almeidajeff opened a new pull request, #4222:
URL: https://github.com/apache/ambari/pull/4222
## What changes were proposed in this pull request?
On a freshly installed cluster, VMAGENT never receives component scrape
targets for
HDFS/YARN/HBase. The per-host telemetry assignment stays empty until
something unrelated
forces a recompile — a cluster config change, or an ambari-server restart.
Root cause, following the chain:
1. `ServiceComponentHostImpl` publishes `ServiceComponentInstalledEvent`
from its constructor,
right after persisting the host component row with desired state `INIT`.
2. `TelemetryHolder` subscribes to that event as its only per-component hook.
3. `TelemetryAssignmentCompiler.compileCluster()` skips any component that
is not in an
installed state, and `isInstalled()` accepts only `INSTALLED`,
`STARTING`, `STARTED`,
`STOPPING`, `UPGRADING`, `DISABLED` and `UNKNOWN` — `INIT` is not among
them.
4. `handleEvent()`, which processes the real state transitions, refreshes
`HostLevelParamsHolder` but never `TelemetryHolder`.
So the only assignment ever compiled for a host is the one built at `INIT`,
which by
definition contains no component targets, and nothing revisits it on the
normal
install/start path.
Changes:
- `ServiceComponentHostImpl` now refreshes `TelemetryHolder` inside
`handleEvent()`, in the
same block that already publishes `HostComponentsUpdateEvent` on a real
status change.
- `TelemetryHolder.getCurrentData(Long)` is widened from `protected` to
`public` so it is
callable from there, matching how `HostLevelParamsHolder` already exposes
it.
## How was this patch tested?
Two new tests, both run on trunk with this patch applied:
-
**`TelemetryAssignmentCompilerTest.testTargetsAppearOnlyAfterComponentLeavesInitState`**
—
asserts a component in `INIT` contributes no targets while `INSTALLED` and
`STARTED` each
contribute one. This documents why subscribing to
`ServiceComponentInstalledEvent` cannot
work, independently of the fix.
-
**`ServiceComponentHostTest.testTelemetryIsRefreshedOnComponentStateTransition`**
— asserts
that a real state transition repopulates the host's telemetry assignment.
The cached
assignment is dropped after `createEvent()` rather than before, because
creating a config
publishes `ClusterConfigChangedEvent`, which `TelemetryHolder` also
refreshes on — the very
mechanism that masks this bug on a real cluster.
```
$ mvn -pl ambari-server surefire:test \
-Dtest='TelemetryAssignmentCompilerTest,ServiceComponentHostTest#testTelemetryIsRefreshedOnComponentStateTransition'
[INFO] T E S T S
[INFO] Running
org.apache.ambari.server.agent.stomp.TelemetryAssignmentCompilerTest
[INFO] Running
org.apache.ambari.server.state.svccomphost.ServiceComponentHostTest
[INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 3.590
s -- in org.apache.ambari.server.agent.stomp.TelemetryAssignmentCompilerTest
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 21.39
s -- in org.apache.ambari.server.state.svccomphost.ServiceComponentHostTest
[INFO] Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
[INFO] BUILD SUCCESS
```
The second test was verified to be a genuine regression test: with the
`TelemetryHolder` refresh in `handleEvent()` reverted, it fails as expected.
```
[ERROR]
ServiceComponentHostTest.testTelemetryIsRefreshedOnComponentStateTransition:576
A real state transition must refresh the host's telemetry assignment
[ERROR] Tests run: 1, Failures: 1, Errors: 0, Skipped: 0
[INFO] BUILD FAILURE
```
Not covered by automated tests: the end-to-end behaviour on a live cluster
(installing
VICTORIAMETRICS alongside HDFS/YARN/HBase and confirming VMAGENT receives
component scrape
targets with no unrelated config change).
<img width="2090" height="971" alt="image"
src="https://github.com/user-attachments/assets/12e4f09c-9a96-415e-86a9-d13b517da2cc";
/>
<img width="2089" height="967" alt="image"
src="https://github.com/user-attachments/assets/c0e30106-78fe-4460-b3f4-1bfc02dcd66d";
/>
<img width="2081" height="932" alt="image"
src="https://github.com/user-attachments/assets/dc2b73e8-4994-463c-a4fc-9c873064d927";
/>
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