Change file descriptor limit to 65535 (#37537)

Some systems default to a nofile ulimit of 65535. To reduce the pain of
deploying Elasticsearch to such systems, this commit lowers the required
limit from 65536 to 65535.

distribution/packages/src/common/env/elasticsearch

@@ -36,7 +36,7 @@ ES_STARTUP_SLEEP_TIME=5
 # Specifies the maximum file descriptor number that can be opened by this process
 # When using Systemd, this setting is ignored and the LimitNOFILE defined in
 # /usr/lib/systemd/system/elasticsearch.service takes precedence
-#MAX_OPEN_FILES=65536
+#MAX_OPEN_FILES=65535
 
 # The maximum number of bytes of memory that may be locked into RAM
 # Set to "unlimited" if you use the 'bootstrap.memory_lock: true' option

distribution/packages/src/common/systemd/elasticsearch.service

@@ -29,7 +29,7 @@ StandardOutput=journal
 StandardError=inherit
 
 # Specifies the maximum file descriptor number that can be opened by this process
-LimitNOFILE=65536
+LimitNOFILE=65535
 
 # Specifies the maximum number of processes
 LimitNPROC=4096

distribution/packages/src/deb/init.d/elasticsearch

@@ -39,7 +39,7 @@ ES_HOME=/usr/share/$NAME
 #ES_JAVA_OPTS=
 
 # Maximum number of open files
-MAX_OPEN_FILES=65536
+MAX_OPEN_FILES=65535
 
 # Maximum amount of locked memory
 #MAX_LOCKED_MEMORY=

distribution/packages/src/rpm/init.d/elasticsearch

@@ -33,7 +33,7 @@ fi
 
 # Sets the default values for elasticsearch variables used in this script
 ES_HOME="/usr/share/elasticsearch"
-MAX_OPEN_FILES=65536
+MAX_OPEN_FILES=65535
 MAX_MAP_COUNT=262144
 ES_PATH_CONF="${path.conf}"
 

docs/reference/setup/install/docker.asciidoc

@@ -336,7 +336,7 @@ needed, adjust them in the Daemon, or override them per container, for example
 using `docker run`:
 +
 --
-  --ulimit nofile=65536:65536
+  --ulimit nofile=65535:65535
 
 NOTE: One way of checking the Docker daemon defaults for the aforementioned
 ulimits is by running:

docs/reference/setup/install/sysconfig-file.asciidoc

@@ -5,7 +5,7 @@
 
 `MAX_OPEN_FILES`::
 
-    Maximum number of open files, defaults to `65536`.
+    Maximum number of open files, defaults to `65535`.
 
 `MAX_LOCKED_MEMORY`::
 

docs/reference/setup/sysconfig/configuring.asciidoc

@@ -25,7 +25,7 @@ open file handles (`ulimit -n`) to 65,536, you can do the following:
 [source,sh]
 --------------------------------
 sudo su  <1>
-ulimit -n 65536 <2>
+ulimit -n 65535 <2>
 su elasticsearch <3>
 --------------------------------
 <1> Become `root`.
@@ -46,7 +46,7 @@ the `limits.conf` file:
 
 [source,sh]
 --------------------------------
-elasticsearch  -  nofile  65536
+elasticsearch  -  nofile  65535
 --------------------------------
 
 This change will only take effect the next time the `elasticsearch` user opens

docs/reference/setup/sysconfig/file-descriptors.asciidoc

@@ -12,15 +12,15 @@ file descriptors can be disastrous and will most probably lead to data loss.
 Make sure to increase the limit on the number of open files descriptors for
 the user running Elasticsearch to 65,536 or higher.
 
-For the `.zip` and `.tar.gz` packages, set <<ulimit,`ulimit -n 65536`>> as
-root before starting Elasticsearch,   or set `nofile` to `65536` in
+For the `.zip` and `.tar.gz` packages, set <<ulimit,`ulimit -n 65535`>> as
+root before starting Elasticsearch,   or set `nofile` to `65535` in
 <<limits.conf,`/etc/security/limits.conf`>>.
 
 On macOS, you must also pass the JVM option `-XX:-MaxFDLimit`
 to Elasticsearch in order for it to make use of the higher file descriptor limit.
 
 RPM and Debian packages already default the maximum number of file
-descriptors to 65536 and do not require further configuration.
+descriptors to 65535 and do not require further configuration.
 
 You can check the `max_file_descriptors` configured for each node
 using the <<cluster-nodes-stats>> API, with:

qa/vagrant/src/test/resources/packaging/tests/60_systemd.bats

@@ -234,7 +234,7 @@ setup() {
     local max_processes=$(cat /proc/$pid/limits | grep "Max processes" | awk '{ print $3 }')
     [ "$max_processes" == "4096" ]
     local max_open_files=$(cat /proc/$pid/limits | grep "Max open files" | awk '{ print $4 }')
-    [ "$max_open_files" == "65536" ]
+    [ "$max_open_files" == "65535" ]
     local max_address_space=$(cat /proc/$pid/limits | grep "Max address space" | awk '{ print $4 }')
     [ "$max_address_space" == "unlimited" ]
     systemctl stop elasticsearch.service

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

@@ -258,7 +258,7 @@ static class FileDescriptorCheck implements BootstrapCheck {
         private final int limit;
 
         FileDescriptorCheck() {
-            this(1 << 16);
+            this(65535);
         }
 
         protected FileDescriptorCheck(final int limit) {

server/src/test/java/org/elasticsearch/bootstrap/BootstrapChecksTests.java

@@ -181,7 +181,7 @@ long getMaxHeapSize() {
 
     public void testFileDescriptorLimits() throws NodeValidationException {
         final boolean osX = randomBoolean(); // simulates OS X versus non-OS X
-        final int limit = osX ? 10240 : 1 << 16;
+        final int limit = osX ? 10240 : 65535;
         final AtomicLong maxFileDescriptorCount = new AtomicLong(randomIntBetween(1, limit - 1));
         final BootstrapChecks.FileDescriptorCheck check;
         if (osX) {