • Writing to any node is supported, but not recommended • Suggested to use a proxy-layer • MaxScale (for MariaDB subscribers) • ProxySQL MariaDB Cluster
Group Inc., 2019 18 On premise → GCP 1. Take a backup on premise 2. Use backup to seed first node in GCE 3. Bootstrap first node 4. Start node 2 and 3 → they will perform SST 5. Set up async replication from on prem to first node 6. Setup proxies and load-balancers 7. Cut over application to new load-balancer MariaDB Cluster - migration path
Group Inc., 2019 19 MariaDB Cluster - conclusion Pro Con Lift and shift from on-prem to the cloud Will not keep scaling You can put nodes in different zones within the same region Will not scale to multi-region Proxy will perform read-write split All the perks from using Galera All the benefits from using Galera
Group Inc., 2019 21 • Default replication method for years in MySQL world • Very stable and reliable • Minimum 2 nodes (1 master + 1 replica/slave) • Can be multi-region • What about master high availability? Regular (asynchronous) replication
Group Inc., 2019 23 • Master is single-point-of-failure (spof) • How to detect master failure? • What to do when failure is detected? • How to announce changes in topology to the application • ... • Slaves scale out pretty well but • There is no global load balancer for port 3306 • ... Problems
Group Inc., 2019 24 Orchestrator is a High Availability and replication management tool. • Works with ALL flavours of MySQL / MariaDB • Can be use for multiple purposes • discovery • visualisation • refactoring • recovery Master high availability using Orchestrator
Group Inc., 2019 25 Orchestrator - discovery Orchestrator can (and will) discover your entire replication technology as soon as you connect it to a single server in the topology. It will use SHOW SLAVE HOSTS, SHOW PROCESSLIST, SHOW SLAVE STATUS to try and connect to the other servers in the topology. Requirement: the orchestrator_topology_user needs to be created on every server in the cluster so it can connect.
Group Inc., 2019 27 Orchestrator - refactoring Orchestrator can be used to refactor the topology. This can be done from the command line tool, via the API or even via the web interface by dragging and dropping. You can do things like • Repoint a slave to a new master • Promote a server to a (co-)master • Start / Stop slave • ...
Group Inc., 2019 28 Orchestrator - recovery All of these features are nice, but they still require a human to execute them. This doesn’t help you much when your master goes down at 3AM and you get paged to resolve this. Orchestrator can be configured to automatically recover your topology from an outage.
Group Inc., 2019 29 Orchestrator - how recovery works? To be able to perform a recovery, Orchestrator first needs to detect a failure. As indicated before Orchestrator connects to every server in the topology and gathers information from each of the instances. Orchestrator uses this information to make decisions on the best action to take. They call this the holistic approach.
Group Inc., 2019 31 Orchestrator HA Orchestrator was written with High Availability as a basic concept. You can easily run multiple Orchestrator instances with a shared MySQL backend. All instances will collect all information but they will allow only one instance to be the “active node” and to make changes to the topology. To eliminate a single-point-of-failure in the database backend you can use either master-master replication (2 nodes) or Galera synchronous replication (3 nodes).
