BIP 0022: Difference between revisions

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Update BIP text with latest version from https://github.com/bitcoin/bips/blob/b5723035e23896d0/bip-0022.mediawiki
 
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{{bip}}
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<pre>
<pre>
   BIP: 22
   BIP: 22
   Title: getmemorypool
  Layer: API/RPC
   Title: getblocktemplate - Fundamentals
   Author: Luke Dashjr <luke+bip22@dashjr.org>
   Author: Luke Dashjr <luke+bip22@dashjr.org>
   Status: Draft
  Comments-Summary: No comments yet.
  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0022
   Status: Final
   Type: Standards Track
   Type: Standards Track
   Created: 28-02-2012
   Created: 2012-02-28
  License: BSD-2-Clause
</pre>
</pre>


Line 14: Line 19:
This BIP describes a new JSON-RPC method for "smart" Bitcoin miners and proxies.
This BIP describes a new JSON-RPC method for "smart" Bitcoin miners and proxies.
Instead of sending a simple block header for hashing, the entire block structure is sent, and left to the miner to (optionally) customize and assemble.
Instead of sending a simple block header for hashing, the entire block structure is sent, and left to the miner to (optionally) customize and assemble.
==Copyright==
This BIP is licensed under the BSD 2-clause license.


==Specification==
==Specification==


===JSON-RPC Method: getmemorypool===
===Block Template Request===


A JSON-RPC method is defined, called "getmemorypool".
A JSON-RPC method is defined, called "getblocktemplate".
It accepts exactly one argument, which MUST be an Object of request parameters.
It accepts exactly one argument, which MUST be an Object of request parameters.
If the request parameters include a "mode" key, that is used to explicitly select between [[#Block Template Request|"template"]], [[#Block Proposal|"proposal"]], and [[#Block Submission|"submit"]] calls.
If the request parameters include a "mode" key, that is used to explicitly select between the default "template" request or a [[bip-0023.mediawiki#Block Proposal|"proposal"]].
Otherwise, it defaults to [[#Block Submission|a submission]] if there is a "data" key (including the String-type argument mentioned above), and [[#Block Template Request|a template request]] if not.


===Block Template Request===
Block template creation can be influenced by various parameters:
Block template creation can be influenced by various parameters:
{| class="wikitable"
{| class="wikitable"
!colspan=3|template request
!colspan=4|template request
|-
|-
! Key !! Type !! Description
! Key !! Required !! Type !! Description
|-
|-
| capabilities || Array of Strings || SHOULD contain a list of the following, to indicate client-side support: [[#Long Polling|"longpoll"]], "coinbasetxn", "coinbasevalue", [[#Block Proposal|"proposal"]], [[#Logical Services|"serverlist"]], "workid", and any of the [[#Mutations|mutations]]
| capabilities || No || Array of Strings || SHOULD contain a list of the following, to indicate client-side support: [[#Optional: Long Polling|"longpoll"]], "coinbasetxn", "coinbasevalue", [[bip-0023.mediawiki#Block Proposal|"proposal"]], [[bip-0023.mediawiki#Logical Services|"serverlist"]], "workid", and any of the [[bip-0023.mediawiki#Mutations|mutations]]
|-
|-
| mode || String || MUST be "template" or omitted
| mode || No || String || MUST be "template" or omitted
|}
|}


getmemorypool MUST return a JSON Object containing the following keys:
getblocktemplate MUST return a JSON Object containing the following keys:
{| class="wikitable"
{| class="wikitable"
!colspan=3| template
!colspan=4| template
|-
|-
! Key !! Type !! Description
! Key !! Required !! Type !! Description
|-
|-
| bits || String || the compressed difficulty in hexadecimal
| bits || Yes || String || the compressed difficulty in hexadecimal
|-
|-
| curtime || Number || the current time as seen by the server (recommended for block time) - note this is not necessarily the system clock, and must fall within the mintime/maxtime rules
| curtime || Yes || Number || the current time as seen by the server (recommended for block time) - note this is not necessarily the system clock, and must fall within the mintime/maxtime rules
|-
|-
| height || Number || the height of the block we are looking for
| height || Yes || Number || the height of the block we are looking for
|-
|-
| previousblockhash || String || the hash of the previous block, in big-endian hexadecimal
| previousblockhash || Yes || String || the hash of the previous block, in big-endian hexadecimal
|-
|-
| sigoplimit || Number || number of sigops allowed in blocks
| sigoplimit || No || Number || number of sigops allowed in blocks
|-
|-
| sizelimit || Number || number of bytes allowed in blocks
| sizelimit || No || Number || number of bytes allowed in blocks
|-
|-
| transactions || Array of Objects || Objects containing [[#Transactions Object Format|information for Bitcoin transactions]] (excluding coinbase)
| transactions || Should || Array of Objects || Objects containing [[#Transactions Object Format|information for Bitcoin transactions]] (excluding coinbase)
|-
|-
| version || Number || always 1 (at least for bitcoin)
| version || Yes || Number || always 1 or 2 (at least for bitcoin) - clients MUST understand the implications of the version they use (eg, comply with [[bip-0034.mediawiki|BIP 0034]] for version 2)
|-
|-
| coinbaseaux || Object || data that SHOULD be included in the coinbase's scriptSig content. Only the values (hexadecimal byte-for-byte) in this Object should be included, not the keys.
| coinbaseaux || No || Object || data that SHOULD be included in the coinbase's scriptSig content. Only the values (hexadecimal byte-for-byte) in this Object should be included, not the keys. This does not include the block height, which is required to be included in the scriptSig by [[bip-0034.mediawiki|BIP 0034]]. It is advisable to encode values inside "PUSH" opcodes, so as to not inadvertently expend SIGOPs (which are counted toward limits, despite not being executed).
|-
|-
| coinbasetxn || String or Object || coinbase transaction, format specified by "tx:cb" parameter
| coinbasetxn || this or ↓ || Object || [[#Transactions Object Format|information for coinbase transaction]]
|-
|-
| coinbasevalue || Number || total funds available for the coinbase (in Satoshis)
| coinbasevalue || this or ↑ || Number || total funds available for the coinbase (in Satoshis)
|-
|-
| workid || String || if provided, this value must be returned with results (see [[#Block Submission|Block Submission]])
| workid || No || String || if provided, this value must be returned with results (see [[#Block Submission|Block Submission]])
|}
|}


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| data || String || transaction data encoded in hexadecimal (byte-for-byte)
| data || String || transaction data encoded in hexadecimal (byte-for-byte)
|-
|-
| depends || Array of Numbers || other transactions (by 1-based index in "transactions" list) that must be present in the final block if this one is; if key is not present, dependencies are unknown and clients MUST NOT assume there aren't any
| depends || Array of Numbers || other transactions before this one (by 1-based index in "transactions" list) that must be present in the final block if this one is; if key is not present, dependencies are unknown and clients MUST NOT assume there aren't any
|-
|-
| fee || Number || difference in value between transaction inputs and outputs (in Satoshis); for coinbase transactions, this is a negative Number of the total collected block fees (ie, not including the block subsidy); if key is not present, fee is unknown and clients MUST NOT assume there isn't one
| fee || Number || difference in value between transaction inputs and outputs (in Satoshis); for coinbase transactions, this is a negative Number of the total collected block fees (ie, not including the block subsidy); if key is not present, fee is unknown and clients MUST NOT assume there isn't one
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===Block Submission===
===Block Submission===


When getmemorypool is called with a "data" key, and "mode" either set to "submit" or omitted, it is interpreted as a potential block (or share).
A JSON-RPC method is defined, called "submitblock", to submit potential blocks (or shares).
It accepts two arguments:
the first is always a String of the hex-encoded block data to submit;
the second is an Object of parameters, and is optional if parameters are not needed.


{| class="wikitable"
{| class="wikitable"
!colspan=3|getmemorypool parameters
!colspan=3|submitblock parameters (2nd argument)
|-
|-
! Key !! Type !! Description
! Key !! Type !! Description
|-
| data || String || MUST be hex-encoded block data
|-
| mode || String || MUST be "submit" or omitted
|-
|-
| workid || String || if the server provided a workid, it MUST be included with submissions
| workid || String || if the server provided a workid, it MUST be included with submissions
Line 108: Line 114:


This method MUST return either null (when a share is accepted), a String describing briefly the reason the share was rejected, or an Object of these with a key for each merged-mining chain the share was submitted to.
This method MUST return either null (when a share is accepted), a String describing briefly the reason the share was rejected, or an Object of these with a key for each merged-mining chain the share was submitted to.


