It gets a little more readable when we break it up:
Visualize:
rejected execution of org.elasticsearch.transport.TransportService$7@4a40b87 on EsThreadPoolExecutor
[
search, queue capacity = 1000, org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor@d30a796
[
Running, pool size = 49, active threads = 49, queued tasks = 998, completed tasks = 202672
]
]
rejected execution of org.elasticsearch.transport.TransportService$7@7878caaa on EsThreadPoolExecutor
[
search, queue capacity = 1000, org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor@d30a796
[
Running, pool size = 49, active threads = 49, queued tasks = 999, completed tasks = 202807
]
]
rejected execution of org.elasticsearch.transport.TransportService$7@5d8b23a8 on EsThreadPoolExecutor
[
search, queue capacity = 1000, org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor@d30a796
[
Running, pool size = 49, active threads = 49, queued tasks = 999, completed tasks = 202937
]
]
The error is coming from Elasticsearch and saying that searches are getting rejected because the thread pool has run out of capacity. There are either too many searches going on, or the searches are touching too many shards. There is a good explanation of the situation in this discussion topic, with some suggestions on how to resolve it: Elasticsearch sizing and queue capacity