Group Inc., 2019 32 Orchestrator HA (2) Since version 3.x of Orchestrator there is “Orchestrator-on-Raft”. Orchestrator now implements the ‘raft consensus protocol’. This will • Ensure that a leader node is elected from the available nodes • Ensure that the leader node has a quorum (majority) at all times • Allow to run Orchestrator without a shared database backend • Allow to run without a MySQL backend but use a sqlite backend
Group Inc., 2019 33 • Managed Instance Group requiring 3 nodes • Orchestrator nodes using • Raft for leader elections • SQLite backend for local state • Orchestrator database is auto-healing so no data replication is required Orchestrator in GCP
Group Inc., 2019 36 • We introduce a proxy layer • to help with read write splitting • to prevent application connections to break on failover • to have an easy to manage endpoint • Proxy options • ProxySQL • MaxScale • In this example I will use ProxySQL Read write splitting
Group Inc., 2019 37 • Layer 7 proxy, understands MySQL protocol • Uses "hostgroups" to group hosts together (example one hostgroup for master and one for slaves) • Query rules to redirect traffic to hostgroups example: by default all queries go to master hostgroup add query rule to have regex ^SELECT to go to slaves • ProxySQL clustering • Proxy's will share configuration • On GCP, start with 2 instances in Managed Instance Group with autoscaling, add load balancer for traffic ProxySQL
Group Inc., 2019 40 • Up until this slide ProxySQL and MaxScale are interchangeable • Hostgroups and Query rules can be replaced by the read-write-split-service. • We picked ProxySQL because of what comes next: How do we connect Orchestrator and the proxy in a safe way? Why ProxySQL over MaxScale
Group Inc., 2019 41 • Consul • Distributed key-value store • Orchestrator has native support for Consul • Works across DC's • Consul-template • Connects to a consul service • Updates a templated file everytime consul is update • Runs arbitrary command on every update Consul and Consul-template
Group Inc., 2019 42 • Orchestrator detects failure • Orchestrator takes action, promoting new master • Orchestrator updates Consul KV store • Consul distributes values and notifies watchers • Consul-template receives a notification • Consul-template recreates query file and launches configured command Consul workflow
Group Inc., 2019 43 • Orchestrator has built-in support to update master entries in the Consul KV store • But if we want the new master to be taken out of the reader pool we need to implement some "hooks" to update Consul • Example # cat /usr/local/orchestrator/postfailoverhook.sh #!/bin/bash CONSUL_EXEC="/usr/local/bin/consul" CONSUL_SLAVE_PREFIX="mysql/slave" echo "Failover occurred. Running custom PostMasterFailoverProcesses Hook" # orchestrator needs to make call to consul so the following is accomplished: # 1. remove new master from slave group # 2. put old master in slave group echo "Removing new master from slave pool: ${CONSUL_SLAVE_PREFIX}/${ORC_FAILURE_CLUSTER_ALIAS}/${ORC_SUCCESSOR_HOST}" ${CONSUL_EXEC} kv delete ${CONSUL_SLAVE_PREFIX}/${ORC_FAILURE_CLUSTER_ALIAS}/${ORC_SUCCESSOR_HOST} echo "Adding old master to slave pool: ${CONSUL_SLAVE_PREFIX}/${ORC_FAILURE_CLUSTER_ALIAS}/${ORC_FAILED_HOST}" ${CONSUL_EXEC} kv put ${CONSUL_SLAVE_PREFIX}/${ORC_FAILURE_CLUSTER_ALIAS}/${ORC_FAILED_HOST} Orchestrator hooks
Group Inc., 2019 44 • Example of "query" file {{ if keyExists "mysql/master/testcluster/hostname" }} DELETE FROM mysql_servers where hostgroup_id=10; REPLACE into mysql_servers (hostgroup_id, hostname) values ( 10, " {{ key "mysql/master/testcluster/hostname" }}" ); {{ end }} DELETE FROM mysql_servers where hostgroup_id=11; {{ range tree "mysql/slave/testcluster" }} REPLACE INTO mysql_servers (hostgroup_id, hostname) values ( 11, " {{ .Key }}{{ .Value }}" ); {{ end }} LOAD MYSQL SERVERS TO RUNTIME; SAVE MYSQL SERVERS TO DISK; • Example command command = "/bin/bash -c 'mysql --defaults-file=/etc/proxysql-admin.my.cnf < /opt/consul-template/templates/proxysql.sql'" command_timeout = "60s" Consul-template examples
Group Inc., 2019 46 • WePay https://wecode.wepay.com/posts/highly-available-mysql-clusters-at- wepay • Implementation done by our sibling-team • Chosen for HAProxy over ProxySQL because they needed end-to-end SSL encryption • ProxySQL 1.4.x does not support client-side SSL • ProxySQL 2.x does support full end-to-end SSL encryption but was not GA yet at time of implementation. Publicly shared example
Group Inc., 2019 47 • We would want to create a multi-region setup • Will be able to work on read-heavy environment that can tolerate some "stale" reads. • Master will still be a single instance that runs in one region. • 1 or more slave(s) in each region • ProxySQL cluster with internal load balancer in each region, applications connect to local proxy cluster • Orchestrator and Consul server can be scale to 1 instance per region (recommended max 3 instances so not every region might have an instance) Where to go from here?
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