YutaLin commented on code in PR #215: URL: https://github.com/apache/ozone-site/pull/215#discussion_r2666279440
########## docs/04-user-guide/01-client-interfaces/02-ofs.md: ########## @@ -1,7 +1,396 @@ --- sidebar_label: ofs --- +<!-- cspell:ignore Unsets snapshottable reencryption --> # ofs: Hadoop Compatible Interface -**TODO:** File a subtask under [HDDS-9858](https://issues.apache.org/jira/browse/HDDS-9858) and complete this page or section. +The Hadoop compatible file system interface allows storage backends like Ozone to be easily integrated into Hadoop eco-system. Ozone file system is a Hadoop compatible file system. + +:::warning +Currently, Ozone supports two schemes: `o3fs://` and `ofs://`. + +The biggest difference between `o3fs` and `ofs` is that `o3fs` supports operations only at a **single bucket**, while `ofs` supports operations across all volumes and buckets and provides a full view of all the volume/buckets. +::: + +## The Basics + +Examples of valid ofs paths: + +```text +ofs://om1/ +ofs://om3:9862/ +ofs://omservice/ +ofs://omservice/volume1/ +ofs://omservice/volume1/bucket1/ +ofs://omservice/volume1/bucket1/dir1 +ofs://omservice/volume1/bucket1/dir1/key1 + +ofs://omservice/tmp/ +ofs://omservice/tmp/key1 +``` + +Volumes and mount(s) are located at the root level of an ofs Filesystem. +Buckets are listed naturally under volumes. +Keys and directories are under each buckets. + +Note that for mounts, only temp mount `/tmp` is supported at the moment. + +## Configuration + +Please add the following entry to the `core-site.xml`. + +```xml +<property> + <name>fs.ofs.impl</name> + <value>org.apache.hadoop.fs.ozone.RootedOzoneFileSystem</value> +</property> +<property> + <name>fs.defaultFS</name> + <value>ofs://om-host.example.com/</value> +</property> +``` + +This will make all the volumes and buckets to be the default Hadoop compatible file system and register the ofs file system type. + +You also need to add the Ozone filesystem JAR file to the classpath: + +```bash +export HADOOP_CLASSPATH=/opt/ozone/share/ozone/lib/ozone-filesystem-hadoop3-*.jar:$HADOOP_CLASSPATH +``` + +:::note +With Hadoop 2.x, use the Hadoop 2.x version. +::: + +Once the default Filesystem has been setup, users can run commands like ls, put, mkdir, etc. +For example: + +```bash +hdfs dfs -ls / +``` + +Note that ofs works on all buckets and volumes. Users can create buckets and volumes using mkdir, such as create volume named volume1 and bucket named bucket1: + +```bash +hdfs dfs -mkdir /volume1 +hdfs dfs -mkdir /volume1/bucket1 +``` + +Or use the put command to write a file to the bucket. + +```bash +hdfs dfs -put /etc/hosts /volume1/bucket1/test +``` + +For more usage, see: https://issues.apache.org/jira/secure/attachment/12987636/Design%20ofs%20v1.pdf + +## Differences from o3fs + +<!-- TODO: Link to o3fs documentation when created --> + +### Creating files + +ofs doesn't allow creating keys(files) directly under root or volumes. +Users will receive an error message when they try to do that: + +```bash +ozone fs -touch /volume1/key1 +# Output: touch: Cannot create file under root or volume. +``` + +### Simplify fs.defaultFS + +With ofs, fs.defaultFS (in `core-site.xml`) no longer needs to have a specific volume and bucket in its path like o3fs did. +Simply put the OM host or service ID (in case of HA): + +```xml +<property> + <name>fs.defaultFS</name> + <value>ofs://omservice</value> +</property> +``` + +The client would then be able to access every volume and bucket on the cluster without specifying the hostname or service ID. + +```bash +ozone fs -mkdir -p /volume1/bucket1 +``` + +### Volume and bucket management directly from FileSystem shell + +Admins can create and delete volumes and buckets easily with Hadoop FS shell. +Volumes and buckets are treated similar to directories so they will be created if they don't exist with `-p`: + +```bash +ozone fs -mkdir -p ofs://omservice/volume1/bucket1/dir1/ +``` + +Note that the supported volume and bucket name character set rule still applies. +For instance, bucket and volume names don't take underscore(`_`): + +```bash +$ ozone fs -mkdir -p /volume_1 +mkdir: Bucket or Volume name has an unsupported character : _ +``` + +## Mounts and Configuring /tmp + +In order to be compatible with legacy Hadoop applications that use /tmp/, we have a special temp mount located at the root of the FS. +This feature may be expanded in the feature to support custom mount paths. + +Currently Ozone supports two configurations for /tmp. The first (default), is a tmp directory for each user comprised of a mount volume with a user specific temp bucket. The second (configurable through `ozone-site.xml`), a sticky-bit like tmp directory common