===Optional: Long Polling===
===Optional: Long Polling===
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! Key !! Type !! Description
! Key !! Type !! Description
|-
|-
| longpollid || String || unique identifier for [[#Long Polling|long poll request]]; MUST be omitted if the server does not support long polling
| longpollid || String || identifier for long poll request; MUST be omitted if the server does not support long polling
|-
|-
| longpolluri || String || if provided, an alternate URI to use for [[#Long Polling|longpoll requests]]
| longpolluri || String || if provided, an alternate URI to use for long poll requests
|-
|-
| submitold || Boolean || only relevant for [[#Long Polling|long poll]] responses: indicates if work received prior to this response remains potentially valid (default) and should have its shares submitted; if false, the miner may wish to discard its share queue
| submitold || Boolean || only relevant for long poll responses: indicates if work received prior to this response remains potentially valid (default) and should have its shares submitted; if false, the miner may wish to discard its share queue
|}
|}


If the server supports long polling, it MUST include a "longpollid" key in block templates.
If the server supports long polling, it MUST include a "longpollid" key in block templates, and it MUST be unique for each event:
any given "longpollid" should check for only one condition and not be reused.
For example, a server which has a long poll wakeup only for new blocks might use the previous block hash.
However, clients should not assume the "longpollid" has any specific meaning.
It MAY supply the "longpolluri" key with a relative or absolute URI, which MAY specify a completely different resource than the original connection, including port number.
It MAY supply the "longpolluri" key with a relative or absolute URI, which MAY specify a completely different resource than the original connection, including port number.
If "longpolluri" is provided by the server, clients MUST only attempt to use that URI for longpoll requests.
If "longpolluri" is provided by the server, clients MUST only attempt to use that URI for longpoll requests.
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It is, however, forbidden to simply retry immediately with no delay after more than one failure.
It is, however, forbidden to simply retry immediately with no delay after more than one failure.
In the case of a "Forbidden" response (for example, HTTP 403), a client SHOULD NOT attempt to retry without user intervention.
In the case of a "Forbidden" response (for example, HTTP 403), a client SHOULD NOT attempt to retry without user intervention.
===Optional: Basic Pool Extensions===
{| class="wikitable"
! colspan="3" | template request
|-
! Key !! Type !! Description
|-
| target || String || desired target for block template
|}
{| class="wikitable"
!colspan="3"| template
|-
! Key !! Type !! Description
|-
| expires || Number || how many seconds (beginning from when the server sent the response) this work is valid for, at most
|-
| target || String || the number which valid results must be less than, in big-endian hexadecimal
|}
===Optional: Block Proposal===
Servers may indicate support for proposing blocks by including a capability string in their original template:
{| class="wikitable"
!colspan="3"| template
|-
! Key !! Type !! Description
|-
| capabilities || Array of Strings || MAY contain "proposal" to indicate support for [[#Block Proposal|block proposal]]
|}
If supported, a miner MAY propose a block to the server for general validation at any point before the job expires.
This is accomplished by calling getmemorypool with two keys:
{| class="wikitable"
!colspan=3| getmemorypool parameters
|-
! Key !! Type !! Description
|-
| data || String || MUST be hex-encoded block data
|-
| mode || String || MUST be "proposal"
|-
| workid || String || if the server provided a workid, it MUST be included with proposals
|}
The block data MUST be validated and checked against the server's usual acceptance rules (excluding the check for a valid proof-of-work).
If it is found to be in violation of any of these rules, the server MUST return a String giving the reason for the rejection (see [[#Example Rejection Reasons|example rejection reasons]]).
If it is acceptable as-is, the server MAY return a true Boolean.
Otherwise, the server may return a new block template (with or without changes); in this case, any missing keys are assumed to default to those in the proposed block or, if not applicable, the original block template it was based on.
It is RECOMMENDED that servers which merely need to track the proposed block for later share/* submissions, return a simple Object of the form:
{"workid":"new workid"}
Clients SHOULD assume their proposed block will remain valid if the only changes they make are to the portion of the coinbase scriptSig they themselves provided (if any) and the time header.
Servers SHOULD NOT break this assumption without good cause.
===Optional: Mutations===
{| class="wikitable"
! colspan="3" | template request
|-
! Key !! Type !! Description
|-
| nonces || Number || size of nonce range the miner needs; if not provided, the server SHOULD assume the client requires 2<sup>32</sup>
|}
{| class="wikitable"
!colspan=3| template
|-
! Key !! Type !! Description
|-
| fulltarget || String || the number which full results should be less than, in big-endian hexadecimal (see [[#Mutations|"share/*" mutations]])
|-
| maxtime || Number || the maximum time allowed
|-
| maxtimeoff || Number || the maximum time allowed (as a moving offset from "curtime" - every second, the actual maxtime is incremented by 1; for example, "maxtimeoff":0 means "time" may be incremented by 1 every second)
|-
| mintime || Number || the minimum time allowed
|-
| mintimeoff || Number || the minimum time allowed (as a moving offset from "curtime")
|-
| mutable || Array of Strings || different manipulations that the server explicitly allows to be made (see [[#Mutations|Mutations]])
|-
| noncerange || String || two 32-bit integers, concatenated in big-endian hexadecimal, which represent the valid ranges of nonces the miner may scan
|}
If the block template contains a "mutable" key, it is a list of these to signify modifications the miner is allowed to make:
{| class="wikitable"
!colspan=2| mutations
|-
! Value !! Significance
|-
| coinbase/append
| append the provided coinbase scriptSig
|-
| coinbase
| provide their own coinbase; if one is provided, it may be replaced or modified (implied if "coinbasetxn" omitted)
|-
| generation
| add or remove outputs from the coinbase/generation transaction (implied if "coinbasetxn" omitted)
|-
| time/increment
| change the time header to a value after "time" (implied if "maxtime" or "maxtimeoff" are provided)
|-
| time/decrement
| change the time header to a value before "time" (implied if "mintime" is provided)
|-
| time
| modify the time header of the block
|-
| transactions/add (or "transactions")
| add other valid transactions to the block (implied if "transactions" omitted from result)
|-
| prevblock
| use the work with other previous-blocks; this implicitly allows removing transactions that are no longer valid, unless they are part of the "txrequired" count; it also implies adjusting "height" as necessary
|-
|colspan="2" style="font-size:80%;font-style:italic"| Affecting the format of requests, but not the blocks themselves:
|-
| submit/hash
| each transaction being sent in a request, that the client is certain the server knows about, may be replaced by its hash in little-endian hexadeciaml, prepended by a ":" character
|-
| submit/coinbase
| if the "transactions" provided by the server are used as-is with no changes, only return the block header and coinbase transaction
|-
| submit/truncate
| if the "coinbasetxn" and "transactions" provided by the server are used as-is with no changes, only return the block header
|-
| share/coinbase
| same as "submit/coinbase", but only if the block hash is less than "target"
|-
| share/merkle
| if the block hash is less than "target", but not less than "fulltarget", only return the block header, coinbase transaction, and merkle tree connecting that transaction to the root (in the form of repeated right-side SHA256 hashes)
|-
| share/truncate
| same as "submit/truncate", but only if the block hash is less than "target"
|}
Note that miners are NOT required to implement any of these mutations.
==== Format of Data for Merkle-Only Shares ====
The format used for submitting shares with the "share/merkle" mutation shall be the 80-byte block header, followed by the coinbase transaction, and then finally the little-endian SHA256 hashes of each link in the merkle chain connecting it to the merkle root.
===Optional: Full Node Optimization===
{| class="wikitable"
! colspan="3" | template request
|-
! Key !! Type !! Description
|-
| tx || String || format of response "transactions" key elements ("obj" per default; "hash" per full node optimization)
|}
If the miner is running a full node, they may request to receive the "transactions" key in their template populated with transaction ids instead of the full data.
This is done by specifying a "tx" key in the request set to "hash".
Note that the "coinbasetxn" key in the template will remain in "obj" format.
''FIXME'': Describe gettransaction RPC method?
===Optional: Logical Services===
{| class="wikitable"
!colspan=3| template
|-
! Key !! Type !! Description
|-
| serverlist || Array of Objects || list of servers in this [[#Logical Services|single logical service]]
|}
If the "serverlist" parameter is provided, clients MAY choose to intelligently treat the server as part of a larger single logical service.
Each host Object in the Array is comprised of the following fields:
{| class="wikitable"
!colspan=3| serverlist element
|-
! Key !! Type !! Description
|-
| uri || String || URI of the individual server; if authentication information is omitted, the same authentication used for this request MUST be assumed
|-
| avoid ||  Number || number of seconds to avoid using this server
|-
| priority || Number || an integer priority of this host (default: 0)
|-
| sticky || Number || number of seconds to stick to this server when used
|-
| update || Boolean || whether this server may update the serverlist (default: true)
|-
| weight || Number || a relative weight for hosts with the same priority (default: 1)
|}
When choosing which actual server to get the next job from, URIs MUST be tried in order of their "priority" key, lowest Number first.
Where the priority of URIs is the same, they should be chosen from in random order, weighed by their "weight" key.
Work proposals and submissions MUST be made to the same server that issued the job.
Clients MAY attempt to submit to other servers if, and only if, the original server cannot be reached.
If cross-server share submissions are desired, services SHOULD instead use the equivalent domain name system (DNS) features (RFCs [http://tools.ietf.org/html/rfc1794 1794] and [http://tools.ietf.org/html/rfc2782 2782]).
Updates to the Logical Service server list may only be made by the original server, or servers listed with the "update" key missing or true.
Clients MAY choose to advertise serverlist capability to servers with a false "update" key, but if so, MUST treat the server list provided as a subset of the current one, only considered in the context of this server.
At least one server with "update" privilege MUST be attempted at least once daily.
If the "sticky" key is provided, then when that server is used, it should be used consistently for at least that many seconds, if possible.
A permanent change in server URI MAY be indicated with a simple "serverlist" parameter:
"serverlist":[{"uri": "http://newserver"}]
A temporary delegation to another server for 5 minutes MAY be indicated likewise:
"serverlist":[{"uri": "", avoid: 300}, {"uri": "http://newserver", "update": false}]


