kraken

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// Copyright (c) 2016-2019 Uber Technologies, Inc.
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//
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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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//
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//     http://www.apache.org/licenses/LICENSE-2.0
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//
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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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package agentclient
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import (
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	"errors"
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	"fmt"
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	"io"
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	"io/ioutil"
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	"net/url"
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	"github.com/uber/kraken/core"
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	"github.com/uber/kraken/utils/httputil"
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)
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// Client errors.
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var (
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	ErrTagNotFound = errors.New("tag not found")
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)
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// Client defines a client for accessing the agent server.
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type Client interface {
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	GetTag(tag string) (core.Digest, error)
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	Download(namespace string, d core.Digest) (io.ReadCloser, error)
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}
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// HTTPClient provides a wrapper for HTTP operations on an agent.
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type HTTPClient struct {
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	addr string
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}
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// New creates a new client for an agent at addr.
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func New(addr string) *HTTPClient {
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	return &HTTPClient{addr}
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}
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// GetTag resolves tag into a digest. Returns ErrTagNotFound if the tag does
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// not exist.
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func (c *HTTPClient) GetTag(tag string) (core.Digest, error) {
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	resp, err := httputil.Get(fmt.Sprintf("http://%s/tags/%s", c.addr, url.PathEscape(tag)))
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	if err != nil {
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		if httputil.IsNotFound(err) {
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			return core.Digest{}, ErrTagNotFound
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		}
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		return core.Digest{}, err
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	}
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	defer resp.Body.Close()
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	b, err := ioutil.ReadAll(resp.Body)
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	if err != nil {
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		return core.Digest{}, fmt.Errorf("read body: %s", err)
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	}
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	d, err := core.ParseSHA256Digest(string(b))
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	if err != nil {
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		return core.Digest{}, fmt.Errorf("parse digest: %s", err)
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	}
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	return d, nil
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}
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// Download returns the blob of d. Callers should close the returned ReadCloser
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// when done reading the blob.
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func (c *HTTPClient) Download(namespace string, d core.Digest) (io.ReadCloser, error) {
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	resp, err := httputil.Get(
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		fmt.Sprintf(
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			"http://%s/namespace/%s/blobs/%s",
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			c.addr, url.PathEscape(namespace), d))
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	if err != nil {
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		return nil, err
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	}
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	return resp.Body, nil
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}
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