# How to Test a Protocol Proposal¶

In this tutorial we show how to test a newly developed protocol and, in particular, how to test the migration process from its predecessor. We also provide a short guide on how to read the migration code.

We start by describing the branch that contains the protocol proposal that is under development.

## The master Branch¶

The current proposal is developed in the branch master, which contains both the new protocol and its migration code from the current active protocol. The current protocol proposal under development is referred to as the Alpha protocol.

Since the commits for migration code are only used once, we keep them clearly separated by marking them with the tag Migration:. The first step when developing a new protocol is to revert the migration commits from the previous protocol. The rest of the commits are used as a base for current proposals.

We next describe how to run unit tests and how to activate the Alpha protocol in sandboxed node.

## Unit Tests and Sandboxed Mode¶

The first step for tweaking and testing the current proposal is to checkout the latest code and run unit tests:

$git checkout master$ git pull
$make$ make test


We can run a node and a client in sandboxed mode by invoking:

$./src/bin_node/tezos-sandboxed-node.sh 1 --connections 0 &$ eval ./src/bin_client/tezos-init-sandboxed-client.sh 1


By default, the sandbox starts from the genesis block at level 0, and the sandbox’s active protocol is the Genesis protocol. Once the sandbox is started, the Alpha protocol can be activated by invoking the command:

$tezos-activate-alpha  This command inserts a new block after which the active protocol is the Alpha protocol. From this point on, making the chain progress is straightforward because the sandbox contains accounts bootstrap1 to bootstrap5 with implicit credentials that allow them to bake blocks by using the usual RPCs in the shell (see Sandboxed mode): $ tezos-client bake for bootstrap1 --minimal-timestamp


### Adding New Protocol Tests in OCaml¶

Be sure you first read the introduction on the testing ecosystem for Tezos. In addition to system tests written in Python or written in OCaml with Tezt, unit tests and integration tests for the protocol in OCaml can be found in src/proto_alpha/lib_protocol/test. It is strongly recommended to write unit tests and integration tests in addition to the system tests. To test a new component, create a new file in this directory and add the module in main.ml. To print the errors of the Error monad correctly, alcotests must be wrapped into the function tztest defined in the module Test defined at the same level.

Some helpers are available in the module Tezos_alpha_test_helpers defined in the subdirectory helpers. For instance, it contains context, operation and block fixtures that can be used in tests requiring these components.

## Testing Migration Code¶

The remainder of the tutorial is organized as follows. Section Manual migration testing provides detailed indications on how to test a migration, and Section Wrap up the manual migration procedure summarizes these indications by collecting all the steps needed to test the migration. Section Automatic migration testing with Tezt describes how to test a migration automatically by using a test within the Tezt framework, and Section Wrap up the automatic migration procedure with Tezt collects all the steps needed to automatically test the migration. To conclude, Section Tips and tricks indicates how to use the shell to inspect the context, and Section Anatomy of migration code contains a primer on how to read and write migration code.

## Manual Migration Testing¶

The most delicate part of migrating to a new protocol is to produce a new context from the context of its predecessor. The migration code takes care of producing the new context, which often involves converting large data structures. Therefore, it is important to bench the migration running time and the size of the context produced. For these reasons it is imperative to test the migration on a real context imported from Mainnet, bench it, and manually inspect the content of the storage. We refer to this procedure as migration on a context imported from Mainnet.

However, sometimes we may want to perform some preliminary tests and run the migration on an empty context that we populate manually. We can do so by running a node in sandboxed mode, and by activating the predecessor of the Alpha protocol on the genesis block. We refer to this procedure as migration on the sandbox.

This section describes a manual migration procedure in which the developer is in charge of setting up the migration environment and of manually baking the blocks that would eventually trigger the migration. For convenience, we have batched parts of this manual migration procedure by providing scripts that encompass some of its steps.

We defer to Section Automatic migration testing with Tezt the description of an automatic migration procedure in which the migration is triggered within the Tezt framework.

We will illustrate the migration procedure through an example where the version of the Alpha protocol to which we migrate is 007.

