[arvados.git] / sdk / go / keepclient / keepclient.go

/* Provides low-level Get/Put primitives for accessing Arvados Keep blocks. */
package keepclient

import (
        "bytes"
        "crypto/md5"
        "errors"
        "fmt"
        "git.curoverse.com/arvados.git/sdk/go/arvadosclient"
        "git.curoverse.com/arvados.git/sdk/go/streamer"
        "io"
        "io/ioutil"
        "net/http"
        "regexp"
        "strconv"
        "strings"
        "sync"
)

// A Keep "block" is 64MB.
const BLOCKSIZE = 64 * 1024 * 1024

// Error interface with an error and boolean indicating whether the error is temporary
type Error interface {
        error
        Temporary() bool
}

// multipleResponseError is of type Error
type multipleResponseError struct {
        error
        isTemp bool
}

func (e *multipleResponseError) Temporary() bool {
        return e.isTemp
}

// BlockNotFound is a multipleResponseError where isTemp is false
var BlockNotFound = &ErrNotFound{multipleResponseError{
        error:  errors.New("Block not found"),
        isTemp: false,
}}

// ErrNotFound is a multipleResponseError where isTemp can be true or false
type ErrNotFound struct {
        multipleResponseError
}

var InsufficientReplicasError = errors.New("Could not write sufficient replicas")
var OversizeBlockError = errors.New("Exceeded maximum block size (" + strconv.Itoa(BLOCKSIZE) + ")")
var MissingArvadosApiHost = errors.New("Missing required environment variable ARVADOS_API_HOST")
var MissingArvadosApiToken = errors.New("Missing required environment variable ARVADOS_API_TOKEN")
var InvalidLocatorError = errors.New("Invalid locator")

// ErrNoSuchKeepServer is returned when GetIndex is invoked with a UUID with no matching keep server
var ErrNoSuchKeepServer = errors.New("No keep server matching the given UUID is found")

// ErrIncompleteIndex is returned when the Index response does not end with a new empty line
var ErrIncompleteIndex = errors.New("Got incomplete index")

const X_Keep_Desired_Replicas = "X-Keep-Desired-Replicas"
const X_Keep_Replicas_Stored = "X-Keep-Replicas-Stored"

// Information about Arvados and Keep servers.
type KeepClient struct {
        Arvados            *arvadosclient.ArvadosClient
        Want_replicas      int
        localRoots         *map[string]string
        writableLocalRoots *map[string]string
        gatewayRoots       *map[string]string
        lock               sync.RWMutex
        Client             *http.Client
        Retries            int
        BlockCache         *BlockCache

        // set to 1 if all writable services are of disk type, otherwise 0
        replicasPerService int

        // Any non-disk typed services found in the list of keepservers?
        foundNonDiskSvc bool
}

// MakeKeepClient creates a new KeepClient by contacting the API server to discover Keep servers.
func MakeKeepClient(arv *arvadosclient.ArvadosClient) (*KeepClient, error) {
        kc := New(arv)
        return kc, kc.DiscoverKeepServers()
}

// New func creates a new KeepClient struct.
// This func does not discover keep servers. It is the caller's responsibility.
func New(arv *arvadosclient.ArvadosClient) *KeepClient {
        defaultReplicationLevel := 2
        value, err := arv.Discovery("defaultCollectionReplication")
        if err == nil {
                v, ok := value.(float64)
                if ok && v > 0 {
                        defaultReplicationLevel = int(v)
                }
        }

        kc := &KeepClient{
                Arvados:       arv,
                Want_replicas: defaultReplicationLevel,
                Client: &http.Client{Transport: &http.Transport{
                        TLSClientConfig: arvadosclient.MakeTLSConfig(arv.ApiInsecure)}},
                Retries: 2,
        }
        return kc
}

// Put a block given the block hash, a reader, and the number of bytes
// to read from the reader (which must be between 0 and BLOCKSIZE).
//
// Returns the locator for the written block, the number of replicas
// written, and an error.
//
// Returns an InsufficientReplicas error if 0 <= replicas <
// kc.Wants_replicas.
func (kc *KeepClient) PutHR(hash string, r io.Reader, dataBytes int64) (string, int, error) {
        // Buffer for reads from 'r'
        var bufsize int
        if dataBytes > 0 {
                if dataBytes > BLOCKSIZE {
                        return "", 0, OversizeBlockError
                }
                bufsize = int(dataBytes)
        } else {
                bufsize = BLOCKSIZE
        }

        t := streamer.AsyncStreamFromReader(bufsize, HashCheckingReader{r, md5.New(), hash})
        defer t.Close()

        return kc.putReplicas(hash, t, dataBytes)
}

// PutHB writes a block to Keep. The hash of the bytes is given in
// hash, and the data is given in buf.
//
// Return values are the same as for PutHR.
func (kc *KeepClient) PutHB(hash string, buf []byte) (string, int, error) {
        t := streamer.AsyncStreamFromSlice(buf)
        defer t.Close()
        return kc.putReplicas(hash, t, int64(len(buf)))
}

