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Init package libbeat/statestore (elastic#19117)
Initialize support for the statestore package. The addition of the statestore package is split up into multiple changeset to ease review. The final version of the package can be found [here](https://github.com/urso/beats/tree/fb-input-v2-combined/libbeat/statestore). Once finalized, the libbeat/statestore package contains: - The statestore frontend and interface for use within Beats - Interfaces for the store backend - A common set of tests store backends need to support - a storetest package for testing new features that require a store. The testing helpers use map[string]interface{} that can be initialized or queried after the test run for validation purposes. - The default memlog backend + tests This change includes the frontend and backend interfaces only. Once merged we will add the tests and finally the memlog store.
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Steffen Siering
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Jun 12, 2020
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| Original file line number | Diff line number | Diff line change |
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| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you under | ||
| // the Apache License, Version 2.0 (the "License"); you may | ||
| // not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
|
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| package backend | ||
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| // Registry provides access to stores managed by the backend storage. | ||
| type Registry interface { | ||
| // Access opens a store. The store will be closed by the frontend, once all | ||
| // accessed stores have been closed. | ||
| // | ||
| // The Store instance returned must be threadsafe. | ||
| Access(name string) (Store, error) | ||
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| // Close is called on shutdown after all stores have been closed. | ||
| // An implementation of Registry is not required to check for the stores to be closed. | ||
| Close() error | ||
| } | ||
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| // ValueDecoder is used to decode values into go structs or maps within a transaction. | ||
| // A ValueDecoder is supposed to be invalidated by beats after the loop operations has returned. | ||
| type ValueDecoder interface { | ||
| Decode(to interface{}) error | ||
| } | ||
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| // Store provides access to key value pairs. | ||
| type Store interface { | ||
| // Close should close the store and release all used resources. | ||
| Close() error | ||
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| // Has checks if the key exists. No error must be returned if the key does | ||
| // not exists, but the bool return must be false. | ||
| // An error return value must indicate internal errors only. The store is | ||
| // assumed to be in a 'bad' but recoverable state if 'Has' fails. | ||
| Has(key string) (bool, error) | ||
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| // Get decodes the value for the given key into value. | ||
| // Besides internal implementation specific errors an error is assumed | ||
| // to be returned if the key does not exist or the type of the value | ||
| // passed is incompatible to the actual value in the store (decoding error). | ||
| Get(key string, value interface{}) error | ||
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| // Set inserts or overwrites a key pair in the store. | ||
| // The `value` parameters can be assumed to be a struct or a map. Besides | ||
| // internal implementation specific errors, an error should be returned if | ||
| // the value given can not be encoded. | ||
| Set(key string, value interface{}) error | ||
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| // Remove removes and entry from the store. | ||
| Remove(string) error | ||
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| // Each loops over all key value pairs in the store calling fn for each pair. | ||
| // The ValueDecoder is used by fn to optionally decode the value into a | ||
| // custom struct or map. The decoder must be executable multiple times, but | ||
| // is assumed to be invalidated once fn returns | ||
| // The loop shall return if fn returns an error or false. | ||
| Each(fn func(string, ValueDecoder) (bool, error)) error | ||
| } |
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| @@ -0,0 +1,91 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you under | ||
| // the Apache License, Version 2.0 (the "License"); you may | ||
| // not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
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| package statestore | ||
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| import ( | ||
| "errors" | ||
| "fmt" | ||
| ) | ||
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| // ErrorAccess indicates that an error occured when trying to open a Store. | ||
| type ErrorAccess struct { | ||
| name string | ||
| cause error | ||
| } | ||
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| // Store reports the name of the store that could not been accessed. | ||
| func (e *ErrorAccess) Store() string { return e.name } | ||
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| // Unwrap returns the cause for the error or nil if the cause is unknown or has | ||
| // not been reported by the backend | ||
| func (e *ErrorAccess) Unwrap() error { return e.cause } | ||
