This section describes how to control the Connector responses in the event of the loss of a required Datasource or all Managers.
Summary: Whenever no Primary datasource is found, the Connector will reject connection requests.
This feature controls how long the Connector waits for the given type of DataSource to come ONLINE before forcibly disconnecting the client application.
By default, wait indefinitely for a resource to become available.
Prior to software versions 5.3.2/6.0.1, the ONHOLD state would reject
new connection attempts instead of pausing them.
Also, waitIfUnavailableTimeout
was ignored, and
connection attempts were never severed after timeout.
There are two (2) parameters involved in this decision-making. They are:
waitIfUnavailable
(default:
true
)
If waitIfUnavailable
is true
,
then the Connector will wait for up to the time period specified by
waitIfUnavailableTimeout
to make a connection for a
given QOS. If the timeout expires, the Connector will disconnect the
client application (reject connection attempts and close ongoing
connections).
If waitIfUnavailable
is false
,
the Connector will immediately disconnect the client with an error if
a connection for a given QOS cannot be made immediately.
waitIfUnavailableTimeout
(default: 0, wait
indefinitely)
If waitIfUnavailable
is true
,
the Connector will wait for up to
waitIfUnavailableTimeout
number of seconds before
disconnecting the client. If waitIfUnavailable
is
false
, this parameter is ignored. If this parameter
is set to zero (0) seconds, the Connector will wait indefinitely
(client connection requests will hang forever).
waitIfUnavailable
is specific to data source availability and will be considered if everything else is online: connector and data service.
This will typically be used during a switch or failover while the primary changes: the client application will request a primary (RW_STRICT QoS), which at some
point is not available since both new and old primaries are offline. With waitIfUnavailable=true
, the connector will wait for the new one to
come online (Upto waitIfUnavailableTimeout
seconds), allowing seamless failover. If set to false, there will be a period of time during
switch/failover where client applications will get errors trying to connect AND reconnect/retry failing requests.
For example, to immediately reject connections upon Datasource loss:
Click the link below to switch examples between Staging and INI methods...
shell>tpm query staging
tungsten@db1:/opt/continuent/software/tungsten-clustering-6.1.25-6 shell>echo The staging USER is `tpm query staging| cut -d: -f1 | cut -d@ -f1`
The staging USER is tungsten shell>echo The staging HOST is `tpm query staging| cut -d: -f1 | cut -d@ -f2`
The staging HOST is db1 shell>echo The staging DIRECTORY is `tpm query staging| cut -d: -f2`
The staging DIRECTORY is /opt/continuent/software/tungsten-clustering-6.1.25-6 shell>ssh {STAGING_USER}@{STAGING_HOST}
shell>cd {STAGING_DIRECTORY}
shell> ./tools/tpm configure alpha \
--property=waitIfUnavailable=false
Run the tpm command to update the software with the Staging-based configuration:
shell> ./tools/tpm update
For information about making updates when using a Staging-method deployment, please see Section 10.3.7, “Configuration Changes from a Staging Directory”.
shell> vi /etc/tungsten/tungsten.ini
[alpha]
...
property=waitIfUnavailable=false
Run the tpm command to update the software with the INI-based configuration:
shell>tpm query staging
tungsten@db1:/opt/continuent/software/tungsten-clustering-6.1.25-6 shell>echo The staging DIRECTORY is `tpm query staging| cut -d: -f2`
The staging DIRECTORY is /opt/continuent/software/tungsten-clustering-6.1.25-6 shell>cd {STAGING_DIRECTORY}
shell>./tools/tpm update
For information about making updates when using an INI file, please see Section 10.4.4, “Configuration Changes with an INI file”.
PLEASE NOTE: this will make switch and failover much less transparent to the application since the connections will error until the new Primary is elected and back online.
Updating these values require a connector restart (via tpm update) for the changes to be recognized.
These entries will NOT work if placed into
[defaults]
, each service must be handled
individually.
Summary: Whenever the Connector loses sight of the managers for a given data service, it will either suspend or reject new connection requests.
waitIfDisabled
applies to both:
Whole offline data service: client application tries to connect to a composite or physical data service that is offline, e.g. during a full site outage where the client application requests access to a local primary without allowing redirection to remote site.
connector offline or onhold: typically when the connector looses connectivity to all managers in
the cluster, it will first go onhold, then offline. In both cases, waitIfDisabled defines what to do in such case: throw an error
to the client application or wait until network is back and access to a manager is possible. For example, when the connector is isolated
from the cluster, setting waitIfDisabled=true
will make new connection requests "hang" until either the connector gets back network access
to a manager OR waitIfDisabledTimeout
is reached
By default, suspend requests indefinitely until Manager communications are re-established.
This feature controls how long the Connector waits during a manager loss event to either suspend or reject the client connection.
Here is the decision chain and associated settings for what happens when the connector loses sight of the managers:
Delay for the value of delayBeforeOnHoldIfNoManager
seconds which is 0/no delay by default.
Change state to ON-HOLD
and begin the countdown
timer starting from the
delayBeforeOfflineIfNoManager
value.