### Checkout Latest Code and Tweak Migration¶

We start by checking out the latest code for the Alpha protocol:

$git checkout master$ git pull


Now we could tweak our migration by adding any desired feature. For instance, we could log the point at which migration takes place by editing the file src/proto_alpha/lib_protocol/init_storage.ml. This can be done by modifying the match expression of the function prepare_first_block in the said file to include the following lines:

| Carthage_006 ->
Logging.log_notice "\nSTITCHING!\n" ;


After making sure that our master branch contains all the migration code that we want to test, we need to commit the changes locally:

$git commit -am 'My awesome feature'  The next section summarizes how to prepare the migration once we have tweaked the Alpha protocol. ### Prepare the Migration¶ Preparing the migration comprises the following steps: 1. snapshot the Alpha protocol, if so wished, 2. link the snapshot Alpha protocol in the build system, if we wished to snapshot the Alpha protocol, 3. set user-activated upgrade that will trigger the migration at a given level, 4. patch the shell to obtain a yes-node that can fake baker signatures, if we wish to import the context from Mainnet, 5. create a yes-wallet that stores such fake signatures, if we wish to import the context from Mainnet, 6. compile the project, and 7. import a context from Mainnet, if so wished. Steps 1–7 can be batched by invoking the script scripts/prepare_migration_test.sh in the way we explain below. Alternatively, each of the steps above can be performed individually by invoking the corresponding commands/scripts that we detail in the rest of the section. Before preparing the migration, we need to choose on which context the migration will run. When on the sandbox, the steps 4, 5 and 7 above are omitted because the sandbox starts on an empty context, and the sandbox automatically contains accounts with implicit credentials that will allow us to bake blocks and make the chain progress. When on a context imported from Mainnet, we will use a snapshot file (do not mistake snapshot a protocol, like in step 1 above, with snapshot a node, which results in a snapshot file like in here) that contains the real status of a Mainnet’s node at a particular moment in time (see Snapshots). Such a snapshot file can be downloaded from several sites on the internet. For instance, the site TulipTools stores daily snapshot files from both Mainnet and Testnet, in both full and rolling mode (see History modes). For the purposes of testing the migration, a snapshot file in rolling mode is enough. It is important to use a snapshot file that is recent enough as to contain the predecessor of the Alpha protocol. It is also important to note down the level at which the snapshot file was taken, which determines at which level we want to trigger the migration. The site TulipTools conveniently indicates the date and the level (the block) at which each snapshot file was taken. In our example we will use a snapshot file ~/mainnet_2020-07-14_12 00.rolling that was downloaded from TulipTools on July the 14th of 2020, and which was taken at level 1039318. The next subsections explain each of the individual steps 1–7. ### 1. Snapshot the Alpha Protocol¶ Snapshotting the Alpha protocol is an optional procedure whose objective is to convert the Alpha protocol to a format that could be injected into Mainnet, which is done by performing the following three steps: • specify the version and name of the current protocol in raw_context.ml, • compute the protocol’s hash in TEZOS_PROTOCOL, and • replace names and protocol hashes in various places in the code base. If so wished, these three steps can be performed by the script scripts/snapshot_alpha.sh, which receives a parameter with the name of the Alpha protocol. This name parameter follows the convention <tag_starting_with_version_letter>_<version_number>. For historical reasons version 004 corresponds to letter a. A valid name for the Alpha protocol in our example would be d_007, since version 007 corresponds to letter d. We can snapshot the protocol by invoking the following: $ ./scripts/snapshot_alpha.sh d_007


The script creates a new directory src/proto_007_<short_hash> where <short_hash> is a short hash that coincides with the first eight characters of the hash computed by the script and written in the file TEZOS_PROTOCOL.

If the Alpha protocol has been snapshot, proceed to Section 2. Link the snapshot Alpha protocol in the build system below, which details how to link the snapshot code in the build system. Otherwise proceed directly to Section 3. Set user-activated upgrade.

The currently active protocol supports self-amending through the voting procedure of Tezos. However, such procedure needs to go through several voting periods that involve several quorums of bakers, and we would rather test our migration in a less involved way. Besides the amendments driven by the protocol, Tezos also supports user-activated upgrades, which are triggered by the shell. The user-activated upgrades allow the user to specify the level at which the next protocol will be adopted, which can be used to perform emergency bug fixes, but which is also useful to test migrations.

Depending on whether we test the migration on the sandbox or on a realistic context imported from Mainnet, we would like to set the user-activated upgrades respectively at a small level (some blocks after the genesis block at level 0) or at a high level (some blocks after the status imported from Mainnet, which contains several hundreds of thousands of blocks). By convention, when setting a user-activated upgrade the scripts would consider that the migration is on the sandbox if the level is less or equal than 28082, and on a real context imported from Mainnet otherwise, and the scripts would behave differently.

If we are testing the migration on the sandbox, the user-activated upgrade allows us to activate the predecessor of the Alpha protocol by using an activation command after the sandbox starts, and to automatically trigger the activation of the Alpha protocol when the sandbox reaches a given level. Using this mechanism, we can start the sandbox, activate the predecessor of the Alpha protocol, populate the empty context at will by using the shell of the predecessor protocol, and then have the migration triggered automatically at the desired level. The script scripts/user_activated_upgrade.sh receives the path of the protocol to which we would like to upgrade, and the desired level.

