ES URL with Trailing Slash Causes Exception

[andrewkroh]

Adding an slash to the end of the configured ES URL causes an exception in ES when the template is installed at startup. It looks like the Beat uses a URL with a double slash in it like http://localhost:9200//_template/auditbeat-6.0.0-rc. This double slash can be avoided during the construction of the URL within Beats.

For confirmed bugs, please report:

• Version: 6.0.0-rc2 tested with ES 5.4.1
• Steps to Reproduce: Append a slash to the ES URL.

output.elasticsearch:
  hosts: ["10.100.6.80:9200/"]

sudo ./beat setup --template -e -d "*" --strict.perms=false

From Beats:

2017/11/02 16:46:45.394290 beat.go:625: CRIT Exiting: Error loading Elasticsearch template: could not load template: couldn't load template: couldn't load json. Error: 500 Internal Server Error. Response body: {"error":{"root_cause":[{"type":"string_index_out_of_bounds_exception","reason":"String index out of range: 0"}],"type":"string_index_out_of_bounds_exception","reason":"String index out of range: 0"},"status":500}
Exiting: Error loading Elasticsearch template: could not load template: couldn't load template: couldn't load json. Error: 500 Internal Server Error. Response body: {"error":{"root_cause":[{"type":"string_index_out_of_bounds_exception","reason":"String index out of range: 0"}],"type":"string_index_out_of_bounds_exception","reason":"String index out of range: 0"},"status":500}

From ES:

[2017-11-02T12:46:45,380][WARN ][r.suppressed             ] path: //_template/auditbeat-6.0.0-rc2, params: {index=, id=auditbeat-6.0.0-rc2, type=_template}
java.lang.StringIndexOutOfBoundsException: String index out of range: 0
	at java.lang.String.charAt(String.java:658) ~[?:1.8.0_111]
	at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.validateIndexOrAliasName(MetaDataCreateIndexService.java:167) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.validateIndexName(MetaDataCreateIndexService.java:142) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.validate(MetaDataCreateIndexService.java:495) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.access$000(MetaDataCreateIndexService.java:106) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService$1.execute(MetaDataCreateIndexService.java:239) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.ClusterStateUpdateTask.execute(ClusterStateUpdateTask.java:45) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.service.ClusterService.executeTasks(ClusterService.java:633) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.service.ClusterService.calculateTaskOutputs(ClusterService.java:611) ~[elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.service.ClusterService.runTasks(ClusterService.java:570) [elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.service.ClusterService$ClusterServiceTaskBatcher.run(ClusterService.java:262) [elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.service.TaskBatcher.runIfNotProcessed(TaskBatcher.java:150) [elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.cluster.service.TaskBatcher$BatchedTask.run(TaskBatcher.java:188) [elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:569) [elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:247) [elasticsearch-5.4.1.jar:5.4.1]
	at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:210) [elasticsearch-5.4.1.jar:5.4.1]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_111]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_111]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_111]