Talk about BootstrapCheck of Elasticsearch.

  elasticsearch

Order

This article mainly studies the BootstrapCheck of Elasticsearch.

BootstrapCheck

elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/bootstrap/BootstrapCheck.java

public interface BootstrapCheck {

    /**
     * Encapsulate the result of a bootstrap check.
     */
    final class BootstrapCheckResult {

        private final String message;

        private static final BootstrapCheckResult SUCCESS = new BootstrapCheckResult(null);

        public static BootstrapCheckResult success() {
            return SUCCESS;
        }

        public static BootstrapCheckResult failure(final String message) {
            Objects.requireNonNull(message);
            return new BootstrapCheckResult(message);
        }

        private BootstrapCheckResult(final String message) {
            this.message = message;
        }

        public boolean isSuccess() {
            return this == SUCCESS;
        }

        public boolean isFailure() {
            return !isSuccess();
        }

        public String getMessage() {
            assert isFailure();
            assert message != null;
            return message;
        }

    }

    /**
     * Test if the node fails the check.
     *
     * @param context the bootstrap context
     * @return the result of the bootstrap check
     */
    BootstrapCheckResult check(BootstrapContext context);

    default boolean alwaysEnforce() {
        return false;
    }

}
  • The Bootstrapcheck interface defines the Check method, which returns BootstrapCheckResult, and also defines a default method alwaysEnforce, which returns false by default

BootstrapChecks

elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/bootstrap/BootstrapChecks.java

final class BootstrapChecks {

    private BootstrapChecks() {
    }

    static final String ES_ENFORCE_BOOTSTRAP_CHECKS = "es.enforce.bootstrap.checks";

    //......

    // the list of checks to execute
    static List<BootstrapCheck> checks() {
        final List<BootstrapCheck> checks = new ArrayList<>();
        checks.add(new HeapSizeCheck());
        final FileDescriptorCheck fileDescriptorCheck
            = Constants.MAC_OS_X ? new OsXFileDescriptorCheck() : new FileDescriptorCheck();
        checks.add(fileDescriptorCheck);
        checks.add(new MlockallCheck());
        if (Constants.LINUX) {
            checks.add(new MaxNumberOfThreadsCheck());
        }
        if (Constants.LINUX || Constants.MAC_OS_X) {
            checks.add(new MaxSizeVirtualMemoryCheck());
        }
        if (Constants.LINUX || Constants.MAC_OS_X) {
            checks.add(new MaxFileSizeCheck());
        }
        if (Constants.LINUX) {
            checks.add(new MaxMapCountCheck());
        }
        checks.add(new ClientJvmCheck());
        checks.add(new UseSerialGCCheck());
        checks.add(new SystemCallFilterCheck());
        checks.add(new OnErrorCheck());
        checks.add(new OnOutOfMemoryErrorCheck());
        checks.add(new EarlyAccessCheck());
        checks.add(new G1GCCheck());
        checks.add(new AllPermissionCheck());
        checks.add(new DiscoveryConfiguredCheck());
        return Collections.unmodifiableList(checks);
    }

    //......
}
  • The checks method of BootstrapChecks returns a series of Bootstrap Checks, including HeapSizeCheck, FileDescriptorCheck, MaxNumberOfThreadsCheck, MaxSizeVirtualMemoryCheck, MaxFileSizeCheck, etc.

FileDescriptorCheck

    static class FileDescriptorCheck implements BootstrapCheck {

        private final int limit;

        FileDescriptorCheck() {
            this(65535);
        }

        protected FileDescriptorCheck(final int limit) {
            if (limit <= 0) {
                throw new IllegalArgumentException("limit must be positive but was [" + limit + "]");
            }
            this.limit = limit;
        }

        public final BootstrapCheckResult check(BootstrapContext context) {
            final long maxFileDescriptorCount = getMaxFileDescriptorCount();
            if (maxFileDescriptorCount != -1 && maxFileDescriptorCount < limit) {
                final String message = String.format(
                        Locale.ROOT,
                        "max file descriptors [%d] for elasticsearch process is too low, increase to at least [%d]",
                        getMaxFileDescriptorCount(),
                        limit);
                return BootstrapCheckResult.failure(message);
            } else {
                return BootstrapCheckResult.success();
            }
        }

        // visible for testing
        long getMaxFileDescriptorCount() {
            return ProcessProbe.getInstance().getMaxFileDescriptorCount();
        }

    }
  • FileDescriptorCheck requires max file descriptors to be no less than 65535.

ClientJvmCheck

elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/bootstrap/BootstrapChecks.java

    static class ClientJvmCheck implements BootstrapCheck {

        @Override
        public BootstrapCheckResult check(BootstrapContext context) {
            if (getVmName().toLowerCase(Locale.ROOT).contains("client")) {
                final String message = String.format(
                        Locale.ROOT,
                        "JVM is using the client VM [%s] but should be using a server VM for the best performance",
                        getVmName());
                return BootstrapCheckResult.failure(message);
            } else {
                return BootstrapCheckResult.success();
            }
        }

        // visible for testing
        String getVmName() {
            return JvmInfo.jvmInfo().getVmName();
        }

    }
  • ClientJvmCheck requires jvm to be server VM

G1GCCheck

    static class G1GCCheck implements BootstrapCheck {

        @Override
        public BootstrapCheckResult check(BootstrapContext context) {
            if ("Oracle Corporation".equals(jvmVendor()) && isJava8() && isG1GCEnabled()) {
                final String jvmVersion = jvmVersion();
                // HotSpot versions on Java 8 match this regular expression; note that this changes with Java 9 after JEP-223
                final Pattern pattern = Pattern.compile("(\\d+)\\.(\\d+)-b\\d+");
                final Matcher matcher = pattern.matcher(jvmVersion);
                final boolean matches = matcher.matches();
                assert matches : jvmVersion;
                final int major = Integer.parseInt(matcher.group(1));
                final int update = Integer.parseInt(matcher.group(2));
                // HotSpot versions for Java 8 have major version 25, the bad versions are all versions prior to update 40
                if (major == 25 && update < 40) {
                    final String message = String.format(
                            Locale.ROOT,
                            "JVM version [%s] can cause data corruption when used with G1GC; upgrade to at least Java 8u40", jvmVersion);
                    return BootstrapCheckResult.failure(message);
                }
            }
            return BootstrapCheckResult.success();
        }

        // visible for testing
        String jvmVendor() {
            return Constants.JVM_VENDOR;
        }

        // visible for testing
        boolean isG1GCEnabled() {
            assert "Oracle Corporation".equals(jvmVendor());
            return JvmInfo.jvmInfo().useG1GC().equals("true");
        }

        // visible for testing
        String jvmVersion() {
            assert "Oracle Corporation".equals(jvmVendor());
            return Constants.JVM_VERSION;
        }

        // visible for testing
        boolean isJava8() {
            assert "Oracle Corporation".equals(jvmVendor());
            return JavaVersion.current().equals(JavaVersion.parse("1.8"));
        }

    }
  • If G1GCCheck opens G1 for oracle java8, it requires update to be 40 years later to avoid data corruption.

Summary

  • The Bootstrapcheck interface defines the Check method, which returns BootstrapCheckResult, and also defines a default method alwaysEnforce, which returns false by default
  • The checks method of BootstrapChecks returns a series of Bootstrap Checks, including HeapSizeCheck, FileDescriptorCheck, MaxNumberOfThreadsCheck, MaxSizeVirtualMemoryCheck, MaxFileSizeCheck, etc.
  • FileDescriptorCheck requires max file descriptors not to be less than 65535; ClientJvmCheck requires jvm to be servervm; If G1GCCheck opens G1 for oracle java8, it requires update to be 40 years later to avoid data corruption.

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