How To Solve Issues Related to Log – Registered two transport handlers for action ; handlers: ;

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Updated: Feb-20

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Troubleshooting background

To troubleshoot Elasticsearch log “Registered two transport handlers for action ; handlers: ;” it’s important to understand common problems related to Elasticsearch concepts: recovery. See detailed explanations below complete with common problems, examples and useful tips.

Recovery in Elasticsearch

What it is

In Elasticsearch, recovery refers to the process of recovering an index/shard when something goes wrong. You can recover an index/shards in many ways such as by re-indexing the data from a  backup/failover cluster to the current one or by restoring from an Elasticsearch snapshot. Alternatively, Elasticsearch may be performing recoveries automatically in some cases, such as when a node restarts or when a node disconnects and connects again. There is an API to check the updated status of index/shard recoveries.

GET /<index>/_recoveryGET /_recovery

In summary, recovery can happen in the following situations:

  • Node startup or failure ( local store recovery )
  • Replication of Primary shards to replica shards
  • Relocation of a shard to a different node in the same cluster
  • Restoring a Snapshot
Examples:

Getting recovery information about several indices:

GET my_index1,my_index2/_recovery
Common Problems Related to Recovery Settings
  • When a node is disconnected from the cluster, all of its shards go to an unassigned state. After a certain time, the shards will be allocated somewhere else on other nodes. This setting determines the number of concurrent shards per node that will be recovered.
PUT _cluster/settings{  "transient" :  {     "cluster.routing.allocation.node_concurrent_recoveries" : 3 }}
  • You can also control when to start recovery after a node disconnects. ( This is useful if the node just restarts, for example, because you may not want to initiate any recovery for such transient events )
PUT _all/_settings{  "settings": {    "index.unassigned.node_left.delayed_timeout": "6m"  }}
  • Elasticsearch limits the speed that is allocated to recovery in order to avoid overloading the cluster. This setting can be updated to make the recovery faster or slower, depending on your requirements.
PUT _cluster/settings{  "transient" :  {     "indices.recovery.max_bytes_per_sec" : "100mb"}}


To help troubleshoot related issues we have gathered selected Q&A from the community and issues from Github , please review the following for further information :

1 Multiple Registrations Of Transport  

2Assembly Elasticsearch Guice Runtim  


Log Context

Log ”registered two transport handlers for action {}; handlers: {}; {}” classname is TransportService.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

<pre class="wp-block-syntaxhighlighter-code">     protected <Request extends TransportRequest> void registerRequestHandler(RequestHandlerRegistry<Request> reg) {
        synchronized (requestHandlerMutex) {
            RequestHandlerRegistry replaced = requestHandlers.get(reg.getAction());
            requestHandlers = MapBuilder.newMapBuilder(requestHandlers).put(reg.getAction(); reg).immutableMap();
            if (replaced != null) {
                logger.warn("registered two transport handlers for action {}; handlers: {}; {}"; reg.getAction(); reg; replaced);
            }
        }
    }

    public void removeHandler(String action) {




</pre>


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