Configuring HARP v23
TPA will install and configure HARP when failover_manager is set
to harp, which is the default for BDR-Always-ON clusters.
Installing HARP
You must provide the harp-manager and harp-proxy packages. Please
contact EDB to obtain access to these packages.
Configuring HARP
See the HARP documentation for more details on HARP configuration.
| Variable | Default value | Description |
|---|---|---|
cluster_name | `` | The name of the cluster. |
harp_consensus_protocol | `` | The consensus layer to use (etcd or bdr) |
harp_location | location | The location of this instance (defaults to the location parameter) |
harp_ready_status_duration | 10 | Amount of time in seconds the node's readiness status will persist if not refreshed. |
harp_leader_lease_duration | 6 | Amount of time in seconds the Lead Master lease will persist if not refreshed. |
harp_lease_refresh_interval | 2000 | Amount of time in milliseconds between refreshes of the Lead Master lease. |
harp_dcs_reconnect_interval | 1000 | The interval, measured in ms, between attempts that a disconnected node tries to reconnect to the DCS. |
harp_dcs_priority | 500 | In the case two nodes have an equal amount of lag and other qualified criteria to take the Lead Master lease, this acts as an additional ranking value to prioritize one node over another. |
harp_stop_database_when_fenced | false | Rather than simply removing a node from all possible routing, stop the database on a node when it is fenced. |
harp_fenced_node_on_dcs_failure | false | If HARP is unable to reach the DCS then fence the node. |
harp_maximum_lag | 1048576 | Highest allowable variance (in bytes) between last recorded LSN of previous Lead Master and this node before being allowed to take the Lead Master lock. |
harp_maximum_camo_lag | 1048576 | Highest allowable variance (in bytes) between last received LSN and applied LSN between this node and its CAMO partner(s). |
harp_camo_enforcement | lag_only | Whether CAMO queue state should be strictly enforced. |
harp_use_unix_sock | false | Use unix domain socket for manager database access. |
harp_request_timeout | 250 | Time in milliseconds to allow a query to the DCS to succeed. |
harp_watch_poll_interval | 500 | Milliseconds to sleep between polling DCS. Only applies when harp_consensus_protocol is bdr. |
harp_proxy_timeout | 1 | Builtin proxy connection timeout, in seconds, to Lead Master. |
harp_proxy_keepalive | 5 | Amount of time builtin proxy will wait on an idle connection to the Lead Master before sending a keepalive ping. |
harp_proxy_max_client_conn | 75 | Maximum number of client connections accepted by harp-proxy (max_client_conn) |
harp_ssl_password_command | None | a custom command that should receive the obfuscated sslpassword in the stdin and provide the handled sslpassword via stdout. |
harp_db_request_timeout | 10s | similar to dcs -> request_timeout, but for connection to the database itself. |
You can use the harp-config hook to execute tasks after the HARP configuration files have been installed (e.g., to install additional configuration files).
Consensus layer
The --harp-consensus-protocol argument to tpaexec configure is
mandatory for the BDR-Always-ON architecture.
etcd
If the --harp-consensus-protocol etcd option is given to tpaexec
configure, then TPA will set harp_consensus_protocol to etcd
in config.yml and give the etcd role to a suitable subset of the
instances, depending on your chosen layout.
HARP v2 requires etcd v3.5.0 or above, which is available in the products/harp/release package repositories provided by EDB.
You can configure the following parameters for etcd:
| Variable | Default value | Description |
|---|---|---|
| etcd_peer_port | 2380 | The port used by etcd for peer communication |
| etcd_client_port | 2379 | The port used by clients to connect to etcd |
bdr
If the --harp-consensus-protocol bdr option is given to tpaexec
configure, then TPA will set harp_consensus_protocol to bdr
in config.yml. In this case the existing BDR instances will be used
for consensus, and no further configuration is required.
Configuring a separate user for harp proxy
If you want harp proxy to use a separate readonly user, you can specify that
by setting harp_dcs_user: username under cluster_vars. TPA will use
harp_dcs_user setting to create a readonly user and set it up in the DCS
configuration.
Custom SSL password command
The command provided by harp_ssl_password_command will be used by HARP
to de-obfuscate the sslpassword given in connection string. If
sslpassword is not present then harp_ssl_password_command is
ignored. If sslpassword is not obfuscated then
harp_ssl_password_command is not required and should not be specified.
Configuring the harp service
You can configure the following parameters for the harp service:
| Variable | Default value | Description |
|---|---|---|
harp_manager_restart_on_failure | false | If true, the harp-manager service is overridden so it's restarted on failure. The default is false to comply with the service installed by the harp-manager package. |