If you getting this error - "Error Accessing Store" 

Or in case you have seen in the Store screen a message that alert about a Red cluster status with unassigned shards,

 you should read and do the following steps:

The store is divided into nodes (some used to keep data , others can handle communication and there is one Master that coordinates the work).

To know each node's role you can learn from the Node Type marked in red

Shards need to be allocated/assigned to data nodes so they can be populated with data.

If shards are unassigned to data node no data can flow to the system and this the problem we want to solve.

This situation is usually happens when there is an unexpected recovery of the cluster and at the time of recovery automatic assignment of shards was not applicable for unknown reason.

What can you do ?

There is a script at /app/scripts/realloc_shards.sh <Node Name>

The scripts gets data node name (of with Type = D) and scan all shards and reallocate unassigned shards to the available data node provided.

In the example above we should run command

/app/scripts/realloc_shards.sh MonTie-es-raw-trans-Node-2

This operation may take a while depends on your installation and amount of data. Refreshing the screen in "head" application available from Store dashboard will show updated state of the assigned and unassigned shards.

Below is example of successfull execution:

Reallocation node: MonTier-es-raw-trans-Node-2
Testing index 1;wdp-syslog-sys-error_i14
About to reallocate. index=wdp-syslog-sys-error_i14, shard=1, node=MonTier-es-raw-trans-Node-2
Reallocation return code is : 0, output={"acknowledged":true,"state":{"version":882,"state
Testing index 1;wdp-syslog_i260
About to reallocate. index=wdp-syslog_i260, shard=1, node=MonTier-es-raw-trans-Node-2
Reallocation return code is : 0, output={"acknowledged":true,"state":{"version":884,"state
Testing index 1;wdp-service-resources_i5
About to reallocate. index=wdp-service-resources_i5, shard=1, node=MonTier-es-raw-trans-Node-2
Reallocation return code is : 0, output={"acknowledged":true,"state":{"version":886,"state
Testing index 1;internal-operations_i6
About to reallocate. index=internal-operations_i6, shard=1, node=MonTier-es-raw-trans-Node-2
Reallocation return code is : 0, output={"acknowledged":true,"state":{"version":888,"state
Testing index 1;logical-tran-compact_i16
About to reallocate. index=logical-tran-compact_i16, shard=1, node=MonTier-es-raw-trans-Node-2
...