In our example above, where the Alpha protocol was snapshot into src/proto_007_<short_hash>, we can set the user-activated upgrade such that the migration is triggered at level three by invoking:

$./scripts/user_activated_upgrade.sh src/proto_007_* 3  If we had opted for not snapshotting the Alpha protocol, we could pass the path src/proto_alpha as the parameter of the command above. Now we consider the case when testing the migration on a context imported from the snapshot file. In that case, we should recall the level at which the snapshot file was taken from the beginning of Section Prepare the migration. In our example, this level is 1039318. The user-activated upgrade allows us to start the node imported from Mainnet, which would have the predecessor of the Alpha protocol already active if the snapshot is recent enough, and then have the migration triggered automatically at the desired level, which has to be strictly bigger than the level at which the snapshot file was taken. In our example, where we the Alpha protocol was snapshot into src/proto_007_<short_hash>, we can set the user-activated upgrade such that the migration is triggered three levels after the level 1039321 at which the snapshot was taken by invoking: $ ./scripts/user_activated_upgrade.sh src/proto_007_* 1039321


As before, if we had opted for not snapshotting the Alpha protocol, we could pass the path src/proto_alpha as the parameter of the command above.

If we are testing the migration on an empty context on the sandbox, then we should proceed directly to Section 6. Compile the project. Otherwise, the next two subsections detail how to produce credentials that will allow us to make the chain that we imported from Mainnet progress.

### 4. Patch the Shell to Obtain a Yes-Node¶

If we would start a node imported from Mainnet, how could we bake new blocks and make the chain progress? We do not know the private keys of existing bakers in Mainnet!

In order to produce credentials to make the chain imported from Mainnet progress, we modify the code to produce a yes-node that forges and verifies fake signatures. This can be achieved with a small patch to src/lib_crypto/signature.ml that replaces each signature with a concatenation of a public key and a message, such that this fake signature is still unique for each key and message. This patch is encoded as the git diff contained in the file scripts/yes-node.patch. We can apply such patch by invoking:

$patch -p1 < scripts/yes-node.patch  If the patch was already applied, for instance if we run the command above twice by mistake, then we should answer with the default n option to the two messages that the patch tool displays, or otherwise the patch would fail or we would revert it: Reversed (or previously applied) patch detected! Assume -R? [n] n Apply anyway? [n] n  ### 5. Create a Yes-Wallet¶ We also need to create a yes-wallet, which is a special wallet where secret keys actually encode the same bytes as their corresponding public keys. By adding to the yes-wallet the existing accounts of large bakers in Mainnet, e.g. foundation1 to foundation8, we would have enough rights to bake blocks at will. We can do so by running: $ dune exec scripts/yes-wallet/yes_wallet.exe /tmp/yes-wallet


This command creates a yes-wallet and places the yes-wallet folder in the system’s temp directory (in our example, /tmp) as given by the path argument /tmp/yes-wallet. If no path argument was given, the command would create the yes-wallet folder in the default path ./yes-wallet.

### 6. Compile the Project¶

At this point we have to compile the Alpha protocol (or the snapshot Alpha protocol, in case we opted for it) that we will activate when running the migration, as well as the shell if we patched it. We can compile the whole project under the src folder by invoking:

$./tezos-node identity generate --data-dir /tmp/tezos-node-mainnet_2020-07-14_12\ 00  The ./tezos-node snapshot import command accepts an option --block <block_hash> that instructs the command to check that the hash of the last block in the imported chain is <block_hash>. This mechanism helps the developer to check that the imported chain contains blocks that are part of the current main chain of the Tezos network. The web TulipTools provides the first ten characters of the hash of the last block in a given snapshot file. Although we will not be using the --block option in this tutorial, the developer is encouraged to check that this prefix corresponds to the hash of a real block in Mainnet. Importing the context from a snapshot file is optional and should be performed only if we want to test the migration on a realistic context from Mainnet. Otherwise the migration will run on the sandbox. ### Batch Steps 1–7 Above¶ The script scripts/prepare_migration_test.sh batches steps 1–7 above. The script first receives a parameter [manual | auto], which distinguishes whether the migration testing is manual or automatic. Here we focus on the case manual. The next parameter is optional and contains a name in the format <tag_starting_with_version_letter>_<version_number>. If some name is passed, then the Alpha protocol is snapshot into src/proto_<version_number>_<short_hash>. If the name is omitted, then the Alpha protocol in src/proto_alpha will be used for the migration testing. Now the script takes the level at which we want to set the user-activated upgrade. The script distinguishes whether the migration is on the sandbox or on an imported context based on this level. (Recall that a level less or equal than 28082 corresponds to the sandbox, and a level greater than 28082 corresponds to an imported context.) In our example, if we want to test the migration on the sandbox and want to trigger it at level three, we can use: $ ./scripts/prepare_migration_test.sh manual d_007 3


