HDFS-12973. RBF: Document global quota supporting in federation. Contributed by Yiqun Lin.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/federation/RouterAdmin.java

@@ -84,7 +84,8 @@ public void printUsage() {
         + "[-readonly] -owner <owner> -group <group> -mode <mode>]\n"
         + "\t[-rm <source>]\n"
         + "\t[-ls <path>]\n"
-        + "\t[-setQuota <path> -ns <nsQuota> -ss <ssQuota>]\n"
+        + "\t[-setQuota <path> -nsQuota <nsQuota> -ssQuota "
+        + "<quota in bytes or quota size string>]\n"
         + "\t[-clrQuota <path>\n";
     System.out.println(usage);
   }

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md

@@ -428,12 +428,16 @@ Usage:
           [-add <source> <nameservice> <destination> [-readonly] -owner <owner> -group <group> -mode <mode>]
           [-rm <source>]
           [-ls <path>]
+          [-setQuota <path> -nsQuota <nsQuota> -ssQuota <quota in bytes or quota size string>]
+          [-clrQuota <path>]
 
 | COMMAND\_OPTION | Description |
 |:---- |:---- |
 | `-add` *source* *nameservice* *destination* | Add a mount table entry or update if it exists. |
 | `-rm` *source* | Remove mount point of specified path. |
 | `-ls` *path* | List mount points under specified path. |
+| `-setQuota` *path* `-nsQuota` *nsQuota* `-ssQuota` *ssQuota* | Set quota for specified path. See [HDFS Quotas Guide](./HdfsQuotaAdminGuide.html) for the quota detail. |
+| `-clrQuota` *path* | Clear quota of given mount point. See [HDFS Quotas Guide](./HdfsQuotaAdminGuide.html) for the quota detail. |
 
 The commands for managing Router-based federation. See [Mount table management](./HDFSRouterFederation.html#Mount_table_management) for more info.
 

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSRouterFederation.md

@@ -127,6 +127,11 @@ Examples users may encounter include the following.
 * Copy file/folder in two different nameservices.
 * Write into a file/folder being rebalanced.
 
+### Quota management
+Federation supports and controls global quota at mount table level.
+For performance reasons, the Router caches the quota usage and updates it periodically. These quota usage values
+will be used for quota-verification during each WRITE RPC call invoked in RouterRPCSever. See [HDFS Quotas Guide](./HdfsQuotaAdminGuide.html)
+for the quota detail.
 
 ### State Store
 The (logically centralized, but physically distributed) State Store maintains:
@@ -199,6 +204,21 @@ Mount table permission can be set by following command:
 
 The option mode is UNIX-style permissions for the mount table. Permissions are specified in octal, e.g. 0755. By default, this is set to 0755.
 
+Router-based federation supports global quota at mount table level. Mount table entries may spread multiple subclusters and the global quota will be
+accounted across these subclusters.
+
+The federation admin tool supports setting quotas for specified mount table entries:
+
+    [hdfs]$ $HADOOP_HOME/bin/hdfs dfsrouteradmin -setQuota /path -nsQuota 100 -ssQuota 1024
+
+The above command means that we allow the path to have a maximum of 100 file/directories and use at most 1024 bytes storage space. The parameter for *ssQuota*
+supports multiple size-unit suffix (e.g. 1k is 1KB, 5m is 5MB). If no suffix is specified then bytes is assumed.
+
+Ls command will show below information for each mount table entry:
+
+    Source                    Destinations              Owner                     Group                     Mode                      Quota/Usage
+    /path                     ns0->/path                root                      supergroup                rwxr-xr-x                 [NsQuota: 50/0, SsQuota: 100 B/0 B]
+
 Client configuration
 --------------------
 
@@ -322,6 +342,15 @@ Monitor the namenodes in the subclusters for forwarding the client requests.
 | dfs.federation.router.monitor.namenode | | The identifier of the namenodes to monitor and heartbeat. |
 | dfs.federation.router.monitor.localnamenode.enable | `true` | If `true`, the Router should monitor the namenode in the local machine. |
 
+### Quota
+
+Global quota supported in federation.
+
+| Property | Default | Description|
+|:---- |:---- |:---- |
+| dfs.federation.router.quota.enable | `false` | If `true`, the quota system enabled in the Router. |
+| dfs.federation.router.quota-cache.update.interval | 60s | How often the Router updates quota cache. This setting supports multiple time unit suffixes. If no suffix is specified then milliseconds is assumed. |
+
 Metrics
 -------