269 lines
9.0 KiB
Markdown
269 lines
9.0 KiB
Markdown
---
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layout: api
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page_title: KV Store - HTTP API
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sidebar_current: api-kv-store
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description: |-
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The /kv endpoints access Consul's simple key/value store, useful for storing
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service configuration or other metadata.
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---
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# KV Store Endpoints
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The `/kv` endpoints access Consul's simple key/value store, useful for storing
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service configuration or other metadata.
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It is important to note that each datacenter has its own KV store, and there is
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no built-in replication between datacenters. If you are interested in
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replication between datacenters, please view the
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[Consul Replicate](https://github.com/hashicorp/consul-replicate) project.
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~> Values in the KV store cannot be larger than 512kb.
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For multi-key updates, please consider using [transaction](/api/txn.html).
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## Read Key
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This endpoint returns the specified key. If no key exists at the given path, a
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404 is returned instead of a 200 response.
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For multi-key reads, please consider using [transaction](/api/txn.html).
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| Method | Path | Produces |
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| ------ | ---------------------------- | -------------------------- |
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| `GET` | `/kv/:key` | `application/json` |
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The table below shows this endpoint's support for
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[blocking queries](/api/index.html#blocking-queries),
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[consistency modes](/api/index.html#consistency-modes), and
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[required ACLs](/api/index.html#acls).
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| Blocking Queries | Consistency Modes | ACL Required |
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| ---------------- | ----------------- | ------------ |
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| `YES` | `all` | `key:read` |
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### Parameters
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- `key` `(string: "")` - Specifies the path of the key to read.
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- `dc` `(string: "")` - Specifies the datacenter to query. This will default to
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the datacenter of the agent being queried. This is specified as part of the
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URL as a query parameter.
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- `recurse` `(bool: false)` - Specifies if the lookup should be recursive and
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`key` treated as a prefix instead of a literal match. This is specified as
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part of the URL as a query parameter.
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- `raw` `(bool: false)` - Specifies the response is just the raw value of the
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key, without any encoding or metadata. This is specified as part of the URL as
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a query parameter.
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- `keys` `(bool: false)` - Specifies to return only keys (no values or
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metadata). Specifying this implies `recurse`. This is specified as part of the
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URL as a query parameter.
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- `separator` `(string: '/')` - Specifies the character to use as a separator
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for recursive lookups. This is specified as part of the URL as a query
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parameter.
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### Sample Request
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```text
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$ curl \
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https://consul.rocks/v1/kv/my-key
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```
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### Sample Response
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#### Metadata Response
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```json
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[
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{
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"CreateIndex": 100,
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"ModifyIndex": 200,
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"LockIndex": 200,
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"Key": "zip",
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"Flags": 0,
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"Value": "dGVzdA==",
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"Session": "adf4238a-882b-9ddc-4a9d-5b6758e4159e"
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}
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]
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```
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- `CreateIndex` is the internal index value that represents when the entry was
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created.
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- `ModifyIndex` is the last index that modified this key. This index corresponds
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to the `X-Consul-Index` header value that is returned in responses, and it can
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be used to establish blocking queries by setting the `?index` query parameter.
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You can even perform blocking queries against entire subtrees of the KV store:
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if `?recurse` is provided, the returned `X-Consul-Index` corresponds to the
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latest `ModifyIndex` within the prefix, and a blocking query using that
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`?index` will wait until any key within that prefix is updated.
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- `LockIndex` is the number of times this key has successfully been acquired in
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a lock. If the lock is held, the `Session` key provides the session that owns
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the lock.
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- `Key` is simply the full path of the entry.
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- `Flags` is an opaque unsigned integer that can be attached to each entry.
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Clients can choose to use this however makes sense for their application.
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- `Value` is a base64-encoded blob of data.
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#### Keys Response
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When using the `?keys` query parameter, the response structure changes to an
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array of strings instead of an array of JSON objects. Listing `/web/` with a `/`
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separator may return:
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```json
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[
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"/web/bar",
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"/web/foo",
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"/web/subdir/"
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]
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```
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Using the key listing method may be suitable when you do not need the values or
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flags or want to implement a key-space explorer.
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#### Raw Response
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When using the `?raw` endpoint, the response is not `application/json`, but
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rather the content type of the uploaded content.
