Log I/O exception while trying to read – How To Solve Related Issues

Log I/O exception while trying to read – How To Solve Related Issues

Opster Team

Jan-20, Version: 1.7-8.0


Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up  which can resolve issues causing many log errors (free and no installation required)


This guide will help you check for common problems that cause the log “I/O exception while trying to read” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: bootstrap checks.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to discover the cause of many errors and provides suitable actionable recommendations. 

Quick Overview

Elasticsearch reads the value of vm.max_map_count from the file /proc/sys/vm/max_map_count in case of a Linux based operating system. and in rare cases, when this file isn’t present or Elasticsearch isn’t able to read the file, it throws the I/O exception. Fix:  This warning appears in specific and uncommon circumstances, such as when the Elasticsearch process isn’t able to read the file or the file itself isn’t present or has been deleted. In order to fix the issue, ensure the file is present and that the Elasticsearch process has read access. You could also try changing the values slightly using the root use to make sure the file is not corrupt. Please see Elasticsearch source code useful for this.

Log Context

Log “I/O 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")

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