gorqlite/cluster.go

package gorqlite

/*
	this file holds most of the cluster-related stuff:

	types:
		peer
		rqliteCluster 
	Connection methods:
		assembleURL (from a peer)
		updateClusterInfo (does the full cluster discovery via status)
*/

/* *****************************************************************

   imports

 * *****************************************************************/

import "bytes"
import "encoding/json"
import "errors"
import "fmt"
import "strings"

//import "os"
//import "reflect"

/* *****************************************************************

	type: peer

	this is an internal type to abstact peer info.

	note that hostname is sometimes used for "has this struct been 
	inialized" checks.

 * *****************************************************************/


type peer struct {
	hostname           string   //   hostname or "localhost"
  port               string   //   "4001" or port, only ever used as a string
}

func (p *peer) String() string {
	return fmt.Sprintf("%s:%s",p.hostname,p.port)
}

/* *****************************************************************

  type: rqliteCluster

	internal type that abstracts the full cluster state (leader, peers)

 * *****************************************************************/

type rqliteCluster struct {
	leader peer
	otherPeers []peer
	conn *Connection
}

/* *****************************************************************

  method: rqliteCluster.makePeerList()

	in the api calls, we'll want to try the leader first, then the other
	peers.  to make looping easy, this function returns a list of peers
	in the order the try them: leader, other peer, other peer, etc.

 * *****************************************************************/

func (rc *rqliteCluster) makePeerList() []peer {
	trace("%s: makePeerList() called",rc.conn.ID)
	var peerList []peer
	peerList = append(peerList,rc.leader)
	for _, p := range rc.otherPeers {
		peerList = append(peerList,p)
	}

	trace("%s: makePeerList() returning this list:",rc.conn.ID)
	for n, v := range peerList {
		trace("%s: makePeerList() peer %d -> %s",rc.conn.ID,n,v.hostname + ":" + v.port)
	}

	return peerList
}

/* *****************************************************************

	method: Connection.assembleURL()

	tell it what peer to talk to and what kind of API operation you're
	making, and it will return the full URL, from start to finish.
	e.g.:

	https://mary:secret2@server1.example.com:1234/db/query?transaction&level=strong

	note: this func needs to live at the Connection level because the
	Connection holds the username, password, consistencyLevel, etc.

 * *****************************************************************/

func (conn *Connection) assembleURL(apiOp apiOperation, p peer) string {
	var stringBuffer bytes.Buffer

	if ( conn.wantsHTTPS == true ) {
		stringBuffer.WriteString("https")
	} else {
		stringBuffer.WriteString("http")
	}
	stringBuffer.WriteString("://")
	if ( conn.username != "" && conn.password != "" ) {
		stringBuffer.WriteString(conn.username)
		stringBuffer.WriteString(":")
		stringBuffer.WriteString(conn.password)
		stringBuffer.WriteString("@")
	}
	stringBuffer.WriteString(p.hostname)
	stringBuffer.WriteString(":")
	stringBuffer.WriteString(p.port)

	switch apiOp {
		case api_STATUS:
			stringBuffer.WriteString("/status")
		case api_QUERY:
			stringBuffer.WriteString("/db/query")
		case api_WRITE:
			stringBuffer.WriteString("/db/execute")
	}

	if ( apiOp == api_QUERY || apiOp == api_WRITE ) {
		stringBuffer.WriteString("?timings&transaction&level=")
		stringBuffer.WriteString(consistencyLevelNames[conn.consistencyLevel])
	}

	switch apiOp {
		case api_QUERY:
			trace("%s: assembled URL for an api_QUERY: %s",conn.ID,stringBuffer.String())
		case api_STATUS:
			trace("%s: assembled URL for an api_STATUS: %s",conn.ID,stringBuffer.String())
		case api_WRITE:
			trace("%s: assembled URL for an api_WRITE: %s",conn.ID,stringBuffer.String())
	}

	return stringBuffer.String()
}

/* *****************************************************************

	method: Connection.updateClusterInfo()

	upon invocation, updateClusterInfo() completely erases and refreshes
	the Connection's cluster info, replacing its rqliteCluster object
	with current info.

	the web heavy lifting (retrying, etc.) is done in rqliteApiGet()

 * *****************************************************************/

func (conn *Connection) updateClusterInfo() error {
	trace("%s: updateClusterInfo() called",conn.ID)

	// start with a fresh new cluster
	var rc rqliteCluster
	rc.conn = conn

	responseBody, err := conn.rqliteApiGet(api_STATUS)
	if ( err != nil ) { return err }
	trace("%s: updateClusterInfo() back from api call OK",conn.ID)
	
	sections := make(map[string]interface{})
	err = json.Unmarshal(responseBody,&sections)
	if ( err != nil ) { return err }
	sMap := sections["store"].(map[string]interface{})
	leaderRaftAddr := sMap["leader"].(string)
	trace("%s: leader from store section is %s",conn.ID,leaderRaftAddr)

	// leader in this case is the RAFT address
	// we want the HTTP address, so we'll use this as
	// a key as we sift through APIPeers

	meta := sMap["meta"].(map[string]interface{})
	apiPeers := meta["APIPeers"].(map[string]interface{})

	for raftAddr, httpAddr := range apiPeers {
		trace("%s: examining httpAddr %s",conn.ID,httpAddr)

		/* httpAddr are usually hostname:port */
		var p peer
		parts := strings.Split(httpAddr.(string),":")
		p.hostname = parts[0]
		p.port = parts[1]

		// so is this the leader?
		if ( leaderRaftAddr == raftAddr ) {
			trace ("%s: found leader at %s",conn.ID,httpAddr)
			rc.leader = p
		} else {
			rc.otherPeers = append(rc.otherPeers, p)
		}
	}

	if ( rc.leader.hostname == "" ) {
		return errors.New("could not determine leader from API status call")
	}

	// dump to trace
	trace("%s: here is my cluster config:",conn.ID)
	trace("%s: leader   : %s",conn.ID,rc.leader.String())
	for n, v := range rc.otherPeers {
		trace("%s: otherPeer #%d: %s",conn.ID,n,v.String())
	}	

	// now make it official
	conn.cluster = rc

	return nil
}