cproxy_multiget.c

/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
#include <assert.h>
#include "memcached.h"
#include "cproxy.h"
#include "log.h"

/* Callback to g_hash_table_foreach that frees the multiget_entry list.
 */
void multiget_foreach_free(const void *key,
                           const void *value,
                           void *user_data) {
    (void)key;
    downstream *d = user_data;
    assert(d);

    proxy_td *ptd = d->ptd;
    assert(ptd);

    proxy_stats_cmd *psc_get_key =
        &ptd->stats.stats_cmd[STATS_CMD_TYPE_REGULAR][STATS_CMD_GET_KEY];

    int length = 0;
    multiget_entry *entry = (multiget_entry*)value;

    while (entry != NULL) {
        if (entry->hits == 0) {
            psc_get_key->misses++;
        }

        // TODO: Update key-level stats misses.

        multiget_entry *curr = entry;
        entry = entry->next;
        curr->upstream_conn = NULL;
        curr->next          = NULL;
        free(curr);

        length++;
    }

    // TODO: Track key-level multiget squashes (length > 1).
}

/* Callback to g_hash_table_foreach that clears out multiget_entries
 * which have the given upstream conn (passed as user_data).
 */
void multiget_remove_upstream(const void *key,
                              const void *value,
                              void *user_data) {
    (void)key;
    multiget_entry *entry = (multiget_entry *) value;
    assert(entry != NULL);

    conn *uc = user_data;
    assert(uc != NULL);

    while (entry != NULL) {
        // Just clear the slots, because glib hash table API
        // doesn't allow for key/value modifications during iteration.
        //
        if (entry->upstream_conn == uc) {
            entry->upstream_conn = NULL;
            entry->opaque = 0;
        }

        entry = entry ->next;
    }
}

bool multiget_ascii_downstream(downstream *d, conn *uc,
    int (*emit_start)(conn *c, char *cmd, int cmd_len),
    int (*emit_skey)(conn *c, char *skey, int skey_len, int vbucket, int key_index),
    int (*emit_end)(conn *c),
    mcache *front_cache) {
    assert(d != NULL);
    assert(d->downstream_conns != NULL);
    assert(uc != NULL);
    assert(uc->noreply == false);

    proxy_td *ptd = d->ptd;
    assert(ptd != NULL);

    proxy_stats_cmd *psc_get =
        &ptd->stats.stats_cmd[STATS_CMD_TYPE_REGULAR][STATS_CMD_GET];
    proxy_stats_cmd *psc_get_key =
        &ptd->stats.stats_cmd[STATS_CMD_TYPE_REGULAR][STATS_CMD_GET_KEY];

    int nwrite = 0;
    int nconns = mcs_server_count(&d->mst);

    for (int i = 0; i < nconns; i++) {
        if (d->downstream_conns[i] != NULL &&
            d->downstream_conns[i] != NULL_CONN &&
            cproxy_prep_conn_for_write(d->downstream_conns[i]) == false) {
            d->ptd->stats.stats.err_downstream_write_prep++;
            cproxy_close_conn(d->downstream_conns[i]);
            return false;
        }
    }

    // Snapshot the volatile only once.
    //
    uint32_t msec_current_time_snapshot = msec_current_time;

    int   uc_num = 0;
    conn *uc_cur = uc;

    while (uc_cur != NULL) {
        assert(uc_cur->cmd == -1);
        assert(uc_cur->item == NULL);
        assert(uc_cur->state == conn_pause);
        assert(IS_ASCII(uc_cur->protocol));
        assert(IS_PROXY(uc_cur->protocol));

        char *command = uc_cur->cmd_start;
        assert(command != NULL);

        char *space = strchr(command, ' ');
        assert(space > command);

        int cmd_len = space - command;
        assert(cmd_len == 3 || cmd_len == 4); // Either get or gets.

