[
https://issues.apache.org/jira/browse/TINKERPOP-2569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17425704#comment-17425704
]
ASF GitHub Bot commented on TINKERPOP-2569:
-------------------------------------------
xiazcy commented on pull request #1476:
URL: https://github.com/apache/tinkerpop/pull/1476#issuecomment-937997343
> I'ts not trying to connect, but won't it try to connect if i send a
request through it? That seemed to happen in my testing. In that sense the
Cluster object is still sorta valid though it failed to connect, no?
Right, I meant it wouldn't be actively re-trying to connect in the
background if there is no live host at initialization (it will just throw the
`NoHostAvailableException`), but yes, `submit` should start the `init()`
process again if a request is sent through. I guess it would make better sense
to give an error message instead. I will make that change.
Thanks Stephen!
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: commits-unsubscr...@tinkerpop.apache.org
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
> 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
> Priority: Minor
>
> 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.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
