Pin agent version for integration tests

[pchila]

What does this PR do?

Pin elastic agent version to 9.0.0 for both packaging and integration tests to avoid issues while testing with previous minors and upgrade paths.
Elastic agent code and dependencies are still main/9.1.0-SNAPSHOT we simply package the agent as if it was a 9.0.0 version.

This change is not meant to be permanent and it's only meant to unblock merging PRs to main

Why is it important?

To avoid blocking PR merging on main

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

[mergify]

This pull request does not have a backport label. Could you fix it @pchila? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[cmacknz]

The fleet bootstrap tests are failing because the --install-servers option is missing, there's already an issue for that.

A bunch of new tests are failing because they can't read the package version file which I've never seen happen before.

Error initializing version information: reading package version from file "/opt/Elastic/Agent/data/elastic-agent-9.0.0-SNAPSHOT-8ec1c4/package.version": open /opt/Elastic/Agent/data/elastic-agent-9.0.0-SNAPSHOT-8ec1c4/package.version: no such file or directory

[pchila]

The fleet bootstrap tests are failing because the --install-servers option is missing, there's already an issue for that.

From what I see in the code --install-servers is passed in the fleet bootstrap tests

elastic-agent/testing/integration/fleetserver_test.go

Line 118 in 093fb58

InstallServers: true,

elastic-agent/pkg/testing/fixture_install.go

Lines 157 to 159 in 093fb58

	if i.InstallServers {
	args = append(args, "--install-servers")
	}

so the issue could be elsewhere, possible fleet-server is not starting for other reasons

A bunch of new tests are failing because they can't read the package version file which I've never seen happen before.

I will try disabling TestUpgradeBrokenPackageVersion as it's known to have issues with version bumps and package.version file removal

elastic-agent/testing/integration/upgrade_broken_package_test.go

Line 28 in a5de320

func TestUpgradeBrokenPackageVersion(t *testing.T) {

[pchila]

From what I see in the code --install-servers is passed in the fleet bootstrap tests

elastic-agent/testing/integration/fleetserver_test.go

Line 118 in 093fb58

InstallServers: true,

Adding some information after looking more closely to the errors for fleet server bootstrap tests, we have this log line

{"log.level":"info","@timestamp":"2025-01-31T17:55:59.323Z","log.origin":{"function":"github.com/elastic/elastic-agent/internal/pkg/agent/cmd.waitForFleetServer.func1","file.name":"cmd/enroll_cmd.go","file.line":829},"message":"Fleet Server - Error - failed version compatibility check with elasticsearch (Agent: 9.1.0-SNAPSHOT, Elasticsearch: 9.0.0): unsupported version","ecs.version":"1.6.0"}

It looks like we cannot start fleet-server version 9.1.0 on a 9.0.0 Elasticsearch: there's a 9.1.0-SNAPSHOT stack available in CFT region so I am going to force Integration tests to use that version

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube