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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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// 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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// 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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// 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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