===Optional: Template Tweaking===
===Optional: Template Tweaking===
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|-
|-
| sizelimit || Number or Boolean || maximum number of bytes to use for the entire block
| sizelimit || Number or Boolean || maximum number of bytes to use for the entire block
|-
| maxversion || Number || highest block version number supported
|}
|}


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Servers SHOULD respect these desired maximums, but are NOT required to:
Servers SHOULD respect these desired maximums, but are NOT required to:
clients SHOULD check that the returned template satisfies their requirements appropriately.
clients SHOULD check that the returned template satisfies their requirements appropriately.
===Optional: Backward Compatibility===
Servers MAY choose to implement the following behaviours to remain backward compatible with pre-standard bitcoind 0.5 and 0.6 getmemorypool methods:
* If the parameters Object is omitted, it should be accepted as a [[#Block Template Request|template request]], except that the format of the "transactions" key in the template changes. This same format can be requested explicitly by adding a "tx" key to the request set to "hex".
* If there is a single String argument instead of the parameters Object, it should be accepted as the "data" key for a [[#Block Submission|submission]]. In this case, the response format is changed to either true (if a share is accepted) or false (if a share is rejected, regardless of reason).
{| class="wikitable"
! colspan="3" | template request
|-
! Key !! Type !! Description
|-
| tx || String || format of response "transactions" key elements ("obj" per default; "hex" per backward compat)
|}
The format of the "transactions" key in block templates with the "hex" format should be:
{| class="wikitable"
!colspan=3| template
|-
! Key !! Type !! Description
|-
| transactions ("hex" format) || Array of Strings || data for Bitcoin transactions (excluding coinbase) encoded in hexadecimal (byte-for-byte)
|}


===Appendix: Example Rejection Reasons===
===Appendix: Example Rejection Reasons===
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==Motivation==
==Motivation==


There is reasonable concerns about mining currently being too centralized on pools, and the amount of control these pools hold.
bitcoind's JSON-RPC server can no longer support the load of generating the work required to productively mine Bitcoin, and external software specializing in work generation has become necessary.
By exposing the details of the block proposals to the miners, they are enabled to audit and possibly modify the block before hashing it.
At the same time, new independent node implementations are maturing to the point where they will also be able to support miners.