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```
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)k<><6B><EFBFBD><EFBFBD><EFBFBD><EFBFBD>z^<5E>-<2D>ɑj<C991>q<EFBFBD><71><EFBFBD><EFBFBD>#u<>-R<>r<EFBFBD><72>T<EFBFBD>D<EFBFBD><44>٬<EFBFBD>Y<EFBFBD><59>l,<2C>ιK<CEB9><4B>Fm<46><6D>}<7D>#e<><65>
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```
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(Yes, that is intentionally a bunch of gibberish characters to showcase the
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response)
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## Create/Update Key
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This endpoint
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| Method | Path | Produces |
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| ------ | ---------------------------- | -------------------------- |
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| `PUT` | `/kv/:key` | `application/json` |
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Even though the return type is `application/json`, the value is either `true` or
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`false`, indicating whether the create/update succeeded.
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The table below shows this endpoint's support for
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[blocking queries](/api/index.html#blocking-queries),
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[consistency modes](/api/index.html#consistency-modes), and
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[required ACLs](/api/index.html#acls).
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| Blocking Queries | Consistency Modes | ACL Required |
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| ---------------- | ----------------- | ------------ |
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| `NO` | `none` | `key:write` |
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### Parameters
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- `key` `(string: "")` - Specifies the path of the key to read.
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- `dc` `(string: "")` - Specifies the datacenter to query. This will default to
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the datacenter of the agent being queried. This is specified as part of the
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URL as a query parameter.
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- `flags` `(int: 0)` - Specifies an unsigned value between `0` and `(2^64)-1`.
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Clients can choose to use this however makes sense for their application. This
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is specified as part of the URL as a query parameter.
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- `cas` `(int: 0)` - Specifies to use a Check-And-Set operation. This is very
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useful as a building block for more complex synchronization primitives. If the
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index is 0, Consul will only put the key if it does not already exist. If the
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index is non-zero, the key is only set if the index matches the `ModifyIndex`
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of that key.
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- `acquire` `(string: "")` - Specifies to use a lock acquisition operation. This
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is useful as it allows leader election to be built on top of Consul. If the
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lock is not held and the session is valid, this increments the `LockIndex` and
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sets the `Session` value of the key in addition to updating the key contents.
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A key does not need to exist to be acquired. If the lock is already held by
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the given session, then the `LockIndex` is not incremented but the key
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contents are updated. This lets the current lock holder update the key
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contents without having to give up the lock and reacquire it. **Note that an update
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that does not include the acquire parameter will proceed normally even if another
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session has locked the key.**
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For an example of how to use the lock feature, see the [Leader Election Guide]
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(/docs/guides/leader-election.html).
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- `release` `(string: "")` - Specifies to use a lock release operation. This is
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useful when paired with `?acquire=` as it allows clients to yield a lock. This
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will leave the `LockIndex` unmodified but will clear the associated `Session`
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of the key. The key must be held by this session to be unlocked.
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### Sample Payload
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The payload is arbitrary, and is loaded directly into Consul as supplied.
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### Sample Requests
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```bash
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$ curl \
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--request PUT \
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--data @contents \
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https://consul.rocks/v1/kv/my-key
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# or
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$ curl \
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--request PUT \
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--data-binary @contents \
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https://consul.rocks/v1/kv/my-key
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```
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### Sample Response
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```json
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true
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```
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## Delete Key
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This endpoint deletes a single key or all keys sharing a prefix.
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| Method | Path | Produces |
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| -------- | ---------------------------- | -------------------------- |
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| `DELETE` | `/kv/:key` | `application/json` |
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The table below shows this endpoint's support for
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[blocking queries](/api/index.html#blocking-queries),
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[consistency modes](/api/index.html#consistency-modes), and
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[required ACLs](/api/index.html#acls).
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| Blocking Queries | Consistency Modes | ACL Required |
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| ---------------- | ----------------- | ------------ |
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| `NO` | `none` | `key:write` |
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### Parameters
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- `recurse` `(bool: false)` - Specifies to delete all keys which have the
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specified prefix. Without this, only a key with an exact match will be
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deleted.
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- `cas` `(int: 0)` - Specifies to use a Check-And-Set operation. This is very
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useful as a building block for more complex synchronization primitives. Unlike
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`PUT`, the index must be greater than 0 for Consul to take any action: a 0
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index will not delete the key. If the index is non-zero, the key is only
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deleted if the index matches the `ModifyIndex` of that key.
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### Sample Request
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```text
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$ curl \
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--request DELETE \
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https://consul.rocks/v1/kv/my-key
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```
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### Sample Response
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```json
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true
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```
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