Execute a command when best block changes (-blocknotify=<cmd>) #714

pull luke-jr wants to merge 1 commits into bitcoin:master from luke-jr:blknotify changing 2 files +76 −1

luke-jr commented at 7:34 PM on December 19, 2011: member

This supercedes pull request #555 in a more flexible manner, including Windows support.

To get the same behaviour as: -blknotifypidfile=/path/to/some.pid Now you do: -blocknotify='kill -USR1 $(</path/to/some.pid)"

You can also use this with multiple pidfiles on the command line, or with cURL to issue a web request.

in src/main.cpp:None in df4881dd9c outdated

1210 | @@ -1204,6 +1211,60 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
1211 |      nTransactionsUpdated++;
1212 |      printf("SetBestChain: new best=%s  height=%d  work=%s\n", hashBestChain.ToString().substr(0,20).c_str(), nBestHeight, bnBestChainWork.ToString().c_str());
1213 |  
1214 | +    if (!fInitialDownload)
1215 | +    {
1216 | +        // Support block notification
1217 | +        string strCmd = mapArgs["-blknotify"];
1218 | +        if(strCmd != "")

gavinandresen commented at 8:08 PM on December 19, 2011:

Two nits: space between if and paren. And using GetArg("-blknotify", "") instead of indexing into mapArgs is probably a good idea for when we add a "getargs" RPC command to dump out the contents of mapArgs (indexing directly into mapArgs will add an empty string to it even if the user never specifies -blknotify at all).

in src/main.cpp:None in 9f1d3214f7 outdated

1210 | @@ -1204,6 +1211,60 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
1211 |      nTransactionsUpdated++;
1212 |      printf("SetBestChain: new best=%s  height=%d  work=%s\n", hashBestChain.ToString().substr(0,20).c_str(), nBestHeight, bnBestChainWork.ToString().c_str());
1213 |  
1214 | +    if (!fInitialDownload)
1215 | +    {
1216 | +        // Support block notification
1217 | +        std::string strCmd = GetArg("-blknotify", "");

gavinandresen commented at 4:59 PM on December 23, 2011:

-blocknotify, yes?

luke-jr commented at 5:10 PM on December 23, 2011:

Good catch. Fixed.

makomk commented at 12:46 PM on January 1, 2012: none

On Linux, this leaks a zombie process every time the best block changes, which is probably going to result in PID exhaustion and stuff breaking eventually. Try for example 578e6df8827b74c97a2553b04a6d445ae7628b34 in addition.
Execute a command when best block changes (-blocknotify=<cmd>) 7546ad986f
luke-jr commented at 2:04 AM on January 2, 2012: member

Good catch. Fixed the most graceful way I could find: by detatching the blocknotify process.

I avoided SIGCHLD since it has the potential to not play nice with other stuff.
luke-jr commented at 8:58 PM on January 3, 2012: member

Superceded by #743
luke-jr closed this on Jan 3, 2012
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#555 SIGUSR1 new block notifications