annotate mod_presence_cache/README.markdown @ 1981:1f815f57fa57

mod_storage_lmdb: Factor out a transaction wrapper
author Kim Alvefur <zash@zash.se>
date Fri, 18 Dec 2015 22:00:00 +0100
parents 65beed3ac500
children 39d958f4a0c3
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1 ---
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2 summary: Cache presence incoming presence
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3 ...
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4
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5 Introduction
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6 ============
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7
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8 This module stores presence from users contact even when they are
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9 offline, so that the client can see who is online faster when they sign
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10 in, and won't have to wait for remote servers to reply.
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11
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12 Note that in its current form, the number of presence stanzas sent to a
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13 client is doubled, as the client would get both the cached stanzas and
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14 replies to presence probes. Also see [mod\_throttle\_presence].
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16 By default, only binary (online or offline) state is stored. It can
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17 optionally store the full presence but this requires much more memory
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18 and bandwidth.
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19
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20 Configuration
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21 =============
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22
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23 Just enable the module.
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24
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25 modules_enabled = {
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26 -- more modules
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27 "presence_cache";
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28 }
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29
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30 Advanced configuration
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31 ======================
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32
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33 To enable *experimental* full stanza caching:
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34
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35 presence_cache_full = false
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36
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37 This will usually double the presence data sent to clients, pending
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38 support for deduplication.
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39
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40 TODO
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41 ====
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42
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43 - Deduplication, i.e don's send stanzas that are identical to the last
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44 seen.
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45 - Cache invalidation or expiry, eg if a remote server goes down or is
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46 gone a long time.
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47 - Sending probes at some interval to keep the cache reasonably fresh.
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49