to all users comprised of a mount volume and a common temp bucket. + +Important: To use it, first, an **admin** needs to create the volume tmp (the volume name is hardcoded for now) and set its ACL to world ALL access. +Namely: + +```bash +ozone sh volume create tmp +ozone sh volume setacl tmp -al world::a +``` + +These commands only need to be done **once per cluster**. + +### For /tmp directory per user (default) + +Then, **each user** needs to mkdir first to initialize their own temp bucket once. + +```bash +$ ozone fs -mkdir /tmp +2020-06-04 00:00:00,050 [main] INFO rpc.RpcClient: Creating Bucket: tmp/0238 ... +``` + +After that they can write to it just like they would do to a regular directory. e.g.: + +```bash +ozone fs -touch /tmp/key1 +``` + +### For a sharable /tmp directory common to all users + +To enable the sticky-bit common /tmp directory, update the `ozone-site.xml` with the following property + +```xml +<property> + <name>ozone.om.enable.ofs.shared.tmp.dir</name> + <value>true</value> +</property> +``` + +Then after setting up the volume tmp as **admin**, also configure a tmp bucket that serves as the common /tmp directory for all users, for example, + +```bash +$ ozone sh bucket create /tmp/tmp +$ ozone sh volume setacl tmp -a user:anyuser:rwlc \ + user:adminuser:a,group:anyuser:rwlc,group:adminuser:a tmp/tmp +``` + +where, anyuser is username(s) admin wants to grant access and, adminuser is the admin username. + +Users then access the tmp directory as, + +```bash +ozone fs -put ./NOTICE.txt ofs://om/tmp/key1 +``` + +## Delete with trash enabled + +In order to enable trash in Ozone, Please add these configs to `core-site.xml` + +```xml +<property> + <name>fs.trash.interval</name> + <value>10</value> +</property> +<property> + <name>fs.trash.classname</name> + <value>org.apache.hadoop.fs.ozone.OzoneTrashPolicy</value> +</property> +``` + +When keys are deleted with trash enabled, they are moved to a trash directory under each bucket, because keys aren't allowed to be moved(renamed) between buckets in Ozone. + +```bash +$ ozone fs -rm /volume1/bucket1/key1 +2020-06-04 00:00:00,100 [main] INFO fs.TrashPolicyDefault: Moved: 'ofs://id1/volume1/bucket1/key1' to trash at: ofs://id1/volume1/bucket1/.Trash/hadoop/Current/volume1/bucket1/key1 +``` + +This is very similar to how the HDFS encryption zone handles trash location. + +### Note + +1. The flag `-skipTrash` can be used to delete files permanently without being moved to trash. + +2. Deletes at bucket or volume level with trash enabled are not allowed. One must use skipTrash in such cases. + i.e `ozone fs -rm -R ofs://vol1/bucket1` or `ozone fs -rm -R o3fs://bucket1.vol1` are not allowed without skipTrash + +## Recursive listing + +ofs supports recursive volume, bucket and key listing. + +i.e. `ozone fs -ls -R ofs://omservice/` will recursively list all volumes, buckets and keys the user has LIST permission to if ACL is enabled. +If ACL is disabled, the command would just list literally everything on that cluster. + +This feature wouldn't degrade server performance as the loop is on the client. +Think it as a client is issuing multiple requests to the server to get all the information. + +## Migrating from HDFS + +This guide helps you migrate applications from HDFS to Ozone by detailing the API-level compatibility of the Ozone File System (ofs). + +To ensure a smooth transition, you should first verify that your existing applications will work with ofs. You can check for potential incompatibilities by identifying the HDFS APIs your applications use. + +- **For Cluster Administrators**: Analyze the NameNode audit logs on your source HDFS cluster to identify the operations performed by your applications. +- **For Application Developers**: Review your application's source code to identify which `FileSystem` or `DistributedFileSystem` APIs are being called. + +Once you have a list of APIs, compare it against the tables below to identify any unsupported operations. + +### Supported FileSystem APIs + +The following standard `FileSystem` APIs are supported by ofs. + +| Operation | NameNode audit log | Description | Support | +|-------------------------|---------------------------|-----------------------------------------------------|---------------| +| `access` | `checkAccess` | Checks if the user can access a path. | Supported | +| `create` | `create` | Creates a new file. | Supported | +| `open` | `open` | Opens a file for reading. | Supported | +| `rename` | `rename` | Renames a file or directory. | Supported [1] | Review Comment: Hi @echonesis, that's a good feedback, thanks! -- This is an automated message from the Apache Git Service. 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