If on the contrary we have imported a realistic context from the snapshot file ~/mainnet_2020-07-14_12\ 00.rolling taken at level 1039318, and we want to trigger the migration three levels after the level at which the snapshot file was taken, we can use:

$./scripts/prepare_migration_test.sh manual d_007 1039321 ~/mainnet_2020-07-14_12\ 00.rolling  In the latter case both the context and the yes-wallet folder will be placed in the system’s temp directory. In our example the temp directory is /tmp, and the context and yes-wallet would be placed in paths /tmp/tezos-node-mainnet_2020-07-14_12\ 00 and /tmp/yes-wallet respectively. If the script detects that the yes-wallet folder already exists int /tmp, then it will clean it by removing spurious files /tmp/yes-wallet/blocks and /tmp/yes-wallet/wallet_locks, and it will not create a new yes-wallet folder. If the script detects that the folder /tmp/tezos-node-mainnet_2020-07-14_12 00 already exists, or if the developer passes the path of a folder instead of the path of a snapshot file, then the script will use the corresponding folder as the original folder, and will not import a new context. In case we opted for not snapshotting the Alpha protocol, we could batch steps 1–7 by respectively using the commands above, but omitting the name parameter d_007. The script scripts/prepare_migration_test.sh receives an optional <block_hash> as the last argument which, if passed, will be used for the option --block <block_hash> to the ./tezos-node snapshot import command when importing the context form Mainnet. After performing the steps 1–7, the migration will be ready to be tested. The next two subsections respectively detail how to run the migration on the sandbox and on a context imported from Mainnet. ### Run the Migration on the Sandbox¶ If we run the migration on an empty context, then we would start a sandboxed node as usual. In our example we can run the following: $ ./src/bin_node/tezos-sandboxed-node.sh 1 --connections 0 &


We can also start the client:

$eval ./src/bin_client/tezos-init-sandboxed-client.sh 1  Instead of command tezos-activate-alpha, the sandboxed client script src/bin_client/tezos-init-sandboxed-client.sh now accepts a command tezos-activate-XXX-<short_hash> that activates the predecessor protocol with version number XXX and short hash <short_hash>. In our example, the predecessor protocol is 006 with short hash PsCARTHA. (Check the folder src for the version number and short hash of the predecessor protocol for migrations to versions different from 007.) We can activate this protocol by invoking: $ tezos-activate-006-PsCARTHA


Activation of the predecessor protocol produces one block and increases the level by one. This unavoidable increase of the level has to be taken into account when setting the desired level for the user-activated upgrade.

Now we can use the client commands to bake blocks until we reach the level at which migration will be triggered, which in our example is 3. Since activating the predecessor protocol increases the level by one, we need to bake two more blocks:

$tezos-client bake for bootstrap1 --minimal-timestamp$ tezos-client bake for bootstrap1 --minimal-timestamp


At this moment migration will be triggered and the protocol proto_007_<short_hash> will become active, and we will see the log message STITCHING!.

The migration can be tested again by restarting the sandboxed node and client, by activating the predecessor of the Alpha protocol, and by baking two blocks.

### Run the Migration on a Context Imported From Mainnet¶

If we run the migration on a context imported from Mainnet, then we would start the node using the context imported from the snapshot file. Since importing a snapshot file is very time consuming, we will leave the original folder unchanged, and every time we want to run the test, we will copy its contents to a fresh test folder. In our example, we can do this by taking advantage of an environment variable test-directory and the tool mktemp as follows:

$test_directory=$(mktemp -d -t "tezos-node-mainnet_2020-07-14_12 00-XXXX") && cp -r "/tmp/tezos-node-mainnet_2020-07-14_12 00/." "$test_directory"  This command creates a fresh test folder in the system’s temp directory (in our example /tmp) whose name is tezos-node-mainnet_2020-07-14_12 00-XXXX, where the XXXX are four random alphanumerical characters, and sets the environment variable test-directory to the path of the test folder, such that we can run the node in the test folder later. Then it copies the contents of the original context folder into the test folder. Now, we can run the tezos-node command by specifying the test folder $test-directory as the data directory. We will also specify the RPC address localhost, such that the RPCs will be available at the url localhost:8732. In our example, by invoking the following:

$./tezos-node run --connections 0 --data-dir "$test_directory" --rpc-addr localhost &