To encourage widespread adoption, this BIP should be a complete superset of the existing centralized getwork protocol, so pools are not required to make substantial changes to adopt it.
A common standard for communicating block construction details is necessary to ensure compatibility between the full nodes and work generation software.


==Rationale==
==Rationale==
Line 464: Line 235:
* Servers might not have access to the transaction database, or miners may wish to include transactions not broadcast to the network as a whole.
* Servers might not have access to the transaction database, or miners may wish to include transactions not broadcast to the network as a whole.
* Miners may opt not to do full transaction verification, and may not have access to the transaction database on their end.
* Miners may opt not to do full transaction verification, and may not have access to the transaction database on their end.
Why allow servers to restrict the complete coinbase and nonce range?
* This is necessary to provide a complete superset of JSON-RPC getwork functionality, so that pools may opt to enable auditing without significantly changing or increasing the complexity of their share validation or mining policies.
* Since noncerange is optional (both for getwork and this BIP), neither clients nor servers are required to support it.
Why specify "time/*" mutations at all?
* In most cases, these are implied by the mintime/mintimecur/maxtime/maxtimecur keys, but there may be cases that there are no applicable minimums/maximums.
What is the purpose of the "prevblock" mutation?
* There are often cases where a miner has processed a new block before the server. If the server allows "prevblock" mutation, the miner may begin mining on the new block immediately, without waiting for a new template.
Why must both "mintime"/"maxtime" and "mintimeoff"/"maxtimeoff" keys be supported?
* In some cases, the limits may be unrelated to the current time (such as the Bitcoin network itself; the minimum is always a fixed median time)
* In other cases, the limits may be bounded by other rules (many pools limit the time header to within 5 minutes of when the share is submitted to them).
Is "target" really needed?
* Some pools work with higher targets, and should not be expected to waste bandwidth ignoring shares that don't meet it.
* Required to be a proper superset of getwork.
* As mining hashrates grow, some miners may need the ability to request a higher target from their pools to be able to manage their bandwidth use.


What is the purpose of "workid"?
What is the purpose of "workid"?
Line 488: Line 240:


Why should "sigops" be provided for transactions?
Why should "sigops" be provided for transactions?
* Due to the [[BIP 0016]] changes regarding rules on block sigops, it is impossible to count sigops from the transactions themselves (the sigops in the scriptCheck must also be included in the count).
* Due to the [[bip-0016.mediawiki|BIP 0016]] changes regarding rules on block sigops, it is impossible to count sigops from the transactions themselves (the sigops in the scriptCheck must also be included in the count).
 
What is the purpose of the "hash" transaction list format?
* Non-mining tools may wish to simply get a list of memory pool transactions.
* Humans may wish to view their current memory pool.
 
What is the purpose of the "hex" transaction list format?
* Mainly backward compatibility with bitcoind 0.5 and 0.6.
 
== To Be Resolved ==
* Since "data" is a key on the params Object now, perhaps "submit/hash" and "share/merkle" should use new keys for their non-block-format data?


==Reference Implementation==
==Reference Implementation==


* [https://gitorious.org/bitcoin/eloipool Eloipool]
* [https://gitorious.org/bitcoin/eloipool Eloipool (server)]
* [https://github.com/bitcoin/bitcoin/pull/936/files bitcoind]
* [http://gitorious.org/bitcoin/libblkmaker libblkmaker (client)]
* [https://github.com/bitcoin/bitcoin/pull/936/files bitcoind (minimal server)]


[[Category:BIP|D]]
==See Also==
* [[bip-0023.mediawiki|BIP 23: getblocktemplate - Pooled Mining]]

Latest revision as of 17:58, 24 September 2019

This page describes a BIP (Bitcoin Improvement Proposal).
Please see BIP 2 for more information about BIPs and creating them. Please do not just create a wiki page.

Please do not modify this page. This is a mirror of the BIP from the source Git repository here.

 
  BIP: 22
  Layer: API/RPC
  Title: getblocktemplate - Fundamentals
  Author: Luke Dashjr <luke+bip22@dashjr.org>
  Comments-Summary: No comments yet.
  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0022
  Status: Final
  Type: Standards Track
  Created: 2012-02-28
  License: BSD-2-Clause

Abstract

This BIP describes a new JSON-RPC method for "smart" Bitcoin miners and proxies. Instead of sending a simple block header for hashing, the entire block structure is sent, and left to the miner to (optionally) customize and assemble.

