bigtable/search/search.go (362 lines of code) (raw):
// Copyright 2019 Google LLC
//
// Licensed 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
//
// https://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.
// Search is a sample web server that uses Cloud Bigtable as the storage layer
// for a simple document-storage and full-text-search service.
// It has four functions:
// - Initialize and clear the table.
// - Add a document. This adds the content of a user-supplied document to the
// Bigtable, and adds references to the document to an index in the Bigtable.
// The document is indexed under each unique word in the document.
// - Search the index. This returns documents containing each word in a user
// query, with snippets and links to view the whole document.
// - Copy table. This copies the documents and index from another table and
// adds them to the current one.
package main
import (
"bytes"
"context"
"flag"
"fmt"
"html/template"
"io"
"log"
"net/http"
"strconv"
"strings"
"sync"
"time"
"unicode"
"cloud.google.com/go/bigtable"
)
var (
addTemplate = template.Must(template.New("").Parse(`<html><body>
Added {{.Title}}
</body></html>`))
contentTemplate = template.Must(template.New("").Parse(`<html><body>
<b>{{.Title}}</b><br><br>
{{.Content}}
</body></html>`))
searchTemplate = template.Must(template.New("").Parse(`<html><body>
Results for <b>{{.Query}}</b>:<br><br>
{{range .Results}}
<a href="/content?name={{.Title}}">{{.Title}}</a><br>
<i>{{.Snippet}}</i><br><br>
{{end}}
</body></html>`))
)
const (
indexColumnFamily = "i"
contentColumnFamily = "c"
mainPage = `
<html>
<head>
<title>Document Search</title>
</head>
<body>
Initialize and clear table:
<form action="/reset" method="post">
<div><input type="submit" value="Init"></div>
</form>
Search for documents:
<form action="/search" method="post">
<div><input type="text" name="q" size=80></div>
<div><input type="submit" value="Search"></div>
</form>
Add a document:
<form action="/add" method="post">
Document name:
<div><textarea name="name" rows="1" cols="80"></textarea></div>
Document text:
<div><textarea name="content" rows="20" cols="80"></textarea></div>
<div><input type="submit" value="Submit"></div>
</form>
Copy data from another table:
<form action="/copy" method="post">
Source table name:
<div><input type="text" name="name" size=80></div>
<div><input type="submit" value="Copy"></div>
</form>
</body>
</html>
`
)
func main() {
var (
project = flag.String("project", "", "The name of the project.")
instance = flag.String("instance", "", "The name of the Cloud Bigtable instance.")
tableName = flag.String("table", "docindex", "The name of the table containing the documents and index.")
port = flag.Int("port", 8080, "TCP port for server.")
)
flag.Parse()
// Make an admin client.
adminClient, err := bigtable.NewAdminClient(context.Background(), *project, *instance)
if err != nil {
log.Fatal("Bigtable NewAdminClient:", err)
}
// Make a regular client.
client, err := bigtable.NewClient(context.Background(), *project, *instance)
if err != nil {
log.Fatal("Bigtable NewClient:", err)
}
// Open the table.
table := client.Open(*tableName)
// Set up HTML handlers, and start the web server.
http.HandleFunc("/search", func(w http.ResponseWriter, r *http.Request) { handleSearch(w, r, table) })
http.HandleFunc("/content", func(w http.ResponseWriter, r *http.Request) { handleContent(w, r, table) })
http.HandleFunc("/add", func(w http.ResponseWriter, r *http.Request) { handleAddDoc(w, r, table) })
http.HandleFunc("/reset", func(w http.ResponseWriter, r *http.Request) { handleReset(w, r, *tableName, adminClient) })
http.HandleFunc("/copy", func(w http.ResponseWriter, r *http.Request) { handleCopy(w, r, *tableName, client, adminClient) })
http.HandleFunc("/", handleMain)
if err := http.ListenAndServe(":"+strconv.Itoa(*port), nil); err != nil {
log.Fatal(err)
}
}
// handleMain outputs the home page.
func handleMain(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, mainPage)
}
// tokenize splits a string into tokens.
