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125 lines
5.2 KiB
Go
125 lines
5.2 KiB
Go
/*
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Copyright 2015 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/*
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Package bigtable is an API to Google Cloud Bigtable.
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See https://cloud.google.com/bigtable/docs/ for general product documentation.
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Setup and Credentials
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Use NewClient or NewAdminClient to create a client that can be used to access
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the data or admin APIs respectively. Both require credentials that have permission
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to access the Cloud Bigtable API.
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If your program is run on Google App Engine or Google Compute Engine, using the Application Default Credentials
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(https://developers.google.com/accounts/docs/application-default-credentials)
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is the simplest option. Those credentials will be used by default when NewClient or NewAdminClient are called.
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To use alternate credentials, pass them to NewClient or NewAdminClient using option.WithTokenSource.
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For instance, you can use service account credentials by visiting
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https://cloud.google.com/console/project/MYPROJECT/apiui/credential,
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creating a new OAuth "Client ID", storing the JSON key somewhere accessible, and writing
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jsonKey, err := ioutil.ReadFile(pathToKeyFile)
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...
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config, err := google.JWTConfigFromJSON(jsonKey, bigtable.Scope) // or bigtable.AdminScope, etc.
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...
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client, err := bigtable.NewClient(ctx, project, instance, option.WithTokenSource(config.TokenSource(ctx)))
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...
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Here, `google` means the golang.org/x/oauth2/google package
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and `option` means the google.golang.org/api/option package.
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Reading
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The principal way to read from a Bigtable is to use the ReadRows method on *Table.
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A RowRange specifies a contiguous portion of a table. A Filter may be provided through
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RowFilter to limit or transform the data that is returned.
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tbl := client.Open("mytable")
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...
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// Read all the rows starting with "com.google.",
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// but only fetch the columns in the "links" family.
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rr := bigtable.PrefixRange("com.google.")
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err := tbl.ReadRows(ctx, rr, func(r Row) bool {
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// do something with r
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return true // keep going
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}, bigtable.RowFilter(bigtable.FamilyFilter("links")))
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...
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To read a single row, use the ReadRow helper method.
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r, err := tbl.ReadRow(ctx, "com.google.cloud") // "com.google.cloud" is the entire row key
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...
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Writing
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This API exposes two distinct forms of writing to a Bigtable: a Mutation and a ReadModifyWrite.
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The former expresses idempotent operations.
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The latter expresses non-idempotent operations and returns the new values of updated cells.
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These operations are performed by creating a Mutation or ReadModifyWrite (with NewMutation or NewReadModifyWrite),
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building up one or more operations on that, and then using the Apply or ApplyReadModifyWrite
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methods on a Table.
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For instance, to set a couple of cells in a table,
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tbl := client.Open("mytable")
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mut := bigtable.NewMutation()
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mut.Set("links", "maps.google.com", bigtable.Now(), []byte("1"))
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mut.Set("links", "golang.org", bigtable.Now(), []byte("1"))
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err := tbl.Apply(ctx, "com.google.cloud", mut)
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...
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To increment an encoded value in one cell,
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tbl := client.Open("mytable")
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rmw := bigtable.NewReadModifyWrite()
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rmw.Increment("links", "golang.org", 12) // add 12 to the cell in column "links:golang.org"
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r, err := tbl.ApplyReadModifyWrite(ctx, "com.google.cloud", rmw)
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...
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Retries
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If a read or write operation encounters a transient error it will be retried until a successful
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response, an unretryable error or the context deadline is reached. Non-idempotent writes (where
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the timestamp is set to ServerTime) will not be retried. In the case of ReadRows, retried calls
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will not re-scan rows that have already been processed.
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Authentication
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See examples of authorization and authentication at
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https://godoc.org/cloud.google.com/go#pkg-examples.
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*/
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package bigtable // import "cloud.google.com/go/bigtable"
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// Scope constants for authentication credentials.
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// These should be used when using credential creation functions such as oauth.NewServiceAccountFromFile.
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const (
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// Scope is the OAuth scope for Cloud Bigtable data operations.
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Scope = "https://www.googleapis.com/auth/bigtable.data"
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// ReadonlyScope is the OAuth scope for Cloud Bigtable read-only data operations.
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ReadonlyScope = "https://www.googleapis.com/auth/bigtable.readonly"
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// AdminScope is the OAuth scope for Cloud Bigtable table admin operations.
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AdminScope = "https://www.googleapis.com/auth/bigtable.admin.table"
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// InstanceAdminScope is the OAuth scope for Cloud Bigtable instance (and cluster) admin operations.
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InstanceAdminScope = "https://www.googleapis.com/auth/bigtable.admin.cluster"
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)
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// clientUserAgent identifies the version of this package.
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// It should be bumped upon significant changes only.
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const clientUserAgent = "cbt-go/20160628"
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// resourcePrefixHeader is the name of the metadata header used to indicate
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// the resource being operated on.
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const resourcePrefixHeader = "google-cloud-resource-prefix"
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