Initial implementation of an elasticsearch indexer in Go

Closes #1 (closed)

elastic/client.go

+package elastic
+
+import (
+	"context"
+	"strings"
+
+	"github.com/aws/aws-sdk-go/aws/credentials"
+	"github.com/aws/aws-sdk-go/aws/signer/v4"
+	"github.com/deoxxa/aws_signing_client"
+	"gopkg.in/olivere/elastic.v5"
+)
+
+var (
+	// TODO: make this configurable / detectable.
+	// Limiting to 10MiB lets us work on small AWS clusters, but unnecessarily
+	// increases round trips in larger or non-AWS clusters
+	MaxBulkSize = 10 * 1024 * 1024
+	BulkWorkers = 2
+)
+
+type Client struct {
+	client *elastic.Client
+	bulk   *elastic.BulkProcessor
+}
+
+func (c *Client) Close() error {
+	return c.bulk.Close()
+}
+
+func NewClient(config *Config) (*Client, error) {
+	opts := []elastic.ClientOptionFunc{elastic.SetURL(config.URL...)}
+
+	// Sniffer should look for HTTPS URLs if at-least-one initial URL is HTTPS
+	for _, url := range config.URL {
+		if strings.HasPrefix(url, "https:") {
+			opts = append(opts, elastic.SetScheme("https"))
+			break
+		}
+	}
+
+	if config.AWS {
+		credentials := credentials.NewStaticCredentials(config.AccessKey, config.SecretKey, "")
+		signer := v4.NewSigner(credentials)
+		awsClient, err := aws_signing_client.New(signer, nil, "es", config.Region)
+		if err != nil {
+			return nil, err
+		}
+
+		opts = append(opts, elastic.SetHttpClient(awsClient), elastic.SetSniff(false))
+	}
+
+	client, err := elastic.NewClient(opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	bulk, err := client.BulkProcessor().
+		Workers(BulkWorkers).
+		BulkSize(MaxBulkSize).
+		Do(context.Background())
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &Client{client: client, bulk: bulk}, nil
+}