Opster Team
Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.
To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them. Take a self-guided product tour to see for yourself (no registration required).
This guide will help you check for common problems that cause the log ” IO exception while trying to read ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: checks.

Log Context
Log “IO exception while trying to read [{}]” classname is BootstrapChecks.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
} catch (final NumberFormatException e) { logger.warn(() -> new ParameterizedMessage("unable to parse vm.max_map_count [{}]"; rawProcSysVmMaxMapCount); e); } } } catch (final IOException e) { logger.warn(() -> new ParameterizedMessage("I/O exception while trying to read [{}]"; path); e); } return -1; } SuppressForbidden(reason = "access /proc/sys/vm/max_map_count")
Find & fix Elasticsearch problems
Opster AutoOps diagnoses & fixes issues in Elasticsearch based on analyzing hundreds of metrics.
Fix Your Cluster IssuesConnect in under 2 minutes
Arpit Ghiya
Senior Lead SRE at Coupa