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102 lines
3.5 KiB
Markdown
102 lines
3.5 KiB
Markdown
#Etcd File System
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## Structure
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[TODO]
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## Node
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In **etcd**, the **node** is the base from which the filesystem is constructed.
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**etcd**'s file system is Unix-like with two kinds of nodes: file and directories.
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- A **file node** has data associated with it.
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- A **directory node** has child nodes associated with it.
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All nodes, regardless of type, have the following attributes and operations:
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### Attributes:
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- **Expiration Time** [optional]
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The node will be deleted when it expires.
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- **ACL**
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The path to the node's access control list.
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### Operation:
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- **Get** (path, recursive, sorted)
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Get the content of the node
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- If the node is a file, the data of the file will be returned.
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- If the node is a directory, the child nodes of the directory will be returned.
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- If recursive is true, it will recursively get the nodes of the directory.
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- If sorted is true, the result will be sorted based on the path.
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- **Create** (path, value[optional], ttl [optional])
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Create a file. Create operation will help to create intermediate directories with no expiration time.
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- If the file already exists, create will fail.
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- If the value is given, set will create a file.
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- If the value is not given, set will crate a directory.
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- If ttl is given, the node will be deleted when it expires.
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- **Update** (path, value[optional], ttl [optional])
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Update the content of the node.
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- If the value is given, the value of the key will be updated.
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- If ttl is given, the expiration time of the node will be updated.
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- **Delete** (path, recursive)
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Delete the node of given path.
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- If the node is a directory:
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- If recursive is true, the operation will delete all nodes under the directory.
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- If recursive is false, error will be returned.
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- **TestAndSet** (path, prevValue [prevIndex], value, ttl)
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Atomic *test and set* value to a file. If test succeeds, this operation will change the previous value of the file to the given value.
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- If the prevValue is given, it will test against previous value of
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the node.
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- If the prevValue is empty, it will test if the node is not existing.
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- If the prevValue is not empty, it will test if the prevValue is equal to the current value of the file.
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- If the prevIndex is given, it will test if the create/last modified index of the node is equal to prevIndex.
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- **Renew** (path, ttl)
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Set the node's expiration time to (current time + ttl)
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## ACL
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### Theory
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Etcd exports a Unix-like file system interface consisting of files and directories, collectively called nodes.
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Each node has various meta-data, including three names of the access control lists used to control reading, writing and changing (change ACL names for the node).
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We are storing the ACL names for nodes under a special *ACL* directory.
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Each node has ACL name corresponding to one file within *ACL* dir.
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Unless overridden, a node naturally inherits the ACL names of its parent directory on creation.
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For each ACL name, it has three children: *R (Reading)*, *W (Writing)*, *C (Changing)*
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Each permission is also a node. Under the node it contains the users who have this permission for the file referring to this ACL name.
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### Example
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[TODO]
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### Diagram
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[TODO]
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### Interface
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Testing permissions:
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- (node *Node) get_perm()
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- (node *Node) has_perm(perm string, user string)
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Setting/Changing permissions:
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- (node *Node) set_perm(perm string)
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- (node *Node) change_ACLname(aclname string)
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## User Group
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[TODO]
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