Details
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Bug
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Status: Open
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Major
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Resolution: Unresolved
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2.1.0, 2.1.1, 2.1.2
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None
Description
There were several inconsistencies noted in how component cardinality is presently handled by the Ambari UI. some of these inconsistencies might be considered a reasonable limitation if a warning is displayed to alert the user about the inconsistency.
1) A MASTER component is shown on the "Assign Masters" page with a selection that does not match the minimum cardinality specified in the service definition. For instance, 2+ will still result in only 1 host being assigned for the component. The user has to manually click on + and add additional hosts. There is no warning either that the selection does not match the requirement (e.g. minimum of 2).
2) There is no option that allows zero MASTER components from the outset of a new installation (assuming optional MASTER components could be a requirement for some services). As the behavior is today, the only way to achieve a cardinality of 0 for MASTER component would be to use a cardinality of 0+ and then delete the instance of the component post-install.
3) If a MASTER component specifies a cardinality of ALL then this is not represented correctly as one instance/host for the component is pre-selected. Instead, maybe there should be an indication that the component will be installed on every host and the user be disallowed from any selection that is an obvious inconsistency.
3) Clubbing together of SLAVE and CLIENT via the "Assign Slaves and Clients" page gives rise to a couple of problems.
i) With a cardinality ALL for SLAVE as well as for CLIENT component, ALL is enforced by skipping the "Assign Slaves and Clients" Page. This might be fine though an alternate representation for cardinality ALL might be preferable as would be apparent from the rest of the details provided here.
If the SLAVE of any selected service has some cardinality other than ALL then the page is not skipped. This means somebody could try selecting the number of CLIENTs as well via the checkboxes. If the CLIENT cardinality is ALL then the checkbox selection is ignored silently and without any warnings.
ii) Combinations of cardinality for components of multiple services when multiple services are being installed or added, can be hard to respresent via the UI. For instance, when CLIENT component for these services have conflicting cardinality, the user would not be able to completely get rid of the warning message and might see for example:
" Exactly 3 Service1 Client components should be installed in cluster.
Exactly 2 Service2 Client components should be installed in cluster."
Obviously, one or the other could be resolved but not both.
One might just have to proceed ignoring the warning or else choose to install the services separately, one at a time. Maybe no change is needed here but I am including this observation for completeness.
4) Validation of MASTER and CLIENT component cardinality via stack advisor logic might not be working as expected as some warnings are not surfaced out to the user or for that matter to the log.