// PutB writes a block to Keep. It computes the hash itself.
//
// Return values are the same as for PutHR.
func (kc *KeepClient) PutB(buffer []byte) (string, int, error) {
        hash := fmt.Sprintf("%x", md5.Sum(buffer))
        return kc.PutHB(hash, buffer)
}

// PutR writes a block to Keep. It first reads all data from r into a buffer
// in order to compute the hash.
//
// Return values are the same as for PutHR.
//
// If the block hash and data size are known, PutHR is more efficient.
func (kc *KeepClient) PutR(r io.Reader) (locator string, replicas int, err error) {
        if buffer, err := ioutil.ReadAll(r); err != nil {
                return "", 0, err
        } else {
                return kc.PutB(buffer)
        }
}

func (kc *KeepClient) getOrHead(method string, locator string) (io.ReadCloser, int64, string, error) {
        if strings.HasPrefix(locator, "d41d8cd98f00b204e9800998ecf8427e+0") {
                return ioutil.NopCloser(bytes.NewReader(nil)), 0, "", nil
        }

        var errs []string

        tries_remaining := 1 + kc.Retries

        serversToTry := kc.getSortedRoots(locator)

        numServers := len(serversToTry)
        count404 := 0

        var retryList []string

        for tries_remaining > 0 {
                tries_remaining -= 1
                retryList = nil

                for _, host := range serversToTry {
                        url := host + "/" + locator

                        req, err := http.NewRequest(method, url, nil)
                        if err != nil {
                                errs = append(errs, fmt.Sprintf("%s: %v", url, err))
                                continue
                        }
                        req.Header.Add("Authorization", fmt.Sprintf("OAuth2 %s", kc.Arvados.ApiToken))
                        resp, err := kc.Client.Do(req)
                        if err != nil {
                                // Probably a network error, may be transient,
                                // can try again.
                                errs = append(errs, fmt.Sprintf("%s: %v", url, err))
                                retryList = append(retryList, host)
                        } else if resp.StatusCode != http.StatusOK {
                                var respbody []byte
                                respbody, _ = ioutil.ReadAll(&io.LimitedReader{R: resp.Body, N: 4096})
                                resp.Body.Close()
                                errs = append(errs, fmt.Sprintf("%s: HTTP %d %q",
                                        url, resp.StatusCode, bytes.TrimSpace(respbody)))

                                if resp.StatusCode == 408 ||
                                        resp.StatusCode == 429 ||
                                        resp.StatusCode >= 500 {
                                        // Timeout, too many requests, or other
                                        // server side failure, transient
                                        // error, can try again.
                                        retryList = append(retryList, host)
                                } else if resp.StatusCode == 404 {
                                        count404++
                                }
                        } else {
                                // Success.
                                if method == "GET" {
                                        return HashCheckingReader{
                                                Reader: resp.Body,
                                                Hash:   md5.New(),
                                                Check:  locator[0:32],
                                        }, resp.ContentLength, url, nil
                                } else {
                                        resp.Body.Close()
                                        return nil, resp.ContentLength, url, nil
                                }
                        }

                }
                serversToTry = retryList
        }
        DebugPrintf("DEBUG: %s %s failed: %v", method, locator, errs)

        var err error
        if count404 == numServers {
                err = BlockNotFound
        } else {
                err = &ErrNotFound{multipleResponseError{
                        error:  fmt.Errorf("%s %s failed: %v", method, locator, errs),
                        isTemp: len(serversToTry) > 0,
                }}
        }
        return nil, 0, "", err
}

// Get() retrieves a block, given a locator. Returns a reader, the
// expected data length, the URL the block is being fetched from, and
// an error.
//
// If the block checksum does not match, the final Read() on the
// reader returned by this method will return a BadChecksum error
// instead of EOF.
func (kc *KeepClient) Get(locator string) (io.ReadCloser, int64, string, error) {
        return kc.getOrHead("GET", locator)
}

// Ask() verifies that a block with the given hash is available and
// readable, according to at least one Keep service. Unlike Get, it
// does not retrieve the data or verify that the data content matches
// the hash specified by the locator.
//
// Returns the data size (content length) reported by the Keep service
// and the URI reporting the data size.
func (kc *KeepClient) Ask(locator string) (int64, string, error) {
        _, size, url, err := kc.getOrHead("HEAD", locator)
        return size, url, err
}

// GetIndex retrieves a list of blocks stored on the given server whose hashes
// begin with the given prefix. The returned reader will return an error (other
// than EOF) if the complete index cannot be retrieved.
//
// This is meant to be used only by system components and admin tools.
// It will return an error unless the client is using a "data manager token"
// recognized by the Keep services.
func (kc *KeepClient) GetIndex(keepServiceUUID, prefix string) (io.Reader, error) {
        url := kc.LocalRoots()[keepServiceUUID]
        if url == "" {
                return nil, ErrNoSuchKeepServer
        }

        url += "/index"
        if prefix != "" {
                url += "/" + prefix
        }

        req, err := http.NewRequest("GET", url, nil)
        if err != nil {
                return nil, err
        }

        req.Header.Add("Authorization", fmt.Sprintf("OAuth2 %s", kc.Arvados.ApiToken))
        resp, err := kc.Client.Do(req)
        if err != nil {
                return nil, err
        }

        defer resp.Body.Close()

        if resp.StatusCode != http.StatusOK {
                return nil, fmt.Errorf("Got http status code: %d", resp.StatusCode)
        }

        var respBody []byte
        respBody, err = ioutil.ReadAll(resp.Body)
        if err != nil {
                return nil, err
        }