        int cas_emit = (command[3] == 's');

        if (settings.verbose > 1) {
            moxi_log_write("%d: forward multiget %s (%d %d)\n",
                    uc_cur->sfd, command, cmd_len, uc_num);
        }

        while (space != NULL) {
            char *key = space + 1;
            char *next_space = strchr(key, ' ');
            int   key_len;
            bool  key_last;

            if (next_space != NULL) {
                key_len = next_space - key;
                key_last = false;
            } else {
                key_len = strlen(key);
                key_last = true;

                // We've reached the last key.
                //
                psc_get->read_bytes += (key - command + key_len);
            }

            // This key_len check helps skip consecutive spaces.
            //
            if (key_len > 0) {
                ptd->stats.stats.tot_multiget_keys++;

                psc_get_key->seen++;
                psc_get_key->read_bytes += key_len;

                // Update key-based statistics.
                //
                bool do_key_stats =
                    matcher_check(&ptd->key_stats_matcher,
                                  key, key_len, false) == true &&
                    matcher_check(&ptd->key_stats_unmatcher,
                                  key, key_len, false) == false;

                if (do_key_stats) {
                    touch_key_stats(ptd, key, key_len,
                                    msec_current_time_snapshot,
                                    STATS_CMD_TYPE_REGULAR,
                                    STATS_CMD_GET_KEY,
                                    1, 0, 0,
                                    key_len, 0);
                }

                // Handle a front cache hit by queuing response.
                //
                // Note, front cache stats are part of mcache.
                //
                if (!cas_emit) {
                    item *it = mcache_get(front_cache, key, key_len,
                                          msec_current_time_snapshot);
                    if (it != NULL) {
                        assert(it->nkey == key_len);
                        assert(strncmp(ITEM_key(it), key, it->nkey) == 0);

                        cproxy_upstream_ascii_item_response(it, uc_cur, 0);

                        psc_get_key->hits++;
                        psc_get_key->write_bytes += it->nbytes;

                        if (do_key_stats) {
                            touch_key_stats(ptd, key, key_len,
                                            msec_current_time_snapshot,
                                            STATS_CMD_TYPE_REGULAR,
                                            STATS_CMD_GET_KEY,
                                            0, 1, 0,
                                            0, it->nbytes);
                        }

                        // The refcount was inc'ed by mcache_get() for us.
                        //
                        item_remove(it);

                        goto loop_next;
                    }
                }

                bool self = false;
                int  vbucket = -1;

                conn *c = cproxy_find_downstream_conn_ex(d, key, key_len,
                                                         &self, &vbucket);
                if (c != NULL) {
                    if (self) {
                        // Optimization for talking with ourselves,
                        // to avoid extra network hop.
                        //
                        ptd->stats.stats.tot_optimize_self++;

                        item *it = item_get(key, key_len);
                        if (it != NULL) {
                            cproxy_upstream_ascii_item_response(it, uc_cur,
                                                                cas_emit);

                            psc_get_key->hits++;
                            psc_get_key->write_bytes += it->nbytes;

                            if (do_key_stats) {
                                touch_key_stats(ptd, key, key_len,
                                                msec_current_time_snapshot,
                                                STATS_CMD_TYPE_REGULAR,
                                                STATS_CMD_GET_KEY,
                                                0, 1, 0,
                                                0, it->nbytes);
                            }

                            // The refcount was inc'ed by item_get() for us.
                            //
                            item_remove(it);

                            if (settings.verbose > 1) {
                                moxi_log_write("optimize self multiget hit: %s\n",
                                        key);
                            }
                        } else {
                            psc_get_key->misses++;

                            if (do_key_stats) {
                                touch_key_stats(ptd, key, key_len,
                                                msec_current_time_snapshot,
                                                STATS_CMD_TYPE_REGULAR,
                                                STATS_CMD_GET_KEY,
                                                0, 0, 1,
                                                0, 0);
                            }

                            if (settings.verbose > 1) {
                                moxi_log_write("optimize self multiget miss: %s\n",
                                        key);
                            }
                        }

