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Add hack for Docker cgroups #22757

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Merged
jasontedor merged 2 commits into from
Jan 24, 2017
Merged

Add hack for Docker cgroups #22757

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1401bef
Add hack for Docker cgroups
jasontedor Jan 24, 2017
413c39c
Cleanup cgroups hierarchy hack
jasontedor Jan 24, 2017
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16 changes: 14 additions & 2 deletions core/src/main/java/org/elasticsearch/monitor/os/OsProbe.java
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,6 @@
import java.nio.file.Path;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
Expand Down Expand Up @@ -191,6 +190,10 @@ private String readSingleLine(final Path path) throws IOException {
// pattern for lines in /proc/self/cgroup
private static final Pattern CONTROL_GROUP_PATTERN = Pattern.compile("\\d+:([^:,]+(?:,[^:,]+)?):(/.*)");

// this property is to support a hack to workaround an issue with Docker containers mounting the cgroups hierarchy inconsistently with
// respect to /proc/self/cgroup; for Docker containers this should be set to "/"
private static final String CONTROL_GROUPS_HIERARCHY_OVERRIDE = System.getProperty("es.cgroups.hierarchy.override");

/**
* A map of the control groups to which the Elasticsearch process belongs. Note that this is a map because the control groups can vary
* from subsystem to subsystem. Additionally, this map can not be cached because a running process can be reclassified.
Expand All @@ -209,7 +212,16 @@ private Map<String, String> getControlGroups() throws IOException {
// at this point we have captured the subsystems and the control group
final String[] controllers = matcher.group(1).split(",");
for (final String controller : controllers) {
controllerMap.put(controller, matcher.group(2));
if (CONTROL_GROUPS_HIERARCHY_OVERRIDE != null) {
/*
* Docker violates the relationship between /proc/self/cgroups and the /sys/fs/cgroup hierarchy. It's possible that this
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@dliappis dliappis Jan 25, 2017 •
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@jasontedor Very minor typo, but should be /proc/self/cgroup

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@jasontedor jasontedor Jan 25, 2017

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Thanks @dliappis, I pushed cb822b4.

* will be fixed in future versions of Docker with cgroup namespaces, but this requires modern kernels. Thus, we provide
* an undocumented hack for overriding the control group path. Do not rely on this hack, it will be removed.
*/
controllerMap.put(controller, CONTROL_GROUPS_HIERARCHY_OVERRIDE);
} else {
controllerMap.put(controller, matcher.group(2));
}
}
}
return controllerMap;
Expand Down