Copyright

This BIP is licensed under the BSD 2-clause license.

Specification

Block Template Request

A JSON-RPC method is defined, called "getblocktemplate". It accepts exactly one argument, which MUST be an Object of request parameters. If the request parameters include a "mode" key, that is used to explicitly select between the default "template" request or a "proposal".

Block template creation can be influenced by various parameters:

template request
Key Required Type Description
capabilities No Array of Strings SHOULD contain a list of the following, to indicate client-side support: "longpoll", "coinbasetxn", "coinbasevalue", "proposal", "serverlist", "workid", and any of the mutations
mode No String MUST be "template" or omitted

getblocktemplate MUST return a JSON Object containing the following keys:

template
Key Required Type Description
bits Yes String the compressed difficulty in hexadecimal
curtime Yes Number the current time as seen by the server (recommended for block time) - note this is not necessarily the system clock, and must fall within the mintime/maxtime rules
height Yes Number the height of the block we are looking for
previousblockhash Yes String the hash of the previous block, in big-endian hexadecimal
sigoplimit No Number number of sigops allowed in blocks
sizelimit No Number number of bytes allowed in blocks
transactions Should Array of Objects Objects containing information for Bitcoin transactions (excluding coinbase)
version Yes Number always 1 or 2 (at least for bitcoin) - clients MUST understand the implications of the version they use (eg, comply with BIP 0034 for version 2)
coinbaseaux No Object data that SHOULD be included in the coinbase's scriptSig content. Only the values (hexadecimal byte-for-byte) in this Object should be included, not the keys. This does not include the block height, which is required to be included in the scriptSig by BIP 0034. It is advisable to encode values inside "PUSH" opcodes, so as to not inadvertently expend SIGOPs (which are counted toward limits, despite not being executed).
coinbasetxn this or ↓ Object information for coinbase transaction
coinbasevalue this or ↑ Number total funds available for the coinbase (in Satoshis)
workid No String if provided, this value must be returned with results (see Block Submission)

Transactions Object Format

The Objects listed in the response's "transactions" key contains these keys:

template "transactions" element
Key Type Description
data String transaction data encoded in hexadecimal (byte-for-byte)
depends Array of Numbers other transactions before this one (by 1-based index in "transactions" list) that must be present in the final block if this one is; if key is not present, dependencies are unknown and clients MUST NOT assume there aren't any
fee Number difference in value between transaction inputs and outputs (in Satoshis); for coinbase transactions, this is a negative Number of the total collected block fees (ie, not including the block subsidy); if key is not present, fee is unknown and clients MUST NOT assume there isn't one
hash String hash/id encoded in little-endian hexadecimal
required Boolean if provided and true, this transaction must be in the final block
sigops Number total number of SigOps, as counted for purposes of block limits; if key is not present, sigop count is unknown and clients MUST NOT assume there aren't any

Only the "data" key is required, but servers should provide the others if they are known.

Block Submission

A JSON-RPC method is defined, called "submitblock", to submit potential blocks (or shares). It accepts two arguments: the first is always a String of the hex-encoded block data to submit; the second is an Object of parameters, and is optional if parameters are not needed.

submitblock parameters (2nd argument)
Key Type Description
workid String if the server provided a workid, it MUST be included with submissions

This method MUST return either null (when a share is accepted), a String describing briefly the reason the share was rejected, or an Object of these with a key for each merged-mining chain the share was submitted to.

Optional: Long Polling

template request
Key Type Description
capabilities Array of Strings miners which support long polling SHOULD provide a list including the String "longpoll"
longpollid String "longpollid" of job to monitor for expiration; required and valid only for long poll requests
template
Key Type Description
longpollid String identifier for long poll request; MUST be omitted if the server does not support long polling
longpolluri String if provided, an alternate URI to use for long poll requests
submitold Boolean only relevant for long poll responses: indicates if work received prior to this response remains potentially valid (default) and should have its shares submitted; if false, the miner may wish to discard its share queue

If the server supports long polling, it MUST include a "longpollid" key in block templates, and it MUST be unique for each event: any given "longpollid" should check for only one condition and not be reused. For example, a server which has a long poll wakeup only for new blocks might use the previous block hash. However, clients should not assume the "longpollid" has any specific meaning. It MAY supply the "longpolluri" key with a relative or absolute URI, which MAY specify a completely different resource than the original connection, including port number. If "longpolluri" is provided by the server, clients MUST only attempt to use that URI for longpoll requests.