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| // Error creates a descriptive error string. | ||
| func (e *ErrorAccess) Error() string { | ||
| if e.cause == nil { | ||
| return fmt.Sprintf("failed to open store '%v'", e.name) | ||
| } | ||
| return fmt.Sprintf("failed to open store '%v': %v", e.name, e.cause) | ||
| } | ||
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| // ErrorClosed indicates that the operation failed because the store has already been closed. | ||
| type ErrorClosed struct { | ||
| name string | ||
| operation string | ||
| } | ||
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| // Store reports the name of the store that has been closed. | ||
| func (e *ErrorClosed) Store() string { return e.name } | ||
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| // Operation returns a 'readable' name for the operation that failed to access the closed store. | ||
| func (e *ErrorClosed) Operation() string { return e.operation } | ||
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| // Error creates a descriptive error string. | ||
| func (e *ErrorClosed) Error() string { | ||
| return fmt.Sprintf("can not executed %v operation on closed store '%v'", e.operation, e.name) | ||
| } | ||
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| // ErrorOperation is returned when a generic store operation failed. | ||
| type ErrorOperation struct { | ||
| name string | ||
| operation string | ||
| cause error | ||
| } | ||
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| // Store reports the name of the store. | ||
| func (e *ErrorOperation) Store() string { return e.name } | ||
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| // Operation returns a 'readable' name for the operation that failed. | ||
| func (e *ErrorOperation) Operation() string { return e.operation } | ||
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| // Unwrap returns the cause of the failure. | ||
| func (e *ErrorOperation) Unwrap() error { return e.cause } | ||
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| // Error creates a descriptive error string. | ||
| func (e *ErrorOperation) Error() string { | ||
| return fmt.Sprintf("failed in %v operation on store '%v': %v", e.operation, e.name, e.cause) | ||
| } | ||
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| // IsClosed returns true if the cause for an Error is ErrorClosed. | ||
| func IsClosed(err error) bool { | ||
| var tmp *ErrorClosed | ||
| if errors.As(err, &tmp) { | ||
| return true | ||
| } | ||
| return false | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you under | ||
| // the Apache License, Version 2.0 (the "License"); you may | ||
| // not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
|
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| package statestore | ||
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| import ( | ||
| "sync" | ||
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| "github.com/elastic/beats/v7/libbeat/statestore/backend" | ||
| ) | ||
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| // Registry manages multiple key-value stores. | ||
| // When working with a registry, one must access a store. Depending on backend | ||
| // a store can be an index, a table, or a directory. All access to a store is | ||
| // handled by transaction. | ||
| type Registry struct { | ||
| backend backend.Registry | ||
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| mu sync.Mutex | ||
| active map[string]*sharedStore // active/open stores | ||
| wg sync.WaitGroup | ||
| } | ||
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| // ValueDecoder is used to decode retrieved from an actual store. A | ||
| // ValueDecoder instance is valid for the lifetime of the transaction only. | ||
| type ValueDecoder = backend.ValueDecoder | ||
|
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| // NewRegistry creates a new Registry with a configured backend. | ||
| func NewRegistry(backend backend.Registry) *Registry { | ||
| return &Registry{ | ||
| backend: backend, | ||
| active: map[string]*sharedStore{}, | ||
| } | ||
| } | ||
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| // Close closes the backend storage. Close blocks until all stores in use are closed. | ||
| func (r *Registry) Close() error { | ||
| r.wg.Wait() // wait for all stores being closed | ||
| return r.backend.Close() | ||
| } | ||
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| // Get opens a shared store. A store is closed and released only after all it's | ||
| // users have closed the store. | ||
| func (r *Registry) Get(name string) (*Store, error) { | ||
| r.mu.Lock() | ||
| defer r.mu.Unlock() | ||
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| shared := r.active[name] | ||
| if shared == nil { | ||
| backend, err := r.backend.Access(name) | ||
| if err != nil { | ||
| return nil, &ErrorAccess{name: name, cause: err} | ||
| } | ||
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| shared = newSharedStore(r, name, backend) | ||
| defer shared.Release() | ||
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| r.active[name] = shared | ||
| r.wg.Add(1) | ||
| } | ||
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| return newStore(shared), nil | ||
| } | ||
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| func (r *Registry) unregisterStore(s *sharedStore) { | ||
| _, exists := r.active[s.name] | ||
| if !exists { | ||
| panic("removing an unknown store") | ||
| } | ||
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| delete(r.active, s.name) | ||
| r.wg.Done() | ||
| } |
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