bitcoinops · jnewbery · Nov 13, 2018 · Nov 10, 2018 · Nov 11, 2018 · jnewbery
diff --git a/_includes/references.md b/_includes/references.md
@@ -67,6 +67,8 @@
 [newsletter #16]: {{news16}}
 {% assign news17 = "/en/newsletters/2018/10/16/" %}
 [newsletter #17]: {{news17}}
+{% assign news19 = "/en/newsletters/2018/10/30/" %}
+[newsletter #19]: {{news19}}
 
 {% comment %}
 <!--REQUIRES PERIODIC UPDATE: update rpc_version below to latest

diff --git a/_posts/en/newsletters/2018-11-13-newsletter.md b/_posts/en/newsletters/2018-11-13-newsletter.md
@@ -0,0 +1,186 @@
+---
+title: "Bitcoin Optech Newsletter #21"
+permalink: /en/newsletters/2018/11/13/
+name: 2018-11-13-newsletter
+type: newsletter
+layout: newsletter
+lang: en
+---
+This week's newsletter summarizes a few discussions on the Lightning-Dev
+mailing list, suggests an opportunity to develop a new tool some users would
+find helpful, and provides summaries and links to some of the talks at the
+recent Chaincode Lightning Applications residency.  Several notable code
+changes in popular Bitcoin infrastructure projects are also described.
+
+## Action items
+
+None this week.
+
+## News
+
+- **LN developer summit and mailing list activity:** before, during, and
+  after a planned meeting among Lightning Network protocol developers,
+  the [Lightning-Dev mailing list][] saw a surge of new proposals and
+  discussion about earlier proposals.  Below are some highlights:
+
+    - **Advertising node liquidity:** Lisa Neigut [proposes][neigut
+      liquidity] allowing LN nodes advertise that they're willing to
+      provide incoming capacity in exchange for a certain level of fees.
+      Merchants need their payment channels to have incoming capacity in
+      order to be able receive secure offchain payments from
+      customers---the current alternatives are either requiring some of
+      their customers to wait for several onchain confirmations to open
+      a new channel or making manual channel liquidity arrangements with
+      other merchants.  Although solving this problem would be highly
+      advantageous for merchant adoption of LN, it does pose some
+      technical challenges that discussion participants attempt to solve
+      both in this thread and in a [related thread][zmn liquidity].
+
+    - **Making path probing more convenient:** Anthony Towns
+      [proposes][probe cancel] a method for allowing all the nodes along
+      a path to forget about a small-value payment if one of the nodes
+      on the path is offline.  This reduces the resources required in
+      the case of a routing failure by a node that proactively probes
+      its available payment paths to determine which are the fastest and
+      most reliable for sending payments.
+
+- **Opportunity available for providing utility functions outside of
+  Bitcoin Core:** Bitcoin Core's RPC interface currently provides over
+  100 methods and there are often proposals to add even more for utility
+  functions that don't require access to the internal state of the node
+  or wallet.  During last week's developer IRC [meeting][core dev
+  meeting], members of the project reaffirmed their commitment to not
+  provide any new utility functions for things that can just as easily
+  be done outside Bitcoin Core and that are unrelated to normal user
+  workflows.  This will help keep the project focused on its main
+  objectives.
+
+    This does provide a nice opportunity for an independent developer or
+    other third-party to create a separate project for a library, local
+    program, or RPC interface that provides a stable interface to
+    utility functions that work well in conjunction with Bitcoin Core,
+    and which perhaps even provides some of the utility functions that
+    Bitcoin Core already supports for users not running a node.  Some
+    ideas for how to implement such a tool were discussed both during
+    and [after][core dev log] the meeting.
+
+## Lightning Application Residency Videos
+
+As reported previously in [newsletter #19][], Chaincode Labs recently hosted a
+five-day [residency program][] for developing applications on the Lightning
+Network, including presentations from experts in the space. Videos of the
+[presentations][] and [resident demos][] have now been posted online, along
+with the slide decks for the expert presentations. The following
+talks may be of particular interest to members:
+
+- [**The Lightning Protocol - an Application Developers Perspective**][bosworth
+  video] - [Alex Bosworth][bosworth], infrastructure lead at Lightning Labs,
+  gives a comprehensive overview of the Lightning protocol, explaining all of the
+  [BOLTs][], and how they are relevant for developers building on top of the
+  protocol. This talk should be useful for any developers wanting to integrate
+  Lightning into products or services.
+
+- [**Lightning ≈ Bitcoin**][decker video] - [Christian Decker][decker], Core Tech
+  Engineer at Blockstream, describes the similarities and differences between
+  Bitcoin and Lightning payments, highlighting where on-chain transactions are
+  more appropriate then off-chain (and vice versa). He finishes with a summary
+  of enhancements that may be proposed at the November 2018 Lightning protocol
+  meeting.
+
+- [**Integrating Lightning into Bitrefill**][camarena video] - [Justin
+  Camarena][camarena], infrastructure engineer at bitrefill, explains how
+  bitrefill integrated lightning payments into their store. Bitrefill was
+  one of the first Bitcoin merchants to start accepting mainnet Lightning
+  payments, and Justin shows us how they integrated Lightning into their
+  infrastructure, and the challenges they met and overcame along the way.