                        goto loop_next;
                    }

                    // If there's more than one key, create a de-duplication map.
                    // This is used to handle not-my-vbucket errors
                    // where any later retry attempts should avoid
                    // retrying already successfully attempted keys.
                    //
                    // Previously, we used to only have a map when there was more than
                    // one upstream conn.
                    //
                    if (key_last == false &&
                        d->multiget == NULL) {
                        d->multiget = genhash_init(128, skeyhash_ops);
                        if (settings.verbose > 1) {
                            moxi_log_write("%d: cproxy multiget hash table new\n", uc->sfd);
                        }
                    }

                    // See if we've already requested this key via
                    // the multiget hash table, in order to
                    // de-duplicate repeated keys.
                    //
                    bool first_request = true;

                    if (d->multiget != NULL) {
                        if (settings.verbose > 2) {
                            char key_buf[KEY_MAX_LENGTH + 10];
                            assert(key_len <= KEY_MAX_LENGTH);
                            memcpy(key_buf, key, key_len);
                            key_buf[key_len] = '\0';

                            moxi_log_write("<%d multiget_ascii_downstream '%s' %d %d %d\n",
                                    c->sfd, key_buf, vbucket, (int) (key - command), key_len);
                        }

                        // TODO: Use Trond's allocator here.
                        //
                        multiget_entry *entry =
                            calloc(1, sizeof(multiget_entry));
                        if (entry != NULL) {
                            entry->upstream_conn = uc_cur;
                            entry->opaque = 0;
                            entry->hits = 0;
                            entry->next = genhash_find(d->multiget, key);

                            genhash_update(d->multiget, key, entry);

                            if (entry->next != NULL) {
                                first_request = false;
                            }
                        } else {
                            // TODO: Handle out of multiget entry memory.
                        }
                    }

                    if (first_request) {
                        assert(c->item == NULL);
                        assert(c->state == conn_pause);
                        assert(IS_PROXY(c->protocol));
                        assert(c->ilist != NULL);
                        assert(c->isize > 0);

                        if (c->msgused <= 1 &&
                            c->msgbytes <= 0) {
                            emit_start(c, command, cmd_len);
                        }

                        // Provide the preceding space as optimization
                        // for ascii-to-ascii configuration.
                        //
                        emit_skey(c, key - 1, key_len + 1, vbucket, key - command);
                    } else {
                        ptd->stats.stats.tot_multiget_keys_dedupe++;

                        if (settings.verbose > 1) {
                            char buf[KEY_MAX_LENGTH + 10];
                            memcpy(buf, key, key_len);
                            buf[key_len] = '\0';

                            moxi_log_write("%d cproxy multiget dedpue: %s\n",
                                    uc_cur->sfd, buf);
                        }
                    }
                } else {
                    // TODO: Handle when downstream conn is down.
                }
            }

        loop_next:
            space = next_space;
        }

        uc_num++;
        uc_cur = uc_cur->next;
    }

    for (int i = 0; i < nconns; i++) {
        conn *c = d->downstream_conns[i];
        if (c != NULL &&
            c != NULL_CONN &&
            (c->msgused > 1 ||
             c->msgbytes > 0)) {
            emit_end(c);

            conn_set_state(c, conn_mwrite);
            c->write_and_go = conn_new_cmd;

            if (update_event(c, EV_WRITE | EV_PERSIST)) {
                nwrite++;

                if (uc->noreply) {
                    c->write_and_go = conn_pause;
                }
            } else {
                if (settings.verbose > 1) {
                    moxi_log_write("Couldn't update cproxy write event\n");
                }

                d->ptd->stats.stats.err_oom++;
                cproxy_close_conn(c);
            }
        }
    }

    if (settings.verbose > 1) {
        moxi_log_write("forward multiget nwrite %d out of %d\n",
                nwrite, nconns);
    }

    d->downstream_used_start = nwrite;
    d->downstream_used       = nwrite;

