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https://issues.apache.org/jira/browse/TINKERPOP-2569?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stephen Mallette closed TINKERPOP-2569.
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Fix Version/s: 3.5.2
3.4.13
3.6.0
Assignee: Stephen Mallette
Resolution: Fixed
> Reconnect to server if Java driver fails to initialize
> ------------------------------------------------------
>
> Key: TINKERPOP-2569
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2569
> Project: TinkerPop
> Issue Type: Bug
> Components: driver
> Affects Versions: 3.4.11
> Reporter: Stephen Mallette
> Assignee: Stephen Mallette
> Priority: Minor
> Fix For: 3.6.0, 3.4.13, 3.5.2
>
>
> As reported here on SO:
> https://stackoverflow.com/questions/67586427/how-to-recover-with-a-retry-from-gremlin-nohostavailableexception
> If the host is unavailable at {{Client}} initialization then the host is not
> put in a state where reconnect is possible. Essentially, this test for
> {{GremlinServerIntegrateTest}} should pass:
> {code}
> @Test
> public void shouldFailOnInitiallyDeadHost() throws Exception {
> // start test with no server
> this.stopServer();
> final Cluster cluster = TestClientFactory.build().create();
> final Client client = cluster.connect();
> try {
> // try to re-issue a request now that the server is down
> client.submit("g").all().get(3000, TimeUnit.MILLISECONDS);
> fail("Should throw an exception.");
> } catch (RuntimeException re) {
> // Client would have no active connections to the host, hence it
> would encounter a timeout
> // trying to find an alive connection to the host.
> assertThat(re.getCause(),
> instanceOf(NoHostAvailableException.class));
> //
> // should recover when the server comes back
> //
> // restart server
> this.startServer();
> // try a bunch of times to reconnect. on slower systems this may
> simply take longer...looking at you travis
> for (int ix = 1; ix < 11; ix++) {
> // the retry interval is 1 second, wait a bit longer
> TimeUnit.SECONDS.sleep(5);
> try {
> final List<Result> results =
> client.submit("1+1").all().get(3000, TimeUnit.MILLISECONDS);
> assertEquals(1, results.size());
> assertEquals(2, results.get(0).getInt());
> } catch (Exception ex) {
> if (ix == 10)
> fail("Should have eventually succeeded");
> }
> }
> } finally {
> cluster.close();
> }
> }
> {code}
> Note that there is a similar test that first allows a connect to a host and
> then kills it and then restarts it again called {{shouldFailOnDeadHost()}}
> which demonstrates that reconnection works in that situation.
> I thought it might be an easy to fix to simply call
> {{considerHostUnavailable()}} in the {{ConnectionPool}} constructor in the
> event of a {{CompletionException}} which should kickstart the reconnect
> process. The reconnects started firing but they all failed for some reason. I
> didn't have time to investigate further than than.
> Currently the only workaround is to recreate the `Client` if this sort of
> situation occurs.
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