// This is very simple, it's not a good tokenization function.
func tokenize(s string) []string {
wordMap := make(map[string]bool)
f := strings.FieldsFunc(s, func(r rune) bool { return !unicode.IsLetter(r) })
for _, word := range f {
word = strings.ToLower(word)
wordMap[word] = true
}
words := make([]string, 0, len(wordMap))
for word := range wordMap {
words = append(words, word)
}
return words
}
// handleContent fetches the content of a document from the Bigtable and returns it.
func handleContent(w http.ResponseWriter, r *http.Request, table *bigtable.Table) {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
name := r.FormValue("name")
if len(name) == 0 {
http.Error(w, "No document name supplied.", http.StatusBadRequest)
return
}
row, err := table.ReadRow(ctx, name)
if err != nil {
http.Error(w, "Error reading content: "+err.Error(), http.StatusInternalServerError)
return
}
content := row[contentColumnFamily]
if len(content) == 0 {
http.Error(w, "Document not found.", http.StatusNotFound)
return
}
var buf bytes.Buffer
if err := contentTemplate.ExecuteTemplate(&buf, "", struct{ Title, Content string }{name, string(content[0].Value)}); err != nil {
http.Error(w, "Error executing HTML template: "+err.Error(), http.StatusInternalServerError)
return
}
io.Copy(w, &buf)
}
// handleSearch responds to search queries, returning links and snippets for matching documents.
func handleSearch(w http.ResponseWriter, r *http.Request, table *bigtable.Table) {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
query := r.FormValue("q")
// Split the query into words.
words := tokenize(query)
if len(words) == 0 {
http.Error(w, "Empty query.", http.StatusBadRequest)
return
}
// readRows reads from many rows concurrently.
readRows := func(rows []string) ([]bigtable.Row, error) {
results := make([]bigtable.Row, len(rows))
errors := make([]error, len(rows))
var wg sync.WaitGroup
for i, row := range rows {
wg.Add(1)
go func(i int, row string) {
defer wg.Done()
results[i], errors[i] = table.ReadRow(ctx, row, bigtable.RowFilter(bigtable.LatestNFilter(1)))
}(i, row)
}
wg.Wait()
for _, err := range errors {
if err != nil {
return nil, err
}
}
return results, nil
}
// For each query word, get the list of documents containing it.
results, err := readRows(words)
if err != nil {
http.Error(w, "Error reading index: "+err.Error(), http.StatusInternalServerError)
return
}
// Count how many of the query words each result contained.
hits := make(map[string]int)
for _, r := range results {
for _, r := range r[indexColumnFamily] {
hits[r.Column]++
}
}
// Build a slice of all the documents that matched every query word.
var matches []string
for doc, count := range hits {
if count == len(words) {
matches = append(matches, doc[len(indexColumnFamily+":"):])
}
}
// Fetch the content of those documents from the Bigtable.
content, err := readRows(matches)
if err != nil {
http.Error(w, "Error reading results: "+err.Error(), http.StatusInternalServerError)
return
}
type result struct{ Title, Snippet string }
data := struct {
Query string
Results []result
}{query, nil}
// Output links and snippets.
for i, doc := range matches {
var text string
c := content[i][contentColumnFamily]
if len(c) > 0 {
text = string(c[0].Value)
}
if len(text) > 100 {
text = text[:100] + "..."
}
data.Results = append(data.Results, result{doc, text})
}
var buf bytes.Buffer
if err := searchTemplate.ExecuteTemplate(&buf, "", data); err != nil {
http.Error(w, "Error executing HTML template: "+err.Error(), http.StatusInternalServerError)
return
}
io.Copy(w, &buf)
}
// handleAddDoc adds a document to the index.
func handleAddDoc(w http.ResponseWriter, r *http.Request, table *bigtable.Table) {
if r.Method != "POST" {
http.Error(w, "POST requests only", http.StatusMethodNotAllowed)
return
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
name := r.FormValue("name")
if len(name) == 0 {
http.Error(w, "Empty document name!", http.StatusBadRequest)
return
}
content := r.FormValue("content")
if len(content) == 0 {
http.Error(w, "Empty document content!", http.StatusBadRequest)
return
}
var (
writeErr error // Set if any write fails.
mu sync.Mutex // Protects writeErr
wg sync.WaitGroup // Used to wait for all writes to finish.