We will now trigger the migration by baking blocks until the level reaches the one specified when setting the user-activated upgrades. The blocks can be baked with the yes-wallet created in step 5 above, and with any of the accounts foundation1 to foundation8. In our example, we can bake one block by running the following command:

$./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp  If the chosen account foundation1 ceases to have the priority to bake, we can switch to any of the remaining accounts foundation2 to foundation8. We will always be able to make the chain progress since it is virtually impossible that at some moment all the eight accounts cease to have the priority to bake. After baking three blocks the migration will be triggered and the protocol proto_007_<short_hash> will become active. We will see the log message STITCHING!. The migration can be tested again by removing the test folder and the spurious files blocks and wallet_lock in the yes-wallet folder. In our example we can do this with the following command: $ rm -rf "$test_directory" && rm -f /tmp/yes-wallet/{blocks,wallet_lock}  Then we repeat the commands above in order to create a fresh test folder, and to copy the context of the original folder into the test folder. In our example: $ test_directory=$(mktemp -d -t "tezos-node-mainnet_2020-07-14_12 00-XXXX") && cp -r "/tmp/tezos-node-mainnet_2020-07-14_12 00/." "$test_directory"


Now we run the node in the test folder by invoking:

$./tezos-node run --connections 0 --data-dir "$test_directory" --rpc-addr localhost &


And finally, we bake the numbers of blocks specified by the user-activated upgrade, with the command:

$./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp  ## Wrap up the Manual Migration Procedure¶ For convenience, this section collects all the steps needed to test the migration, both on the sandbox and on a context imported from Mainnet. ### Migration on the Sandbox¶ Check out latest code: $ git checkout master
$git pull  Tweak migration by checking that src/proto_alpha/lib_protocol/init_storage.ml includes the following lines: | Carthage_006 -> Logging.log_notice "\nSTITCHING!\n" ;  Commit the feature: $ git commit -am 'My awesome feature'


Prepare migration by snapshotting the Alpha protocol, linking it to the build system, setting user-activate upgrades, and compiling the project:

$./scripts/prepare_migration_test.sh manual d_007 3  (Alternatively, each of these steps could be performed individually by invoking the following fur commands): $ ./scripts/snapshot_alpha.sh d_007
$./scripts/link_protocol.sh src/proto_007_*$ ./scripts/user_activated_upgrade.sh src/proto_007_* 3
$make  Run sandboxed node and client: $ ./src/bin_node/tezos-sandboxed-node.sh 1 --connections 0 &
$eval ./src/bin_client/tezos-init-sandboxed-client.sh 1  Activate predecessor of the Alpha protocol and move chain one level forward: $ tezos-activate-006-PsCARTHA


Bake two more blocks by using account bootstrap1:

$tezos-client bake for bootstrap1 --minimal-timestamp$ tezos-client bake for bootstrap1 --minimal-timestamp


You should see the STITCHING! message!

To test again, restart the sandboxed node and client:

$fg ./src/bin_node/tezos-sandboxed-node.sh 1 --connections 0 ^C$ ./src/bin_node/tezos-sandboxed-node.sh 1 --connections 0 &
$eval ./src/bin_client/tezos-init-sandboxed-client.sh 1  Activate predecessor of the Alpha protocol: $ tezos-activate-006-PsCARTHA


Bake two blocks by using account bootstrap1:

$tezos-client bake for bootstrap1 --minimal-timestamp$ tezos-client bake for bootstrap1 --minimal-timestamp


You should see the STITCHING! message again!

### Migration on a Context Imported From Mainnet¶

Check out latest code:

$git checkout master$ git pull


Tweak migration by checking that src/proto_alpha/lib_protocol/init_storage.ml includes the following lines:

| Carthage_006 ->
Logging.log_notice "\nSTITCHING!\n" ;


Commit the feature:

$git commit -am 'My awesome feature'  Prepare migration by snapshotting the Alpha protocol, linking it to the build system, patching the shell in order to obtain yes-node, creating a yes-wallet, setting user-activated upgrades, importing a context from Mainnet into the original context folder, generating an identity in the same folder, and compiling the project: $ ./scripts/prepare_migration_test.sh manual d_007 1039321 ~/mainnet_2020-07-14_12\ 00.rolling


(Alternatively, each of these steps could be performed individually by invoking the following eight commands):

