Add a 'query' command to query the metadb

cmd/tabacco/query.go

+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"flag"
+	"log"
+	"os"
+	"time"
+
+	"github.com/google/subcommands"
+
+	"git.autistici.org/ai3/tools/tabacco"
+	mdbc "git.autistici.org/ai3/tools/tabacco/metadb/client"
+)
+
+var rpcTimeout = 120 * time.Second
+
+type queryCommand struct {
+	configPath  string
+	host        string
+	numVersions int
+}
+
+func (c *queryCommand) Name() string     { return "query" }
+func (c *queryCommand) Synopsis() string { return "query the backup metadata database" }
+func (c *queryCommand) Usage() string {
+	return `query [<flags>] <atom_pattern>
+        Query the backup metadata database.
+
+`
+}
+
+func (c *queryCommand) SetFlags(f *flag.FlagSet) {
+	f.StringVar(&c.configPath, "config", "/etc/tabacco/agent.yml", "configuration `file`")
+	f.StringVar(&c.host, "host", "", "filter by host")
+	f.IntVar(&c.numVersions, "num-versions", 1, "return the most recent `N` versions")
+}
+
+func (c *queryCommand) buildRequest(f *flag.FlagSet) (*tabacco.FindRequest, error) {
+	if f.NArg() != 1 {
+		return nil, errors.New("error: wrong number of arguments")
+	}
+	return &tabacco.FindRequest{
+		Pattern:     f.Arg(0),
+		Host:        c.host,
+		NumVersions: c.numVersions,
+	}, nil
+}
+
+func (c *queryCommand) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	req, err := c.buildRequest(f)
+	if err != nil {
+		log.Printf("error in request: %v", err)
+		return subcommands.ExitUsageError
+	}
+
+	// Parse configuration and connect to the metadata store.
+	config, err := tabacco.ReadConfig(c.configPath)
+	if err != nil {
+		log.Printf("error reading config: %v", err)
+		return subcommands.ExitFailure
+	}
+	store, err := mdbc.New(config.MetadataStoreBackend)
+	if err != nil {
+		log.Printf("error in metadata client config: %v", err)
+		return subcommands.ExitFailure
+	}
+
+	// Make the RPC.
+	rctx, cancel := context.WithTimeout(ctx, rpcTimeout)
+	defer cancel()
+	result, err := store.FindAtoms(rctx, req)
+
+	if err != nil {
+		log.Printf("FindAtoms() error: %v", err)
+		return subcommands.ExitFailure
+	}
+
+	data, _ := json.MarshalIndent(result, "", "  ")
+	os.Stdout.Write(data)
+
+	return subcommands.ExitSuccess
+}
+
+func init() {
+	subcommands.Register(&queryCommand{}, "")
+}