)
// writeOneColumn writes one column in one row, updates err if there is an error,
// and signals wg that one operation has finished.
writeOneColumn := func(row, family, column, value string, ts bigtable.Timestamp) {
mut := bigtable.NewMutation()
mut.Set(family, column, ts, []byte(value))
err := table.Apply(ctx, row, mut)
if err != nil {
mu.Lock()
writeErr = err
mu.Unlock()
}
}
// Start a write to store the document content.
wg.Add(1)
go func() {
writeOneColumn(name, contentColumnFamily, "", content, bigtable.Now())
wg.Done()
}()
// Start writes to store the document name in the index for each word in the document.
words := tokenize(content)
for _, word := range words {
var (
row = word
family = indexColumnFamily
column = name
value = ""
ts = bigtable.Now()
)
wg.Add(1)
go func() {
// TODO: should use a semaphore to limit the number of concurrent writes.
writeOneColumn(row, family, column, value, ts)
wg.Done()
}()
}
wg.Wait()
if writeErr != nil {
http.Error(w, "Error writing to Bigtable: "+writeErr.Error(), http.StatusInternalServerError)
return
}
var buf bytes.Buffer
if err := addTemplate.ExecuteTemplate(&buf, "", struct{ Title string }{name}); err != nil {
http.Error(w, "Error executing HTML template: "+err.Error(), http.StatusInternalServerError)
return
}
io.Copy(w, &buf)
}
// handleReset deletes the table if it exists, creates it again, and creates its column families.
func handleReset(w http.ResponseWriter, r *http.Request, table string, adminClient *bigtable.AdminClient) {
if r.Method != "POST" {
http.Error(w, "POST requests only", http.StatusMethodNotAllowed)
return
}
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
defer cancel()
adminClient.DeleteTable(ctx, table)
if err := adminClient.CreateTable(ctx, table); err != nil {
http.Error(w, "Error creating Bigtable: "+err.Error(), http.StatusInternalServerError)
return
}
time.Sleep(20 * time.Second)
// Create two column families, and set the GC policy for each one to keep one version.
for _, family := range []string{indexColumnFamily, contentColumnFamily} {
if err := adminClient.CreateColumnFamily(ctx, table, family); err != nil {
http.Error(w, "Error creating column family: "+err.Error(), http.StatusInternalServerError)
return
}
if err := adminClient.SetGCPolicy(ctx, table, family, bigtable.MaxVersionsPolicy(1)); err != nil {
http.Error(w, "Error setting GC policy: "+err.Error(), http.StatusInternalServerError)
return
}
}
w.Write([]byte("<html><body>Done.</body></html>"))
return
}
// copyTable copies data from one table to another.
func copyTable(src, dst string, client *bigtable.Client, adminClient *bigtable.AdminClient) error {
if src == "" || src == dst {
return nil
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
// Open the source and destination tables.
srcTable := client.Open(src)
dstTable := client.Open(dst)
var (
writeErr error // Set if any write fails.
mu sync.Mutex // Protects writeErr
wg sync.WaitGroup // Used to wait for all writes to finish.
)
copyRowToTable := func(row bigtable.Row) bool {
mu.Lock()
failed := writeErr != nil
mu.Unlock()
if failed {
return false
}
mut := bigtable.NewMutation()
for family, items := range row {
for _, item := range items {
// Get the column name, excluding the column family name and ':' character.
columnWithoutFamily := item.Column[len(family)+1:]
mut.Set(family, columnWithoutFamily, bigtable.Now(), item.Value)
}
}
wg.Add(1)
go func() {
// TODO: should use a semaphore to limit the number of concurrent writes.
if err := dstTable.Apply(ctx, row.Key(), mut); err != nil {
mu.Lock()
writeErr = err
mu.Unlock()
}
wg.Done()
}()
return true
}
// Create a filter that only accepts the column families we're interested in.
filter := bigtable.FamilyFilter(indexColumnFamily + "|" + contentColumnFamily)
// Read every row from srcTable, and call copyRowToTable to copy it to our table.
err := srcTable.ReadRows(ctx, bigtable.InfiniteRange(""), copyRowToTable, bigtable.RowFilter(filter))
wg.Wait()
if err != nil {
return err
}
return writeErr
}
// handleCopy copies data from one table to another.
func handleCopy(w http.ResponseWriter, r *http.Request, dst string, client *bigtable.Client, adminClient *bigtable.AdminClient) {
if r.Method != "POST" {
http.Error(w, "POST requests only", http.StatusMethodNotAllowed)
return
}
src := r.FormValue("name")
if src == "" {
http.Error(w, "No source table specified.", http.StatusBadRequest)
return
}
if err := copyTable(src, dst, client, adminClient); err != nil {
http.Error(w, "Failed to rebuild index: "+err.Error(), http.StatusInternalServerError)
return
}
fmt.Fprint(w, "Copied table.\n")
}