$./scripts/snapshot_alpha.sh d_007$ ./scripts/link_protocol.sh src/proto_007_*
$./scripts/user_activated_upgrade.sh src/proto_007_* 1039321$ patch -p1 < scripts/yes-node.patch
$dune exec scripts/yes-wallet/yes_wallet.exe /tmp/yes-wallet$ make
$./tezos-node snapshot import ~/mainnet_2020-07-14_12\ 00.rolling --data-dir /tmp/mainnet_2020-07-14_12\ 00$ ./tezos-node identity generate --data-dir /tmp/mainnet_2020-07-14_12\ 00


Copy original folder into test folder:

$test_directory=$(mktemp -d -t "tezos-node-mainnet_2020-07-14_12 00-XXXX") && cp -r "/tmp/tezos-node-mainnet_2020-07-14_12 00/." "$test_directory"  Run the node: $ ./tezos-node run --connections 0 --data-dir "$test_directory" --rpc-addr localhost &  Bake three blocks by using accounts foundation1 to foundation8: $ ./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp
$./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp$ ./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp


You should see the STITCHING! message!

To test again, kill the node:

$fg ./tezos-node run --connections 0 --data-dir "$test_directory" --rpc-addr localhost
^C


Clean up by removing test folder and copying original folder into fresh test folder, and by removing files /tmp/yes-wallet/wallet_lock and /tmp/yes-wallet/blocks:

$rm -rf "$test_directory" && rm -f /tmp/yes-wallet/{blocks,wallet_lock};
$test_directory=$(mktemp -d -t "tezos-node-mainnet_2020-07-14_12 00-XXXX") && cp -r "/tmp/tezos-node-mainnet_2020-07-14_12 00/." "$test_directory"  Run the node: ./tezos-node run --connections 0 --data-dir "$test_directory" --rpc-addr localhost &


And bake three blocks:

$./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp$ ./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp
$./tezos-client -d /tmp/yes-wallet bake for foundation1 --minimal-timestamp  You should see the STITCHING! message again! ## Automatic Migration Testing With Tezt¶ The migration can be automatically tested inside the Tezt framework (see Tezt: OCaml Tezos Test Framework) with the test file tezt/manual_tests/migration.ml. The automatic migration runs on a context imported from Mainnet, and proceeds as follows. First, the migration needs to be prepared by applying steps analogous to the steps 1–7 of Section Prepare the migration above, but with the differences that we detail in the next paragraph. Then, the test file tezt/manual_tests/migration.ml is executed: this test starts a node on the imported context, activates the new protocol on the next baked block, and then bakes blocks until a new cycle starts. Once the execution of the test file ends, the developer can manually run the node on the resulting context and inspect the storage manually to check that the migration code is correct. In the automatic test, the operations to the storage are internally triggered by the protocol, and some of these operations are only completed at the end of the cycle. Baking until a new cycle starts helps to check that the migration code is compatible with the actions triggered by the protocol at the end of a cycle. Consequently, the execution of the test file may take a significant amount of time (something between a few minutes and half an hour). Preparing the automatic migration with Tezt can be done with the script scripts/prepare_migration_test.sh, by passing the parameter auto as the first argument. As in Section Batch steps 1–7 above, the developer can decide whether to snapshot the Alpha protocol by passing an optional second parameter to the script with a protocol name in the format <tag_with_version_letter>_<version_number>. Recall that snapshotting the Alpha protocol may be useful for producing a realistic hash of the protocol in the file src/proto_<version_number>_<short_hash>/lib_protocol/TEZOS_PROTOCOL. When passing auto as the first parameter, the script scripts/prepare_migration_test.sh also receives a parameter <path/to/snapshot.rolling> with the path to a snapshot file, and it proceeds as follows: since the automatic migration always runs on a context imported from Mainnet, the script patches the shell in order to obtain a yes-node and imports the context from the file <path/to/snapshot.rolling>. It is enough to provide a snapshot file taken with the rolling history mode (extension .rolling), although the script also accepts snapshot files taken with the full or the archive history mode (extensions .full and .archive respectively). The script creates a folder under the system’s temp directory (in our example /tmp) with the same name as the snapshot file, and imports the context there. If a folder already exists in the system’s temp directory with the same name as the snapshot file, then the script assumes that the context was already imported and uses it as the original folder for the migration. In our example, we can prepare the automatic migration with the following command: $ ./scripts/prepare_migration_test.sh auto d_007 ~/mainnet_2020-07-14_12\ 00.rolling


This command snapshots the Alpha protocol into src/proto_007_<short_hash> and links it in the build system, and then patches the shell in order to obtain a yes-node. If the folder /tmp/mainnet_2020-07-14_12 00 does not exist already, then it creates that folder and imports the context from the snapshot file ~/mainnet_2020-07-14_12 00.rolling into it. As explained in Section Batch steps 1–7 above, the script scripts/prepare_migration_test.sh may receive an optional <block_hash> parameter as the last argument which, if present, will be used for the option --block <block_hash> of the command ./tezos-node snapshot import when importing the context form Mainnet.