        // Got index; verify that it is complete
        // The response should be "\n" if no locators matched the prefix
        // Else, it should be a list of locators followed by a blank line
        if !bytes.Equal(respBody, []byte("\n")) && !bytes.HasSuffix(respBody, []byte("\n\n")) {
                return nil, ErrIncompleteIndex
        }

        // Got complete index; strip the trailing newline and send
        return bytes.NewReader(respBody[0 : len(respBody)-1]), nil
}

// LocalRoots() returns the map of local (i.e., disk and proxy) Keep
// services: uuid -> baseURI.
func (kc *KeepClient) LocalRoots() map[string]string {
        kc.lock.RLock()
        defer kc.lock.RUnlock()
        return *kc.localRoots
}

// GatewayRoots() returns the map of Keep remote gateway services:
// uuid -> baseURI.
func (kc *KeepClient) GatewayRoots() map[string]string {
        kc.lock.RLock()
        defer kc.lock.RUnlock()
        return *kc.gatewayRoots
}

// WritableLocalRoots() returns the map of writable local Keep services:
// uuid -> baseURI.
func (kc *KeepClient) WritableLocalRoots() map[string]string {
        kc.lock.RLock()
        defer kc.lock.RUnlock()
        return *kc.writableLocalRoots
}

// SetServiceRoots updates the localRoots and gatewayRoots maps,
// without risk of disrupting operations that are already in progress.
//
// The KeepClient makes its own copy of the supplied maps, so the
// caller can reuse/modify them after SetServiceRoots returns, but
// they should not be modified by any other goroutine while
// SetServiceRoots is running.
func (kc *KeepClient) SetServiceRoots(newLocals, newWritableLocals, newGateways map[string]string) {
        locals := make(map[string]string)
        for uuid, root := range newLocals {
                locals[uuid] = root
        }

        writables := make(map[string]string)
        for uuid, root := range newWritableLocals {
                writables[uuid] = root
        }

        gateways := make(map[string]string)
        for uuid, root := range newGateways {
                gateways[uuid] = root
        }

        kc.lock.Lock()
        defer kc.lock.Unlock()
        kc.localRoots = &locals
        kc.writableLocalRoots = &writables
        kc.gatewayRoots = &gateways
}

// getSortedRoots returns a list of base URIs of Keep services, in the
// order they should be attempted in order to retrieve content for the
// given locator.
func (kc *KeepClient) getSortedRoots(locator string) []string {
        var found []string
        for _, hint := range strings.Split(locator, "+") {
                if len(hint) < 7 || hint[0:2] != "K@" {
                        // Not a service hint.
                        continue
                }
                if len(hint) == 7 {
                        // +K@abcde means fetch from proxy at
                        // keep.abcde.arvadosapi.com
                        found = append(found, "https://keep."+hint[2:]+".arvadosapi.com")
                } else if len(hint) == 29 {
                        // +K@abcde-abcde-abcdeabcdeabcde means fetch
                        // from gateway with given uuid
                        if gwURI, ok := kc.GatewayRoots()[hint[2:]]; ok {
                                found = append(found, gwURI)
                        }
                        // else this hint is no use to us; carry on.
                }
        }
        // After trying all usable service hints, fall back to local roots.
        found = append(found, NewRootSorter(kc.LocalRoots(), locator[0:32]).GetSortedRoots()...)
        return found
}

func (kc *KeepClient) cache() *BlockCache {
        if kc.BlockCache != nil {
                return kc.BlockCache
        } else {
                return DefaultBlockCache
        }
}

type Locator struct {
        Hash  string
        Size  int      // -1 if data size is not known
        Hints []string // Including the size hint, if any
}

func (loc *Locator) String() string {
        s := loc.Hash
        if len(loc.Hints) > 0 {
                s = s + "+" + strings.Join(loc.Hints, "+")
        }
        return s
}

var locatorMatcher = regexp.MustCompile("^([0-9a-f]{32})([+](.*))?$")

func MakeLocator(path string) (*Locator, error) {
        sm := locatorMatcher.FindStringSubmatch(path)
        if sm == nil {
                return nil, InvalidLocatorError
        }
        loc := Locator{Hash: sm[1], Size: -1}
        if sm[2] != "" {
                loc.Hints = strings.Split(sm[3], "+")
        } else {
                loc.Hints = []string{}
        }
        if len(loc.Hints) > 0 {
                if size, err := strconv.Atoi(loc.Hints[0]); err == nil {
                        loc.Size = size
                }
        }
        return &loc, nil
}