Clients MAY start a longpoll request with a standard JSON-RPC request (in the case of HTTP transport, POST with data) and same authorization, setting the "longpollid" parameter in the request to the value provided by the server.

This request SHOULD NOT be processed nor answered by the server until it wishes to replace the current block data as identified by the "longpollid". Clients SHOULD make this request with a very long request timeout and MUST accept servers sending a partial response in advance (such as HTTP headers with "chunked" Transfer-Encoding), and only delaying the completion of the final JSON response until processing.

Upon receiving a completed response:

  • Only if "submitold" is provided and false, the client MAY discard the results of past operations and MUST begin working on the new work immediately.
  • The client SHOULD begin working on the new work received as soon as possible, if not immediately.
  • The client SHOULD make a new request to the same long polling URI.

If a client receives an incomplete or invalid response, it SHOULD retry the request with an exponential backoff. Clients MAY implement this backoff with limitations (such as maximum backoff time) or any algorithm as deemed suitable. It is, however, forbidden to simply retry immediately with no delay after more than one failure. In the case of a "Forbidden" response (for example, HTTP 403), a client SHOULD NOT attempt to retry without user intervention.

Optional: Template Tweaking

template request
Key Type Description
sigoplimit Number or Boolean maximum number of sigops to include in template
sizelimit Number or Boolean maximum number of bytes to use for the entire block
maxversion Number highest block version number supported

For "sigoplimit" and "sizelimit", negative values and zero are offset from the server-determined block maximum. If a Boolean is provided and true, the default limit is used; if false, the server is instructed not to use any limits on returned template. Servers SHOULD respect these desired maximums, but are NOT required to: clients SHOULD check that the returned template satisfies their requirements appropriately.

Appendix: Example Rejection Reasons

Possible reasons a share may be rejected include, but are not limited to:

share rejection reasons
Reason Description
bad-cb-flag the server detected a feature-signifying flag that it does not allow
bad-cb-length the coinbase was too long (bitcoin limit is 100 bytes)
bad-cb-prefix the server only allows appending to the coinbase, but it was modified beyond that
bad-diffbits "bits" were changed
bad-prevblk the previous-block is not the one the server intends to build on
bad-txnmrklroot the block header's merkle root did not match the transaction merkle tree
bad-txns the server didn't like something about the transactions in the block
bad-version the version was wrong
duplicate the server already processed this block data
high-hash the block header did not hash to a value lower than the specified target
rejected a generic rejection without details
stale-prevblk the previous-block is no longer the one the server intends to build on
stale-work the work this block was based on is no longer accepted
time-invalid the time was not acceptable
time-too-new the time was too far in the future
time-too-old the time was too far in the past
unknown-user the user submitting the block was not recognized
unknown-work the template or workid could not be identified

Motivation

bitcoind's JSON-RPC server can no longer support the load of generating the work required to productively mine Bitcoin, and external software specializing in work generation has become necessary. At the same time, new independent node implementations are maturing to the point where they will also be able to support miners.

A common standard for communicating block construction details is necessary to ensure compatibility between the full nodes and work generation software.

Rationale

Why not just deal with transactions as hashes (txids)?

  • Servers might not have access to the transaction database, or miners may wish to include transactions not broadcast to the network as a whole.
  • Miners may opt not to do full transaction verification, and may not have access to the transaction database on their end.

What is the purpose of "workid"?

  • If servers allow all mutations, it may be hard to identify which job it is based on. While it may be possible to verify the submission by its content, it is much easier to compare it to the job issued. It is very easy for the miner to keep track of this. Therefore, using a "workid" is a very cheap solution to enable more mutations.

Why should "sigops" be provided for transactions?

  • Due to the BIP 0016 changes regarding rules on block sigops, it is impossible to count sigops from the transactions themselves (the sigops in the scriptCheck must also be included in the count).

Reference Implementation

See Also

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