If we opt for not snapshotting the Alpha protocol, we can prepare the automatic migration with the same command as above, but omitting the optional name parameter d_007.

The automatic test can be run by invoking:

$dune exec ./tezt/manual_tests/main.exe -- --keep-temp migration  By default, the automatic test starts the node, activates the Alpha protocol when the first block is baked, and then bakes as many blocks as to complete a cycle. This behaviour can be personalized by modifying test file tezt/manual_tests/migration.ml. The developer will not see the STITCHING! message when the migration is triggered unless the option -v for verbose is passed to the command above. The option --color improves the output of the test by alternating colors for the output of each process. Nevertheless, if the developer wants to inspect the verbose output of the test, we strongly recommend to use a log file since the output of the whole migration test can be quite big. In our example, we can collect the logs into the file /tmp/tezt.log by passing the options --log-buffer-size 5000 --log-file /tmp/tezt.log to the command above (notice that the option -v is not required when specifying a log file). Each time the automatic test is run, Tezt creates a temporary folder under the system’s temp directory with name tezt-XXXXXX, where the XXXXXX are six random decimal figures. The content of the original context folder is copied on the fly in the test folder tezt-XXXXXX/tezos-node-test, and a yes-wallet folder is created on the fly in tezt-XXXXXX/yes-wallet. The option --keep-temp in the command above keeps the temporary folder for the developer to be able to inspect the storage after the migration has been performed. Assume the temporary folder in our example is /tmp/tezt-526039, the developer can start the node with the migrated context by invoking: $ ./tezos-node run --connections 0 --data-dir /tmp/tezt-526039/tezos-node-test --rpc-addr localhost &


Once the node is up, it is possible to inspect the storage by using the Tezos client and/or the RPCs. New blocks can be baked with any of the accounts foundation1 to foundation8 by using the following command:

$./tezos-client -d /tmp/tezt-526039/yes-wallet bake for foundation1 --minimal-timestamp  If the developer wishes not to start the node that results after the migration, the parameter --keep-temp can be omitted and the Tezt’s temp folder will be automatically deleted when the migration test ends. The migration can be tested again by stopping the node (if it was up) and running the test file with: $ dune exec ./tezt/manual_tests/main.exe -- --keep-temp migration


There is no need to prepare the migration again.

## Wrap up the Automatic Migration Procedure With Tezt¶

Check out latest code:

$git checkout master$ git pull


Tweak migration by checking that src/proto_alpha/lib_protocol/init_storage.ml includes the following lines:

| Carthage_006 ->
Logging.log_notice "\nSTITCHING!\n" ;


Commit the feature:

$git commit -am 'My awesome feature'  Prepare migration by snapshotting the Alpha protocol, linking it in the build system, patching the shell in order to obtain a yes-node and compiling the project: $ ./scripts/prepare_migration_test.sh auto d_007 ~/mainnet_2020-07-14_12\ 00.rolling


Run the migration test:

$dune exec ./tezt/manual_tests/main.exe -- --keep-temp migration  Run the resulting node (assuming temp folder /tmp/tezt-526039): $ ./tezos-node run --connections 0 --data-dir /tmp/tezt-526039/tezos-node-test --rpc-addr localhost &


Use the client, to manually inspect the storage, or for example to bake new blocks with the following command:

$./tezos-client -d /tmp/tezt-526039/yes-wallet bake for foundation1 --minimal-timestamp  To test again, kill the node: $ fg
./tezos-node run --connections 0 --data-dir /tmp/tezt-526039/tezos-node-test --rpc-addr localhost
^C


And run the migration test:

$dune exec ./tezt/manual_tests/main.exe -- --keep-temp migration  ## Tips and Tricks¶ Migrating a context mostly concerns editing existing data structures. For this reason it is important to inspect the resulting context with the RPCs context/raw/json and context/raw/bytes. The former RPC displays the json value relative to a key of the context, using its json format. This is possible thanks to the storage functors of Tezos, which are used to register every piece of storage in a node and are aware of the json structure of the data. The latter RPC is more low level and simply returns the bytes corresponding to a key. Both RPCs support the option depth to control how much of the subtree of the key should be displayed. For example, if we use context/raw/json to inspect the size of the current listings, which informs of how many rolls are allowed to vote in the current period, we get: $ curl -s localhost:8732/chains/main/blocks/head/context/raw/json/votes/listings_size
56639


On the other hand, if instead we use context/raw/bytes to inspect the data corresponding to the same key, we obtain a string of bytes in hexadecimal format:

$curl -s localhost:8732/chains/main/blocks/head/context/raw/bytes/votes/listings_size "0000dd3f"  This string of bytes can be converted using the OCaml toplevel to obtain the same value retrieved before: utop # let h = 0x0000dd3f ;; val h : int = 56639  In our migration example above, we can inspect the json output of a specific contract: $ curl -s localhost:8732/chains/main/blocks/head/context/raw/json/contracts/index/tz3bvNMQ95vfAYtG8193ymshqjSvmxiCUuR5 | jq .
{
"balance": "2913645407940",
"big_map": [],
"change": "2705745048",
"counter": "0",
"delegate": "tz3bvNMQ95vfAYtG8193ymshqjSvmxiCUuR5",
"delegate_desactivation": 125,
"delegated": [],
"frozen_balance": [],
"manager": "p2pk66n1NmhPDEkcf9sXEKe9kBoTwBoTYxke1hx16aTRVq8MoXuwNqo",
"roll_list": 50696,
"spendable": true
}


The raw/json interface conveniently hides the disk representation of data and keys. Notice how the hashes of public keys are not stored as is, but instead they are encrypted using the more efficient base58 format.

In this case, in order to inspect the low level representation in bytes, which we would often need to, we have to convert hashes of public keys using utop and the functions of_b58check and to_b58check of module Contract_repr:

# let's borrow some code from the protocol tests
$dune utop src/proto_007_*/lib_protocol/test/ # open Tezos_protocol_alpha.Protocol ;; # let b58check_to_path c = Contract_repr.of_b58check c |> fun (Ok c) -> Contract_repr.Index.to_path c [] |> String.concat "/" ;; # b58check_to_path "tz3bvNMQ95vfAYtG8193ymshqjSvmxiCUuR5" ;; ff/18/cc/02/32/fc/0002ab07ab920a19a555c8b8d93070d5a21dd1ff33fe # let path_to_b58check p = String.split_on_char '/' p |> Contract_repr.Index.of_path |> fun (Some c) -> Contract_repr.to_b58check c ;; # path_to_b58check "ff/18/cc/02/32/fc/0002ab07ab920a19a555c8b8d93070d5a21dd1ff33fe" ;; "tz3bvNMQ95vfAYtG8193ymshqjSvmxiCUuR5"  On the other hand, we could have inspected the data corresponding to the same key above with raw/bytes, as we do below: $ curl -s localhost:8732/chains/main/blocks/head/context/raw/bytes/contracts/index/ff/18/cc/02/32/fc/0002ab07ab920a19a555c8b8d93070d5a21dd1ff33fe | jq .
{
"balance": "c4ddb296e654",
"change": "98c9998a0a",
"counter": "00",
"delegate": "02ab07ab920a19a555c8b8d93070d5a21dd1ff33fe",
"delegate_desactivation": "0000007d",
"delegated": {
"15": {
"bb": {
"9a": {
"84": {
"b5": {
}
}
}
}
},
...
},
"frozen_balance": {
"114": {
"deposits": "80e0f09f9b0a",
"fees": "93bb48",
"rewards": "809ee9b228"
},
...
},
"roll_list": "0000c608",
"spendable": "696e69746564"
}


Observe that while the value in json format above shows a big_map field that is empty (i.e. "big_map": [],), the low-level representation of the same value reveals that the field containing such an empty big_map is not stored at all.

## Anatomy of Migration Code¶

The migration code is triggered in init_storage.ml:prepare_first_block, so that function is the entry point to start reading it. Notice that constants are migrated in raw_context.ml:prepare_first_block, which takes a Context.t and returns a Raw_context.t containing the new constants. Migrating other data can usually be done by manipulating the Raw_context.t, and such code should be placed in the match case Alpha_previous of init_storage.ml:prepare_first_block.

Conversions of data structures from the previous protocol are typically found in storage.ml,i, which may involve the functors in storage_functors.ml,i. Each migration is very custom, but there are two recurring schemas that emerged over time.

For high-level changes, the interface offered by the storage_functors is usually expressive enough. The migration would copy the code to read the data structures in the previous version and simply rename it by adding a suffix with the previous version number (in our example above where we are migrating to version 007, the identifiers in the old code would be renamed by appending the suffix _006 to them). The values are then written using the code for the data structures of the current protocol, thus performing the migration. The last step in the migration would be to manually remove any remaining code with a suffix corresponding to the previous version (_006 in our example).

Some migrations may require breaking the interface offered by the storage_functors, and to modify the file raw_context.mli` directly. In this case we usually copy the data to a temporary path, perform the conversion, and then recursively remove the temporary path.