In the ON-HOLD
state, the connector will hang all
new connections and allow existing connections to continue.
When the delayBeforeOfflineIfNoManager
timer
expires (30 seconds by default), change state to
OFFLINE
.
Once OFFLINE
, the Connector with break existing
connections because there is no authoritative Manager node from the
Connector's perspective. Without a Manager link, any change to the
cluster configuration will remain invisible to the Connector,
potentially leading to writes on a Replica node.
By default, all new connection requests will hang in the
OFFLINE
state.
If waitIfDisabled
is set to
false
, then the Connector will instead reject all
new connections.
There are multiple parameters involved in this decision-making. They are:
delayBeforeOnHoldIfNoManager
(in seconds, default:
0
, i.e. no delay)
When the connector loses sight of the managers, delay before going
ON-HOLD
for the value of
delayBeforeOnHoldIfNoManager
seconds, which is 0/no
delay by default.
delayBeforeOfflineIfNoManager
(in seconds, default:
30)
Once ON-HOLD
, delay before going
OFFLINE
for the value of
delayBeforeOfflineIfNoManager
seconds, 30 by
default.
waitIfDisabled
(default: true
)
If the Dataservice is OFFLINE
because it is unable
to communicate with any Manager, the waitIfDisabled
parameter determines whether to suspend connection requests or to
reject them. If waitIfDisabled
is
true
(the default), then the Connector will wait
indefinitely for manager communications to be re-established. If
waitIfDisabled
is set to false
,
the Connector will return an error immediately.
To check for data service state, use the tungsten-connector/bin/connector cluster-status command. For example:
shell> connector cluster-status
Executing Tungsten Connector Service --cluster-status ...
+--------------+--------------------+-------------+--------------+--------+--------+--------------------------------------+------------------+-----------------+------------------+--------------------+---------------------+
| Data service | Data service state | Data source | Is composite | Role | State | High water | Last shun reason | Applied latency | Relative latency | Active connections | Connections created |
+--------------+--------------------+-------------+--------------+--------+--------+--------------------------------------+------------------+-----------------+------------------+--------------------+---------------------+
| europe | OFFLINE | c1 | false | master | ONLINE | 0(c1-bin.000002:0000000000000510;-1) | MANUALLY-SHUNNED | 0.0 | 5193.0 | 0 | 3 |
| europe | OFFLINE | c2 | false | slave | ONLINE | 0(c1-bin.000002:0000000000000510;-1) | | 1.0 | 5190.0 | 0 | 0 |
| europe | OFFLINE | c3 | false | slave | ONLINE | 0(c1-bin.000002:0000000000000510;-1) | | 2.0 | 5190.0 | 0 | 1 |
+--------------+--------------------+-------------+--------------+--------+--------+--------------------------------------+------------------+-----------------+------------------+--------------------+---------------------+
For more information, see Connector On-Hold State.
For example, to decrease the ON-HOLD
time to 15
seconds:
Click the link below to switch examples between Staging and INI methods...
shell>tpm query staging
tungsten@db1:/opt/continuent/software/tungsten-clustering-6.1.25-6 shell>echo The staging USER is `tpm query staging| cut -d: -f1 | cut -d@ -f1`
The staging USER is tungsten shell>echo The staging HOST is `tpm query staging| cut -d: -f1 | cut -d@ -f2`
The staging HOST is db1 shell>echo The staging DIRECTORY is `tpm query staging| cut -d: -f2`
The staging DIRECTORY is /opt/continuent/software/tungsten-clustering-6.1.25-6 shell>ssh {STAGING_USER}@{STAGING_HOST}
shell>cd {STAGING_DIRECTORY}
shell> ./tools/tpm configure alpha \
--property=delayBeforeOfflineIfNoManager=15
Run the tpm command to update the software with the Staging-based configuration:
shell> ./tools/tpm update
For information about making updates when using a Staging-method deployment, please see Section 10.3.7, “Configuration Changes from a Staging Directory”.
shell> vi /etc/tungsten/tungsten.ini
[alpha]
...
property=delayBeforeOfflineIfNoManager=15
Run the tpm command to update the software with the INI-based configuration:
shell>tpm query staging
tungsten@db1:/opt/continuent/software/tungsten-clustering-6.1.25-6 shell>echo The staging DIRECTORY is `tpm query staging| cut -d: -f2`
The staging DIRECTORY is /opt/continuent/software/tungsten-clustering-6.1.25-6 shell>cd {STAGING_DIRECTORY}
shell>./tools/tpm update
For information about making updates when using an INI file, please see Section 10.4.4, “Configuration Changes with an INI file”.
For example, to immediately reject connections upon Manager loss:
shell> ./tools/tpm configure alpha \
--property=waitIfDisabled=false
[alpha]
...
property=waitIfDisabled=false
PLEASE NOTE: this will make switch and failover much less transparent to the application since the connections will error until communications with at least one manager has been established and the Connector is back online.
Updating these values require a connector restart (via tpm update) for the changes to be recognized.
These entries will NOT work if placed into
[defaults]
, each service must be updated
individually.