+  For those interested in a high level overview of bitrefill's experience
+  with Lightning, the [talk by Sergej Kotliar at Building on Bitcoin][kotliar
+  BoB], covered in [newsletter #3][] will also be of interest.
+
+- [**Zap - UX, Design and Product approach**][mallers video] -
+  [Jack Mallers][mallers], founder of Zap, explains his approach to product
+  design and user experience. Lightning can potentially solve a lot of user
+  experience issues associated with using Bitcoin, but also brings up some user
+  experience challenges of its own. Jack explains how he thinks about user
+  experience in Zap, the UX challenges he's faced building the product and how
+  he's solved them.
+
+## Notable code changes
+
+*Notable code changes this week in [Bitcoin Core][core commits],
+[LND][lnd commits], [C-lightning][cl commits], and [libsecp256k1][secp
+commits].*
+
+{% include linkers/github-log.md
+  refname="core commits"
+  repo="bitcoin/bitcoin"
+  start="742ee213499194f97e59dae4971f1474ae7d57ad"
+  end="e70a19e7132dac91b7948fcbfac086f86fec3d88"
+%}
+{% include linkers/github-log.md
+  refname="lnd commits"
+  repo="lightningnetwork/lnd"
+  start="6b19df162a161079ab794162b45e8f4c7bb8beec"
+  end="d4b042dc1946ece8b60d538ade8e912f035612fe"
+%}
+{% include linkers/github-log.md
+  refname="cl commits"
+  repo="ElementsProject/lightning"
+  start="d5bb536ef0c08a813f767b3fb016eb20292de4dd"
+  end="62e6a9ff542e40364b67a7aa419e33ed72b96a42"
+%}
+{% include linkers/github-log.md
+  refname="secp commits"
+  repo="bitcoin-core/secp256k1"
+  start="1086fda4c1975d0cad8d3cad96794a64ec12dca4"
+  end="1086fda4c1975d0cad8d3cad96794a64ec12dca4"
+%}
+
+- [Bitcoin Core #14410][] adds an `ischange` field to the
+  [getaddressinfo][rpc getaddressinfo] RPC indicating whether the wallet
+  used the address in a change output.
+
+- [Bitcoin Core #14060][] makes configurable the maximum number of
+  messages the [ZeroMQ][] (ZMQ) interface will queue for a client.  The
+  default High-Water Mark (HWM) allows up to 1,000 messages to be queued
+  before some messages are dropped.  A new HWM may be chosen by setting
+  one of the following configuration options to the desired maximum
+  number of queued messages (or the maximum queue size may be made
+  unlimited by setting it to `0`): `zmqpubhashtxhwm`,
+  `zmqpubhashblockhwm`, `zmqpubrawblockhwm`, and `zmqpubrawtxhwm`.
+  The greater the queue size, the more memory the program will use.
+
+- [LND #1782][] adds a `num_inactive_channels` field to the `getinfo` RPC
+  with the number of the node's inactive channels (similar to the
+  existing counts of pending and active channels).
+
+- [LND #1944][] adds a `pub_key` field to the `sendtoroute` RPC so that
+  LND doesn't need to get the pubkey from an external source.  This
+  allows routing payments through private channels that are not listed
+  on the public network.
+
+{% include references.md %}
+{% include linkers/issues.md issues="14410,14060,1782,1944" %}
+
+[lightning-dev mailing list]: https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
+[neigut liquidity]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-November/001532.html
+[zmn liquidity]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-November/001555.html
+[walletless opens]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-November/001539.html
+[eltoo protocol]: https://blockstream.com/eltoo.pdf
+[probe cancel]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-November/001554.html
+[core dev meeting]: http://www.erisian.com.au/meetbot/bitcoin-core-dev/2018/bitcoin-core-dev.2018-11-08-19.00.log.html#l-49
+[core dev log]: http://www.erisian.com.au/bitcoin-core-dev/log-2018-11-08.html#l-668
+[zeromq]: http://zeromq.org/
+[residency program]: https://lightningresidency.com
+[presentations]: https://lightningresidency.com/#videos
+[resident demos]: https://www.youtube.com/playlist?list=PLpLH33TRghT2jmuP9YQRo-e8gk969Q2F_
+[bosworth video]: https://www.youtube.com/watch?v=1R5DNUcCYRg&list=PLpLH33TRghT1SbxinAsNDS6L7RkAjC8ME&index=6&t=0s
+[bosworth]: https://twitter.com/alexbosworth
+[BOLTs]: https://github.com/lightningnetwork/lightning-rfc
+[decker video]: https://www.youtube.com/watch?v=8lMLo-7yF5k&list=PLpLH33TRghT1SbxinAsNDS6L7RkAjC8ME&index=5&t=0s
+[decker]: https://twitter.com/Snyke
+[camarena video]: https://www.youtube.com/watch?v=RZtx6ZMLDrQ&list=PLpLH33TRghT1SbxinAsNDS6L7RkAjC8ME&index=12&t=0s
+[camarena]: https://twitter.com/juscamarena
+[kotliar BoB]: https://www.youtube.com/watch?v=Cpid31c6HZc&feature=youtu.be&t=8m49s
+[mallers video]: https://www.youtube.com/watch?v=R0C83h-ZM-4&list=PLpLH33TRghT1SbxinAsNDS6L7RkAjC8ME&index=17&t=0s
+[mallers]: https://twitter.com/JackMallers