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DDS queries to data center fail with NoHostAvailableException



Decision Data Store queries to one of the two data centers fail with NoHostAvailableException.

Error Messages

ERROR - x.y.z: PRRuntimeError
 at com.pega.pegarules.session.internal.mgmt.base.ThreadRunner.runActivitiesAlt(
 at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.runActivitiesAlt(
Caused by: Exception during data set execution
 at com.pegarules.generated.dataset.ra_action_accountsbdp_6e745915dc5e304972da588f9c48d8c1.perform(
 at com.pega.pegarules.session.internal.mgmt.Executable.doAction(
Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (no host was tried)
 at com.datastax.driver.core.exceptions.NoHostAvailableException.copy(
Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (no host was tried)
 at com.datastax.driver.core.RequestHandler.reportNoMoreHosts(
 at com.datastax.driver.core.RequestHandler.access$1000(
 at com.datastax.driver.core.RequestHandler$SpeculativeExecution.sendRequest(
 at com.datastax.driver.core.RequestHandler.startNewExecution(
 at com.datastax.driver.core.RequestHandler.sendRequest(
 at com.datastax.driver.core.SessionManager.execute(
 at com.datastax.driver.core.SessionManager.prepareAsync(
 at com.datastax.driver.core.AbstractSession.prepare(
 ... 86 more

Steps to Reproduce

  1. Log in to the application
  2. Add an additional data center with new nodes in the Cassandra cluster
  3. Configure new nodes to the new data centre using and GossippingPropertyFileSnitch
  4. Run the flow

Root Cause

The data center name was not passed to the Cassandra load balancing policy. This prevented the read/write privileges from the existing data centers.


  1. Apply HFix-39935
  2. Navigate to prconfig set all nodes as dnode/cassandra_datacenter=name_of_the_datacenter. Ensure the 'name_of_the_datacenter' should match the name of the correct Cassandra data center
  3. Apply the entry to all the nodes (Web nodes ,DDS nodes) and add the respective data center names and restart them


Published May 22, 2019 - Updated October 8, 2020

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