    if (cproxy_dettach_if_noreply(d, uc) == false) {
        d->upstream_suffix = "END\r\n";
        d->upstream_suffix_len = 0;
        d->upstream_retry = 0;

        cproxy_start_downstream_timeout(d, NULL);
    }

    return nwrite > 0;
}

void multiget_ascii_downstream_response(downstream *d, item *it) {
    assert(d);
    assert(it);
    assert(it->nkey > 0);
    assert(ITEM_key(it) != NULL);

    proxy_td *ptd = d->ptd;
    assert(ptd);

    proxy_stats_cmd *psc_get_key =
        &ptd->stats.stats_cmd[STATS_CMD_TYPE_REGULAR][STATS_CMD_GET_KEY];

    proxy *p = ptd->proxy;
    assert(p);

    uint32_t front_cache_lifespan =
        ptd->behavior_pool.base.front_cache_lifespan;

    if (front_cache_lifespan > 0) {
        if (matcher_check(&p->front_cache_matcher,
                          ITEM_key(it), it->nkey, false) == true &&
            matcher_check(&p->front_cache_unmatcher,
                          ITEM_key(it), it->nkey, false) == false) {
            mcache_set(&p->front_cache, it,
                       front_cache_lifespan + msec_current_time,
                       true, false);
        }
    }

    if (d->multiget != NULL) {
        // The ITEM_key is not NULL or space terminated.
        //
        char key_buf[KEY_MAX_LENGTH + 10];
        assert(it->nkey <= KEY_MAX_LENGTH);
        memcpy(key_buf, ITEM_key(it), it->nkey);
        key_buf[it->nkey] = '\0';

        multiget_entry *entry_first = genhash_find(d->multiget, key_buf);

        if (entry_first != NULL) {
            entry_first->hits++;

            multiget_entry *entry = entry_first;
            while (entry != NULL) {
                // The upstream might have been closed mid-request.
                //
                // TODO: Revisit the -1 cas_emit parameter.
                //
                conn *uc = entry->upstream_conn;
                if (uc != NULL) {
                    cproxy_upstream_ascii_item_response(it, uc, -1);

                    psc_get_key->hits++;
                    psc_get_key->write_bytes += it->nbytes;

                    if (matcher_check(&ptd->key_stats_matcher,
                                      ITEM_key(it), it->nkey, false) == true &&
                        matcher_check(&ptd->key_stats_unmatcher,
                                      ITEM_key(it), it->nkey, false) == false) {
                        touch_key_stats(ptd, ITEM_key(it), it->nkey,
                                        msec_current_time,
                                        STATS_CMD_TYPE_REGULAR,
                                        STATS_CMD_GET_KEY,
                                        0, 1, 0,
                                        0, it->nbytes);
                    }

                    if (entry != entry_first) {
                        ptd->stats.stats.tot_multiget_bytes_dedupe += it->nbytes;
                    }
                }

                entry = entry->next;
            }
        }
    } else {
        // TODO: We're not tracking miss stats in the simple case.
        // Do we always need to use a multiget hashtable?
        // Or, perhaps misses equals number of requests - number of hits.
        //
        conn *uc = d->upstream_conn;
        while (uc != NULL) {
            // TODO: Revisit the -1 cas_emit parameter.
            //
            cproxy_upstream_ascii_item_response(it, uc, -1);

            psc_get_key->hits++;
            psc_get_key->write_bytes += it->nbytes;

            if (matcher_check(&ptd->key_stats_matcher,
                              ITEM_key(it), it->nkey, false) == true &&
                matcher_check(&ptd->key_stats_unmatcher,
                              ITEM_key(it), it->nkey, false) == false) {
                touch_key_stats(ptd, ITEM_key(it), it->nkey,
                                msec_current_time,
                                STATS_CMD_TYPE_REGULAR,
                                STATS_CMD_GET_KEY,
                                0, 1, 0,
                                0, it->nbytes);
            }

            uc = uc->next;
        }
    }
}