Pre-requisites
An HA installation requires the following components:
-
Two or more clusters with matching Kinetica installations managed by
KAgent
If the clusters are not managed, KAgent should be
installed and then the clusters should be
added to it.
-
Two nodes (across the clusters) have RabbitMQ installed
-
etcd
-
The KAgent UI
Configuration
Enable HA
HA is enabled on a ring using the KAgent UI. To enable HA using KAgent:
-
Log into the KAgent service with a web browser:
http://<kagent-host>:8081
-
From the left menu, click Manage.
-
On the Rings page, next to the ring containing your clusters, click
Enable HA.
-
Click Enable to confirm setup. The High Availability package
will be installed on each cluster and automatically configured.
-
Click Close. HA is now enabled for the ring.
Config HA
KAgent exposes the most important High Availability configuration settings
via the KAgent UI. Information about the settings can be found in the table
below.
All HA configuration settings can be edited via the etcd modify
configuration window on the KAgent Rings
dashboard. However, the settings can only be
edited if the database is shutdown. | Setting | Description | Default Value |
|---|
qos | Quality of service; limits the number of messages that are prefetched and queued locally on the cluster for better consumption performance. | 1000 |
startup_queue_limit | The database appears down until the queue is drained of the set number of requests. | 100000 |
max_request_failures | Determines how many times a cluster can fail to receive a request that was successful on another cluster. | 3 |
request_failure_pause | Time to pause in seconds between request send retries. | 3 |
discard_failed_requests | If true, then requests that exceed the maximum failures (and timeout) will be discarded. | true |
-
Log into the KAgent service with a web browser:
http://<kagent-host>:8081
-
From the left menu, click Manage.
-
On the Rings page, next to the ring containing your clusters, click
Config HA.
-
Adjust the settings as necessary.
-
Click Update.
APIs
Any client API connection made to a cluster within an HA ring will automatically
be configured to fail over from one cluster in the ring to another in the event
of an outage. A client API connection can be configured manually to fail over
from one cluster to another in a set of clusters that are not part of an HA ring
by specifying the cluster URLs at the time of connection.
The enabled failover mode (active/active or active/passive) is governed by
whether a primary URL is specified or implied as follows:
- Active/Active - No primary URL is specified and more than one URL is
specified
- Active/Passive - A primary URL is specified, or a single URL is specified
For more information on the HA failover modes, consult
Failover Modes.
If using either failover mode and a cluster is not reachable, the API
will attempt to re-establish the current cluster connection a configurable
number of times. Failing that, it will attempt to amend the connection by
connecting to one of the other clusters in either the ring or the set of URLs
specified at the initial time of connection. If no other clusters can be
reached, the connection fails.
C++
For more information on C++ API database object instantiation, review
the C++ API Reference. Active/Active Configuration
To instantiate a Kinetica connection object with failover in C++, pass a
comma-delimited list of head node URLs to the constructor:
gpudb::GPUdb gpudb("http://172.1.2.3:9191,http://172.1.2.4:9191,http://172.1.2.5:9191");
If you provide a single URL to the GPUdb constructor, the failover mode
will instead be Active/Passive and the URL will be treated as the primary
URL.
Active/Passive Configuration
To designate a cluster from the list to always attempt to go to first, specify a
primary URL:
gpudb::GPUdb::Options options = gpudb::GPUdb::Options().setPrimaryUrl("http://172.1.2.4:9191");
gpudb::GPUdb gpudb("http://172.1.2.3:9191,http://172.1.2.4:9191,http://172.1.2.5:9191", options);
Java
For more information on Java API database object instantiation, review
the Java API Reference. Active/Active Configuration
To instantiate a Kinetica connection object with failover in Java, pass a
comma-delimited list of head node URLs to the constructor:
GPUdb gpudb = new GPUdb("http://172.1.2.3:9191,http://172.1.2.4:9191,http://172.1.2.5:9191");
If you provide a single URL to the GPUdb constructor, the failover mode
will instead be Active/Passive and the URL will be treated as the primary
URL.
Active/Passive Configuration
To designate a cluster from the list to always attempt to go to first, specify a
primary URL:
GPUdb.Options options = new GPUdb.Options().setPrimaryUrl("http://172.1.2.4:9191");
GPUdb gpudb = new GPUdb("http://172.1.2.3:9191,http://172.1.2.4:9191,http://172.1.2.5:9191", options);
Python
Active/Active Configuration
To instantiate a Kinetica connection object with failover in Python, pass
a list of head node URLs to the constructor:
kinetica = gpudb.GPUdb(host=['http://172.1.2.3:9191','http://172.1.2.4:9191','http://172.1.2.5:9191'])
If you provide a single URL to the GPUdb constructor, the failover mode
will instead be Active/Passive and the URL will be treated as the primary
URL.
Active/Passive Configuration
To designate a cluster from the list to always attempt to go to first, specify a
primary host:
kinetica = gpudb.GPUdb(host=['http://172.1.2.3:9191','http://172.1.2.4:9191','http://172.1.2.5:9191'], primary_host='http://172.1.2.3:9191')
Connectors
Any Kinetica connectors used to interface with an HA cluster ring should also be
configured to fail over from one cluster to another.
ODBC
See Failover Connections for the ODBC/JDBC failover configuration.
External Data
When using an external table or when loading
data via /insert/records/fromfiles (LOAD INTO, in
SQL), the source of data needs to be accessible to all clusters within the ring
or it needs to be synced between locations accessible to each cluster
individually.
Similarly, when using a data source, the source
needs to be accessible to all clusters within the ring.
Management
Once HA has been configured, several commands are available to aid in the
management of the cluster.
To start HA, run the following as the root user on every node
with the RabbitMQ service installed:
To stop HA, run the following as the root user on every node with
the RabbitMQ service installed:
