[Fleet] Prevent upgrades of agents already in updating state (#133763) (#133863)

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>
(cherry picked from commit ba05c2c6a9)

Co-authored-by: Cristina Amico <criamico@users.noreply.github.com>

x-pack/plugins/fleet/common/services/is_agent_upgradeable.test.ts

@@ -14,11 +14,15 @@ const getAgent = ({
   upgradeable = false,
   unenrolling = false,
   unenrolled = false,
+  updating = false,
+  upgraded = false,
 }: {
   version: string;
   upgradeable?: boolean;
   unenrolling?: boolean;
   unenrolled?: boolean;
+  updating?: boolean;
+  upgraded?: boolean;
 }): Agent => {
   const agent: Agent = {
     id: 'de9006e1-54a7-4320-b24e-927e6fe518a8',
@@ -94,6 +98,12 @@ const getAgent = ({
   if (unenrolled) {
     agent.unenrolled_at = '2020-10-01T14:43:27.255Z';
   }
+  if (updating) {
+    agent.upgrade_started_at = new Date(Date.now()).toISOString();
+  }
+  if (upgraded) {
+    agent.upgraded_at = new Date(Date.now()).toISOString();
+  }
   return agent;
 };
 describe('Fleet - isAgentUpgradeable', () => {
@@ -186,4 +196,14 @@ describe('Fleet - isAgentUpgradeable', () => {
       )
     ).toBe(false);
   });
+  it('returns false if agent reports upgradeable, but is already updating', () => {
+    expect(
+      isAgentUpgradeable(getAgent({ version: '7.9.0', upgradeable: true, updating: true }), '8.0.0')
+    ).toBe(false);
+  });
+  it('returns true if agent was recently upgraded', () => {
+    expect(
+      isAgentUpgradeable(getAgent({ version: '7.9.0', upgradeable: true, upgraded: true }), '8.0.0')
+    ).toBe(true);
+  });
 });

x-pack/plugins/fleet/common/services/is_agent_upgradeable.ts

@@ -24,6 +24,10 @@ export function isAgentUpgradeable(agent: Agent, kibanaVersion: string, versionT
   if (!agent.local_metadata.elastic.agent.upgradeable) {
     return false;
   }
+  // check that the agent is not already in the process of updating
+  if (agent.upgrade_started_at && !agent.upgraded_at) {
+    return false;
+  }
   if (versionToUpgrade !== undefined) {
     return (
       isNotDowngrade(agentVersion, versionToUpgrade) &&